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UBC Theses and Dissertations

Estimation of genetic and environmental parameters of lifetime production traits and longevity in Holstein-Friesian… Hoque, Mozzamel 1980

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ESTIMATION OF GENETIC AND ENVIRONMENTAL PARAMETERS OF LIFETIME PRODUCTION TRAITS AND LONGEVITY IN HOLSTEIN-FRIESIAN COWS By MOZZAMEL (HOQUE B . S c , Dacca U n i v e r s i t y , B a n g l a d e s h , 1961 M . S c , Texas A & M U n i v e r s i t y , U.S.A., 1965 A THESIS SUBMITTED IN THE REQUIREMENTS DOCTOR OF PARTIAL FULFILMENT OF FOR THE DEGREE OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES Department o f A n i m a l S c i e n c e We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA March 1980 (2) Mozzamel Hoque, 198 0 In presenting th is thes is in p a r t i a l fu l f i lment of the requirements for an advanced degree at the Univers i ty of B r i t i s h Columbia, I agree that the L ibrary sha l l make it f ree ly ava i l ab le for reference and study. I fur ther agree that permission for extensive copying of th is thes is for scho la r ly purposes may be granted by the Head of my Department or by his representat ives . It is understood that copying or pub l ica t ion of th is thes is fo r f inanc ia l gain s h a l l not be allowed without my wri t ten permission. Department of Animal Science The Univers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date A p r i l 15, 1980 ABSTRACT T h i s study was undertaken to evaluate the g e n e t i c and environmental aspects of l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s of d a i r y c a t t l e . Canadian Record of Performance (ROP) data of 51,599 H o l s t e i n cows which f i r s t freshened from September, 1957 through February, 1966 were used, thus a l l o w i n g cows time to complete 8 or more years of p r o d u c t i v e l i f e by the end of 1974. These data i n c l u d e d 23018 f i r s t l a c t a t i o n and 28581 m u l t i p l e l a c t a t i o n cows from 2090 herds across Canada. The performance t r a i t s i n c l u d e d were f i r s t l a c t a t i o n 305-day milk and f a t y i e l d s ; f i r s t l a c t a t i o n herd year d e v i a t i o n m i l k and f a t y i e l d s ; l a s t l a c t a t i o n 305-day milk and f a t y i e l d s ; l a s t l a c t a t i o n l e n g t h ; t o t a l l i f e t i m e m i l k and f a t y i e l d s ; m i l k and f a t y i e l d s per day of p r o d u c t i v e l i f e ; age a t c u l l i n g ; l e n g t h of p r o d u c t i v e l i f e ; and number of l a c t a t i o n s completed. E f f e c t s which might have a s i g n i f i c a n t i n f l u e n c e on t r a i t s under study were those of herd, year, season and year by season i n t e r a c t i o n . The c o v a r i a b l e s used were age a t f i r s t c a l v i n g f o r the f i r s t l a c t a t i o n cows, and age a t f i r s t c a l v i n g and c a l v i n g i n t e r v a l f o r the m u l t i p l e l a c t a t i o n cows. A l l e f f e c t s were eva l u a t e d by l e a s t squares technique. T r a i t s under study f o r f i r s t l a c t a t i o n cows were a d j u s t e d f o r age a t f i r s t c a l v i n g , and those f o r - i i i -m u l t i p l e l a c t a t i o n cows were a d j u s t e d f o r b o t h age a t f i r s t c a l v i n g and c a l v i n g i n t e r v a l ; t h e r e s u l t i n g a d j u s t e d d a t a were a n a l y z e d on w i t h i n h e r d - y e a r - s e a s o n b a s i s f o r e s t i m a t i o n o f g e n e t i c p a r a m e t e r s . H e r i t a b i l i t y o f each t r a i t and p h e n o t y p i c and g e n e t i c c o r r e l a t i o n s among th e t r a i t s were d e r i v e d from p a t e r n a l h a l f - s i b a n a l y s i s u s i n g d a u g h t e r s o f 138 s i r e s o f f i v e groups a c c o r d i n g t o s i r e ' s y e a r o f b i r t h . Two s e p a r a t e s e t s o f h e r i t a b i l i t y e s t i m a t e s were o b t a i n e d ; e s t i m a t e s f o r ( i ) combined f i r s t and m u l t i p l e l a c t a t i o n and ( i i ) m u l t i p l e l a c t a t i o n cows were: f i r s t l a c t a t i o n 305-day m i l k .22 and .20, f i r s t l a c t a t i o n 305-day f a t .25 and .25, f i r s t l a c t a t i o n h e r d -y e a r d e v i a t i o n m i l k .22 and .20, f i r s t l a c t a t i o n h e r d - y e a r d e v i a t i o n f a t y i e l d .24 and .25, l a s t l a c t a t i o n 305-day m i l k .14 and .11, l a s t l a c t a t i o n 305-day f a t y i e l d .16 and .14, l a s t l a c t a t i o n l e n g t h .06 and .07, l i f e t i m e m i l k .11 and .11, l i f e t i m e f a t y i e l d .12 and .12, m i l k p e r day o f p r o d u c t i v e l i f e .21 and .21, f a t y i e l d per day o f p r o d u c t i v e l i f e .25 and .28, c u l l i n g age .10 and .09, l e n g t h o f p r o d u c t i v e l i f e .10 and .09, and number o f l a c t a t i o n s .09 and .08, r e s p e c t i v e l y . The average a n n u a l p h e n o t y p i c and g e n e t i c t r e n d s were 72 kg and 31.2 kg, r e s p e c t i v e l y f o r f i r s t l a c t a t i o n m i l k , 2.89 kg and .91 kg, r e s p e c t i v e l y f o r f i r s t l a c t a t i o n f a t . - i v -Genetic c o r r e l a t i o n s of f i r s t l a c t a t i o n m i l k and f a t y i e l d s with l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s ranged from .34 to .93 and .41 to .47, r e s p e c t i v e l y f o r combined f i r s t and m u l t i p l e l a c t a t i o n cows. The g e n e t i c c o r r e l a t i o n s among measures of l i f e t i m e p r o d u c t i o n ranged from .46 to .96 and among l o n g e v i t y t r a i t s were .99 or above f o r the same s e t of data. Separate estimates of g e n e t i c c o r r e l a t i o n s based on m u l t i p l e l a c t a t i o n cows on l y were a l l lower w i t h h i g h e r standard e r r o r than the estimates obtained from combined set of data. The g e n e t i c c o r r e l a t i o n s t h a t were c o n s i d e r e d as having high p r e d i c t i v e value were: f i r s t l a c t a t i o n m i l k c o r r e l a t e d h i g h l y and p o s i t i v e l y with l a s t l a c t a t i o n m i l k and m i l k per day of p r o d u c t i v e l i f e ; f i r s t l a c t a t i o n f a t y i e l d h i g h l y and p o s i t i v e l y c o r r e l a t e d with l a s t l a c t a t i o n f a t y i e l d and f a t y i e l d per day of p r o d u c t i v e l i f e . S i r e s were ranked d i f f e r e n t l y based on t h e i r expected breeding v a l u e s (EBV) f o r p r o d u c t i o n and l o n g e v i t y t r a i t s . The c o r r e l a t i o n s of EBV's f o r f i r s t l a c t a t i o n y i e l d s w i t h l i f e t i m e p r o d u c t i o n and with l o n g e v i t y were p o s i t i v e (.31 to .89). The EBV's f o r f i r s t l a c t a t i o n m i l k and f a t y i e l d s were found to be good p r e d i c t o r s of EBV's f o r m i l k and f a t y i e l d s per day of p r o d u c t i v e l i f e , r e s p e c t i v e l y . Genetic c o r r e l a t i o n s of f i r s t l a c t a t i o n m i l k y i e l d w ith l i f e t i m e m i l k y i e l d (.56) and milk y i e l d per day of p r o d u c t i v e l i f e (.93) i n d i c a t e t h a t continued s e l e c t i o n on f i r s t l a c t a t i o n m i l k p r o d u c t i o n i s an e f f e c t i v e means of m a x i m i z i n g l i f e t i m e m i l k and m i l k per day o f p r o d u c t i v e l i f e . S i g n i f i c a n t p o s i t i v e g e n e t i c a s s o c i a t i o n o f f i r s t l a c t a t i o n p r o d u c t i o n w i t h l i f e t i m e performance and l o n g e v i t y suggest t h a t h i g h p r o d u c i n g h e i f e r s produce more m i l k and f a t d u r i n g t h e i r l i f e t i m e and remain i n herds l o n g e r t h a n lower p r o d u c i n g h e i f e r s . These r e l a t i o n s f u r t h e r i n d i c a t e t h a t t h e method o f A . I . s i r e e v a l u a t i o n u s i n g d a u g h t e r s ' f i r s t l a c t a t i o n l e v e l o f p r o d u c t i o n s h o u l d r e s u l t i n proven b u l l s w h i c h w i l l s i r e d a u g h t e r s w h i c h w i l l produce w e l l i n l a t e r l i f e and w i l l remain i n t h e herd l o n g e r . - v i -TABLE OF CONTENTS Page ABSTRACT i i TABLE '.OF CONTENTS v i LIST OF TABLES v i i i LIST OF FIGURES x i LIST OF APPENDICES x i i ACKNOWLEDGEMENTS x i i i INTRODUCTION 1 LITERATURE REVIEW 6 L o n g e v i t y and D i s p o s a l Reasons 6 Sources o f V a r i a t i o n i n L i f e t i m e P r o d u c t i o n and L o n g e v i t y 11 H e r i t a b i l i t y E s t i m a t e s o f F i r s t L a c t a t i o n M i l k and F a t Y i e l d s 19 R e l a t i o n s h i p Between F i r s t and L a t e r ' L a c t a t i o n s 19 I n h e r i t a n c e of L o n g e v i t y and L i f e t i m e P r o d u c t i o n . 21 R e l a t i o n s h i p s o f F i r s t L a c t a t i o n Y i e l d s W i t h L i f e t i m e Performance and L o n g e v i t y 22 R e l a t i o n s h i p o f S i r e B r e e d i n g V a l u e and S u r v i v a l o f T e s t e d Daughters 2 4 MATERIALS AND METHODS 2 6 Source and D e s c r i p t i o n o f Data 26 Performance T r a i t s 2 8 S t a t i s t i c a l Technique 30 A n a l y s e s f o r e n v i r o n m e n t a l parameters 30 Adjustment o f d a t a 38 - V l l -A n a l y s e s f o r E s t i m a t i o n o f G e n e t i c Parameters . . . .40 E s t i m a t i o n o f h e r i t a b i l i t y 46 E s t i m a t i o n o f g e n e t i c t r e n d 48 E s t i m a t i o n o f g e n e t i c c o r r e l a t i o n 49 E s t i m a t i o n o f p h e n o t y p i c and e n v i r o n m e n t a l c o r r e l a t i o n s 51 E s t i m a t i o n o f b r e e d i n g v a l u e 52 RESULTS AND DISCUSSION". 54 Means and V a r i a t i o n s o f T r a i t s 54 E n v i r o n m e n t a l Parameters A f f e c t i n g L i f e t i m e P r o d u c t i o n and L o n g e v i t y . 56 R e l a t i o n s h i p s o f Age a t F i r s t C a l v i n g w i t h P r o d u c t i o n and L o n g e v i t y 68 R e l a t i o n s h i p s o f C a l v i n g I n t e r v a l w i t h P r o d u c t i o n and L o n g e v i t y 7 2 Adjustment o f Data 74 E s t i m a t i o n s o f G e n e t i c Parameters 7 5 G e n e t i c t r e n d s 7 9 G e n e t i c components o f v a r i a n c e and c o v a r i a n c e 8 5 H e r i t a b i l i t y e s t i m a t e s 87 c o r r e l a t i o n s 95 1" • ;• Phenb'typic''cori?eiations 99 -:T G e n e t i c " c o r r e l a t i o n s 102 R e l a t i o n s h i p s o f E x p e c t e d B r e e d i n g V a l u e s f o r F i r s t L a c t a t i o n Y i e l d s w i t h L i f e t i m e P r o d u c t i o n and L o n g e v i t y 107 CONCLUSIONS 1 1 5 BIBLIOGRAPHY 1 2 4 - v i i i -LIST OF TABLES T a b l e Page 1 Comparative c u l l i n g r a t e and l e n g t h o f h e r d l i f e i n d i f f e r e n t c o u n t r i e s 7 2 Summary o f r e c e n t r e s e a r c h on d a i r y cow d i s p o s a l s 8 3 D i s p o s a l r e a s o n s by l a c t a t i o n number when d i s p o s e d 10 4 Means, s t a n d a r d d e v i a t i o n s (SD), and c o e f f i c i e n t s o f v a r i a t i o n (CV) of t r a i t s , u s i n g d a t a o f combined Groups 1 & 2, c a l c u l a t e d w i t h i n h e r d - y e a r - s e a s o n o f f i r s t c a l v i n g 55 5 Summary o f the a n a l y s i s o f v a r i a n c e - c o v a r i a n c e f o r e n v i r o n m e n t a l e f f e c t s : f o r Group 1 58 6 Summary o f the a n a l y s i s o f v a r i a n c e -c o v a r i a n c e f o r e n v i r o n m e n t a l e f f e c t s : f o r Group 2 59 7 Average y e a r l y and s e a s o n a l t r e n d s i n p r o d u c t i o n and l o n g e v i t y t r a i t s based on l e a s t squares c o n s t a n t s o b t a i n e d from a n a l y s e s on models 1 and 2 62 8 W i t h i n h e r d c o r r e l a t i o n s o f age a t f i r s t c a l v i n g ( a g e ) , average c a l v i n g i n t e r v a l (C.I.Av.) and l a s t c a l v i n g i n t e r v a l (C.I.L.) w i t h p r o d u c t i o n and l o n g e v i t y 7 0 9 W i t h i n h e r d r e g r e s s i o n s ( a d j u s t e d ) f o r y e a r and season e f f e c t s ) o f age a t f i r s t c a l v i n g (Age), average c a l v i n g i n t e r v a l ( C . I . A v . ) , and l a s t c a l v i n g i n t e r v a l (C.I.L.) on p r o d u c t i o n and l o n g e v i t y t r a i t s 71 10 Number of s i r e s and da u g h t e r s i n each g e n e t i c group: f o r Groups 1 and 2 combined 7 6 - i x -11 Summary o f the a n a l y s i s o f v a r i a n c e f o r a d j u s t e d d a t a : f o r Groups 1 and 2 combined 7 7 12 Summary o f the a n a l y s i s o f v a r i a n c e f o r a d j u s t e d d a t a : f o r Group 2 7 8 13 G e n e t i c group l e a s t squares c o n s t a n t s and g e n e t i c p r o g r e s s p e r y e a r f o r p r o d u c t i o n and l o n g e v i t y t r a i t s : f o r Groups 1 and 2 combined 80 14 The e x p e c t e d components o f v a r i a n c e and c o v a r i a n c e f o r two t r a i t s f i t t i n g t h e same model. 86 15 H e r i t a b i l i t y e s t i m a t e s f o r f i r s t l a c t a t i o n y i e l d s , l i f e t i m e • p r o d u c t i o n , and l o n g e v i t y t r a i t s - • • • • • .88 16 H e r i t a b i l i t y e s t i m a t e s of f i r s t t h r e e l a c t a t i o n s i n H o l s t e i n 90 17 H e r i t a b i l i t y e s t i m a t e s o f l i f e t i m e p r o d u c t i o n and l o n g e v i t y i n H o l s t e i n 92 18 P h e n o t y p i c c o r r e l a t i o n s (above d i a g o n a l ) and g e n e t i c c o r r e l a t i o n s (below d i a g o n a l ) : f o r combined Groups 1 and 2 96 19 P h e n o t y p i c c o r r e l a t i o n s (above d i a g o n a l ) and g e n e t i c c o r r e l a t i o n s (below d i a g o n a l ) : f o r Group 2 97 2 0 Summary o f p h e n o t y p i c (above) and g e n e t i c (below) c o r r e l a t i o n s o f f i r s t l a c t a t i o n y i e l d s w i t h l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s 101 21 P h e n o t y p i c (above d i a g o n a l ) and g e n e t i c (below d i a g o n a l ) c o r r e l a t i o n s among l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s : f o r Groups 1 & 2 combined 103 22 D i f f e r e n c e s i n average e x p e c t e d b r e e d i n g v a l u e s (EBV) f o r v a r i o u s g r o u p i n g s o f b u l l s 108 Product-moment c o r r e l a t i o n s between b r e e d i n g v a l u e s o f s i r e s f o r l i f e t i m e p r o d u c t i o n t r a i t s and l o n g e v i t y Product-moment c o r r e l a t i o n s between e x p e c t e d b r e e d i n g "values (EBV) f o r f i r s t l a c t a t i o n y i e l d s , l i f e t i m e p r o d u c t i o n and l o n g e v i t y R e g r e s s i o n s o f e x p e c t e d b r e e d i n g v a l u e (EBV) m i l k and/or e x p e c t e d b r e e d i n g v a l u e f a t on e x p e c t e d b r e e d i n g v a l u e s f o r l i f e t i m e p r o d u c t i o n and l o n g e v i t y - x i -LIST OF FIGURES F i g u r e Page 1 Y e a r l y t r e n d s o f f i r s t l a c t a t i o n m i l k y i e l d 63 2 Y e a r l y t r e n d s o f f i r s t l a c t a t i o n f a t y i e l d 64 3 Y e a r l y t r e n d s o f l i f e t i m e m i l k and l i f e t i m e f a t y i e l d s : f o r Group 2 65 4 Y e a r l y t r e n d s o f l e n g t h o f p r o d u c t i v e l i f e and number o f l a c t a t i o n s completed: f o r Group 2 66 5 G e n e t i c group t r e n d s o f f i r s t l a c t a t i o n m i l k and f a t y i e l d s : f o r Groups 1 and 2 combined 81 6 G e n e t i c group t r e n d s o f l i f e t i m e m i l k and l i f e t i m e f a t y i e l d s : f o r Groups 1 and 2 combined 82 7 G e n e t i c group t r e n d s o f l e n g t h o f p r o d u c t i v e l i f e and number of l a c t a t i o n s completed: f o r Groups 1 and 2 combined 8 3 - x i i -LIST OF APPENDICES Appendix Page 1 Year l e a s t square means f o r Group 1 cows 132 2 Year l e a s t square means f o r Group 2 cows 133 3 Season l e a s t square means f o r Group 1 and Group 2 cows 134 4 S i r e and e r r o r components of v a r i a n c e and c o v a r i a n c e 135 5 Environmental c o r r e l a t i o n s f o r Groups 1 and 2 combined (above diagonal) and Group 2 (below diagonal) cows 138 6 Expected breeding values (EBV) of s i r e s f o r p r o d u c t i o n and l o n g e v i t y t r a i t s 139 - x i i i -ACKNOWLEDGEMENTS The author wishes to express s i n c e r e a p p r e c i a t i o n to Dr. John Hodges, h i s graduate a d v i s o r , f o r h i s constant encouragement, v a l u a b l e advice and guidance dur i n g the re s e a r c h and i n the w r i t i n g of t h i s t h e s i s . A p p r e c i a t i o n i s extended t o h i s graduate committee member, Dr. R.G. Peterson, f o r h i s suggestion and c o n s t r u c t i v e c r i t i c i s m d u r i n g the data analyses and the p r e p a r a t i o n of t h i s manuscript. The author i s a l s o g r a t e f u l to the other members of h i s graduate committee: Dr. B.D. Owen, Dr. J.A. S h e l f o r d and Dr. Oscar S z i k l a i f o r t h e i r i n t e r e s t and f o r revi e w i n g t h i s t h e s i s . The author i s indebted to Dr. Walter, R. Harvey (Department o f D a i r y Science, Ohio S t a t e U n i v e r s i t y , U.S.A.) whose computer program was used i n the data a n a l y s e s . Thanks are a l s o extended t o Mrs. Mabel S t r i k e r and Mr. Do-Kyu Lee f o r t h e i r a s s i s t a n c e i n computer programming. A p p r e c i a t i o n i s extended to A g r i c u l t u r e Canada f o r permissi o n to use t h e i r d a i r y R.O.P. r e c o r d s . The f i n a n c i a l support of the Bangladesh A g r i c u l t u r a l U n i v e r s i t y , Bangladesh through the I.D.A. c r e d i t No. 407-BD i s g r a t e f u l l y acknowledged. F i n a l l y , the author wishes to thank h i s w i f e Kastury and sons T a n b i r and T a s l i m f o r the encouragement and t h e i r understanding and p a t i e n c e d u r i n g t h i s study. - 1 -INTRODUCTION The p r o f i t a b i l i t y o f a d a i r y cow i s c l o s e l y r e l a t e d b o t h t o her d a i l y and her l i f e t i m e p r o d u c t i o n . L i f e t i m e p r o d u c t i o n , even though a r e l i a b l e measure of p r o f i t a b i l i t y , s h o u l d not be used as a c r i t e r i o n o f m e r i t i n a s e l e c t i o n program u n l e s s i t i s a t l e a s t p a r t l y under g e n e t i c c o n t r o l . V a r i a b l e e s t i m a t e s o f h e r i t a b i l i t y f o r l i f e t i m e t r a i t s have been r e p o r t e d . G i l l and A l l a i r e (1976) e s t i m a t e d h e r i t a b i l i t i e s o f l i f e t i m e m i l k and l i f e t i m e f a t as .25 and .26, r e s p e c t i v e l y , whereas Hargrove e t a l . (1969) r e p o r t e d .18 f o r b o t h t r a i t s . H e r i t a b i l i t y e s t i m a t e s f o r m i l k p e r day o f l i f e r e p o r t e d i n t h e l i t e r a t u r e v a r y between .28 and .40 ( G i l l and A l l a i r e , 1976; Hargrove e t a l . , 1969) . I t u s u a l l y t a k e s from one t o t h r e e y e a r s o f m i l k p r o d u c t i o n f o r a d a i r y cow t o repay her c o s t o f r e a r i n g . T h i s v a r i e s w i t h f e e d and l a b o u r c o s t s , m i l k y i e l d and v a l u e o f m i l k . Most cows have p a i d f o r themselves by the age o f t h r e e t o f i v e y e a r s . Beyond t h a t , m i l k revenue over d i r e c t c o s t s becomes g r o s s p r o f i t . Annual d e p r e c i a t i o n r a n k s , a f t e r f e e d and l a b o u r , as t h e t h i r d l a r g e s t c o s t o f m i l k p r o d u c t i o n . A l o n g p r o d u c t i v e l i f e i s t h e r e f o r e b e n e f i c i a l by s p r e a d i n g r e a r i n g c o s t s o ver more y e a r s . Longer average m i l k i n g l i f e i n d a i r y c a t t l e may i n c r e a s e p r o f i t s by r e d u c i n g r e p l a c e m e n t c o s t s p e r cow, i n c r e a s i n g average herd p r o d u c t i o n , r e d u c i n g r eplacement numbers wh i c h must be r e a r e d , and c r e a t i n g g r e a t e r o p p o r t u n i t y f o r c u l l i n g from among h e i f e r s (Rendel and Robertson, 19 50). C o n f l i c t i n g r e p o r t s have appeared concerning the h e r i t a b i l i t y o f l o n g e v i t y . Wilcox e t a l . (1957) found an estimate of .37, whereas Parker e t a_l. (1960) and Evans et a l . (1964) o b t a i n e d no g e n e t i c component. Other estimates of h e r i t a b i l i t y f o r l o n g e v i t y i n H o l s t e i n range from .05 to .18 (Plowman and Gaalaas, 1960; M i l l e r e t a l . , 1967; White and N i c h o l s , 1965). Many of these estimates were based on data from one or very few herds w i t h s i r e s used o n l y w i t h i n one herd. However, Plowman and Gaalaas estimated .15 f o r l e n g t h of h e r d l i f e from a l a r g e number of dam-daughter p a i r s from many herds. S e l e c t i o n f o r l o n g e v i t y i s not expected to be very e f f e c t i v e because of i t s low h e r i t a b i l i t y . I t must a l s o be r e c o g n i z e d t h a t s e l e c t i o n f o r l o n g e v i t y , i f e f f e c t i v e , would tend to i n c r e a s e the g e n e r a t i o n i n t e r v a l i f average herd age i s i n c r e a s e d , thus d e c r e a s i n g the r a t e of annual g e n e t i c improvement. S e l e c t i o n on milk y i e l d occurs mainly d u r i n g the f i r s t l a c t a t i o n (Seath, 1940; Johansson, 1962; White and N i c h o l s , 1965; and A l l a i r e and Henderson, 1966). Genetic c o r r e l a t i o n between y i e l d i n f i r s t and l a t e r l a c t a t i o n s ranges from .48 to .80 (Barker and Robertson, 1966; Hargrove e t a l . , 1969; and L i n and A l l a i r e , 1978). The phenotypic r e l a t i o n s h i p between f i r s t l a c t a t i o n y i e l d s and average herd l i f e to about f i f t h - l a c t a t i o n has been found to be p o s i t i v e (Van Vleck, 1964 - 3 -H i n k s , 1966; and G a alaas and Plowman, 1963). T h e r e a f t e r , t h e r e l a t i o n s h i p i s unknown a l t h o u g h i t has been suggested t h a t i t may not i n c r e a s e beyond about t h e f i f t h l a c t a t i o n ( H i n k s , 1966; M i l l e r e t a l . , 1967; White and N i c h o l s , 1965) depending on p o p u l a t i o n and management reg i m e s . P o s s i b l y h i g h y i e l d s i n t h e f i r s t l a c t a t i o n a r e a s s o c i a t e d w i t h p h y s i c a l o r p h y s i o l o g i c a l c h a r a c t e r i s t i c s t e n d i n g t o l i m i t f u r t h e r i n c r e a s e s i n p r o d u c t i v e o r e c o n o m i c a l h e r d l i f e . B a k e l s (1959) o b s e r v e d t h a t h e r d l i f e o f German Brown cows was reduced when t h e i r f i r s t l a c t a t i o n y i e l d exceeded 3,400 kg of m i l k . White and N i c h o l s (1965) a l s o noted a d e c l i n e i n t h e number o f l a c t a t i o n s completed by H o l s t e i n cows when t h e i r f i r s t l a c t a t i o n y i e l d r e ached 6,300 kg. H i n k s (1966) r e p o r t e d t h a t a h i g h f i r s t l a c t a t i o n y i e l d p r e d i s p o s e d a n i m a l s t o d i s p o s a l f o r r e a s o n s o t h e r t h a n y i e l d i n l a t e r l i f e . I n A . I . b r e e d i n g system, th e p e r c e n t a g e o f t o t a l a n n u a l g e n e t i c improvement a c h i e v e d by female s e l e c t i o n i s r e l a t i v e l y low, t h u s , s e l e c t i o n f o r l o n g p r o d u c t i v e l i f e w i l l be u s e f u l (1) o n l y i n c h o i c e among s i r e s (2) o n l y i f p r e d i c t o r s o f l o n g e v i t y p o s s e s s i n g c o n s i d e r a b l e g e n e t i c v a r i a t i o n can be found and (3) o n l y i f t h e s e p r e d i c t o r s o f l o n g e v i t y can be used when young b u l l s e n t e r a s t u d o r a t t h e time b u l l s f i r s t a c h i e v e a progeny t e s t o r b o t h ( M i l l e r e t aJL., 1967). S e l e c t i o n o f young b u l l s from o l d e r dams a l s o t e n ds t o i n c r e a s e g e n e r a t i o n i n t e r v a l . However, r e l a t i v e l y few s i r e s a r e r e q u i r e d t o s i r e t h e n e x t g e n e r a t i o n o f young b u l l s f o r - 4 -A.I. and there i s scope f o r s e l e c t i o n on i n d i c a t o r s of l o n g e v i t y from b u l l s w i t h s i m i l a r l y d e s i r a b l e m i l k p r o o f s . The g e n e t i c c o n t r i b u t i o n of a s i r e to p o p u l a t i o n improvement can be determined by, among other t h i n g s , h i s breeding v a l u e and the r e l a t i v e l e n g t h of l i f e of h i s daughters i n the p o p u l a t i o n . Since an e a r l y and acc u r a t e a p p r a i s a l i s e s s e n t i a l f o r the maximum g e n e t i c progress, the e v a l u a t i o n of young s i r e s must be based almost e n t i r e l y on f i r s t l a c t a t i o n performance of t h e i r daughters. The s u r v i v a l of t e s t e d daughters o f A.I. s i r e s i n subsequent l a c t a t i o n s would be u s e f u l to measure the acceptance of s i r e s daughters i n l a t e r stages of t h e i r l i f e , and when compared w i t h m i l k p r o o f s would be u s e f u l i n choosing s i r e s from which sons are d e s i r a b l e f o r use i n young s i r e t e s t i n g program. Only l i m i t e d i n f o r m a t i o n i s a v a i l a b l e i n these areas. Burnside and Wi l t o n (1970) r e p o r t e d a negative c o r r e l a t i o n of .47 between milk r a t i n g o f s i r e s and percentage of daughters c u l l e d a n n u a l l y f o r low m i l k p r o d u c t i o n i n second and l a t e r l a c t a t i o n s and .30 between m i l k r a t i n g of s i r e and percentage o f daughters c u l l e d a n n u a l l y f o r udder problems i n second and l a t e r l a c t a t i o n s . Robertson and Barker (1966) r e p o r t e d a p o s i t i v e r e l a t i o n between the h e i f e r progeny t e s t of a b u l l and the p r o p o r t i o n of h i s daughters s u r v i v i n g to l a t e r l a c t a t i o n s . S u r v i v a l of s i r e progeny i s a l s o i n f l u e n c e d by other f a c t o r s . Herds d i f f e r , i n p r o d u c t i o n , c u l l i n g p o l i c y and i n s i r e s used to breed cows. The year i n which a cow begins her f i r s t - 5 -l a c t a t i o n may i n f l u e n c e h e r s u r v i v a l as r e l a t e d t o t h e economic s i t u a t i o n a t t h a t t i m e . Thus t h e c o r r e l a t i o n o f m i l k p r o o f and h e r d l i f e o f t e s t e d d a u g h t e r s s h o u l d be o b t a i n e d f r e e from e f f e c t s o f h e r d and y e a r - s e a s o n . T h i s r e s e a r c h was conducted t o examine t h e d i f f e r e n c e s i n l i f e t i m e p r o d u c t i o n and l e n g t h o f p r o d u c t i v e l i f e o f H o l s t e i n - F r i e s i a n cows i n Record o f Performance h e r d s due t o h e r d , y e a r , season and g e n e t i c f a c t o r s . The s t u d y a l s o i n v e s t i g a t e d t h e r e l a t i o n s h i p o f e a r l y r e p r o d u c t i v e performance and p r o d u c t i o n i n t h e f i r s t l a c t a t i o n w i t h l i f e t i m e y i e l d s and l e n g t h o f h e r d l i f e . A f u r t h e r o b j e c t i v e was t o s t u d y t h e r e l a t i o n o f s i r e s b r e e d i n g v a l u e s f o r m i l k and f a t w i t h l i f e t i m e performance, and l o n g e v i t y . - 6 -LITERATURE REVIEW Longev i t y and D i s p o s a l Reasons The a b i l i t y both to produce and to reproduce f o r many years are d e s i r a b l e c h a r a c t e r i s t i c s i n d a i r y c a t t l e , from an economic and p o s s i b l e breed improvement st a n d p o i n t . L o n g e v i t y i n d a i r y c a t t l e i s the summation of g e n e r a l h e a l t h , f e r t i l i t y and p r o d u c t i o n . The demand f o r b r e e d i n g stock, and • p r i c e of m i l k and beef a l s o a f f e c t l e n g t h of p r o d u c t i v e l i f e . S t u d i e s to determine the age d i s t r i b u t i o n of cows and the l e n g t h of h e r d l i f e have been e x t e n s i v e . R e s u l t s of some of these s t u d i e s are summarized i n Table 1. The causes of the v a r i a t i o n i n the l e n g t h of h e r d l i f e of d a i r y cows have a l s o been i n v e s t i g a t e d i n g r e a t d e t a i l . Recent r e p o r t s on d a i r y cow d i s p o s a l s are more d e t a i l e d w i t h r e s p e c t t o reasons than e a r l i e r s t u d i e s (Table 2 ) . These s t u d i e s i n d i c a t e d t h a t although low m i l k p r o d u c t i o n and breeding problems are the main reasons f o r d i s p o s a l of d a i r y cows, ot h e r f a c t o r s a l s o c o n t r i b u t e t o n a t u r a l wastage and c u l l i n g i n d a i r y herds. Batra e t a l . (1971) estimated the annual d i s p o s a l r a t e of H o l s t e i n cows i n r e g i s t e r e d herds of constant s i z e i n Canada du r i n g September 1967 t o August 1968 t o be 19.9%. T h e i r study i n d i c a t e d d i f f e r e n t d i s p o s a l p a t t e r n s i n herds of i n c r e a s i n g , d e c r e a s i n g and of constant i n s i z e and the authors have concluded t h a t herds of constant s i z e should r e f l e c t the Table 1. Comparative c u l l i n g r a t e and length of h e r d l i f e i n d i f f e r e n t c o u n t r i e s . Canada U.S. U.K. A u s t r a l i a Netherlands Reference Batra et a l . (1971) Andrus et a l . (1970) Beynon (1978) Amiel and Moodie (1973) Renkema and Stelwagen (1979) Period of Study 1967-68 1962-66 Breed H o l s t e i n H o l s t e i n Number o f Cows 19,336 199,411 Removal (%) 19.9 Length of H e r d l i f e (yrs) 3.08 1976-77 1968-69 Friesian"'" 39,454 2,610 22.1 22 4.8 4.2' F r i e s i a n 22 4.5 i 1 2 87% of the herds were F r i e s i a n s Number of l a c t a t i o n s completed. T a b l e 2. Summary o f r e c e n t r e s e a r c h on d a i r y Reference c o w . d i s p o s a l s . White A m i e l Hargrove and B u r n s i d e and Reasons f o r e t a l . N i c h o l s e t a l . Moodie Spooner D i s p o s a l (1969) (1965) (1971) (1973) (1978) P e r i o d 1949-66 1958-63 1967-68 1968-69 1975-78 Breed H o l s t e i n H o l s t e i n H o l s t e i n F r i e s i a n Number o f Cows 1,861 7,317 19,336 2,610 2,936 1 _ _ f i n - - ( i n per cent) — D a i r y Purpose 12.4 9.6 25.8 7.7 2 11.6 B r e e d i n g Problems 30.3 15.7 20.8 16.0 34.7 M i l k P r o d u c t i o n 22.1 36.9 15.5 16. 4 20.7 Mammary System 2.9 13. 5 10.2 5.2 8.7 Type 0.8 0.4 9.4 M a s t i t i s 8.0 5.8 5.4 11.1 13. 8 3 Other r e a s o n s 23.4 18.5 21.9 34. 2 10.5 I C O I 1 T o t a l number of a n i m a l s c u l l e d . 2 I n c l u d e s s u r p l u s and a n i m a l s r e a r e d f o r s a l e . 3 I n c l u d e a b o r t i o n , f o o t and l e g problems, c a l v i n g problems, i n j u r y and hardware d i s e a s e , problem cows, o l d age and death. - 9 -t y p i c a l d i s p o s a l p a t t e r n . B u r n s i d e e t a l . (1971), u s i n g d a t a o f Canadian Record o f Performance herds f o r t h e p e r i o d 1967-68 found r e p r o d u c t i o n and low m i l k p r o d u c t i o n were major causes o f v o l u n t a r y h e r d r e movals. Cows c u l l e d a n n u a l l y f o r t h e s e problems ranged from 13.4% t o 24.4% and from 15.5% to 28.3%, r e s p e c t i v e l y . Young cows were c u l l e d more h e a v i l y f o r low p r o d u c t i o n than t h e i r o l d e r herdmates, whereas more of the o l d e r cows were removed f o r r e p r o d u c t i o n , d i s e a s e s and weakness i n udders. R e p o r t s from o t h e r c o u n t r i e s show s i m i l a r t r e n d s i n c u l l i n g r a t e by age o f cows (Tabel 3 ) . S e a t h (1940), Johansson (1962) and White and N i c h o l s (1965) have a l s o c l a i m e d t h a t most o f t h e e f f e c t i v e s e l e c t i o n f o r p r o d u c t i o n t r a i t s i s p r a c t i s e d e a r l y i n an a n i m a l ' s l i f e and t h a t f a r mers a r e more concerned t h e r e a f t e r w i t h the c o n t r o l o f d i s e a s e and w i t h t h e maintenance o f b r e e d i n g e f f i c i e n c y . A st u d y by A l l a i r e e t al_ . (1976) showed a d i f f e r e n t t r e n d i n c u l l i n g r e a s o n by age of cows. They r e p o r t e d t h a t most f r e q u e n t p r i m a r y r e a s o n s f o r removal p r i o r t o 2 y e a r s o f age were d i s e a s e , t y p e , and r e p r o d u c t i o n . I n - l a t e r ages, p r o d u c t i o n , m a s t i t i s and g e n e r a l h e a l t h a c c o u n t e d f o r most of t h e c u l l i n g d e c i s i o n s . P r o p o r t i o n a t e l y , most removals f o r low r e p r o d u c t i o n o c c u r r e d d u r i n g 2 t o 3 y e a r s , most removals f o r low p r o d u c t i o n d u r i n g 3 t o 4 y e a r s , most removals due t o m i l k i n g c h a r a c t e r i s t i c s d u r i n g 5 t o 6 y e a r s , and most removals f o r g e n e r a l h e a l t h o c c u r r e d a f t e r 10 y e a r s o f age. The c r i t i c a l age f o r d i s e a s e was d u r i n g f i r s t 5 months o f l i f e . Table 3. D i s p o s a l reasons by l a c t a t i o n number when disposed. Reference L a c t a t i o n Burnside 0 1 Conner Spooner Reasons f o r and D i s p o s a l Number et a l . Hodges - . • (1971) (1963) (1978) P e r i o d 1967-68 1957-60 1975-78 Breed H o l s t e i n F r i e s i a n Number of Cows 19,336 — o 2,936 2 M i l k P r o d u c t i o n 1 22.0 24.5 26.6 2 19.1 38.9 32.8 3+ 11.8 18.4 17.7 Breeding Problems 1 15.1 4.4 37.9 2 17.6 13.1 36.0 3+ 24.2 10. 3 34.0 Mammary System 1 8.1 6. 0 2 8.1 3+ 11.8 — 10.3 Da i r y Purpose 1 34.6 38.9 5.5 2 35.7 20.7 3+ 19.1 10.6 14.4 J Diseases 1 3.9 13. 8 10.8 2 4.9 13.1 8.7 3+ 8.7 15.4 16.8 1 Percentages of numbers disposed f o r a l l reasons. 2 T o t a l number of animals c u l l e d . 3 Includes s u r p l u s and animals reared f o r s a l e . - 11 -Spooner (197 8) obser v e d b r e e d i n g problems, p a r t i c u l a r l y t h e f a i l u r e t o c o n c e i v e were o f major imp o r t a n c e i n c u l l i n g d e c i s i o n s a t a l l ages, and t h a t i n f e c t i o u s d i s e a s e s , i n c l u d i n g m a s t i t i s became o f i n c r e a s i n g importance as t h e a n i m a l got o l d e r . Sources o f V a r i a t i o n i n L i f e t i m e P r o d u c t i o n and L o n g e v i t y The s o u r c e s o f v a r i a t i o n w h i c h a f f e c t l i f e t i m e p r o d u c t i o n and l o n g e v i t y i n d a i r y cows have been e s t a b l i s h e d , t h e s e i n c l u d e b r e e d , age a t f i r s t c a l v i n g , c a l v i n g i n t e r v a l , h e r d management and l e v e l o f p r o d u c t i o n , y e a r l y change i n m i l k and beef p r i c e s , season o f c a l v i n g and g e n e t i c f a c t o r s . Breed S i g n i f i c a n t i n t e r a c t i o n between breeds and major d i s p o s a l r e a s o n s was o b s e r v e d by B u r n s i d e e t a l . (1971), and O'Bleness and Van V l e c k (1962). B u r n s i d e e t a l . noted t h a t r e l a t i v e l y lower p e r c e n t a g e o f J e r s e y s were c u l l e d f o r b r e e d i n g problems and h i g h e r p e r c e n t a g e c u l l e d f o r low p r o d u c t i o n , whereas r e l a t i v e l y l o wer p e r c e n t a g e o f H o l s t e i n s were c u l l e d f o r low p r o d u c t i o n and h i g h e r p e r c e n t a g e f o r mammary system problems. H i g h e s t i n c i d e n c e o f d i s p o s a l because o f r e p r o d u c t i v e problems were i n Guernseys, f o l l o w e d c l o s e l y by H o l s t e i n s . S i m i l a r b reed d i f f e r e n c e s were a l s o - 12 -obs e r v e d by O'Bleness and Van V l e c k . A r e l a t i v e l y h i g h i n c i d e n c e o f m i l k f e v e r d eaths i n J e r s e y s compared t o o t h e r breeds were obse r v e d by b o t h t h e groups o f w o r k e r s . Breed d i f f e r e n c e i n the l e n g t h o f p r o d u c t i v e l i f e was ob s e r v e d by Andrus e t a l . (1970). They e s t i m a t e d l i f e e x p e c t e n c y o f H o l s t e i n , J e r s e y , Guernsey and A y r s h i r e as 3.08, 3.20, 3.17 and 2.93 y e a r s , r e s p e c t i v e l y . Age a t f i r s t c a l v i n g F i r s t l a c t a t i o n y i e l d i n c r e a s e s w i t h age a t c a l v i n g , but w i t h i n t h e l i m i t s n o r m a l l y e n c o u n t e r e d i n p r a c t i c e , age a t c a l v i n g does not have a marked e f f e c t on e i t h e r y i e l d s o f m i l k o r f a t . Lamb and Kopland (1963) o b s e r v e d t h a t cows f r e s h e n i n g a t 25 months o f age had t h e h i g h e s t p r o d u c t i o n o f m i l k and m i l k f a t p e r day of l i f e , w i t h p r o d u c t i o n p e r day d e c r e a s i n g as t h e age a t f i r s t f r e s h e n i n g i n c r e a s e d p a s t 25 months. H i g h e s t t o t a l l i f e t i m e p r o d u c t i o n was made by cows f i r s t f r e s h e n i n g a t 30 months f o l l o w e d by t h o s e f r e s h e n i n g a t 27 and 28 months o f age. Hargrove e t a l . (1969) o b t a i n e d n e g a t i v e p h e n o t y p i c c o r r e l a t i o n s o f age a t f i r s t c a l v i n g w i t h t h e number o f l a c t a t i o n s i n i t i a t e d , p r o d u c t i v e l i f e and t o t a l number o f days i n m i l k . Cows c a l v i n g l a t e f o r t h e f i r s t t i me had more days open and, c o n s e q u e n t l y , more p r o d u c t i o n a f t e r 3 05 days i n m i l k l a t e r i n l i f e . Optimum age a t f i r s t c a l v i n g w h i c h maximized l i f e t i m e m i l k p r o d u c t i o n was 27 months f o r - 13 -H o l s t e i n . P u r i and Sharma (1965) o b t a i n e d a highly-s i g n i f i c a n t n e g a t i v e c o r r e l a t i o n between age a t f i r s t c a l v i n g and y i e l d s i n f i r s t two l a c t a t i o n s (-.55) i n Zebu cows. C a l v i n g i n t e r v a l Lamb and Kopland (1963) o b s e r v e d c a l v i n g i n t e r v a l between 12 and 13 months r e s u l t e d i n h i g h e s t p r o d u c t i o n per day of l i f e , whereas cows w i t h c a l v i n g i n t e r v a l between 13 and 15 months s t a y e d i n t h e h e r d l o n g e r and a c h i e v e d a h i g h e r l i f e t i m e p r o d u c t i o n . The h i g h e s t p r o d u c e r s w i t h i n the h e r d had l o n g e r average c a l v i n g i n t e r v a l s t h a n t h e i r c o n t e m p o r a r i e s p r o d u c i n g l e s s m i l k ( M i l l e r e t a_l. , 1967) . They e x p l a i n e d t h i s a s s o c i a t i o n as e n v i r o n m e n t a l , p a r t l y due t o more i n t e n s e c u l l i n g o f low p r o d u c e r s t h a t do not b r e e d r i g h t back and p a r t l y due t o cows i n h i g h p r o d u c t i o n not r e t u r n i n g t o e s t r u s as q u i c k l y a f t e r p a r t u r i t i o n as lower p r o d u c e r s . They o b t a i n e d p h e n o t y p i c and g e n e t i c c o r r e l a t i o n s between c a l v i n g i n t e r v a l and m i l k p r o d u c t i o n r a n g i n g from .19 t o .21 and .43 t o .65, r e s p e c t i v e l y . P h e n o t y p i c c o r r e l a t i o n s between l e n g t h o f h e r d l i f e and c a l v i n g i n t e r v a l were e s s e n t i a l l y z e r o , whereas g e n e t i c c o r r e l a t i o n s v a r i e d between .24 and .72. I n t e r p r e t a t i o n o f t h e s e r e l a t i o n s h i p s i s d i f f i c u l t , because t h e t e r m i n a l l a c t a t i o n does not r e s u l t i n a c a l v i n g i n t e r v a l measurement. - 14 -E v e r e t t e t a l . (1966) a l s o o b t a i n e d a h i g h g e n e t i c c o r r e l a t i o n between 120-day m i l k p r o d u c t i o n and c a l v i n g i n t e r v a l i n H o l s t e i n (.46), but th e y found a low n e g a t i v e p h e n o t y p i c c o r r e l a t i o n (-.04) between t h e s e v a r i a b l e s . Rennie (1956) e s t i m a t e d i n t r a h erd and y e a r l i n e a r r e g r e s s i o n s o f m i l k and f a t y i e l d s on l e n g t h o f c u r r e n t c a l v i n g i n t e r v a l as 33.3 kg o f m i l k and 1.1 kg of f a t , p e r 10 days and f o r p r e c e d i n g c a l v i n g i n t e r v a l as 27.6 kg o f m i l k and 1.04 kg o f f a t , p e r 10 days i n c r e a s e i n c a l v i n g i n t e r v a l . The v a r i a t i o n i n t h e l e n g t h o f c a l v i n g i n t e r v a l i s m a i n l y due t o v a r i a t i o n i n t h e number o f days open. E f f e c t s o f days open on m i l k p r o d u c t i o n have been s t u d i e d e x t e n s i v e l y . Smith and L e g a t e s (19 62) r e p o r t e d t h a t number o f days open d u r i n g the l a c t a t i o n s i g n i f i c a n t l y i n f l u e n c e d 305-day m i l k y i e l d but not 90-day m i l k y i e l d . T h i s was e x p l a i n e d as due l a r g e l y t o t h e i n f l u e n c e o f g e s t a t i o n . W i l t o n e t a l . (1967) c o n c l u d e d t h a t t h e e f f e c t o f days open on the r e c o r d s o f i n d i v i d u a l cows i s more i m p o r t a n t t h a n t h e e f f e c t on s i r e p r o o f s , s i n c e t h e r e i s l i t t l e chance f o r t h e e f f e c t s t o be randomized f o r a s i n g l e cow; t h u s , a d j u stment o f r e c o r d s f o r days open i n brood cow e v a l u a t i o n seems a d v i s i b l e . S c h a e f f e r and Henderson (1972) s t a t e d t h a t e f f e c t s o f days open on m i l k p r o d u c t i o n i s l a r g e l y e n v i r o n m e n t a l , t h u s , a d j u stment o f 305-day r e c o r d s f o r days open appears n e c e s s a r y and would n o t i n t r o d u c e g e n e t i c b i a s , because t h e h e r i t a b i l i t y o f days open was found t o be e s s e n t i a l l y z e r o . - 15 -Season o f c a l v i n g Cows f r e s h e n i n g i n t h e f a l l and e a r l y w i n t e r produce c o n s i d e r a b l y more m i l k t h a n t h o s e f r e s h e n i n g i n l a t e w i n t e r , s p r i n g and summer. Lee e t ' a l . (1961) found cows c a l v i n g i n w i n t e r (December t o F e b r u a r y ) and s p r i n g (March t o May) months i n South West U n i t e d S t a t e s produced s i g n i f i c a n t l y more m i l k , F.C.M. and f a t t h a n cows c a l v i n g i n summer months (June t o A u g u s t ) . Other s t u d i e s i n South West U n i t e d S t a t e s by F o s g a t e and Welch (1960) and J:ohnston e t a l . (1956) have i n d i c a t e d t h a t cows c a l v i n g i n w i n t e r and e a r l y s p r i n g have th e h i g h e s t average p r o d u c t i o n . G a c u l a e t a l . (1968) o b s e r v e d h i g h e r y i e l d o f f a t i n December t o May i n P e n s y l v a n i a d a i r y h e r d s . A n n i s e t a l _ . (1959) r e p o r t e d l o w e r m i l k and f a t y i e l d s i n June t o September i n comparison t o o t h e r c a l e n d a r months f o r Washington d a i r y h e r d s . Wunder and M c G i l l i a r d (19 67) observed cows c a l v i n g a t ages 3 o r 4 y e a r s and over were more a d v e r s e l y a f f e c t e d by c a l v i n g i n J u l y and August than were 2 - y e a r - o l d s i n M i c h i g a n H o l s t e i n h e r d s . The i n f l u e n c e o f season o f c a l v i n g was n e a r l y the same f o r cows o f d i f f e r e n t ages d u r i n g September t o December/ M i l l e r e t a l . (1970) a l s o o b s e r v e d o l d e r cows were more s e v e r e l y a f f e c t e d by summer c a l v i n g t h a n f i r s t l a c t a t i o n H o l s t e i n h e i f e r s i n N o r t h E a s t U n i t e d S t a t e s . Maximum m i l k p r o d u c t i o n was a c h i e v e d by l a t e f a l l and e a r l y w i n t e r c a l v i n g a t a l l ages. They suggested t h a t l a c t a t i o n r e c o r d s s h o u l d be a d j u s t e d f o r b o t h season and age o f c a l v i n g - 16 -simultaneously u s i n g m u l t i p l i c a t i v e f a c t o r s . Mao e t a_l. (1974) observed a c o n s i s t e n t p a t t e r n of monthly v a r i a t i o n i n milk y i e l d i n Canadian Record of Performance herds. Summer c a l v e r s produced l e s s than winter c a l v e r s f o r a l l age groups. They a l s o observed age by month of c a l v i n g i n t e r a c t i o n and suggested t h a t j o i n t adjustment f o r age and season a t c a l v i n g i s necessary. Ahunu (197 8) u s i n g B r i t i s h Columbia D.H.I.A. records found cows which freshened i n w i n t e r (October to March) had higher average milk, f a t and p r o t e i n y i e l d s than those which freshened i n summer ( A p r i l to September). Season e f f e c t was observed to account f o r between .3% and 1.9% of the t o t a l v a r i a t i o n i n the f i r s t l a c t a t i o n milk and f a t y i e l d s (Gacula e t aJL. , 1968; Ahunu,1978). S u r v i v a l r a t e may a l s o d i f f e r depending on the season o f c a l v i n g . Kinks (1966) s t a t e d t h a t , s i n c e there are c o n s i d e r a b l e seasonal d i f f e r e n c e s , summer c a l v i n g cows must demonstrate c o n s i d e r a b l y g r e a t e r p r o d u c t i v e m e r i t than t h e i r w i n t e r c a l v i n g herdmates, i f they are to have equal chances of s u r v i v a l . Reports i n the l i t e r a t u r e i n d i c a t e t h a t the i n f l u e n c e of the season o f c a l v i n g on milk and f a t y i e l d s are r e g i o n a l i n nature, thus, c o r r e c t i o n f o r t h e i r e f f e c t s on r e c o r d s would be s p e c i f i c f o r t h a t r e g i o n . - 17 -Year of c a l v i n g P r o d u c t i o n and c u l l i n g r a t e may d i f f e r from year to year depending on f e e d i n g , management, h e a l t h s t a t u s of the herd, m i l k and beef p r i c e , demand f o r breeding stock and other f a c t o r s which might vary with time. Upward trends i n y e a r l y m i l k and f a t y i e l d s have' been r e p o r t e d by many r e s e a r c h e r s . Burnside and Legates (1967) estimated annual progress i n f i r s t l a c t a t i o n m i l k f o r H o l s t e i n d u r i n g p e r i o d 1953 to 1961 as 63 kg. More r e c e n t estimates of y e a r l y progress i n f i r s t l a c t a t i o n y i e l d s were 90 kg m i l k and 1.1 kg f a t (Verde e t a l . , 1972), and 55 kg m i l k (Ahunu, 1978). Van Vleck (1966) and Gacula et a_l. (1968) r e p o r t e d annual progress i n m i l k as 128 kg and 124 kg, r e s p e c t i v e l y . The upward phenotypic t r e n d observed i s probably due i n p a r t to g e n e t i c improvement and p a r t l y t o improved f e e d i n g and management. Estimated annual g e n e t i c trends f o r H o l s t e i n p o p u l a t i o n s r e p o r t e d are: 33 kg m i l k and -.7 kg f a t d u r i n g 1958-1967 (Verde e t a l . , 1972); 45 kg m i l k d u r i n g 1953-1961 (Burnside and Legates, 1967); 82 kg m i l k and 1.5 kg f a t d u r i n g 1957-1969 (Powell and Freeman, 1974); 46 kg m i l k and 1.1 kg f a t d u r i n g 1966-1972 (Kennedy and Moxley, 1975); 41.8 kg m i l k and 1.26 kg f a t d u r i n g 1958-1972 (Schaeffer et a l . , 1975)/ 53 kg milk (Hargrave and Legates, 1971) and 26 kg m i l k (Hintz e t a l . , 1978). - 18 -Herd Herds may d i f f e r i n f e e d i n g and management, i n l e v e l o f p r o d u c t i o n and c u l l i n g p o l i c i e s . Herds a l s o d i f f e r i n s i r e s used t o b r e e d cows; commercial m i l k herds may t e n d t o use s i r e s w i t h h i g h m i l k r a t i n g s w h i l e a p u r e b r e d b r e e d e r chooses s i r e s w i t h h i g h m i l k and t y p e p r o o f s . B u r n s i d e and W i l t o n (1970) o b s e r v e d t h a t h i g h e r p e r c e n t a g e s of cows were c u l l e d f o r poor t y p e i n t h e herds o f h i g h e r p r o d u c t i o n l e v e l s . They a l s o o b s e r v e d a d e c r e a s e i n t h e number o f cows c u l l e d f o r low p r o d u c t i o n w i t h t h e i n c r e a s e i n h e r d l e v e l o f p r o d u c t i o n . H inks (1966) r e p o r t e d a g r e a t e r s e l e c t i o n p r e s s u r e f o r m i l k y i e l d i n t h e low y i e l d i n g herds compared t o h i g h y i e l d i n g h e r d s . He c o n c l u d e d a n i m a l s i n t h e p o o r e r p r o d u c t i v e environment had t o d i s p l a y g r e a t e r i n d i v i d u a l m e r i t i f t h e i r chances o f s u r v i v a l were t o match t h o s e o f t h e i r c o n t e m p o r a r i e s i n h i g h e r y i e l d i n g h e r d s . Most s t u d i e s i n d i c a t e d h e r d as t h e most i m p o r t a n t s o u r c e o f v a r i a t i o n i n l a c t a t i o n y i e l d s and a c c o u n t e d from 27.8% t o 34.0% and from 26.6% t o 31.7% o f t h e t o t a l v a r i a t i o n i n m i l k and f a t y i e l d s , r e s p e c t i v e l y ( B e r e s k i n and Freeman, 1965; Van V l e c k e t a l . , 1961; Verde e t a l . , 1972; and Ahunu, 1978). The o n l y study w h i c h r e p o r t e d l o w e r e s t i m a t e s o f h e r d e f f e c t i s by G a c u l a e t a l . (1968), who o b t a i n e d e s t i m a t e s 10.3% and 15.9% f o r m i l k and f a t y i e l d s , r e s p e c t i v e l y . - 19 -H e r i t a b i l i t y E s t i m a t e s o f F i r s t L a c t a t i o n M i l k and F a t Y i e l d s H e r i t a b i l i t y e s t i m a t e s o f m i l k and f a t p r o d u c t i o n a r e numerous. L a s l e y (1963) l i s t s average e s t i m a t e s o f .36 f o r m i l k y i e l d and .4 f o r f a t y i e l d based on 30 and 17 such r e p o r t s , r e s p e c t i v e l y . These e s t i m a t e s v a r i e d depending upon p o p u l a t i o n and the method o f e s t i m a t i o n . Those u s i n g daughter-dam r e g r e s s i o n ranged from .29 t o .45 f o r m i l k y i e l d ( B r a d f o r d and Van V l e c k , 1964; Rendel e t a l . , 1957; Van V l e c k and B r a d f o r d , 1965; Van V l e c k , 19 66; and Hargrove e t a l . , 1969), whereas e s t i m a t e s from h a l f - s i b c o r r e l a t i o n ranged from .12 t o .37 (Gacula e t aJL. , 1968; G i l l and A l l a i r e , 1976; Van V l e c k , 1966; S c h a e f f e r e t a l . , 1975; and Ahunu, 1978). E s t i m a t e s f o r f a t y i e l d ranged from .18 t o .37 (Hargrove e t a l . , 1969; and B e r e s k i n and Freeman, 1965) and from .14 to..45 (Gacula e t a l . , 1968; G i l l and A l l a i r e , 1976; S c h a e f f e r e t a l . , 1975 and Ahunu, 1978) u s i n g daughter-dam r e g r e s s i o n and h a l f - s i b c o r r e l a t i o n , r e s p e c t i v e l y . R e l a t i o n s h i p Between F i r s t and L a t e r L a c t a t i o n s The f i r s t l a c t a t i o n r e c o r d i s most u s e f u l f o r e a r l y c u l l i n g and f o r p r o v i n g A . I . b u l l s , t h e second and t h i r d r e c o r d s a r e o f more c o n c e r n when e s t i m a t i n g b r e e d i n g v a l u e s o f th e cows. H e r i t a b i l i t y e s t i m a t e s o f t h e f i r s t , second and t h i r d l a c t a t i o n y i e l d s r e p o r t e d i n l i t e r a t u r e d i f f e r from each - 20 -o t h e r (Freeman, 196 0; Johnson and C o r l e y , 1961; B a r r and Van V l e c k , 1963; M a r t o j o e t a l . , 1963; Rendel e t a l . , 1957; Johansson and Hansson, 1940; and Johansson, 1955). The U.S. s t u d i e s seem t o i n d i c a t e t h e f i r s t r e c o r d s a r e more h e r i t a b l e ( m i l k .26 t o .36, f a t .25 t o .43) t h a n second ( m i l k .22 t o .27, f a t .14 t o .35) and t h i r d ( m i l k .21 t o .33, f a t .16 t o .26), and t h a t t h e second and t h i r d r e c o r d s a r e al m o s t e q u a l l y h e r i t a b l e . R e s u l t s r e p o r t e d from Europe g e n e r a l l y show t h e second r e c o r d t o be l e s s r e l i a b l e . These f i n d i n g s j u s t i f y t h e e a r l y c u l l i n g and the s e l e c t i o n o f A . I . b u l l s on t h e i r d a u g h t e r s f i r s t l a c t a t i o n , p r o v i d e d t h e f i r s t r e c o r d i s a l s o as a c c u r a t e as l a t e r r e c o r d s f o r i n d i c a t i n g t h e b r e e d i n g v a l u e s i n l a t e r l a c t a t i o n s . M o l i n u e v o and Lush (1964) i n d i c a t e d t h a t s e l e c t i n g dams on t h e i r f i r s t r e c o r d s would be a t l e a s t as e f f e c t i v e f o r i m p r o v i n g t h e p r o d u c t i o n o f t h e d a u g h t e r s i n t h e i r second and t h i r d l a c t a t i o n s as s e l e c t i n g t h e dams on t h e i r second and t h i r d r e c o r d s . T h i s i s su p p o r t e d by t h e f i n d i n g s of Freeman (1960) and Van V l e c k (1964). Freeman r e p o r t e d h i g h e r g e n e t i c c o r r e l a t i o n s between f i r s t and second l a c t a t i o n m i l k (.68) and f a t (.8) compared t o c o r r e l a t i o n s between f i r s t and t h i r d o r second and t h i r d (.4). Van V l e c k a l s o found h i g h g e n e t i c c o r r e l a t i o n s between t h e f i r s t and l a t e r l a c t a t i o n r e c o r d s (.66 t o .96) i n d i f f e r e n t b r e e d s . The f i r s t l a c t a t i o n r e c o r d though h i g h l y c o r r e l a t e d t o l a t e r l a c t a t i o n r e c o r d s , i s u n l i k e l y t o g i v e i n f o r m a t i o n about o t h e r c h a r a c t e r i s t i c s , such as udder attachment o r l o n g e v i t y , w h i c h do not become c l e a r l y m a n i f e s t e d u n t i l l a t e r i n l i f e . I n h e r i t a n c e o f L o n g e v i t y and L i f e t i m e P r o d u c t i o n L o n g e v i t y i s d e f i n e d as l e n g t h o f l i f e . In usage w i t h d a i r y c a t t l e , t h i s d e f i n i t i o n i s o f t e n q u a l i f i e d t o denote t h e l e n g t h o f t h e p r o d u c t i v e l i f e ( P a r ker e t a l . , 19 60). S e v e r a l w r i t e r s have suggested t h e importance o f i n c r e a s i n g l o n g e v i t y , b o t h from t h e economic s t a n d p o i n t and because i t a f f e c t s t h e p o s s i b i l i t i e s o f i m p r o v i n g t h e b r e e d ( F r a z e r , 1930; G i l m o r e , 1952; and Lush, 1945). C o n f l i c t i n g r e p o r t s have appeared c o n c e r n i n g t h e h e r i t a b i l i t y o f l o n g e v i t y . E s t i m a t e s o f h e r i t a b i l i t y f o r l o n g e v i t y measured i n a v a r i e t y o f ways have ranged from 0.0 t o .37 w i t h v a l u e s near .15 b e i n g most f r e q u e n t (Evans e t a l . , 1964; M i l l e r et. aJL. , 1967 ; P a r k e r e t a^. , 1960; Plowman and G a a l a a s , 1960 ; White and N i c h o l s , 1965; W i l c o x et a l . , 1957; Hargrove et a l . , 1969; and G i l l and A l l a i r e , 1976). W i l c o x e t a_l. s t u d y i n g d a t a i n one h e r d , found a h e r i t a b i l i t y o f .37 f o r t h e number o f s u c c e s s f u l p a r t u r i t i o n s . P a r k e r e t al _ . , however, found a l m o s t no e v i d e n c e of a g e n e t i c b a s i s f o r l o n g e v i t y i n the B e l t s v i l l e h e rd. I t seems p r o b a b l e t h a t a t l e a s t p a r t o f the d i f f e r e n c e s i n t h e s e r e s u l t s c o u l d be due t o c e r t a i n management and/or s e l e c t i o n p r o c e d u r e s i n t h e v a r i o u s h e r d s . E a r l y s t u d i e s were made u s i n g r e c o r d s from one or a few h e r d s , and i n f e r e n c e s were l i m i t e d by s p e c i f i c management and d i s e a s e c o n d i t i o n s - 22 -and by s m a l l numbers of a n i m a l s . Plowman and G a a l a a s , however, used f a i r l y e x t e n s i v e d a t a i n many herds and e s t i m a t e d t h e h e r i t a b i l i t y o f age a t l a s t c a l v i n g as .15;.'.. R e l a t i v e l y h i g h e r e s t i m a t e s o f h e r i t a b i l i t y have been r e p o r t e d f o r l i f e t i m e p r o d u c t i o n compared t o l e n g t h o f h e r d l i f e measured as number of l a c t a t i o n s , age a t l a s t f r e s h e n i n g and l e n g t h of p r o d u c t i o n l i f e (Evans e t a l . , 1964; Hargrove e t a l . , 1969; and G i l l and A l l a i r e , 1976). They o b t a i n e d h e r i t a b i l i t y e s t i m a t e s r a n g i n g from .18 t o .25, .18 t o .26 and .28 t o .4 f o r l i f e t i m e m i l k , l i f e t i m e f a t and m i l k p e r day o f l i f e , r e s p e c t i v e l y . R e l a t i o n s h i p s of F i r s t L a c t a t i o n Y i e l d s W i t h L i f e t i m e  Performance and L o n g e v i t y I n the progeny t e s t i n g o f d a i r y b u l l s , c o n s i d e r a b l e r e l i a n c e has t o be p l a c e d on t h e f i r s t l a c t a t i o n performance o f t h e i r d a u g h t e r s . T h i s i s i n e v i t a b l e because of t h e time needed t o t e s t a b u l l . S i n c e the g e n e t i c c o r r e l a t i o n between h e r d l i f e and f i r s t l a c t a t i o n m i l k y i e l d i s h i g h , s e l e c t i n g b u l l s f o r g e n e t i c m e r i t f o r h i g h m i l k p r o d u c t i o n , would r e s u l t i n an i n c r e a s e i n average h e r d l i f e o f d a u g h t e r s . I f i n t e n s e s e l e c t i o n f o r m i l k p r o d u c t i o n causes a s h a r p i n c r e a s e i n t h e r a t e o f i n v o l u n t a r y c u l l i n g , p r o g r e s s w i l l be hampered due t o a d e c r e a s e i n the i n t e n s i t y o f s e l e c t i o n f o r m i l k p r o d u c t i o n i n t h e n e x t g e n e r a t i o n . - 23 -Some r e p o r t s i n t h e l i t e r a t u r e (Hickman and Henderson, 1955; and Van V l e c k , 1964) have i n d i c a t e d t h a t h i g h f i r s t l a c t a t i o n p r o d u c t i o n i s p o s i t i v e l y a s s o c i a t e d w i t h l e n g t h o f h e r d l i f e . P a r k e r e t aJL. (1960) e s t i m a t e d s m a l l b u t h i g h l y s i g n i f i c a n t c o r r e l a t i o n s between f i r s t l a c t a t i o n p r o d u c t i o n and age a t l a s t c a l v i n g f o r H o l s t e i n (.18) and f o r J e r s e y s (.19) i n a B e l t s v i l l e h e r d . S i m i l a r r e s u l t s were r e p o r t e d by Gaalaas and Plowman (1963) u s i n g d a t a from 79 h e r d s . They r e p o r t e d h i g h l y s i g n i f i c a n t c o r r e l a t i o n s between f i r s t l a c t a t i o n f a t and f i n a l age (.179) and between f i r s t l a c t a t i o n m i l k and f i n a l age (.188). Evans e t a l . (1964) r e p o r t e d s l i g h t l y h i g h e r c o r r e l a t i o n s o f Mature E q u i v a l e n t (ME) f i r s t l a c t a t i o n m i l k w i t h l i f e t i m e p r o d u c t i o n and l e n g t h o f h e r d l i f e (.22 t o .45). L i m i t e d i n f o r m a t i o n i s a v a i l a b l e on the g e n e t i c c o r r e l a t i o n between f i r s t l a c t a t i o n and l i f e t i m e measurements. Robertson and B a r k e r (1966) r e p o r t e d t h e g e n e t i c c o r r e l a t i o n between f i r s t l a c t a t i o n m i l k and s u r v i v a l t o the f i f t h l a c t a t i o n as .71 i n H o l s t e i n . They o b t a i n e d g e n e t i c c o r r e l a t i o n s o f f i r s t l a c t a t i o n m i l k w i t h l i f e t i m e m i l k and l e n g t h o f p r o d u c t i v e l i f e as .85 and .76, r e s p e c t i v e l y ; and t h a t o f f i r s t l a c t a t i o n f a t w i t h l i f e t i m e f a t and l e n g t h of p r o d u c t i v e l i f e as .94 and .84, r e s p e c t i v e l y . G e n e t i c c o r r e l a t i o n s of number o f l a c t a t i o n s completed w i t h f i r s t l a c t a t i o n m i l k and f a t were .62 and .72, r e s p e c t i v e l y i n t h e same s t u d y . Other s t u d i e s , however, showed a d i f f e r e n t t r e n d i n the r e l a t i o n s h i p - 24 -of f i r s t l a c t a t i o n and l i f e t i m e performance. Bakels (1959) observed a reduction i n the length of h e r d l i f e of German Brown cows when t h e i r f i r s t l a c t a t i o n milk exceeded 3,4 00 kg. White and Nichols (1965) also noted a decline i n the number of lactations completed by Holstein cows when th e i r f i r s t l a c t a t i o n y i e l d reached 6,300 kg. High f i r s t l a c t a t i o n y i e l d predisposed B r i t i s h F r i e s i a n cows to disposal f o r reasons other than y i e l d i n the l a t e r stages of l i f e (Hinks, 1966). Relationship of Sire Breeding Value and Survival of  Tested Daughters The average length of l i f e of a b u l l ' s daughters i s probably the best o v e r a l l assessment of his breeding merit as judged by the farmers who are actually milking the daughters (Robertson and Barker, 1966). Thus, i t would be useful to know the length of h e r d l i f e and production subsequent to f i r s t l a c t a t i o n of the tested daughters. Average length of daughter's productive l i f e would measure the acceptance of daughters by t h e i r owners and when compared with the milk proofs could be valuable i n choosing s i r e s from which sons are desired for use i n young s i r e t e s t i n g program. Very limited information i s available on s i r e progeny disposal rate and r e l a t i o n between s i r e breeding value for milk and the length of h e r d l i f e of t h e i r daughters. Burnside and Wilton (1970) reported a negative c o r r e l a t i o n of . 47 between milk ratings of s i r e s and percentages of daughters c u l l e d annually for low milk - 25 -p r o d u c t i o n i n second or l a t e r l a c t a t i o n s and a c o r r e l a t i o n of .3 between milk r a t i n g s of s i r e s and percentages of daughters c u l l e d a n n u a l l y f o r udder problems i n second or l a t e r l a c t a t i o n s . They have a l s o i n d i c a t e d t h a t , i n r e g i s t e r e d herds, s i r e s w i t h h i g h m i l k r a t i n g s may have daughters c u l l e d more f r e q u e n t l y f o r type than f o r low milk p r o d u c t i o n . Robertson and Barker (1966) have found a p o s i t i v e r e l a t i o n between the h e i f e r progeny t e s t of a b u l l and p r o p o r t i o n of h i s daughters s u r v i v i n g to l a t e r l a c t a t i o n s . S c h a e f f e r and Burnside (1974) c a l c u l a t e d c o r r e l a t i o n s ranging from .39 to .44 and .31 to .34 f o r s u r v i v a l r a t e p r o o f s of s i r e s with m i l k and type p r o o f s , r e s p e c t i v e l y and concluded t h a t improvement i n s u r v i v a b i l i t y of daughters c o u l d be o b t a i n e d by u s i n g b u l l s t h a t rank high f o r both m i l k and type p r o o f s . E v e r e t t e t al_. (1976) o b t a i n e d moderate g e n e t i c c o r r e l a t i o n s between milk y i e l d and " s t a y a b i l i t i e s " t o 36, 48, 60, 72 and 84 months of age (.27 to .55) and high g e n e t i c c o r r e l a t i o n s among s t a y a b i l i t i e s at d i f f e r e n t ages (.58 to .99). They have concluded i f s i r e s must be s e l e c t e d on s t a y a b i l i t y , 4 8-month s t a y a b i l i t y would be d e s i r a b l e because of i t s h i g h g e n e t i c c o r r e l a t i o n s w i t h p r o d u c t i o n (.32 to .41) and o l d e r s t a y a b i l i t i e s (.36 to .99) and because b u l l s can be e v a l u a t e d at a younger age. - 26 -MATERIALS AND METHODS Source and D e s c r i p t i o n o f Data Data used i n t h i s s t u d y were o b t a i n e d from the H o l s t e i n Record o f Performance (R.O.P.) d a t a f i l e and were made a v a i l a b l e f o r r e s e a r c h t h r o u g h t h e c o u r t e s y o f A g r i c u l t u r e Canada. The Canadian Record o f Performance program f o r d a i r y c a t t l e i s run under t h e s u p e r v i s i o n o f A g r i c u l t u r e Canada, who r e q u i r e f o r i n c l u s i o n i n t h i s t e s t i n g program t h a t a herd has a minimum o f 15 cows o f one b r e e d , o f which a t l e a s t 10 must be r e g i s t e r e d . Data c o l l e c t e d d u r i n g t h e p e r i o d 1958 t o 1974 formed th e b a s i s o f t h i s s t u d y . Cows f i r s t c a l v e d d u r i n g September 1957 th r o u g h F e b r u a r y 1966 were i n c l u d e d . Records w i t h age a t l a c t a t i o n s t a r t from 18-36 months w i t h no r e c o r d e d d r y p e r i o d , were c o n s i d e r e d as f i r s t l a c t a t i o n s s i n c e l a c t a t i o n number was not r e c o r d e d . These d a t a d i d not have rea s o n s f o r d i s p o s a l coded. Thus, cows s o l d f o r e x p o r t o r s o l d f o r d a i r y purpose c o u l d n o t be d i s t i n g u i s h e d from t h o s e removed f o r o t h e r r e a s o n s . I f a cow's r e c o r d d i d not appear i n two c o n s e q u c i t v e y e a r s subsequent t o her l a s t r e c o r d i n t h e h e r d where she s t a r t e d her f i r s t r e c o r d , she was c o n s i d e r e d c u l l e d . S i n c e about 25.8% of t h e cows l e a v i n g R.O.P. herds a r e s o l d f o r d a i r y purposes ( B u r n s i d e e t a l . , 1971), t h e s i r e p r o o f f o r l i f e t i m e p r o d u c t i o n and l o n g e v i t y would be b i a s e d downwards i f many da u g h t e r s were s o l d f o r t h e d a i r y purposes a f t e r c o m p l e t i n g the f i r s t l a c t a t i o n . - 27 -In o r d e r f o r a cow's r e c o r d o r r e c o r d s t o be i n c l u d e d i n the s t u d y , t h e f o l l o w i n g c r i t e r i a had t o be s a t i s f i e d . 1) E v e r y cow had t o have a f i r s t l a c t a t i o n on t e s t i n a h e r d h a v i n g 6 o r more l a c t a t i n g cows i n t h e y e a r the h e r d s t a r t e d i n t h e t e s t i n g program. O n l y herds on c o n t i n u o u s t e s t f o r a minimum o f t e n y e a r s were i n c l u d e d . 2) A l l f i r s t l a c t a t i o n r e c o r d s s h o u l d have s t a r t e d b e f o r e March 1966, t h u s a l l o w i n g each cow t o complete 8 o r more y e a r s o f p r o d u c t i v e l i f e by t h e end o f 1974. The d a t a base i n c l u d e d 141,231 l a c t a t i o n s from 51,599 cows i n 2090 herds a c r o s s Canada. About 71% o f t h e s e herds were l o c a t e d i n O n t a r i o , 16% i n Quebec and t h e r e s t i n o t h e r p r o v i n c e s . Minimum l e v e l s o f a c c e p t a n c e o f r e c o r d s f o r i n c l u s i o n i n t h e a n a l y s e s were 300 days f o r c a l v i n g i n t e r v a l , 1600 kg f o r 305-day m i l k , 40 kg f o r 305-day f a t , w h i l e the upper l i m i t s were 2000 days f o r c a l v i n g i n t e r v a l , 10500 kg f o r f i r s t l a c t a t i o n 305-day m i l k , 400 kg f o r f i r s t l a c t a t i o n 305-day f a t , 14000 kg f o r l a s t l a c t a t i o n 305-day m i l k , 550 kg f o r l a s t l a c t a t i o n 305-day f a t , 190 months f o r l e n g t h o f p r o d u c t i v e l i f e and 215 months f o r age a t c u l l i n g . These r e s t r i c t i o n s were n e c e s s a r y t o e l i m i n a t e c l e r i c a l e r r o r s i n t h e r e c o r d s . L a c t a t i o n r e c o r d s l e s s t h a n 183 days i n l e n g t h c o u l d n o t be used because t h e d a t a s e t d i d not have t h e 305-day l a c t a t i o n y i e l d s f o r l a c t a t i o n s s h o r t e r than 183 days, t h u s , r e c o r d s from 183 days t o 305 days were c o n s i d e r e d as 305-day l a c t a t i o n b u t no e x t e n s i o n s were made f o r r e c o r d s l e s s than a c t u a l 305-day l a c t a t i o n . - 28 -Performance T r a i t s A t o t a l of f o u r t e e n t r a i t s , w h i c h measured f i r s t l a c t a t i o n y i e l d , l i f e t i m e p r o d u c t i o n and l o n g e v i t y were c o n s i d e r e d i n t h i s i n v e s t i g a t i o n . F i r s t l a c t a t i o n t r a i t s i n c l u d e d 3 05-day m i l k and f a t y i e l d s , and 305-day h e r d - y e a r d e v i a t i o n m i l k and f a t y i e l d s . L i f e t i m e p r o d u c t i o n t r a i t s were l a s t l a c t a t i o n 305-day m i l k and f a t y i e l d s , l a s t 1 l a c t a t i o n l e n g t h , t o t a l l i f e t i m e m i l k and f a t p r o d u c t i o n , and m i l k and f a t y i e l d s p e r day o f p r o d u c t i v e l i f e . L o n g e v i t y was measured by age a t c u l l i n g , l e n g t h o f p r o d u c t i v e l i f e and t h e number o f l a c t a t i o n s completed. D e f i n i t i o n s and n o t a t i o n s used f o r t h e s e t r a i t s a r e g i v e n below. M i l k 1 and M i l k L : m i l k y i e l d s t o 305 days i n t h e f i r s t (kg) and l a s t l a c t a t i o n s , r e s p e c t i v e l y . F a t 1 and F a t L : f a t y i e l d s t o 305 days i n t h e f i r s t (kg) . and l a s t l a c t a t i o n s , r e s p e c t i v e l y . M i l k HY1 and F a t HYl : f i r s t l a c t a t i o n 305-day m i l k and f a t (kg) y i e l d s , r e s p e c t i v e l y , e x p r e s s e d as d e v i a t i o n s from t h e c o r r e s p o n d i n g h e r d - y e a r averages o f t h e herdmates. These d e v i a t i o n s were w e i g h t e d f o r th e number o f herdmates u s i n g t h e - 29 -weighting f a c t o r = n/(n+l), where n•= number of herdmates. M i l k T and Fat T (kg) t o t a l l i f e t i m e m i l k and f a t p r o d u c t i o n , r e s p e c t i v e l y , i n c l u d i n g those beyond 305 days of l a c t a t i o n s , Milk/D and Fat/D (kg) m i l k and f a t produced per day of p r o d u c t i v e l i f e , r e s p e c t i v e l y . These valu e s were obtained d i v i d i n g t o t a l l i f e t i m e m i l k and f a t productions by l e n g t h of p r o d u t i v e l i f e as d e f i n e d below. LLL (days) l a s t l a c t a t i o n length. C u l l a g e (months) age a t d i s p o s a l . Obtained adding l a s t l a c t a t i o n l e n g t h to age a t l a s t c a l v i n g . P l i f e (months) l e n g t h of p r o d u c t i v e l i f e o b t a ined s u b t r a c t i n g age a t f i r s t c a l v i n g from age a t d i s p o s a l . # L a c t number of l a c t a t i o n or l a c t a t i o n s completed by a cow be f o r e d i s p o s a l . - 30 -S t a t i s t i c a l Technique The a n a l y t i c a l technique used i n the present study was designed to account f o r as many p o t e n t i a l sources of v a r i a t i o n as p o s s i b l e f o r each of the performance t r a i t s . A f t e r a ccounting f o r a l l p o s s i b l e sources of environmental v a r i a t i o n s , the v a r i a t i o n due to g e n e t i c causes was enumerated and g e n e t i c parameters f o r each of these t r a i t s were estimated. Analyses f o r environmental parameters A b a s i c p r e c e p t of a c c u r a t e s t a t i s t i c a l a n a l y s i s i s the f o r m u l a t i o n of a p r e c i s e and complete mathematical model. To enable e f f i c i e n t and v a l i d estimates of the e f f e c t s to be c a l c u l a t e d , a l l s i g n i f i c a n t sources of v a r i a t i o n should be i n c l u d e d i n a model. Previous r e s e a r c h has i n d i c a t e d herd, year, season, age a t c a l v i n g , days open and c a l v i n g i n t e r v a l are p o t e n t i a l sources which might a f f e c t the performance t r a i t s l i s t e d above. The r a t i o n a l e f o r i n c l u d i n g them i n or e x c l u d i n g them from the models f o r the present analyses i s d i s c u s s e d below. Herd The f e e d i n g , management and breeding p o l i c i e s unique to a herd w i l l a f f e c t p r o d u c t i o n and l o n g e v i t y of the cows. - 31 -The h e r d e f f e c t w h i c h i s i n c l u d e d i n t h e model f o r each a n a l y s i s , a l s o i n c l u d e s t h e e f f e c t o f l o c a t i o n i n r e s p e c t of c l i m a t e . Year In a h e r d t h e e n v i r o n m e n t a l e f f e c t , e.g. c l i m a t e , f e e d q u a l i t y and management p r a c t i c e s , may v a r y between y e a r s . C u l l i n g i n t e n s i t y may a l s o d i f f e r from y e a r t o y e a r depending on t h e h e a l t h s t a t u s o f t h e h e r d , m i l k and beef p r i c e s and demand f o r b r e e d i n g s t o c k , w h i c h may v a r y w i t h t i m e . A y e a r e f f e c t was, t h e r e f o r e , i n c l u d e d i n t h e model f o r the a n a l y s e s of a l l t h e t r a i t s . . Season Season o f f i r s t c a l v i n g was c o n s i d e r e d i n t h e model because cows o f a l l age groups i n t h e Canadian Record o f Performance herds showed monthly v a r i a t i o n i n m i l k y i e l d , summer c a l v i n g cows tended t o produce l e s s m i l k than w i n t e r c a l v i n g cows. S u r v i v a l r a t e o f cows may a l s o d i f f e r depending on season o f c a l v i n g . Season o f f i r s t c a l v i n g a l s o i n f l u e n c e s th e subsequent c a l v i n g seasons o f a cow depending on t h e average c a l v i n g i n t e r v a l i n t h e h e r d . S e l e c t i o n p r e s s u r e f o r m i l k y i e l d may a l s o d i f f e r i n d i f f e r e n t seasons o f c a l v i n g depending on t h e m i l k m a r k e t i n g system and the number of cows f r e s h e n i n g i n each season. - 32 -Age a t f i r s t c a l v i n g S t u d i e s have i n d i c a t e d t h a t t h e m i l k and f a t y i e l d s i n t h e f i r s t and subsequent l a c t a t i o n s a r e a f f e c t e d by t h e age a t f i r s t c a l v i n g , w i t h a tendency of i n c r e a s e d p r o d u c t i o n w i t h age. S i n c e d a t a used i n t h i s s t u d y i n c l u d e d cows o f v a r i a b l e age a t f i r s t c a l v i n g (18 t o 36 months), i t was c o n s i d e r e d n e c e s s a r y t o i n c l u d e age a t f i r s t c a l v i n g i n t h e model as a c o v a r i a b l e t o a d j u s t f o r i t s e f f e c t on performance t r a i t s . C a l v i n g i n t e r v a l and days open Length o f c a l v i n g i n t e r v a l i s m a i n l y c o n t r o l l e d by t h e number o f days a cow remains open a f t e r p a r t u r i t i o n . S t u d i e s have shown t h a t t h e number o f days open s i g n i f i c a n t l y a f f e c t m i l k y i e l d o f t h e c u r r e n t and t h e f o l l o w i n g l a c t a t i o n s . Thus, t o account f o r d i f f e r e n c e s i n c a l v i n g i n t e r v a l , b o t h average and l a s t c a l v i n g i n t e r v a l s were i n c l u d e d i n the model as c o v a r i a b l e s . I n t e r a c t i o n s among h e r d , y e a r and season Year by season i n t e r a c t i o n was c o n s i d e r e d i n the model s i n c e i t was thought s e a s o n a l e f f e c t might d i f f e r from y e a r t o y e a r . I n t e r a c t i o n s o f h erd w i t h y e a r and season - 33 -c o u l d n o t be c o n s i d e r e d i n the models f o r e n v i r o n m e n t a l e f f e c t s because o f c o m p u t a t i o n a l l i m i t a t i o n s , s i n c e l a r g e number o f herds were used. Herd, y e a r , season, herd by y e a r , herd by season and herd by y e a r by season e f f e c t s were removed from t h e d a t a by c o n s i d e r i n g h e r d - y e a r - s e a s o n s u b c l a s s e s i n t h e a n a l y s e s f o r t h e e s t i m a t i o n o f g e n e t i c p a r a m e t e r s . A n i m a l s s u b j e c t e d t o t h e common causes o f v a r i a t i o n s were grouped t o g e t h e r f o r a n a l y t i c a l purpose. The groups were cows c u l l e d from t h e h e r d a f t e r f i r s t l a c t a t i o n (Group 1 ) , and cows which completed more th a n one l a c t a t i o n b e f o r e c u l l i n g (Group 2 ) . Data o f each group was a n a l y z e d u s i n g a s p e c i f i c l i n e a r model d e s i g n e d t o e s t i m a t e the e f f e c t s unique t o t h e group. The l i n e a r model f o r t h e Group 1 cows T h i s group i n c l u d e d r e c o r d s o f 23018 cows w h i c h were c u l l e d from t h e herds f o r any r e a s o n a f t e r c o m p l e t i o n o f f i r s t l a c t a t i o n . L e a s t squares a n a l y s i s a f t e r Harvey (1976) was used t o e s t i m a t e t h e e f f e c t s o f h e r d , y e a r , season and y e a r by season i n t e r a c t i o n on t h e performance t r a i t s , w h i c h measured p r o d u c t i o n and l o n g e v i t y . Age a t f i r s t c a l v i n g was c o n s i d e r e d as a c o v a r i a b l e t o a d j u s t performance t r a i t s f o r d i f f e r e n c e s due t o t h i s f a c t o r . The l i n e a r model assumed was as f o l l o w s : - 34 -Y i j k i = u + h i + y j + s k + ^ s ) i k + b A i j k i + e i j k i ( 1 ) where Y . .. _ = t h e obser v e d v a l u e o f v a r i o u s performance i n k i c t r a i t s o f t h e l * " * 1 cow f r e s h e n e d i n t h e k*"*1 season o f t h e y e a r i n t h e i * " * 1 h e r d . u = t h e o v e r a l l mean f o r t h e t r a i t when e q u a l f r e q u e n c i e s e x i s t i n a l l s u b c l a s s e s and A. , i s e q u a l t o z e r o , l j k l ^ t1*1 h. = t h e e f f e c t o f t h e i h e r d , l t h y. = t h e e f f e c t o f t h e j y e a r o f f i r s t c a l v i n g . 3 5k s, = t h e e f f e c t o f the kt h season o f f i r s t c a l v i n g . t h t h (ys )- v = the j o i n t e f f e c t o f t h e j y e a r and k 3 K season when t h e e f f e c t o f y e a r and season are h e l d c o n s t a n t . b = r e g r e s s i o n o f t h e dependent v a r i a b l e Y ^ j ] ^ on t h e independent c o n t i n u o u s v a r i a b l e A. ., , each t i m e h o l d i n g t h e f i t t e d d i s c r e a t e l j k l v a r i a b l e s , h e r d ( h . ) , y e a r ( y . ) , season (s,) l 3 K and y e a r by season ( y S j j J c o n s t a n t . A i j k l = a g e a t f :"- r s t c a l v i n g f o r t h e c o r r e s p o n d i n g l j k l t h e.., n = t h e random e f f e c t a s s o c i a t e d w i t h t h e 1 ' i j k l , . J_, , t h c • t h cow f r e s h e n e d xn the k season o f 3 y e a r t h i n t h e i h e r d , w h i c h i s assumed t o be - 35 -n o r m a l l y and i n d e p e n d e n t l y d i s t r i b u t e d w i t h a z e r o mean and t h e same v a r i a n c e , 2 t h a t x s , e. ., n a r e NID (0, (T ) . l j k l e A l l e f f e c t s i n t h e model e x c e p t e. ., , were r e g a r d e d as f i x e d . ^ l j k l " Year e f f e c t was t h e year of f i r s t c a l v i n g . There were two season o f f i r s t c a l v i n g c l a s s i f i c a t i o n s , Season 1 (March t o August) and Season 2 (September t o F e b r u a r y ) . A cow's c a l v i n g age l e s s t h a n o r e q u a l t o 36 months was c o n s i d e r e d as age a t f i r s t c a l v i n g and was e x p r e s s e d i n months. L i n e a r model f o r Group 2 cows T h i s group i n c l u d e d r e c o r d s o f 28581 cows whi c h f i r s t f r e s h e n e d a t o r b e f o r e 36 months of age, produced more t h a n one l a c t a t i o n and were c u l l e d from t h e h e r d b e f o r e 1975. The model assumed was as f o l l o w s : Y i j k r u + h. + y. + s k + ( y s ) j k + b j A . . ^ + b 2 B . j k l + b 3 C . j k l + e. ... (2) l j k l where Y. ., , = t h e o b s e r v e d v a l u e o f a t r a i t o f the 1^ l j k l t h cow f i r s t f r e s h e n e d i n t h e k season of •th . . t h , , j y e a r i n t h e I h e r d . - 36 -u = o v e r a l l mean f o r a t r a i t when e q u a l f r e q u e n c i e s e x i s t i n a l l s u b c l a s s e s and A. ., , , B. , and C. ., T a r e e q u a l t o z e r o , i j k l i } k l ijkl ^ t h h. = t h e e f f e c t o f t h e i h e r d . 1 s k the e f f e c t o f the j t h y e a r o f f i r s t c a l v i n g , t h e e f f e c t o f t h e k season o f f i r s t c a l v i n g . (ys) -v = the j o i n t e f f e c t o f t h e j f c l 1 y e a r and k t h season when t h e e f f e c t o f y e a r and season a r e h e l d c o n s t a n t . t h A i j k l = a ^ e a t ^ ^ r s t f r e s h e n i n g o f t h e 1 a n i m a l i n months. 4 - U B. .. , = average c a l v i n g i n t e r v a l o f t h e 1 a n i m a l i j k l ^ ^ i n days. C. , = l a s t c a l v i n g i n t e r v a l o f the 1 a n i m a l i n i j k l ^ days. b^,b 9 = p a r t i a l r e g r e s s i o n c o e f f i c i e n t s of the and b.j dependent v a r i a b l e (Y) on independent c o n t i n u o u s v a r i a b l e s (A,B and C) h o l d i n g e i j k l h.,y.,s. and ( y s ) . , c o n s t a n t , l j k ]k 2 = random e r r o r , NID (0, ^ j - ). A l l e f f e c t s i n t h e model e x c e p t e. ., , were c o n s i d e r e d f i x e d . c i j k l C a l v i n g i n t e r v a l was d e f i n e d as t h e number o f days between two c o n s e c u t i v e c a l v i n g s . Due t o t h e e x c l u s i o n o f l a c t a t i o n r e c o r d s s h o r t e r t h a n 18 3 days, t h e c a l v i n g i n t e r v a l would be b i a s e d s l i g h t l y upward. Both average and l a s t c a l v i n g i n t e r v a l s were used as c o v a r i a b l e s i n t h e - 37 -model. In cases of cows c u l l e d a f t e r second l a c t a t i o n , both average and l a s t c a l v i n g i n t e r v a l s were the same. The model was analyzed by the same method as used f o r Group 1 cows. To combine the data of the two groups, i t was necessary to a d j u s t f o r one or more c o v a r i a b l e s unique to each group. Since the number of herds (2014) was too l a r g e to f i t constants u s i n g e x i s t i n g computer programs a v a i l a b l e , a l e a s t square technique f o r absorbing one main e f f e c t w i t h l a r g e number of l e v e l s was employed. The data was s o r t e d by herd and equations f o r u + h^ were absorbed i n t o the equations f o r a l l other f i x e d e f f e c t s other than u. An a d d i t i o n a l run u s i n g the reduced model Y.. . = u + y. + s. + (ys) + bA., . + e., , (3) jkl 13 k 1 j k j k l j k l was necessary to o b t a i n the sum of squares f o r herd e f f e c t s , which was d e r i v e d from the d i f f e r e n c e R (u, h, y, s, ys, A) - R (u, y, s, ys, A) where R (u, h, y, ys, A) and R (u, y, s, ys, A) i n d i c a t e the r e d u c t i o n i n sums of squares due to f i t t i n g e f f e c t s i n c l u d e d i n the parentheses. A s i m i l a r technique was a l s o used f o r Group 2. Thus, i t was not p o s s i b l e t o a d j u s t data f o r herd e f f e c t s , moreover, i t was suspected t h a t i n t e r a c t i o n between herd and year might e x i s t , s i n c e records from each herd f o r a minimum of ten years were used. T h e r e f o r e , i n s t e a d of a d j u s t i n g f o r year and season e f f e c t s , estimates of g e n e t i c parameters were obtained on - 38 -w i t h i n h e r d - y e a r - s e a s o n b a s i s u s i n g d a t a a d j u s t e d f o r age a t f i r s t c a l v i n g and c a l v i n g i n t e r v a l . A djustment o f Data B e f o r e combining t h e d a t a from two groups f o r g e n e t i c parameter a n a l y s i s , t h e o b s e r v a t i o n s were a d j u s t e d f o r a p p r o p r i a t e c o v a r i a b l e s u s i n g r e g r e s s i o n t e c h n i q u e . For Group 1, each o b s e r v a t i o n on each o f t h e performance t r a i t s was c o r r e c t e d f o r age a t c a l v i n g u s i n g t h e f o l l o w i n g model: Y i = Y i ~ b < x i " x ) (4) where = e s t i m a t e d v a l u e o f t h e performance t r a i t f o r t he i cow. Y^ = obs e r v e d v a l u e o f t h e performance t r a i t f o r th e i * " * 1 cow. X^ = age a t f i r s t c a l v i n g i n months f o r t h e . t h 1 cow. X = t h e average age a t f i r s t c a l v i n g . b = r e g r e s s i o n c o e f f i c i e n t f o r t h e independent v a r i a b l e X, o b t a i n e d from t h e a n a l y s i s o f the model 1 and p r e s e n t e d i n T a b l e 9. O b s e r v a t i o n s o f each t r a i t f o r Group 2 were c o r r e c t e d f o r age a t f i r s t c a l v i n g , average c a l v i n g i n t e r v a l and l a s t c a l v i n g i n t e r v a l u s i n g t h e f o l l o w i n g r e g r e s s i o n model: Y. = Y. - b l ( X 1 ± - X x) - b 2 ( X 2 . - X 2) - b 3 ( X 3 . - X3> (5) where Y^ = e s t i m a t e d v a l u e o f performance t r a i t f o r t h e i * " * 1 cow. Y^ = o b s e r v e d v a l u e o f performance t r a i t f o r the . t h 1 cow. th X ^ = age i n month o f t h e i cow a t f i r s t c a l v i n g , y^2± = average c a l v i n g i n t e r v a l i n days o f the . t h 1 cow. t h X^^ = l a s t c a l v i n g i n t e r v a l i n days o f t h e i cow. X^,x"2 = mean v a l u e s o f t h e independent v a r i a b l e s and X 3 X^, X 2 and X^. b^,b 2 = p a r t i a l r e g r e s s i o n c o e f f i c i e n t s f o r t h e and b 3 independent v a r i a b l e s X^, X 2 and X 3, o b t a i n e d from t h e a n a l y s i s o f t h e model 2 and p r e s e n t e d i n T a b l e 9. The raw d a t a was a d j u s t e d f o r a p p r o p r i a t e c o v a r i a b l e ( s ) , r e g a r d l e s s o f s i g n i f i c a n c e . T h i s was done due t o r e c o g n i t i o n t h a t an i n s i g n i f i c a n t c o r r e c t i o n term would n e i t h e r a l t e r t h e d a t a s i g n i f i c a n t l y nor i n t r o d u c e b i a s . I n t h i s s t u d y age ad j u s t m e n t was f o r age a t f i r s t c a l v i n g o n l y , and t h e c a l v i n g - 40 -i n t e r v a l a d j u s t m e n t s were, i n f a c t , a d j u s t m e n t s f o r days open, s i n c e the v a r i a t i o n i n g e s t a t i o n l e n g t h w i t h i n a breed i s n e g l i g i b l e . A n a l y s e s f o r E s t i m a t i o n o f G e n e t i c Parameters G e n e t i c parameters were e s t i m a t e d u s i n g c o r r e c t e d d a t a o f Groups 1 and 2 combined and Group 2 s e p a r a t e l y . The s i r e component of v a r i a n c e was t h e s u b j e c t o f prime i n t e r e s t i n t h e p r e s e n t s t u d y . The r e s t r i c t i o n s imposed on a c c e p t i n g a s i r e were based on c o n s i d e r a t i o n o f t h e r e l i a b i l i t y o f t h e e s t i m a t e s o f g e n e t i c parameters produced. R o b e r t s o n (1959) s t a t e d t h a t when e s t i m a t i n g h e r i t a b i l - i t i e s from s i b a n a l y s i s , s m a l l s i b group s i z e ('< 10 i n d i v i d u a l s p e r group) w i l l r e s u l t i n u n a c c e p t a b l y h i g h s t a n d a r d e r r o r s and t h u s u n r e l i a b l e e s t i m a t e s . A c c o r d i n g t o R o b e r t s o n , the s t a n d a r d e r r o r s o f h e r i t a b i l i t i e s a r e m i n i m i z e d when s i b group s i z e i s between 10 and 40 a n i m a l s . On t h i s b a s i s i n each case h a l f - s i b r e c o r d s from t h e s i r e s h a v i n g l a r g e number o f d a u g h t e r s d i s t r i b u t e d i n many h e r d - y e a r - s e a s o n s u b c l a s s e s were used f o r t h e e s t i m a t i o n o f s i r e component o f v a r i a t i o n . F o r combined Group 1 and 2 a n a l y s i s , a t o t a l o f 30,738 cows w i t h i d e n t i f i a b l e s i r e s w h i c h c a l v e d f o r the f i r s t t i m e between September 1957 t h r o u g h F e b r u a r y 1966 were o b t a i n e d from 51,599 o r i g i n a l number of cows. The Group 2 a n a l y s i s used d a t a from 22,392 cows. These s u b s e t s o f d a t a r e p r e s e n t e d 138 s i r e s . The - 41 -f o l l o w i n g r e s t r i c t i o n s were imposed t o i s o l a t e t h e new data-s e t s from t h e b u l k o f t h e d a t a base. 1) Cows which were m i l k e d f o r a minimum o f 18 3 days. 2) Age a t f i r s t c a l v i n g was between 18 and 36 months. 3) Only s i r e s w i t h 30 o r more d a u g h t e r s d i s t r i b u t e d i n 5 o r more h e r d s . These r e s -t r i c t i o n s l e a d t o i n c l u s i o n o f s i r e s w i t h minimum o f 3 2 d a u g h t e r s d i s t r i b u t e d i n a minimum of 23 h e r d - y e a r - s e a s o n s u b c l a s s e s . 4) Only herds w i t h 4 o r more da u g h t e r s r e -p r e s e n t i n g a minimum of 2 s i r e s were i n c l u d e d . These r e s t r i c t i o n s were imposed t o l i m i t r e c o r d s t o s i r e s w i d e l y and e x t e n s i v e l y used i n A r t i f i c i a l I n s e m i n a t i o n and t o e l i m i n a t e c o n f o u n d i n g w i t h h e r d and/or season e f f e c t s . A t o t a l o f 8187 h e r d - y e a r - s e a s o n s (HYS) r e p r e s e n t i n g 1498 h e r d s , 8 y e a r s and 2 seasons were formed f o r t h e combined s e t o f d a t a . The Group 2 d a t a had 7639 h e r d - y e a r - s e a s o n s u b c l a s s e s . A h e r d - y e a r - s e a s o n was d e f i n e d as a y e a r o r season w i t h i n a h e r d , t h i s means t h a t two cows f r e s h e n i n g i n d i f f e r e n t y e a r s and/or seasons i n t h e same h e r d were c l a s s i f i e d i n t o d i f f e r e n t HYS; a l s o two cows f r e s h e n i n g i n t h e same y e a r and/or season b u t i n d i f f e r e n t herds were s e p a r a t e d i n t o d i f f e r e n t HYS. S i r e s were grouped a c c o r d i n g t o t h e y e a r o f b i r t h . Each group r e p r e s e n t s a s e t o f s i r e s b o r n d u r i n g a t h r e e - y e a r p e r i o d and e n t e r i n g s e r v i c e a p p r o x i m a t e l y d u r i n g the same p e r i o d o f t i m e . F o r example, s i r e Group 1 i n c l u d e d a l l s i r e s - 42 -born d u r i n g p e r i o d 1946 t h r o u g h 1948 and w h i c h p r o b a b l y had t h e i r f i r s t d a u g h t e r s c a l v e d about f i v e y e a r s t h e r e a f t e r . T a b l e 10 shows t h e complete c l a s s i f i c a t i o n o f t h e s i r e g r o u p i n g . T h i s g r o u p i n g s t r a t e g y was p r e f e r r e d over g r o u p i n g on t h e b a s i s o f t h e y e a r o f s i r e ' s f i r s t d a u g h t e r ' s appearance i n t h e d a t a , because i n t h i s d a t a s e t about 50% o f t h e s i r e s had a d a u g h t e r ' s r e c o r d i n t h e f i r s t y e a r (1958) and a l s o t h e d i s t r i b u t i o n o f s i r e s by y e a r o f f i r s t d a u g h t e r ' s r e c o r d were v e r y u n e q u a l w i t h 63 s i r e s i n 1958, 20 s i r e s i n 1959, 24 s i r e s i n 1960, 11 s i r e s i n 1961, 9 s i r e s i n 1962, 5 s i r e s i n 1963, and 6 s i r e s i n 1964. The r e a s o n f o r s i r e g r o u p i n g was t o d e f i n e p o p u l a t i o n s w i t h d i f f e r e n t means around w h i c h s i r e g e n e t i c v a l u e s are d i s t r i b u t e d ( S c h a e f f e r e t a l . , 1975). Year g r o u p i n g was used s i n c e i t was assumed t h a t t h e s i r e s born d u r i n g 1958-60 r e -p r e s e n t e d a more r e c e n t p o p u l a t i o n o f z y g o t e s compared t o t h o s e born d u r i n g 1946-48, though th e l a t e r r e p r e s e n t a s e l e c t e d group o f s i r e s , s i n c e t h e y were i n s e r v i c e l o n g b e f o r e t h e p e r i o d o f d a t a c o l l e c t i o n . S i n c e g e n e t i c t r e n d has been upward i n m i l k p r o d u c t i o n i n H o l s t e i n s , t h e average g e n e t i c m e r i t o f s i r e s born d u r i n g 1958 t h r o u g h 1960 s h o u l d be g r e a t e r t h a n t h a t of s i r e s born d u r i n g 1946 t h r o u g h 1948. A c c o r d i n g t o Henderson (1975) s i r e g r o u p i n g i s a l s o n e c e s s a r y f o r removing b i a s , because th e e s t i m a t e d g e n e t i c v a l u e s o f s i r e s t h a t c o n t i n u e i n s e r v i c e o ver a l o n g p e r i o d o f time a f t e r b e i n g r e t u r n e d t o s e r v i c e , g e n e r a l l y tended t o d e c l i n e r e l a t i v e t o o t h e r b u l l s ; a l s o s i r e s o f l a t e r g e n e r a t i o n s appeared t o be u n d e r - e v a l u a t e d r e l a t i v e t o o l d e r s i r e s . - 43 -E s t i m a t i o n o f t h e s i r e component o f v a r i a t i o n was based on a mixed model w i t h h e r d - y e a r - s e a s o n and g e n e t i c group as f i x e d e f f e c t s and s i r e w i t h i n g e n e t i c group as a random e f f e c t . H e rd-year-season e f f e c t s were t r e a t e d as f i x e d t o a v o i d b i a s due t o d i f f e r e n c e s among s i r e s "in average v a l u e s o f HYS w i t h w h i c h t h e y a r e a s s o c i a t e d . The l i n e a r mixed model assumed was: Y. _ = u + HYS. + G . + S . . + e . . 1 1 (6) i j k l 1 j ;jk i j k l where Y. ., , = o b s e r v a t i o n o f t h e performance t r a i t on t h e 1^ d a u g h t e r o f t h e k^ "*1 s i r e w i t h i n t h e j"* " * 1 g e n e t i c group and f i r s t f r e s h e n e d i n t h e I h e r d - y e a r - s e a s o n , u = t h e p o p u l a t i o n mean. t h HYS^ = t h e e f f e c t due t o t h e i h e r d - y e a r - s e a s o n o f f i r s t c a l v i n g , c o n s i d e r e d f i x e d and common t h t o a l l r e c o r d s i n t h e i HYS. G. = a c o n s t a n t common t o a l l r e c o r d s o f 3 t h d a u g h t e r s o f s i r e s i n t h e j g e n e t i c group, c o n s i d e r e d as f i x e d . S., = a random s i r e e f f e c t common t o d a u g h t e r s o f the k*"*1 s i r e w i t h i n t h e group i n d e p e n d e n t l y d i s t r i b u t e d w i t h mean z e r o and common 2 v a r i a n c e (Ts . The b r e e d i n g v a l u e s o f s i r e s - 44 -i n t h e same group a r e r e g a r d e d as a random sample from t h e same p o p u l a t i o n . t h e random e r r o r a s s o c i a t e d w i t h the r e c o r d o f t h e 1 daughter o f the k 1 s i r e w i t h i n t h t h e j group and f i r s t f r e s h e n e d i n t h e i h e r d - y e a r - s e a s o n i n d e p e n d e n t l y d i s t r i b u t e d w i t h mean z e r o and common v a r i a n c e (X ^  • ^ e S i n c e t h e number o f he r d - y e a r - s e a s o n s (8187) was t o o l a r g e t o f i t c o n s t a n t s , h e r d - y e a r - s e a s o n e f f e c t was absorbed and e s t i m a t e s o f a l l o t h e r e f f e c t s i n t h e model were o b t a i n e d u s i n g l e a s t s quares method (Harvey, 1968). The d e s i g n o f a n a l y s i s o f v a r i a n c e and e x p e c t e d mean squares f o r the model i s shown below: e i j k l Mean Expected Source of Variation Sum of Squares Squares Mean Squares Within herd-year-season (HYS) YXY - R (u, HYS) Total Reduction R(u, HYS, G, S) - R(u, HYS) Genetic group (G) S^z"1^ (adjusted for HYS) MSg (Te2 + k ^ s 2 + k3 9 Q Sire (S)/G BgZg^Bg (adjusted for HYS) MSg Te 2 + kjCs 2 Remainder YXY - R (u, HYS, G, S) MS «"e2 e - 45 -To o b t a i n sum o f squares f o r t h e h e r d - y e a r - s e a s o n e f f e c t an a d d i t i o n a l r u n was n e c e s s a r y u s i n g a reduced model from w h i c h HYS was l e f t o u t . The reduced model assumed was: Y., , = u + G. + S., + e., , (7) j k l 3 3k j k l The sum o f squares f o r h e r d - y e a r - s e a s o n e f f e c t were o b t a i n e d from t h e d i f f e r e n c e R (u, HYS, G, S) - R (u, G, S) where R (u, HYS, G, S) and R (u, G, S) i n d i c a t e t h e r e d u c t i o n i n sums o f squares due t o f i t t i n g c o n s t a n t s f o r t h e e f f e c t s i n c l u d e d i n t h e p a r e n t h e s e s . Sum o f squares f o r s i r e e f f e c t were o b t a i n e d by t h e d i r e c t method, f i t t i n g c o n s t a n t s f o r 13i s i r e s . S i r e and g e n e t i c group l e a s t squares c o n s t a n t s were used t o e s t i m a t e b r e e d i n g v a l u e s o f s i r e s f o r performance t r a i t s . The s i r e component o f v a r i a t i o n was e s t i m a t e d from t h e a n a l y s i s o f v a r i a n c e o f f u l l model (6) as f o l l o w s : „ ( CTe 2 + k n CT -<Te 2 ^ S = : — ( 8 ) which i s <j-- MS - MS 2 s e S k where k-^  = weighted' number o f d a u g h t e r s p e r s i r e . The k-^  v a l u e was c a l c u l a t e d u s i n g t h e method shown by Harvey (1970)for models h a v i n g one random n e s t e d f a c t o r i n mixed model. - 46 -1 s - p . \^ . b . q . . .1 b . J where s = t h e number o f g e n e t i c group - s i r e s u b c l a s s e s . p = t h e number o f g e n e t i c groups. = t h e t h number o f s i r e s i n t h e i g e n e t i c group. b. X = the reduced s e t o f s i r e ^ c o n s t a n t s i n t h e g e n e t i c group. i = the d i a g o n a l elements o f s e c t i o n o f Z m a t r i x . z j j - t h e o f f - d i a g o n a l elements o f s e c t i o n o f Z m a t r i x . The g e n e t i c parameters f o r d i f f e r e n t performance t r a i t s were c a l c u l a t e d as d e s c r i b e d below. E s t i m a t i o n o f h e r i t a b i l i t y The h e r i t a b i l i t y was c a l c u l a t e d from t h e p a t e r n a l h a l f - s i b c o r r e l a t i o n as: where 4 ^ 2 4 (T £ h = . 2 , cr 2 ( 1 0 ) 2 h = h e r i t a b i l i t y i n narrow sense. s\ 2 (j* = s i r e component o f v a r i a n c e , w h i c h i s t h e c o v a r i a n c e between h a l f - s i b s (COVHS). - 47 -2 ^ e = component o f e r r o r v a r i a n c e , w h i c h c o n s i s t s 2 o f t o t a l v a r i a n c e ( (T T) - COVHS. The cov HS = h V A + 1/16 + 1/64 + Thus, C*^ a f t e r removing h e r d - y e a r - s e a s o n and g e n e t i c group e f f e c t s e s t i m a t e s a l l o f t h e e n v i r o n m e n t a l v a r i a n c e p l u s t h e remainder of t h e a d d i t i v e and n o n - a d d i t i v e g e n e t i c v a r i a n c e . ^ 2 Hence 4 t i m e s t h e <T" ( a d d i t i v e v a r i a n c e ) d i v i d e d by s + ( p h e n o t y p i c v a r i a n c e ) i s h e r i t a b i l i t y i n narrow sense ( h 2 ) . The s t a n d a r d e r r o r o f h e r i t a b i l i t y e s t i m a t e was o b t a i n e d by m o d i f y i n g t h e method o f Swiger e t a l . (196 4 ) . Assuming n o r m a l i t y o f t h e i n t r a c l a s s c o r r e l a t i o n ( t ) , t h e s t a n d a r d e r r o r o f h e r i t a b i l i t y [ S.E. (h 2) ] i s : where k x 2 (N-S)(S-1) = i n t r a c l a s s c o r r e l a t i o n c a l c u l a t e d as 2 , . ^ 2 ^ 2 . N = t o t a l number of o b s e r v a t i o n s . N - l = N - (degrees o f freedom f o r f i x e d e f f e c t s ) N-S = degrees o f freedom f o r remainder. S-1 = degrees o f freedom f o r s i r e s w i t h i n g e n e t i c groups. k^ = w e i g h t e d number of d a u g h t e r s p e r s i r e . E s t i m a t i o n o f g e n e t i c t r e n d One-half o f t h e s i r e ' s a d d i t i v e g e n e t i c v a l u e was A. e s t i m a t e d by G_. + S.^, computed from t h e a n a l y s i s o f model •~ . t h 6, where G. i s t h e j l e a s t square g e n e t i c group c o n s t a n t ^ t h and S j k i s t h e l e a s t square c o n s t a n t o f t h e k s i r e w i t h i n t h e j t * 1 group. The change i n v a l u e o f s i r e c o n t r i b u t i o n s from one y e a r t o t h e n e x t can be assumed t o be e q u a l t o t h e change i n v a l u e o f c o n t r i b u t i o n s due t o dams from y e a r t o y e a r ( S c h a e f f e r e_t a l . , 1975). Under t h i s a s sumption t h e change i n average g e n e t i c v a l u e s from y e a r t o y e a r was e s t i m a t e d from t w i c e t h e average d i f f e r e n c e i n t h e average a d d i t i v e g e n e t i c v a l u e s o f s i r e s b e l o n g i n g t o d i f f e r e n t g e n e t i c groups. Sum o f the a d d i t i v e g e n e t i c v a l u e s o f s i r e s w i t h i n a g e n e t i c group was o b t a i n e d as: 5KG. + s j k ) = N K G. + Z s j k where N K i s t h e number of s i r e s i n t h e j 1 " * 1 group. S i n c e S > k = 0, the average a d d i t i v e g e n e t i c v a l u e o f s i r e s i n t h ^ ^ t h e j group was g i v e n by N, G./N = G.. Thus, t h e average d i f f e r e n c e between t h e g e n e t i c group l e a s t s quares c o n s t a n t s d i v i d e d by 3 gave h a l f the y e a r l y g e n e t i c change, s i n c e each g e n e t i c group i n c l u d e d a t h r e e - y e a r p e r i o d . - 49 -E s t i m a t i o n o f g e n e t i c c o r r e l a t i o n G e n e t i c c o r r e l a t i o n was o b t a i n e d d i r e c t l y from t h e o u t p u t o f l e a s t squares a n a l y s i s (Harvey, 1968). C o r r e l a t i o n was computed by d i v i d i n g " f a m i l y " c o v a r i a n c e component e s t i m a t e f o r two t r a i t s by t h e g e o m e t r i c mean o f t h e two " f a m i l y " v a r i a n c e components. I n p a t e r n a l h a l f s i b — 2 c o r r e l a t i o n a n a l y s i s , Q~ c i s t h e " f a m i l y " v a r i a n c e component. Thus, t h e f o r m u l a f o r g e n e t i c c o r r e l a t i o n ( r , .) can y g ( x , y ) ' be r e p r e s e n t e d a s : r / \ = / ~ 0 =— (12) J Q S ( X ) C l s(Y) •s 2 A 2 where (p~ g ^ and (J~ g ^ a r e t h e s i r e components f o r t r a i t s X and Y, r e s p e c t i v e l y and Q ~ s ( x y) ^ s ^ e s-"-re component o f c o v a r i a n c e between x and y. The c o v a r i a n c e [ CTs(x y) ] w a s — 2 s~ 2 ^ 2 a r r i v e d a t by t h e e x p r e s s i o n (J~ (x+y) = (J <-(x) + ( J (Y) + 2 ^ s ( x , y ) and ^ s ( x , y ) = [ 0"* (x+y) - < T g ( x ) - C T g W J 1 / 2 ' s- 2 where (]~ (x+y) i s t h e s i r e component o f t h e sum o f t r a i t s s x and y. Sta n d a r d e r r o r s o f g e n e t i c c o r r e l a t i o n s o b t a i n e d from th e o u t p u t o f l e a s t squares a n a l y s i s , was c a l c u l a t e d by m o d i f y i n g the f o r m u l a g i v e n by T a l l i s (1959) which i s r e p r e s e n t e d below. The v a r i a n c e o f g e n e t i c c o r r e l a t i o n Var > can be w r i t t e n as (rg) - 50 -V a r ( 9 g ) d )c t,t_ s 12 (1+r2) d+r 2) d+tk-l)^) (l+(k-l)t 2) - 2r r f a [ t 1 t 2 ( l + ( k - l ) t 1 ) (l+(k-l)t 2) ] l+(k-l)t, l+(k-l)t~ i — + _ £. r 2 ( t , - t ) 2 + 2 ± f — 2 t l t 2 d.k't,t 0 l 1 2 - 2r r [ t..t,(l-t,) d - t 2 ) ] q w L 1 2 1 ^ (1+r 2)(1+r 2)(l-t n)(1-t ) g w 1 ^ 1 _ t l + 1 _ t 2 L ' q ' * ! ' ^ ' 2 Estimates of r. and r are given by: D W V rb = 12 V11 V22 r v 12 w V11 V22 where t i ' t2 = i n t r a c J - a s s correlations for two t r a i t s . d g = degrees of freedom for sire within genetic group. d^ = degrees of freedom for remainder. k = weighted number of daughters per sire . V^ 2»v^ 2 = are covariances between and within sires, respectively. V ^ l / V 2 2 ' V l l ' V 1 2 = are mean squares between and within sires, respectively. - 51 -S t a n d a r d e r r o r of g e n e t i c c o r r e l a t i o n (S.E. r ) was d e r i v e d y from S.E. - = 4 / V a r ^ } ( 1 3 ) g / g E s t i m a t i o n of p h e n o t y p i c and e n v i r o n m e n t a l c o r r e l a t i o n s P h e n o t y p i c and e n v i r o n m e n t a l c o r r e l a t i o n s were a l s o o b t a i n e d from t h e o u t p u t of the l e a s t squares a n a l y s i s . These parameters were e s t i m a t e d as f o l l o w s : C T e ( x , y ) + C T s ( x , y ) r P ( x ' Y ) = 1^2 . ,2 , » 2 j [ 3 " e ( x ) + <Ts(x)] [(fe(y) + 8*s(y)] ( T e ( x , y ) - 3 ( T s ( x , y ) r E ( x , y ) - - j „ ^ 2 „/s ,2 (14) / _ -~ 2 " ^ ~ 2 7 7 ^ 2 , A 2 J [ < T e ( x ) " 3 CTs(x)][<re(y) " 3 CT s (y)] (15) Where r , . and r„, . r e p r e s e n t p h e n o t y p i c and p ( x , y ) E(x,y) r f if e n v i r o n m e n t a l c o r r e l a t i o n s between t r a i t s x and y; (T . . ^ e(x,y) and CV . . are t h e e r r o r and s i r e components o f c o v a r i a n c e ^ s ( x , y ) ^ 2 ^ 2 between t r a i t s x and y, r e s p e c t i v e l y ; and (T , \ r C\ , \r 1 * 1 V J s ( x ) ^ J e ( x ) ^ 2 ^ 2 (V , . and (T , , are s i r e and e r r o r v a r i a n c e components U s (y) e (y) f o r t r a i t s x and y. In a l l t h e e s t i m a t e s o f g e n e t i c parameters i t was assumed t h a t t h e r e i s no i n t e r a c t i o n o f s i r e w i t h h e r d - y e a r -season e f f e c t s . E s t i m a t i o n of b r e e d i n g v a l u e I n s e x - l i m i t e d t r a i t s b r e e d i n g v a l u e s o f s i r e s a r e based on the performance of t h e i r d a u g h t e r s . I f t h e r e c o r d s o f the daughte r s o f s i r e are made on a comparable b a s i s , the g e n e t i c c o v a r i a n c e between daught e r s ( (J~ , ) i s p r i m a r i l y 1 2 2 a f u n c t i o n o f the a d d i t i v e g e n e t i c v a r i a n c e ( because t h e s i r e e f f e c t i s t h e o n l y g e n e t i c e f f e c t common t o a daughter (d^) o f a s i r e and a n o t h e r daughter (d,,) o f the same s i r e . Assuming t h e p o p u l a t i o n i s m a t i n g a t random, and o n l y t h e a d d i t i v e g e n e t i c v a r i a n c e i s p r e s e n t i n t h e s i r e component, t h e n , t h e s i r e v a r i a n c e i s e q u a l t o t h e c o v a r i a n c e 2 of t h e s i r e ' s d a u g h t e r s i . e . (J = ( J ~ , . The v a r i a n c e s a 1 a 2 of s i r e d aughter average can be shown e q u a l t o (Gacula e t a l . , 1968): 2 2 <T2HYS , / r 2 x CT * J d m + e m s n where CT 2^r i s t h e v a r i a n c e of a s i r e daughter a v e r a g e , ^ d assuming one r e c o r d p e r daughter and t h e r e a re m h e r d - y e a r -seasons and n d a u g h t e r s . A d j u s t i n g r e c o r d s f o r h e r d - y e a r -d 2 2 season e f f e c t s , <J" -r reduces t o : ( j - ^ — = 0" g + — — w i t h the assumption t h a t S_-k and e i a r e i n d e p e n d e n t l y d i s t r i b u t e d . The r e g r e s s i o n of f u t u r e d a u g h t e r s on p r e s e n t d a u g h t e r s can be e x p r e s s e d i n terms o f n daughters by: - 53 -b _ ^ ^ 2 CTs n d n d CT2d ^ 2 + jvL Q-2 u s n n + S — Assuming s i r e ' s mates a r e random samples of the p o p u l a t i o n , t h e g e n e t i c m e r i t o f a s i r e i s e q u a l t o 2 (G.. + S_.j_) , where G_. and S^, a r e t h e l e a s t squares e s t i m a t e s o f t h e g e n e t i c group and t h e s i r e w i t h i n g e n e t i c group e f f e c t s , r e s p e c t i v e l y . T h e r e f o r e , t h e e x p e c t e d b r e e d i n g v a l u e (EBV) o f a s i r e can be e s t i m a t e d a s : EBV = b dnd (G. + S.K) 2n n + - 2 -~ 2 (T (G\ + S j k ) (16) To s t u d y t h e r e l a t i o n s h i p s o f EBV o f s i r e f o r f i r s t l a c t a t i o n y i e l d s w i t h EBV f o r l i f e t i m e , p r o d u c t i o n and l o n g e v i t y , product-moment c o r r e l a t i o n and s t e p w i s e r e g r e s s i o n t e c h n i q u e were employed u s i n g TRP program (1977) a v a i l a b l e a t t h e U n i v e r s i t y o f B.C. Computing C e n t r e . P r e d i c t i o n e q u a t i o n s were f i t t e d t o EBV f o r l i f e t i m e p r o d u c t i o n and l o n g e v i t y . - 54 -RESULTS AND DISCUSSION Means and V a r i a t i o n s of T r a i t s The means, standard d e v i a t i o n s and c o e f f i c i e n t s of v a r i a t i o n of t r a i t s , c a l c u l a t e d w i t h i n herd-year-season of f i r s t c a l v i n g are g i v e n i n Table 4. Means f o r p r o d u c t i o n t r a i t s were comparable to r e p o r t s by other r e s e a r c h e r s (Hargrove et aJL. , 1969; Evans et a l . , 1964; Gaalaas and Plowman, 1963; Lamb and Kopland, 1963; M i l l e r et a l . , 1967; White and N i c h o l s , 1965; G i l l and A l l a i r e , 1976). Since M i l k HY1 and Fat HYl were d e r i v e d by d e v i a t i n g the f i r s t l a c t a t i o n m i l k and f a t , r e s p e c t i v e l y from the corresponding herd-year average o f the herdmates i n d i f f e r e n t l a c t a t i o n s , most of the d e v i a t i o n s were ne g a t i v e , thus, g i v i n g n e gative means f o r both the t r a i t s . The c o e f f i c i e n t s of v a r i a t i o n f o r performance t r a i t s were a l i t t l e h igher than some of the other s t u d i e s which have had a more r e s t r i c t e d d e f i n i t i o n s of l i f e t i m e measurements (Van V l e c k , 1964; Larson et a l . , 1951; White and N i c h o l s , 1965). The data of t h i s study were r e l a t i v e l y f r e e from the r e s t r i c t i o n s , such as a g i v e n number of l a c t a t i o n s or a g i v e n age (Van Vleck, 1964; Larson et a l . , 1951) s i n c e a l l cows i n c l u d e d were assumed to have completed t h e i r p r o d u c t i v e l i f e . The average age a t f i r s t c a l v i n g c a l c u l a t e d w i t h i n herd was 2 9.3 + 2.9 months. T h i s value i s i n agreement with the f i n d i n g s of Hargrove et a l . (1969), G i l l and A l l a i r e T a b l e 4. Means, s t a n d a r d d e v i a t i o n s (SD), and c o e f f i c i e n t s of v a r i a t i o n (CV) of t r a i t s , u s i n g d a t a of combined Groups 1 & 2, c a l c u l a t e d w i t h i n h e r d - y e a r - s e a s o n of f i r s t c a l v i n g . T r a i t a Mean SD b CV(% F i r s t l a c t a t i o n 305-day m i l k y i e l d ( M i l k 1) 4896 703 14. 4 F i r s t l a c t a t i o n 305-day f a t y i e l d ( F a t 1) 183 26 14.2 F i r s t l a c t a t i o n h e r d - y e a r d e v i a t i o n m i l k y i e l d ( M i l k HY1) -639 709 F i r s t l a c t a t i o n h e r d - y e a r d e v i a t i o n f a t y i e l d (Fat HY1) -24 27 L a s t l a c t a t i o n 305-day m i l k y i e l d ( M i l k L) 5513 1149 20.8 L a s t l a c t a t i o n 305-day f a t y i e l d ( Fat L) 207 45 21.7 L a s t l a c t a t i o n l e n g t h (LLL) 342 71 20.8 T o t a l l i f e t i m e m i l k y i e l d ( M i l k T) 20165 15628 77.5 T o t a l l i f e t i m e f a t y i e l d (Fat T) 761 592 77.8 M i l k y i e l d / D a y o f p r o d u c t i v e l i f e (Milk/D) 15. 2 2 13.2 F a t y i e l d / D a y o f p r o d u c t i v e l i f e (Fat/D) .57 . 08 14. 0 Age a t d i s p o s a l ( C u l l a g e ) 72 30 41.7 Length o f p r o d u c t i v e l i f e ( P l i f e ) 43 30 69.8 Number o f l a c t a t i o n s (# L a c t ) 3.3 2.2 66.7 a N o t a t i o n s g i v e n i n the p a r e n t h e s e s f o r the above t r a i t s w i l l be used i n t h e subsequent t a b l e s . T r a i t s a re d e f i n e d i n pages 28 and 29. b U n i t s a r e kg, ex c e p t c u l l a g e and P l i f e which are i n months, LLL i n days and # L a c t i n number. - 56 -(1976) and L i n and A l l a i r e (1978), but i s h i g h e r t h a n t h o s e r e p o r t e d by o t h e r workers (White and N i c h o l s , 1965; Lamb and K o p l a n d , 196 3 ) . T h i s i s p a r t l y due t o the upper l i m i t of 36 months f o r age a t f i r s t c a l v i n g p l a c e d on the d a t a i i n t h e p r e s e n t s t u d y , whereas t h e upper l i m i t was 3 4 months i n d a t a o f White and N i c h o l s (1965). W i t h i n herd average c a l v i n g i n t e r v a l o b t a i n e d i n t h i s s tudy (42 0 + 6 8 days) i s l o n g compared t o o t h e r s t u d i e s ( E v e r e t t e t a l . , 1966/ M i l l e r e t a l . , 1967). A p a r t o f t h i s d i f f e r e n c e may be due t o t h e v e r y h i g h upper l i m i t f o r c a l v i n g i n t e r v a l imposed i n t h i s s t u d y (2 0 00 days) compared t o the upper l i m i t (600 days) imposed by M i l l e r e t aJL. (1967). Some of t he r e g i s t e r e d herds of H o l s t e i n s i n c l u d e d i n t h i s s t u d y were o f h i g h p r o d u c t i o n l e v e l . Farmers appear t o t o l e r a t e l o n g e r c a l v i n g i n t e r v a l f o r h i g h p r o d u c e r s , w h i c h might ac c o u n t f o r a p a r t o f t h e l o n g e r average c a l v i n g i n t e r v a l . E n v i r o n m e n t a l Parameters A f f e c t i n g L i f e t i m e  P r o d u c t i o n and L o n g e v i t y I t was n e c e s s a r y t o acco u n t f o r i d e n t i f i a b l e s y s t e m a t i c e f f e c t s b e f o r e s u b j e c t i n g t h e d a t a t o a n a l y s e s f o r th e g e n e t i c p a r a m e t e r s . To e s t i m a t e t h e e f f e c t s o f h e r d , y e a r , season and y e a r by season i n t e r a c t i o n , and e f f e c t s o f t h r e e c o v a r i a b l e s , t h e d a t a were c l a s s i f i e d i n t o two groups. Age a t f i r s t c a l v i n g , one o f t h e c o v a r i a b l e s , was common t o a l l t r a i t s o f b o t h t h e Group 1 (cows c u l l e d a f t e r f i r s t - 57 -l a c t a t i o n ) and Group 2 (cows c u l l e d a f t e r c o m p l e t i n g more th a n one l a c t a t i o n ) . Average c a l v i n g i n t e r v a l and l a s t c a l v i n g i n t e r v a l were common t o a l l t r a i t s o f t h e Group 2 o n l y . L e a s t squares a n a l y s i s o f v a r i a n c e - c o v a r i a n c e were used t o e s t i m a t e t h e e f f e c t s o f t h e s e f a c t o r s . L e a s t squares c o n s t a n t s a s s o c i a t e d w i t h herd e f f e c t c o u l d n ot be e s t i m a t e d because o f l a r g e number o f herds (2014) i n c l u d e d i n t h i s s t u d y , and no s p e c i f i c i n f e r e n c e s were t o be drawn from t h i s e f f e c t . The l e a s t square c o n s t a n t s a s s o c i a t e d w i t h 8 y e a r s and 2 seasons a l l o w e d d e t e c t i o n o f y e a r l y and s e a s o n a l t r e n d s i n p r o d u c t i o n . Summaries o f t h e r e s u l t s o f l e a s t squares a n a l y s e s f o r Group 1 and Group 2 a r e shown i n T a b l e s 5 and 6, r e s p e c t i v e l y . These t a b l e s show the c o -2 e f f i c i e n t o f d e t e r m i n a t i o n (R ) f o r t h e t o t a l model, w h i c h i s a measure of the p o r t i o n o f t o t a l v a r i a b i l i t y a c counted f o r by t h e e n v i r o n m e n t a l e f f e c t s i n c l u d e d i n t h e model. F o r t h e 2 t r a i t s examined f o r Group 1 cows, t h e t o t a l R ranged from 18.1% f o r l e n g t h o f p r o d u c t i v e l i f e ( P l i f e ) t o 76.2% f o r age 2 a t d i s p o s a l ( C u l l a g e ) . F o r Group 2, t o t a l R ranged from 2 12.5% f o r # L a c t t o 43.3% f o r F a t 1 and Fat/D. These R v a l u e s i n d i c a t e d t h e r e l a t i v e l y s m a l l i m p o r t a n c e o f t h e s y s t e m a t i c , e n v i r o n m e n t a l e f f e c t s c o n s i d e r e d i n t h i s s t u d y i n d e t e r m i n i n g t h e t o t a l v a r i a b i l i t y o f t h e P l i f e and # L a c t . F o r M i l k 1, F a t 1, M i l k / D and Fat/D, however, t h e s e e f f e c t s d e t e r m i n e d a l a r g e p o r t i o n (38.4% t o 43.3%) o f t h e t o t a l v a r i a b i l i t y . 2 The v e r y h i g h t o t a l R f o r c u l l a g e i n Group 1 was due m a i n l y Table 5 . Summary of the analysis of variance-covariance for environmental e f f e c t s : for Group 1. R 2 Values (%) a T r a i t Total C • S • S • T o t a l F i t t e d Herd Year Season Year x Age at Season 1st Calving Milk 1 20.00xl0 9 38.4 33.7 2.43 .89 .02° 2.13 Fat 1 2.86xl0 7 40.1 35.3 2.63 .72 .02c 2.42 Milk HY1 14.34xl0 9 19.6 15.4 0.13 .77 .02 c 3.00 Fat HY1 2.04xl0 7 21.0 16.4 0.19 .55 .01 c 3.43 LLL 11.36xl0 7 18.2 17.4 0.29 .05 .11 0.06 Milk T 44.32xl0 9 28.9 25.0 1.95 .44 .05 1.41 Fat T 65.01xl0 7 29. 5 25.7 2.06 .34 .05 1.52 Milk/D 1.7xl0 5 41.4 37.4 2.39 .54 .04 2.17 Fat/D 2.53x10 41.6 37.6 . 2.55 .38 .02c 2.32 Cullage 4.31xl0 5 76.2 5.0 0.08 .014 .03 47.30' P l i f e 1.26xlO D 18.1 17.3 0.28 .05 .11 0.06 D.F. 23017 2029 2013 7 1 7 •» X a A l l 2 R values s i g n i f i c a n t (P < . 05) unless otherwise stated. b T o t a l corrected sums of squares 2 (kg except cullage, P l i f e i n mo.2 and 2 LLL days ) c Not s i g n i f i c a n t at .05 l e v e l . d T r a i t s are defined i n pages 28, 29 and Table 4. T a b l e 6. Summary o f t h e a n a l y s i s o f v a r i a n c e - c o v a r i a n c e f o r e n v i r o n m e n t a l e f f e c t s : f o r Group 2. R 2 V a l u e s ( % ) a m - 4 . d T r a i t T o t a l b C • S • S • T o t a l f i t t e d Herd Year Season Year x Season Age a t F i r s t C a l v i n g C a l v i n g I n t e r v a l (Avg.) C a l v i n g I n t e r v a l ( L a s t ) M i l k 1 2 2 . 4 2 x l 0 9 41. 9 34.4 2. 80 1.08 .02 c 2. 63 0.44 0. 0 0 C F a t 1 3 . 2 7 x l 0 7 43.3 35.9 2.92 0.92 .01° 3.20 0.30 0.00 C M i l k HY1 1 4 . 8 9 x l 0 9 18. 0 11. 9 0.17 1.07 .02° 4.07 0. 60 0.00° F a t HY1 2 . 1 6 x l 0 7 18. 9 12.4 0.28 0.84 .02° 4.97 0.42 0. 00° M i l k L 4 5 . 4 5 x l 0 9 29.7 26.3 0.82 0.01 C .02° 0.05 0.02 0.73 F a t L 7 . 0 1 x l 0 7 30.0 26.0 0.89 o , o o c .01° 0.06 0. o o c 1. 07 LLL 1 6 . 1 5 x l 0 7 12.8 9.5 0.07 0.03 C .04° 0.01 C 0. o o c 1.00 M i l k T -71. 39X10 1 1 13. 8 11.4 0.12 0.00° .03° o . o o c 0.40 1J.59 F a t T 1 0 . 3 3 x l 0 9 14. 0 11.6 0.12 0.00° .03 C 0.01° 0.38 1.66 M i l k / D 1. 8 0 x l 0 5 43.3 35.8 2.17 0.20 .00° 0.46 2.24 0.11 Fat/D 2 . 8 9 x l 0 2 42.6 35.8 2. 36 0.12 .00° 0.54 1.97 0.15 C u l l a g e 2 . 5 1 x l 0 7 15. 5 10. 3 0.19 0. 00° .03 C 0.78 0.04 1.63 P l i f e 2 . 4 7 x l 0 7 14. 0 10. 5 0.20 o . o o c .03° 0.01 C 0.04 1. 65 # L a c t 1.2-OxIO'5 12. 5 10. 6 0.20 0.00 C .03° 0. 02 1.18 1.26 D.F. 28580 1515 1497 7 1 7 1 1 1 a A l l R v a l u e s a r e s i g n i f i c a n t (P < .05) u n l e s s o t h e r w i s e s t a t e d . 2 2 2 b T o t a l c o r r e c t e d sums o f squares (kg except c u l l a g e , P l i f e i n mo. and LLL days ). c Not s i g n i f i c a n t a t .05 l e v e l . d T r a i t s a r e d e f i n e d i n pages 2 8, 2 9 and T a b l e 4. - 60 -t o the c o n t r i b u t i o n o f age a t f i r s t c a l v i n g ( 4 7 . 3 % ) , w h i c h would be e x p e c t e d s i n c e C u l l a g e was o b t a i n e d by summing age a t f i r s t c a l v i n g and l a c t a t i o n l e n g t h , w h i c h i n most cases were 305 days. 2 The p a r t i a l R v a l u e s a r e a l s o shown f o r t h e i n d i v i d u a l e f f e c t s c o n s i d e r e d i n t h e model, w h i c h gave an i n d i c a t i o n o f the r e l a t i v e i m p o r t a n c e of t h e s e p a r a t e e f f e c t s i n t h e model. A l l e f f e c t s e x c e p t y e a r by season i n t e r a c t i o n f o r a l l f i r s t l a c t a t i o n t r a i t s and Fat/D were s i g n i f i c a n t f o r Group 1 (Table 5 ) . I n Group 2 a l l e f f e c t s e x c e p t y e a r by season f o r a l l t r a i t s ; age a t f i r s t c a l v i n g f o r LLL, M i l k T, F a t T, P l i f e ; average c a l v i n g i n t e r v a l f o r F a t L, LLL; and l a s t c a l v i n g i n t e r v a l f o r a l l f i r s t l a c t a t i o n t r a i t s were s i g n i f i c a n t (Table 6 ) . D i s c u s s i o n s on s i g n i f i c a n t s o u r c e s of v a r i a t i o n a f f e c t i n g p r o d u c t i o n and l o n g e v i t y a r e now p r e s e n t e d . Herd The e f f e c t o f h e r d was s i g n i f i c a n t f o r a l l t h e t r a i t s i n t h i s s t u d y , a c c o u n t i n g f o r between 5% ( f o r c u l l a g e ) and 37.6% ( f o r Fat/D) of t o t a l v a r i a b i l i t y i n Group 1 and between 9.5% ( f o r LLL) and 35.9% ( f o r F a t 1) o f t h e t o t a l v a r i a b i l i t y i n Group 2. Herd e f f e c t r e f l e c t e d t h e e f f e c t s o f n u t r i t i o n , management, c u l l i n g p r a c t i c e s and m i c r o e n v i r o n m e n t a s s o c i a t e d w i t h each h e r d . I n d i v i d u a l e f f e c t o f t h e s e f a c t o r s c o u l d - 61 -not be determined from the i n f o r m a t i o n a v a i l a b l e i n t h i s data s e t . Magnitude of herd e f f e c t on the f i r s t l a c t a t i o n m i l k and f a t y i e l d s (33.7% t o 35.9%) agreed w i t h e a r l i e r s t u d i e s which i n d i c a t e d herd as the s i n g l e most important f a c t o r i n determining the f i r s t l a c t a t i o n m i l k and f a t y i e l d s . Herd e f f e c t s of s i m i l a r magnitude were a l s o observed f o r m i l k and f a t y i e l d s per day of l i f e i n t h i s study. Lower herd 2 R values f o r M i l k HY1 and F a t HYl compared to M i l k 1 and Fat 1, show the e f f i c i e n c y of herd-year d e v i a t i o n s i n removing herd e f f e c t s from the l a c t a t i o n r e c o r d s . Herd e f f e c t s f o r t o t a l l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s were c o n s i s t e n t l y lower i n magnitude compared to f i r s t l a c t a t i o n y i e l d s and p r o d u c t i o n per day of p r o d u c t i v e l i f e . Year Year l e a s t squares means and standard e r r o r s f o r p r o d u c t i o n and l o n g e v i t y t r a i t s f o r Group 1 and Group 2 are presented i n Appendix Tables 1 and 2. Y e a r l y trends i n p r o d u c t i o n and l o n g e v i t y are given i n Table 7. F i g u r e s 1 through 4 show the y e a r l y trends i n M i l k 1, F a t 1, M i l k T, Fat T, P l i f e and # L a c t . Graphs r e p r e s e n t p l o t t i n g of the l e a s t squares constants of each dependent v a r i a b l e a s s o c i a t e d with years a g a i n s t year of f i r s t c a l v i n g . They are, t h e r e f o r e , estimates of year e f f e c t s f r e e from other e f f e c t s i n the model. Table 7. Average yearly and seasonal trends i n production and longevity t r a i t s based on least squares constants obtained form analyses on models 1 and 2. Yearly Trends*3 Seasonal Trends'3 ( F i r s t Calving Period 1958-65) (Season 2 C - Season l c ) f r a i t 3 • 'Group 1 Group 2 Group 1 Group 2 Milk 1 71 73 204 221 Fat 1 2.81 2.98 7 8 Milk HY1 -12.40 -16.07 160 179 Fat HY1 -0.67 -0.82 5 6 Milk L NA 63 NA 36 Fat L NA 2.61 NA 1 LLL 1.83 1.00 2 -3 Milk T 96 78 107 130 Fat T 3.83 4.05 7 0.0 Milk/D 0.20 0.21 0.5 0.3 Fat/D 0.008 0.008 0.01 0.01 Cullage 0.052 -0.527 0.0 -0.4 P l i f e 0.061 -0.529 0.10 -0.4 # Lact NA -0.042 NA 0.0 a b c T r a i t s are defined i n pages 28, 29 and Table 4. Units are kg, except Cullage, P l i f e which are i n months, LLL i n days and # Lact i n number. Season 1 (March-August) , Season 2 (September-February) . Year of f irst calving Year of f i rst calving Year of f i rst calving Year of f i rst calving - 67 -There were i n c r e a s i n g t r e n d s i n t h e f i r s t l a c t a t i o n m i l k and f a t y i e l d s o v e r t h e p e r i o d 1960 t o 1965, due t o b o t h g e n e t i c improvement and b e t t e r n u t r i t i o n and management p r a c t i c e s . Y e a r l y i n c r e a s e s i n t h e f i r s t l a c t a t i o n m i l k and f a t y i e l d s were 71 kg and 2.81 k g , r e s p e c t i v e l y f o r Group 1; and 73 kg and 2.98 kg, r e s p e c t i v e l y f o r Group 2. Y e a r l y i n c r e a s e s i n m i l k and f a t y i e l d s o b t a i n e d i n t h i s s t u d y are w e l l w i t h i n the range o f t h o s e r e p o r t e d . However, some s t u d i e s showed h i g h e r a n n u a l i n c r e a s e i n the f i r s t l a c t a t i o n m i l k r a n g i n g from 90 kg t o 128 kg (Gacula e t a l . , 1968; Verde e t a l . , 1972). L i f e t i m e m i l k and f a t y i e l d s have a l s o i n c r e a s e d a t the r a t e o f 78 kg and 4 kg, r e s p e c t i v e l y , whereas, th e l e n g t h o f p r o d u c t i v e l i f e and the number of l a c t a t i o n completed d e c r e a s e d by .53 month and .04 l a c t a t i o n , r e s p e c t i v e l y i n t h e Group 2 cows (Table 7 ) . Season Though season o f f i r s t c a l v i n g was a s i g n i f i c a n t s o u r c e o f v a r i a t i o n f o r a l l t h e t r a i t s i n Group 1, i t a c c o u n t e d f o r l e s s than 1% o f the t o t a l v a r i a t i o n o f any t r a i t under s t u d y . I n Group 2, season a f f e c t e d s i g n i f i c a n t l y o n l y t h e f i r s t l a c t a t i o n t r a i t s and p r o d u c t i o n p e r day. Season of f i r s t c a l v i n g d i d not a f f e c t s i g n i f i c a n t l y t h e l i f e t i m e p r o d u c t i o n and l o n g e v i t y i n cows which s u r v i v e d c u l l i n g a f t e r f i r s t l a c t a t i o n . Season l e a s t squares means and s t a n d a r d e r r o r s a r e p r e s e n t e d i n - 68 -Appendix Table 3 and seasonal trends i n Table 7. Cows f i r s t f r e s h e n i n g i n season 2 (September to February) produced more m i l k and f a t i n the f i r s t l a c t a t i o n compared to those f i r s t freshened i n season 1 (March - August). There were p r a c t i c a l l y no d i f f e r e n c e between the cows f r e s h e n i n g i n two d i f f e r e n t seasons i n terms of C u l l a g e , P l i f e i n Group 1 and # L a c t i n Group 2, whereas Group 2 cows showed a s l i g h t n e g a t i v e t r e n d i n C u l l a g e and P l i f e . Seasonal t r e n d obtained i n t h i s study agreed i n nature with s t u d i e s r e p o r t e d from North East U n i t e d S t a t e s and Canada (Ahunu, 1978; Mao e t a l . , 1974; Wunder and M c G i l l i a r d , 1967; M i l l e r e t a l . , 1970). Adjustment f o r season e f f e c t was warranted i n view of the seasonal changes i n many aspects of the cow's environment. Included i n these seasonal changes were the change from pasture to s t o r e d feed, a management system s t i l l p r esent on many farms, w h i l e o t h e r farmers u t i l i z e d s t o r e d feeds on a year-round b a s i s . Year by season i n t e r a c t i o n Year by season i n t e r a c t i o n was s i g n i f i c a n t f o r M i l k T, F a t T, Milk/D, LLL, C u l l a g e and P l i f e o n l y i n Group 1, accounting f o r a v e r y s m a l l f r a c t i o n (^ .1%) of the t o t a l v a r i a t i o n i n these t r a i t s , which i n d i c a t e d t h a t the seasonal d i f f e r e n c e s i n these t r a i t s were not c o n s i s t e n t over the y e a r s . R e l a t i o n s h i p s of Age at F i r s t C a l v i n g with P r o d u c t i o n and Longevity Age a t f i r s t c a l v i n g was a s i g n i f i c a n t source of - 69 -v a r i a t i o n f o r a l l t h e t r a i t s i n Group 1 and f o r most of the t r a i t s i n Group 2, a c c o u n t i n g f o r from a p p r o x i m a t e l y z e r o t o 47.3% of t h e t o t a l v a r i a t i o n s i n t h e s e t r a i t s . Age a t f i r s t 2 c a l v i n g a c c o u n t e d f o r h i g h e r R v a l u e s i n a l l f i r s t l a c t a t i o n t r a i t s compared t o t o t a l l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s (2.13% t o 4.97% V e r s u s 0.0% t o 1.52%), e x c e p t i n g t h a t f o r C u l l a g e (47.3%) i n Group 1, w h i c h was due t o r e l a t i o n o f p a r t t o whole as mentioned e a r l i e r i n t h i s C h a p t e r . W i t h i n h e r d p h e n o t y p i c c o r r e l a t i o n s o f age a t f i r s t c a l v i n g w i t h l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s a r e g i v e n i n T a b l e 8. The c o r r e l a t i o n s o f age a t f i r s t c a l v i n g w i t h l i f e t i m e p r o d u c t i o n were a l l p o s i t i v e r a n g i n g between .139 f o r M i l k T t o .191 f o r Fat/D i n case of Group 1 cows, but t h e s e c o r r e l a t i o n s were low and n o n - s i g n i f i c a n t , e x c e p t f o r age a t f i r s t c a l v i n g w i t h M i l k / D and Fat/D, i n Group 2 cows. These r e l a t i o n s h i p s i n d i c a t e d t h a t l a t e c a l v i n g cows produced more m i l k and f a t d u r i n g l i f e t i m e and a l s o per day o f p r o d u c t i v e l i f e compared t o e a r l y c a l v i n g cows. T h i s i s not q u i t e i n agreement w i t h t h e f i n d i n g s o f Hargrove e t a l . (1969), who found n o n - s i g n i f i c a n t n e g a t i v e c o r r e l a t i o n s of age a t f i r s t c a l v i n g w i t h l i f e t i m e m i l k and f a t y i e l d s . However, Lamb and Kopland (1963) found a p o s i t i v e a s s o c i a t i o n between t o t a l l i f e t i m e p r o d u c t i o n and age a t f i r s t c a l v i n g . W i t h i n h e r d p a r t i a l r e g r e s s i o n c o e f f i c i e n t s a d j u s t e d f o r y e a r and season e f f e c t s f o r M i l k T, F a t T, M i l k / D and Fat/D were 56.4 kg, 2.25 kg, .138 kg, and .006 kg, r e s p e c t i v e l y i n Group 1; and 44.4 kg, 2.23 kg, .06 kg and .003 kg, r e s p e c t i v e l y f o r Group 2 (Table 9 ) , f o r each month i n c r e a s e i n f i r s t c a l v i n g age. Table 8. W i t h i n herd c o r r e l a t i o n s of age a t f i r s t c a l v i n g (Age), average c a l v i n g i n t e r v a l (C.I.Av.) and l a s t c a l v i n g i n t e r v a l (C.I.L.) w i t h p r o d u c t i o n and l o n g e v i t y . a T r a i t Group 1 Group 2 Age Age C.I.Av. C.I.L. M i l k 1 . 179* .218* .127* .091* F a t 1 .192* .241* .115* . 088* M i l k HY1 .188* .216* .129* .091* Fa t HY1 .203* .238* .117* . 086* M i l k L NA .039 . 135* .167* Fa t L NA . 041 .143* .188* LLL . 028 .040 .115* .156* M i l k T . 139* .011 .048 .126* F a t ,T .144* .014 .053 .131* Milk/D .185* . 090* -.233* -.142* Fat/D .191* . 098* -.209* -.120* C u l l a g e . 816* .097* . 122* .180* P l i f e .028 -.006 .117* . 177* # L a c t NA -.017 -.041 .050 * a S i g n i f i c a n t l y d i f f e r e n t from zero (P < .01). T r a i t s are d e f i n e d i n pages 28, 29 and Table 4. Table 9. Wi t h i n herd r e g r e s s i o n s (adjusted f o r year and season e f f e c t s ) of age at f i r s t c a l v i n g (Age), average c a l v i n g i n t e r v a l (C.I.Av.), and l a s t c a l v i n g i n t e r v a l (C.I.L.) on p r o d u c t i o n and l o n g e v i t y t r a i t s . T r a i t c Group 1 Group 2 Age Age C.I.Av. C.I.L. M i l k 1 46.6+1.73 b 50.3+1.44 1.31+.092 -.024+.066 Fa t 1 1.88+.064 ' 2.12+.05 .042+.003 .0024+.0025 M i l k HY1 46.8+1.7 51.0+1.4 1.25+.09 -.026+.064 Fat HY1 1. 89+. 063 - 2.14+.05 .04+.003 .002+.002 M i l k L NA 10.19+2.25 .437+.143 1.73+.103 Fat L NA .427+.088 .008+.0056 .083+.004 LLL .59+.15 .836+.149 -.0014+.0095 .121+.0068 M i l k T 56.41+2.77 44.4+31.2 -22.0+2.0 32.1+1.43 Fat T 2.25+.105 2.23+1.19 -.82+.08 1.24+.05 Milk/D .138+.005 .061+.004 -.009+.003 .0014+.0002 Fat/D .006+.0002 .003+.0002 -.0003+.00001 .00006+.000007 Cu l l a g e 1.02+.005 .915+.058 -.013+.0037 .061+.0027 P l i f e .019+.005 -.077+.058 -.014+.0037 .0608+.0027 # L a c t NA -.009+.004 -.005+.0003 .0038+.0002 a U n i t s a re kg, except C u l l a g e , P l i f e , Age i n months, LLL, C.I.Av., C.I.L. i n days and # L a c t i n numbers. b Standard e r r o r o f r e g r e s s i o n . c T r a i t s are d e f i n e d i n pages 28, 29 and Table 4. - 72 -C o r r e l a t i o n s o f l o n g e v i t y t r a i t s w i t h age a t f i r s t c a l v i n g were i n g e n e r a l low e x c e p t i n g t h a t f o r c u l l a g e . V e r y h i g h c o r r e l a t i o n (.82) o f age a t f i r s t c a l v i n g w i t h C u l l a g e f o r Group 1, would be e x p e c t e d i n t h i s s t u d y , s i n c e C u l l a g e was t h e sum o f age a t f i r s t c a l v i n g and l a c t a t i o n l e n g t h . The low n o n - s i g n i f i c a n t n e g a t i v e c o r r e l a t i o n i n d i c a t e d t h e tendency o f l a t e c a l v i n g cows i n Group 2 t o have s h o r t e r p r o d u c t i v e l i f e t h a n e a r l y c a l v i n g cows. Hargrove e t a l . (1969) a l s o r e p o r t e d s i m i l a r t r e n d . W i t h i n h e r d p a r t i a l r e g r e s s i o n s o f # L a c t and P l i f e were -.009 l a c t a t i o n and -.077 month, r e s p e c t i v e l y f o r each month i n c r e a s e i n t h e age a t f i r s t c a l v i n g . R e l a t i o n s h i p s o f C a l v i n g I n t e r v a l w i t h P r o d u c t i o n and L o n g e v i t y Average c a l v i n g i n t e r v a l e f f e c t s were s i g n i f i c a n t f o r a l l t h e t r a i t s e x c e p t F a t L and LLL, a c c o u n t i n g from 0.0% t o 2.24% of t h e v a r i a t i o n . L a s t c a l v i n g i n t e r v a l had s i g n i f i c a n t e f f e c t s on l a s t l a c t a t i o n , l i f e t i m e t r a i t s and l o n g e v i t y , w h i l e f i r s t l a c t a t i o n t r a i t s were not s i g n i f i c a n t l y a f f e c t e d by l a s t c a l v i n g i n t e r v a l (Table 6 ) . . W i t h i n h e r d p h e n o t y p i c c o r r e l a t i o n s o f c a l v i n g i n t e r v a l w i t h p r o d u c t i o n and l o n g e v i t y t r a i t s a r e i n T a b l e 8. F i r s t l a c t a t i o n y i e l d s were s i g n i f i c a n t l y p o s i t i v e l y c o r r e l a t e d w i t h average and l a s t c a l v i n g i n t e r v a l s . S i g n i f i c a n t p o s i t i v e c o r r e l a t i o n o f m i l k y i e l d e x p r e s s e d as d e v i a t i o n from h e r d - y e a r average i n d i c a t e d t h a t t h e h i g h e s t p r o d u c e r s w i t h i n t h e h e r d had l o n g e r c a l v i n g i n t e r v a l s t h a n t h e i r herdmates p r o d u c i n g - 73 -l e s s m i l k , which i s s u p p o r t e d by M i l l e r e t a l . (1967). T h i s a s s o c i a t i o n i s p a r t l y due t o t h e r e a s o n t h a t l a t e c a l v e r s c a r r i e d c a l v e s f o r s h o r t e r p e r i o d s d u r i n g t h e f i r s t l a c t a t i o n . O t her r e a s o n s c o u l d be more i n t e n s e c u l l i n g o f low p r o d u c e r s t h a t d i d not b r e e d r i g h t back and t h a t h i g h p r o d u c e r s might n ot have r e t u r n e d t o e s t r u s as q u i c k l y a f t e r p a r t u r i t i o n as low p r o d u c e r s (Trimberger and F i n c h e r , 1956). L a s t l a c t a t i o n y i e l d s a l s o showed s i g n i f i c a n t p o s i t i v e c o r r e l a t i o n s w i t h b o t h average and l a s t c a l v i n g i n t e r v a l s . S l i g h t l y h i g h e r c o r r e l a t i o n s o f l a s t l a c t a t i o n m i l k and f a t w i t h l a s t c a l v i n g i n t e r v a l (.167 and .18 8) t h a n w i t h average c a l v i n g i n t e r v a l (.135 and .143) i n d i c a t e t h a t p r o b a b l y dairymen a r e p a y i n g more a t t e n t i o n t o the c u r r e n t l a c t a t i o n y i e l d , i r r e s p e c t i v e o f t h e l a c t a t i o n l e n g t h , than e a r l i e r l a c t a t i o n y i e l d s , w h i c h i s f u r t h e r s u p p o r t e d by t h e p o s i t i v e a s s o c i a t i o n between h i g h y i e l d and l o n g c a l v i n g i n t e r v a l . C o r r e l a t i o n s o f average c a l v i n g i n t e r v a l w i t h l i f e t i m e m i l k and f a t p r o d u c t i o n were p o s i t i v e but not s i g n i f i c a n t l y d i f f e r e n t from z e r o , whereas l a s t c a l v i n g i n t e r v a l was s i g n i f i c a n t l y p o s i t i v e l y c o r r e l a t e d w i t h b o t h l i f e t i m e m i l k and f a t . These r e l a t i o n s h i p s i n d i c a t e d t h a t f a r m e r s a r e g i v i n g more t i m e f o r c o n c e p t i o n t o o c c u r i n h i g h y i e l d i n g cows l a t e r i n l i f e t h a n i n e a r l i e r l a c t a t i o n s . S i g n i f i c a n t n e g a t i v e c o r r e l a t i o n s o f average and l a s t c a l v i n g i n t e r v a l s w i t h m i l k and f a t p r o d u c t i o n p e r day o f l i f e e x p l a i n s t h a t t h e p o s i t i v e r e l a t i o n between c a l v i n g i n t e r v a l and l i f e t i m e y i e l d s - 74 -of m i l k and f a t were due to more days i n m i l k which i s supported by f i n d i n g s of Smith and Legates (1962). I n t r a h e r d p a r t i a l r e g r e s s i o n s a d j u s t e d f o r year and season of f i r s t c a l v i n g e f f e c t s f o r M i l k T and Fat T were 32.10 kg and 1.24 kg, r e s p e c t i v e l y f o r each day longer l a s t c a l v i n g i n t e r v a l , whereas these v a l u e s were -22.0 kg and -0.82 kg, r e s p e c t i v e l y f o r average c a l v i n g i n t e r v a l . Age at d i s p o s a l (Cullage) and l e n g t h of p r o d u c t i v e l i f e ( P l i f e ) were p o s i t i v e l y s i g n i f i c a n t l y c o r r e l a t e d w i t h both average and l a s t c a l v i n g i n t e r v a l s , which i s expected, s i n c e the c u l v i n g i n t e r v a l i s a p a r t of the p r o d u c t i v e l i f e . The c o r r e l a t i o n s of the number of l a c t a t i o n s completed w i t h average and l a s t c a l v i n g i n t e r v a l s were e s s e n t i a l l y zero, which was a l s o observed by M i l l e r et a l . (1967). Adjustment of Data Before s u b j e c t i n g data f o r g e n e t i c parameter estimates, r e c o r d s of Group 1 cows were adjus t e d f o r age a t f i r s t c a l v i n g u s i n g r e g r e s s i o n c o e f f i c i e n t s obtained from the a n a l y s i s of model 1 f o l l o w i n g r e g r e s s i o n technique (model 4). P a r t i a l r e g r e s s i o n c o e f f i c i e n t s o b tained from model 2 a n a l y s i s were used to a d j u s t data of Group 2 cows f o r age a t f i r s t c a l v i n g , average c a l v i n g i n t e r v a l and l a s t c a l v i n g i n t e r v a l a c c o r d i n g to r e g r e s s i o n model 5. The r e g r e s s i o n c o e f f i c i e n t s used t o a d j u s t the raw data are given i n Table 9. Adjustments f o r - 75 -h e r d , y e a r , season and y e a r by season e f f e c t s were not done f o r r e a s o n s mentioned e a r l i e r . These e f f e c t s were accounted f o r by e s t i m a t i n g g e n e t i c parameters on w i t h i n h e r d - y e a r -season s u b c l a s s b a s i s . E s t i m a t i o n s o f G e n e t i c Parameters The number o f s i r e s r e p r e s e n t e d i n each g e n e t i c group and t h e number of h a l f - s i b s i n d i f f e r e n t groups are r e p r e s e n t e d i n T a b i e 10. A summary of l e a s t squares a n a l y s i s o f v a r i a n c e a c c o r d i n g t o model 6 f o r Groups 1 and 2 combined and Group 2 s e p a r a t e l y are shown i n T a b l e s 11 and 12. These 2 t a b l e s show R v a l u e s f o r t h e e f f e c t s i n c l u d e d i n t h e m a t h e m a t i c a l model, t h a t i s , t h e p r o p o r t i o n o f t h e t o t a l v a r i a t i o n i n each o f t h e t r a i t t h a t was accounted f o r by f i t t i n g t h e e f f e c t s o f h e r d - y e a r - s e a s o n , g e n e t i c group and s i r e w i t h i n 2 g e n e t i c group. I n combined Groups 1 and 2 d a t a , t o t a l R v a l u e s f o r p r o d u c t i o n t r a i t s w i t h t h e e x c e p t i o n o f M i l k T and F a t T, were h i g h e r (37.6% t o 58.7%) compared t o t h o s e f o r l o n g e v i t y t r a i t s , such as c u l l a g e , P l i f e and # L a c t (33.5% t o 3 4 . 5 % ) ( T a b l e 11). A l a r g e p e r c e n t a g e o f the t o t a l v a r i a t i o n i n M i l k T, F a t T and l o n g e v i t y t r a i t s i s a t t r i b u t a b l e t o r e s i d u a l (over 65%). T h i s r e v e a l s t h a t i n t h e s e a n a l y s e s t h e f a c t o r s w h i c h can be i d e n t i f i e d and measured a r e a p p a r e n t l y o f l i t t l e consequence as s o u r c e s o f v a r i a t i o n among t o t a l l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s , whereas u n i d e n t i f i e d T a b l e 10. Number o f s i r e s and daughters i n each g e n e t i c group: f o r Groups 1 and 2 combined. P e r i o d s D u r i n g Which G e n e t i c Group S i r e s Were Born No. o f S i r e s No. o f Daughters G l January.; .194 6 through.: December .1948 18 3282 G2 J a n u a r y 194 9 t h r o u g h December 1951 23 7919 G3 J a n u a r y 1952 t h r o u g h December 1954 35 7483 G4 J a n u a r y 1955 t h r o u g h December 1957 48 9383 G5 J a n u a r y 1958 t h r o u g h December 1960 14 2671 T o t a l : 138 30738 T a b l e 11. Summary o f f o r Groups t h e a n a l y s i s o f 1 and 2 combined v a r i a n c e f o r a d j u s t e d d a t a : R 2 V a l u e s 3 (%) T r a i t - T o t a lb C • S • S. • . T o t a l F i t t e d Herd-Year Season G e n e t i c Group S i r e / G e n e t i c Group M i l k 1 2 4 . 1 6 x l 0 9 57.2 46.8 . 06 2.02 F a t 1 3 . 5 8 x l 0 7 58.7 48.3 .04 2.21 M i l k HY1 1 7 . 2 8 x l 0 9 37. 6 32.7 . 08 2.93 F a t HY1 2 . 4 8 x l 0 7 38.7 33.4 . 05 3.22 M i l k L 5 0 . 7 4 x l 0 9 43.4 37.4 . 05 1.80 F a t L 7 . 6 5 x l 0 7 43.6 37.6 . 034 2.00 LLL 1 6 . 4 5 x l 0 7 32.0 30.0 . 0 3 C 1.19 M i l k T 80.48X10 1 1 33. 6. 30.4 . 038 1.78 F a t T 1 1 . 5 7 x l 0 9 33.8 30.5 . 033 1.85 M i l k / D 2 . 0 1 x l 0 5 56.0 46.5 . 054 2.00 Fat/D 3 . 0 7 x l 0 2 55.6 46.2 .033 2.40 C u l l a g e 2 . 9 2 x l 0 7 33.6 31.1 . 032 C 1.56 P l i f e 3.OOxlO 7 34. 5 30.7 . 032 C 1.54 # L a c t 1 . 5 4 x l 0 5 33.5 31.1 . 036 1.48 D.F. 30737 8323 8186 4 133 a A l l R v a l u e s a r e s i g n i f i c a n t (P < .05) u n l e s s o t h e r w i s e s t a t e d . 2 2 2 b T o t a l c o r r e c t e d sums o f squares (kg except C u l l a g e , P l i f e i n month and LLL day ). c Not s i g n i f i c a n t a t .05 l e v e l . d T r a i t s a r e d e f i n e d i n pages 28, 29 and Ta b l e 4. Table 12. Summary of the a n a l y s i s of v a r i a n c e f o r adjusted data: f o r Group 2. R 2 V a l u e s 3 (%) T o t a l T o t a l Herd-Year- Genetic S i r e / G e n e t i c T r a i t C.S.S. F i t t e d Season Group Group M i l k 1 16.71xl0 9 64.1 53.4 .04 1. 68 F a t 1 2.44xl0 7 65.8 55.0 .025 1.95 M i l k HY1 11.09xl0 9 44.8 39.6 .054 2.59 F a t HY1 1.60xl0 7 46.3 40.4 . 036 3.07 M i l k L 34.41xl0 9 52.4 46.6 .025° 1.38 F a t L 5.29xl0 7 52. 6 47.0 .016 c 1.63 LLL 12.34xl0 7 39.2 36.8 . 049 1.28 M i l k T 54.33X10 1 1 41.7 38.3 . 045 1.67 Fat T 7.84xl0 9 42.1 38.7 .04 1.79 Milk/D 1.38xl0 5 62.2 52.7 . 055 1.86 Fat/D 2.13xl0 2 62.6 53.3 . 04 2.35 C u l l a g e 1.84xl0 7 40.7 38.3 .028 C 1.48 P l i f e 1.84xl0 7 40.7 38.3 .029 C 1.47 # L a c t 9.47xl0 4 40.7 38.2 . 034° 1.41 D.F. 22391 7775 7638 4 133 a A l l R val u e s are s i g n i f i c a n t (P < .05) unless otherwise s t a t e d . 2 2 2 b T o t a l c o r r e c t e d sums of squares (kg except c u l l a g e , P l i f e i n month and LLL day ). c Not s i g n i f i c a n t a t .05 l e v e l . d T r a i t s are d e f i n e d i n pages 28, 29 and Table 4. - 79 -f a c t o r s grouped together as sources of r e s i d u a l are the cause o f a l a r g e p a r t of the t o t a l v a r i a t i o n i n these t r a i t s . In 2 Group 2 data, the model accounted f o r l a r g e r t o t a l R f o r a l l the t r a i t s compared to combined data s e t . In both the groups, the major p a r t of the t o t a l r e d u c t i o n was due to herd-year-season e f f e c t s a ccounting f o r 30-55% of the t o t a l v a r i a t i o n . Reduction due to herd-year-season e f f e c t s were higher f o r a l l the t r a i t s i n Group 2 a n a l y s i s while r e d u c t i o n due to g e n e t i c group and s i r e w i t h i n g e n e t i c group e f f e c t s were high f o r most of the t r a i t s i n combined data s e t . Genetic group e f f e c t s were s i g n i f i c a n t f o r a l l the t r a i t s , except LLL, C u l l a g e , P l i f e i n combined s e t and M i l k L, Fat L, C u l l a g e , P l i f e , and # Lact i n Group 2 data. S i r e e f f e c t s though s i g n i f i c a n t f o r a l l the t r a i t s , accounted f o r only 1.19% to 3.22% i n Groups 1 and 2 combined and 1.28% to 3.07% i n Group 2. Genetic trends L e a s t squares constants of f i v e g e n e t i c groups and g e n e t i c progress per year f o r p r o d u c t i o n and l o n g e v i t y t r a i t s a re i n Table 13. Genetic group trends i n p r o d u c t i o n and l o n g e v i t y t r a i t s are shown g r a p h i c a l l y i n F i g u r e s 5 through 7. There was p r a c t i c a l l y no g e n e t i c progress i n f i r s t l a c t a t i o n m i l k and f a t y i e l d s among the daughters of the s i r e s born d u r i n g p e r i o d 1952-57, the reason f o r which i s not T a b l e 13. G e n e t i c group l e a s t squares c o n s t a n t s and g e n e t i c p r o g r e s s p e r y e a r f o r p r o d u c t i o n and l o n g e v i t y t r a i t s : f o r Groups 1 and 2 combined. G e n e t i c Group 1 T r a i t 3 G l (1946-48) G2 (1949-51) G3 (1952-54) G4 (1955-57) G5 ? (1958-60) G e n e t i c P r o g r e s s Per Year M i l k 1 -91.8 5.4 -3.3 -5.7 95.4 31.2 F a t 1 -2.82 .77 -.52 -.09 2.66 .91 M i l k HY1 -88.2 6.5 -5.3 -7.7 94.7 30.5 F a t HY1 -2. 67 .85 -.56 -.22 2.60 .88 M i l k L -112.9 -36.9 4.5 18.8 126.5 39.9 F a t L -4.21 -.95 .20 1.13 3.83 1.34 LLL 2. 64 -.70 -.43 2.99 -4.50 -1.19 M i l k T -546.7 -744.8 -271.2 26.2 1536.5 347.2 F a t T -17.45 -27.95 -9.50 1.52 53.40 11. 8 M i l k / D -.19 -.11 . 07 -.04 .26 .08 Fat/D -.0063 -.0033 . 0026 -.0005 . 0075 .0025 C u l l a g e -1.11 -1.14 -.74 .30 2.70 .64 P l i f e -1.11 -1.16 -.75 .29 2.72 .64 # L a c t -.0854 -.0827 -.0612 .0149 .2145 .05 1 U n i t s a r e k g , e x c e p t c u l l a g e , P l i f e a r e i n months, LLL i n days and # L a c t i n number. 2 B i r t h y e a r o f s i r e s . 3 T r a i t s a re d e f i n e d i n pages 28, 29 and T a b l e 4. - 81 -1 2 3 4 5 0 ^ 5 1 ^ 5 ^ ( 1 9 4 6 _ 4 8 ) (1949-51) (1952-54) (1955-57) (1958-60) Genetic group - 82 -Figure 6. Genetic group trends of lifetime milk and lifetime fat yields : For Groups 1 and 2 combined. Birth year (.1946_48) (1949-51) (1952-54) (1955-57) (1958-60) of sires Genetic group - 83 -Figure 7. Genetic group trends of length of productive l i fe and number of lactations completed : For Groups 1 and 2 combined. Genetic group - 84 -known. However, g e n e t i c t r e n d s f o r t o t a l l i f e t i m e p r o d u c t i o n , l e n g t h o f p r o d u c t i v e l i f e and number o f l a c t a t i o n completed were c o n s i s t e n t l y upward d u r i n g t h e whole p e r i o d ( F i g u r e s 6 and 7 ) . Annual g e n e t i c p r o g r e s s c a l c u l a t e d from t w i c e t h e change per y e a r i n average a d d i t i v e g e n e t i c v a l u e s o f s i r e s b e l o n g i n g t o d i f f e r e n t g e n e t i c groups f o r f i r s t l a c t a t i o n m i l k and f a t were 31.2 kg and .91 kg, r e s p e c t i v e l y . These e s t i m a t e s a r e lower than e s t i m a t e s r e p o r t e d f o r H o l s t e i n p o p u l a t i o n s i n N o r t h A m e r i c a . In o t h e r s t u d i e s s i r e g r o u p i n g was made e i t h e r on t h e b a s i s o f y e a r i n w h i c h s i r e e n t e r e d A . I . o r y e a r i n w h i c h f i r s t d aughter appeared i n t h e r e c o r d . In t h i s s t u d y , g r o u p i n g was on t h e b a s i s o f y e a r o f b i r t h , c o v e r i n g a p e r i o d 1946-1960. C o n s i d e r i n g 5 y e a r s as t h e age when most s i r e s produce A . I . d a u g h t e r s , the p r e s e n t s t u d y would r e -p r e s e n t g e n e t i c t r e n d f o r t h e p e r i o d 1951 t h r o u g h 1965. Thus, t h i s s t u d y r e p r e s e n t s an e a r l i e r p e r i o d compared w i t h o t h e r s t u d i e s r e p o r t e d , and g e n e t i c p r o g r e s s might have been s l o w e r d u r i n g t h e e a r l i e r p e r i o d . A nnual g e n e t i c t r e n d f o r l a s t l a c t a t i o n m i l k (39.9 kg) and f a t (1:34 k g ) , w h i c h were completed l a t e r , were h i g h e r compared t o f i r s t l a c t a t i o n m i l k and f a t . Daughters o f t h e s i r e s b o r n d u r i n g t h e l a t e r p e r i o d produced more m i l k and f a t d u r i n g l i f e t i m e and a l s o s t a y e d l o n g e r i n the h e r d compared t o daught e r s o f t h e s i r e s b o r n d u r i n g e a r l i e r p e r i o d , w h i c h i s e v i d e n t from t h e g e n e t i c group t r e n d s f o r t h e s e t r a i t s ( F i g u r e s 6 and 7 ) . The a n n u a l g e n e t i c p r o g r e s s f o r t o t a l m i l k and f a t were 347.2 kg and 11.8 kg, r e s p e c t i v e l y and - 85 -t h o s e f o r l e n g t h o f p r o d u c t i v e l i f e and number o f l a c t a t i o n s completed were .64 month and .05 l a c t a t i o n p e r y e a r . G e n e t i c components o f v a r i a n c e and c o v a r i a n c e Once s i g n i f i c a n t s y s t e m a t i c , e n v i r o n m e n t a l e f f e c t s were e l i m i n a t e d from t h e d a t a by a p p r o p r i a t e a n a l y s i s , i t was presumed t h a t o n l y g e n e t i c and random e n v i r o n m e n t a l v a r i a b i l i t y remained. Because df t h e d e s i g n o f t h e p r e s e n t s t u d y , the g e n e t i c and e n v i r o n m e n t a l components were s e p a r a b l e , and t h i s s e p a r a t i o n y i e l d e d e s t i m a t e s o f v a r i a n c e components, h e r i t a b i l i t i e s , and g e n e t i c , e n v i r o n m e n t a l and p h e n o t y p i c c o r r e l a t i o n s . I n t h e p r e s e n t s t u d y o n l y t h e a d d i t i v e p o r t i o n o f the g e n e t i c v a r i a b i l i t y was- e s t i m a t e d and s i n c e non-a d d i t i v e g e n e t i c v a r i a b i l i t y c o u l d n ot be e s t i m a t e d , i t was assumed t h a t g e n e t i c parameters i n c l u d e d o n l y a d d i t i v e e f f e c t s w h i l e e n v i r o n m e n t a l parameters i n c l u d e d a l l e f f e c t s e x c l u s i v e of a d d i t i v e e f f e c t . S i n c e e s t i m a t e s of a l l p o s s i b l e c o v a r i a n c e s between t r a i t s under s t u d y were d e s i r e d , t h e same l i n e a r model was used f o r a l l t h e t r a i t s . The c o v a r i a n c e i n terms of t h e ex p e c t e d c o v a r i a n c e components c o r r e s p o n d s t o t h e e x p e c t e d v a r i a n c e components when t h e l i n e a r model used t o a n a l y z e t h e two v a r i a b l e s i s t h e same. The ex p e c t e d v a l u e s o f v a r i a n c e and c o v a r i a n c e components f o r t h e random e f f e c t s i n t h e a n a l y s i s o f model 6 are g i v e n i n T a b l e 14. The Table 14. The expected components of variance and covariance for two t r a i t s f i t t i n g the same model. Source Degrees Expected Variance Expected Variance Expected Component of of of Component for Component for Covariance Between Va r i a t i o n Freedom T r a i t #1 T r a i t #2 T r a i t s #1 and #2 2 2 Herd-Year-Season h-1 ^ + k. 6H. ^ + k. 0H_ rr ^ . \ ^„ U e^ 4 1 (fe 2 4 2 u e^e 2 + k 4 GH^ © H 2 Genetic Groups g-1 g* e + k 2 (S:G) 1+k 39G 1 +k2<T (S:G) 2+k 3©G 2 ( T e ^ + k ^ S : G ) 1 (S :G) 2+ k 3 eGj^ e G 2 Sires/Genetic Groups s-g + ^  (T ( S t G ^ Q-e +kx (T (S:G) 2 0 e 1 e 2 + k 1 CT(S:G) 1 (S:G) 2 Residual N...-[<h-l) + (g-l) + (s-g>] ^ ^ C T e i e - 87 -v a r i a n c e component between s i r e s y i e l d s t h e h e r i t a b i l i t y i n t h e narrow sense and t h e r a t i o between t h e s i r e c o v a r i a n c e component, and t h e g e o m e t r i c mean o f t h e s i r e v a r i a n c e components y i e l d s g e n e t i c c o r r e l a t i o n . Between and w i t h i n s i r e v a r i a n c e and c o v a r i a n c e components a s s o c i a t e d w i t h each t r a i t s a re summarized i n Appendix T a b l e 4. The w e i g h t e d number of daug h t e r s p e r s i r e (K^) c a l c u l a t e d u s i n g e q u a t i o n 9 was 121.4 f o r combined s e t o f d a t a and 7 8.3 f o r Group 2 cows. H e r i f a b i l i t y e s t i m a t e s H e r i t a b i l i t y e s t i m a t e s o b t a i n e d from p a t e r n a l h a l f -s i b c o r r e l a t i o n s are g i v e n i n T a b l e 15. The t a b l e shows s e p a r a t e e s t i m a t e s f o r combined Groups 1 and 2 and Group 2. The two s e t s o f e s t i m a t e s a r e e s s e n t i a l l y t h e same e x c e p t i n g t h o s e f o r l a s t l a c t a t i o n m i l k and f a t , w h i c h were h i g h e r (.14 and .16) i n combined s e t compared t o Group 2 d a t a (.11 and .14). S i n c e the p o p u l a t i o n o f cows w h i c h completed more t h a n one l a c t a t i o n (Group 2) r e p r e s e n t a s e l e c t e d group, i t was f e l t t h a t h e r i t a b i l i t y e s t i m a t e s from t h e combined s e t , w h i c h r e p r e s e n t a more random group, a r e more r e l i a b l e . Thus, th e d i s c u s s i o n on h e r i t a b i l i t y e s t i m a t e s w i l l be l i m i t e d t o combined s e t . H e r i t a b i l i t i e s o f f i r s t l a c t a t i o n m i l k and f a t o b t a i n e d i n t h i s s t u d y were lower than some e s t i m a t e s r e p o r t e d (Freeman, 1960; G a c u l a e t a l . , 1968; B l a n c h a r t e t a l . , 1966; T a b l e 15. H e r i t a b i l i t y e s t i m a t e s f o r f i r s t l a c t a t i o n y i e l d s , l i f e t i m e p r o d u c t i o n , and l o n g e v i t y t r a i t s . Groups 1 & 2 Group 2 T r a i t 3 H e r i t a b i l i t y S.E. H e r i t a b i l i t y S.E. M i l k 1 .22 .025 .20 .025 F a t 1 .25 .027 .25 . 029 M i l k HY1 .22 .024 .20 .025 F a t HY1 .24 .027 .25 . 029 M i l k L .14 .017 .11 . 016 F a t L .16 .019 .14 . 019 LLL .06 . 010 .07 .012 M i l k T .11 . 0T5 .11 .016 F a t T .12 .015 .12 .017 M i l k / D .21 . 024 .21 . 026 Fat/D .25 .028 .28 .032 C u l l a g e .10 . 013 .09 .014 P l i f e .10 . 013 .09 .014 # L a c t .09 . 012 .08 .013 a T r a i t s a r e d e f i n e d i n pages 28, 29 and T a b l e 4. - 89 -S c h a e f f e r e t a l . , 1975 and L i n and A l l a i r e , 1978), but were w e l l w i t h i n the range of estimates obtained by other r e s e a r c h e r s (Gaunt et a l . , 1966; Wilcox et a_l. , 1971; G i l l and A l l a i r e , 1976 and Ahunu, 1978) f o r H o l s t e i n p o p u l a t i o n s . Reported estimates range from .12 to .37 f o r m i l k and from .14 to .45 f o r f a t . Some of these s t u d i e s have used daughter-dam r e g r e s s i o n , which method a c c o r d i n g to the study of Van V l e c k and Bradford (1965) g i v e s higher h e r i t a b i l i t y e stimates compared to h a l f - s i b c o r r e l a t i o n method. Lower estimates obtained i n t h i s study may a l s o p a r t l y be due to removal of g e n e t i c trends by u s i n g s i r e grouping. H e r i t a b i l i t y estimates f o r l a s t l a c t a t i o n m i l k and f a t y i e l d s were a l s o lower compared to those a v a i l a b l e i n l i t e r a t u r e , which i s summarized i n Table 16. However, g e n e t i c parameter estimates of l a s t l a c t a t i o n o b tained i n t h i s study are d i f f i c u l t to i n t e r p r e t s i n c e l a s t l a c t a t i o n i n c l u d e d f i r s t and subsequent l a c t a t i o n s up to t e n t h l a c t a t i o n . H e r i t a b i l i t i e s of l a s t l a c t a t i o n m i l k and f a t were lower than the corresponding f i r s t l a c t a t i o n e s t i mates, which i s i n agreement wi t h the e a r l i e r s t u d i e s (Freeman, 1960; Barr and Van V l e c k , 1963; Johnson and C o r l e y , 1961; and Johansson, 1955). The reason f o r lower h e r i t a b i l i t y of l a t e r l a c t a t i o n s , p a r t i c u l a r l y the second l a c t a t i o n , a c c o r d i n g to P i r c h n e r (1969) c o u l d be t h a t most cows s t a r t t h e i r f i r s t l a c t a t i o n w e l l c o n d i t i o n e d and thus can d i s p l a y t h e i r r e a l g e n e t i c p o t e n t i a l much b e t t e r than i n the second l a c t a t i o n , T a b l e 16. H e r i t a b i l i t y e s t i m a t e s o f f i r s t t h r e e l a c t a t i o n s i n H o l s t e i n . Source Freeman (1960) B a r r and Van V l e c k (1963) Johnson and C o r l e y (1961) Johansson (1955) G a c u l a e t a l . (1968) B l a n c h a r t e t a l . (1966) Gaunt e t a l . (1966) W i l c o x e t a l . (1971) G i l l and A l l a i r e (1976) S c h a e f f e r e t a l . (1975) Hargrove e t aJL. (1969) Ahunu (1978) L i n and A l l a i r e (1978) M o l i n u e v o and Lush (19 64) (1) (2) (1) (4) (5) (6) (3) M i l k Y i e l d F a t Y i e l d L a c t a t i o n Number 1 2 3 1 2 3 .36 .24 .26 .43 .35 .26 .26 .27 .21 .35 .22 .16 .33 .22 .33 37 29 24 23 12 29 39 23 39 30 09 08 33 45 29 24 25 14 ,28 37 25 ,29 10 24 09 05 (1) S t a n d a r d d e v i a t i o n s ranged from .02 t o .09. (2) S t a n d a r d d e v i a t i o n s v a r i e d between .05 and .10 (3) S t a n d a r d d e v i a t i o n s ranged from .10 t o .23. (4) S t a n d a r d e r r o r s were .21 and .22. (5) S t a n d a r d e r r o r was .08 f o r both the t r a i t s . (6) S t a n d a r d e r r o r s were .08 and .09. - 91 -which some enter i n d e p l e t e d c o n d i t i o n because.of high p r o d u c t i o n i n the f i r s t l a c t a t i o n . , Though the v a r i a b l e l e n g t h o f f i r s t c a l v i n g i n t e r v a l i s c o n s i d e r e d as an a d d i t i o n a l source o f r e s i d u a l v a r i a t i o n f o r second and subsequent l a c t a t i o n s , t h i s should not a f f e c t h e r i t a b i l i t y estimates i n t h i s study s i n c e the r e c o r d s were ad j u s t e d f o r c a l v i n g i n t e r v a l . A l s o , a cow's t e r m i n a l r e c o r d may o f t e n be abnormal i n ways and f o r reasons not known here. How the mixture of t e r m i n a l and non-terminal r e c o r d s may have a f f e c t e d the r e s u l t s has not been i n v e s t i g a t e d i n t h i s or i n other s t u d i e s . H i s t o r i c a l l y , f i r s t l a c t a t i o n r e c o rds have been c o n s i d e r e d more r e l i a b l e i n s o f a r as they are l e s s b i a s e d by s e l e c t i o n or by p r e f e r e n t i a l f e e d i n g and management. For these reasons, i t was f e l t t h a t f i r s t l a c t a t i o n r e c o r d s p r o v i d e d an unbiased estimate and are more i n keeping with the assumption of random sampling. T o t a l m i l k p r o d u c t i o n d u r i n g l i f e was low but 2 s i g n i f i c a n t l y h e r i t a b l e i n t h i s study (h = .11 + .015), an estimate i n agreement r e - s i g n i f i c a n c e , though not i n magnitude, wit h Hargrove et a l . (1969) (Table 17). H e r i t a b i l i t y 2 estimate f o r t o t a l l i f e t i m e f a t (h = .118 + .015) was a l s o s i g n i f i c a n t but lower i n magnitude compared to o ther s t u d i e s (Hargrove et aJL. , 1969; G i l l and A l l a i r e , 1976). The o v e r a l l impression from p r e v i o u s r e s e a r c h was t h a t the s i g n i f i c a n t , low h e r i t a b i l i t y estimates f o r t o t a l m i l k and f a t i n t h i s study are w i t h i n the range of estimates i n view of •ii Table 17. H e r i t a b i l i t y estimates of l i f e t i m e production and longevity i n Holstein. Lifetime Production Longevity T o t a l T o t a l M i l k / T o t a l P r o d u c t i v e No. o f Source M i l k F a t Day L i f e L i f e L a c t a t i o n s Hargrove et a l . (1969) (1) .18 .18 .148 .15 .14 Plowman and Gaalaas (1960) G i l l and A l l a i r e (1976) (2) .25 .26 .4 .26 .25 .23 White and Nichols (1965) (3) .14 .13 Parker et a l . (1960) .18 .37 Wilcox et a l . (1957) M i l l e r et a l . (1967) .05-.14 Evans et a l . (1964) (4) .28 0.0 (1) Standard error ranged from .08 to .09. (2) Standard error ranged from .09 to .11. (3) , Standard error was .17 for both the t r a i t s . (4) Standard error was .12 f or milk/day and .09 for productive l i f e . - 93 -e r r o r s o f e s t i m a t i o n i n p r e v i o u s s t u d i e s . Though t h e s i r e component f o r l a s t l a c t a t i o n l e n g t h was s i g n i f i c a n t (P < . 0 5 ) , t h e h e r i t a b i l i t y e s t i m a t e 2 was v e r y low (h = .06 + .01) i n d i c a t i n g low g e n e t i c component and a r e l a t i v e l y h i g h e n v i r o n m e n t a l v a r i a b i l i t y i n t h i s t r a i t . T h i s t r a i t i s p r o b a b l y v e r y much dependent on management d e c i s i o n s and depends on economic c o n d i t i o n s , such as r e l a t i v e m i l k and beef p r i c e a t t h e time when c u l l i n g d e c i s i o n i s made. M i l k p e r day o f p r o d u c t i v e l i f e was e s t i m a t e d t o 2 have moderate h e r i t a b i l i t y (h = .28 + .12 t o .4 + .11) by Evans e t a l . (1957) and G i l l and A l l a i r e (1976). The e s t i m a t e 2 from t h i s s t u d y (h = .21 + .024) was lower t h a n t h o s e r e p o r t e d . F a t p e r day o f p r o d u c t i v e l i f e , w i t h moderate h e r i t a b i l i t y o f .25 + .028, o b t a i n e d i n t h i s s t u d y , had no comparison from p r e v i o u s s t u d i e s . The o n l y r e p o r t i n l i t e r a t u r e by L a r s o n e t a l . (1951) gave a h e r i t a b i l i t y e s t i m a t e o f f a t p e r day o f l i f e as z e r o . I n v i e w o f t h e magnitude and r e l a t i v e l y s m a l l s t a n d a r d e r r o r , i t i s c o n s i d e r e d t h a t the p r e s e n t e s t i m a t e i s r e l i a b l e . Three measures o f l o n g e v i t y u t i l i z e d i n t h i s s t u d y , age a t d i s p o s a l , l e n g t h of p r o d u c t i v e l i f e and number of l a c t a t i o n completed e x h i b i t e d s i g n i f i c a n t b ut v e r y low h e r i t a b i l i t i e s of .10 + .013, .10 + .013 and .09 + .012, r e s p e c t i v e l y . White and N i c h o l s (1965) r e p o r t e d a 2 h e r i t a b i l i t y w i t h r a t h e r l a r g e s a m p l i n g e r r o r (h = .14 + .17) - 94 -f o r age a t l a s t c a l v i n g . E s t i m a t e s o f s i m i l a r magnitude has a l s o been r e p o r t e d by Plowman and Gaalaas (196 0) and P a r k e r e t a l . (1960). G i l l and A l l a i r e (1976) r e p o r t e d h i g h e r e s t i m a t e , w h i l e M i l l e r e t a l . (1967) o b t a i n e d e s t i m a t e s (.05 t o .14) w i t h i n w h i c h t h e e s t i m a t e s o f t h i s s t u d y f a l l s . H e r i t a b i l i t y e s t i m a t e s o f v e r y l a r g e v a r i a t i o n have been r e p o r t e d (0.0 t o .25) f o r l e n g t h o f p r o d u c t i v e l i f e . G i l l and A l l a i r e (1976) e s t i m a t e d t h e h e r i t a b i l i t y o f h e r d l i f e as .25 + .09 and Evans e t a_l. (1964) o b t a i n e d p r a c t i c a l l y no g e n e t i c component f o r l e n g t h o f p r o d u c t i v e l i f e . The range of e s t i m a t e s r e p o r t e d f o r t h e number o f l a c t a t i o n s i n i t i a t e d 2 (h = .13 t o .37) i s h i g h e r t h a n t h e e s t i m a t e o b t a i n e d i n the p r e s e n t s t u d y . G e n e t i c improvement i n d a i r y c a t t l e has been a c h i e v e d p r i m a r i l y by s e l e c t i o n f o r t h e a d d i t i v e p o r t i o n o f t h e t o t a l g e n e t i c e f f e c t . To o b t a i n g e n e t i c p r o g r e s s by d i r e c t s e l e c t i o n , t h e t r a i t s must have a s i g n i f i c a n t g e n e t i c component. I n g e n e r a l , a s i g n i f i c a n t g e n e t i c component i n d i c a t e s t h a t s e l e c t i o n on t h a t t r a i t w i l l r e s u l t i n change of t h e p o p u l a t i o n mean i n t h e d e s i r e d d i r e c t i o n . I n t h e p r e s e n t s t u d y , i t i n d i c a t e d t h a t a p o r t i o n o f t h e genotype of t h e cow was r e s p o n s i b l e f o r e s t a b l i s h i n g t h e measured l e v e l o f t r a i t s such as f i r s t l a c t a t i o n y i e l d s and y i e l d s p e r day of p r o d u c t i v e l i f e , and t h a t t h e a d d i t i v e e f f e c t of t h e genes were a major c o n t r o l l i n g f a c t o r i n t h i s genotype. I t was noted t h a t most e s t i m a t e s of f i r s t l a c t a t i o n y i e l d s - 95 -were above .24, i n d i c a t i n g some scope o f g e n e t i c improvement i n t h e s e t r a i t s by d i r e c t s e l e c t i o n . The m a j o r i t y o f t h e h e r i t a b i l i t y e s t i m a t e s o f l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s i n H o l s t e i n ranged between .13 and .18, t h u s , v e r y l i t t l e g e n e t i c p r o g r e s s c o u l d be e x p e c t e d i n t h e s e t r a i t s by d i r e c t s e l e c t i o n . C o r r e l a t i o n s As an a l t e r n a t i v e t o d i r e c t s e l e c t i o n t h e r e i s a n o t h e r approach, namely i n d i r e c t s e l e c t i o n . T h i s method i s e f f e c t i v e when t h e t r a i t s i n v o l v e d i n s e l e c t i o n have a s i g n i f i c a n t g e n e t i c c o r r e l a t i o n and thus s e l e c t i o n f o r one t r a i t w i l l r e s u l t i n a s i m u l t a n e o u s change i n a n o t h e r t r a i t because the i n d i v i d u a l genotypes i n v o l v e d w i t h t h e t r a i t s have some p o r t i o n i n common. The r e l a t i v e s i z e o f t h i s p o r t i o n i s e s t i m a t e d by the g e n e t i c c o r r e l a t i o n . T h i s common genotype a f f e c t s t h e two t r a i t s t h r o u g h the phenomenon o f p l e i o t r o p y o f gene e f f e c t s . Response t o i n d i r e c t s e l e c t i o n depends on t h e h e r i t a b i l i t y o f t h e t r a i t used i n d i r e c t l y , the g e n e t i c v a r i a n c e o f t h e t r a i t i n w h i c h change i s sought, t h e g e n e t i c c o r r e l a t i o n between the two t r a i t s and t h e s e l e c t i o n d i f f e r e n t i a l . The s u c c e s s o f i n d i r e c t s e l e c t i o n compared t o d i r e c t s e l e c t i o n w i l l depend on t h e r e l a t i v e magnitude o f t h e s e f a c t o r s . I n p r a c t i c e , ease and economy o f measure-ment may become a c o n s i d e r a t i o n i n t r a i t s e l e c t i o n . A Table 18. Phenotypic correlations 3(above diagonal) and genetic correlations (below diagonal): for combined Groups 1 and 2. T r a i t Milk 1 Fat 1 Milk HYl Fat HYl Milk L Fat L LLL Milk T Fat T Milk /D Fat /D C u l l age P l i f e #Lact Milk 1 .82 .98 .80 .56 .44 .21 .36 .33 .77 .57 .28 .28 .26 Fat 1 .49 .81 .98 .46 .55 .19 .33 .36 .60 .75 .28 .28 .26 Milk HYl 1.0 .49 .82 .55 .43 .21 .36 .33 .76 .57 .27 .27 .25 Fat HYl .50 1.0 .49 .45 .55 .19 .33 .36 .59 .74 .27 .27 .26 Milk L .83 .47 .83 .48 .90 .35 .58 .56 .72 .60 .51 .51 .49 Fat L .37 .85 .37 .85 .65 .33 .54 .57 .60 .72 .49 .50 .47 LLL * .54 .41 .53 • 4 1 .70 .55 .18 .18 .17 .17 .16 .16 .08 Milk T .56 .49 . 57 .49 .87 .75 .69 .99 .47 .43 .98 .98 .97 Fat T .42 .61 .43 .62 .77 .87 .66 .96 .44 .47 .97 .98 .96 Milk/D . .93 .44 .93 .45 .93 .48 .61 .71 .57 .79 .34 .34 .33 Fat/D .34 .93 .34 .93 .50 .95 .46 .59 .74 .43 .34 .34 .33 Cullage .44 .45 .45 .46 .78 .75 . 66 .98 .97 .57 .57 1.0 .99 P l i f e .44 .46 .45 .47 .78 .75 .66 .98 .97 . 58 .57 1.0 .99 #Lact .41 .44 .42 .45 .76 .74 .61 .98 .97 .55 .56 1.0C 1.0C a A l l c o r r e l a t i o n s s i g n i f i c a n t l y d i f f e r e n t from zero (P < .01). b Standard error of genetic c o r r e l a t i o n ranged from .0 01 to .098. c Values higher than .997 rounded to 1.0. d T r a i t s are defined i n pages 28, 29 and Table 4. Table 19. Phenotypic c o r r e l a t i o n s (above diagonal) and genetic correlations (below diagonal): for Group 2. •. c Milk Fat Milk Fat Milk Fat LLL Milk Fat Milk Fat C u l l - P l i f e #Lact T r a i t 1 1 HYl HYl L L T T /D /D age Milk 1 .79 .98 .77 .39 .26 .16 .30 .26 .72 .51 .18 .18 .16 Fat 1 .38 .77 .98 .29 .40 .15 .26 .31 .54 .71 .18 .18 .17 Milk HYl 1.0 .39 .79 .39 .26 .16 .30 .26 .71 .51 .18 .18 .16 Fat HYl .38 1.0 .39 .28 .39 .15 .26 .31 .53 .70 .18 .18 .17 1 .32 ^ Milk L .71 .26 .72 .27 .87 .44 .46 .43 .72 .58 .35 .35 Fat L .11 .77 .13 .78 .48 .41 .40 .44 .56 .72 .33 .30 .30 1 LLL .44 .38 .45 .38 .66 .52 .28 .28 .23 .23 .25 .25 .16 Milk T .40 .29 .43 .31 .84 .64 .74 .99 .55 .49 .97 .97 . 96 Fat T .21 .48 .25 .50 .68 .84 .71 .94 .51 .54 .97 .97 .95 Milk/D .85 .31 .86 .33 .94 .37 .63 .72 .54 .78 .38 .38 . 36 Fat/D .19 .86 .21 .87 .43 .96 .53 .55 .75 .41 .37 .37 .35 Cullage .19 .24 . 22 .26 .68 .63 .69 .96 .95 .51 .51 1.0 .98 P l i f e .20 .24 .22 . 26 .68 .63 .69 .96 .95 .51 .51 1.0 .98 #Lact .15 .21 .18 .24 .64 .61 .61 .95 .94 .47 .49 .99 .99 a A l l c o r r e l a t i o n s s i g n i f i c a n t l y d i f f e r e n t from zero (P < .01). b Standard errors of genetic c o r r e l a t i o n s ranged from .001 to .12. c T r a i t s are defined i n pages 28, 29 and Table 4. - 98 -r a t i o n a l d e c i s i o n must be reached between t h e s t r e n g t h o f t h e g e n e t i c system and t h e c o n s i d e r a t i o n s o f i t s p r a c t i c a l use. Some d i s c u s s i o n o f t h e r e l a t i o n s h i p s o f f i r s t l a c t a t i o n y i e l d s w i t h l i f e t i m e p r o d u c t i o n and l o n g e v i t y w i l l p r o v i d e some i n f o r m a t i o n f o r making t h i s d e c i s i o n . P h e n o t y p i c c o r r e l a t i o n , w h i c h i n c l u d e s b o t h g e n e t i c and e n v i r o n m e n t a l e f f e c t s may be v e r y u s e f u l f o r p r e d i c t i n g one t r a i t from a n o t h e r t r a i t i n t h e same i n d i v i d u a l , however, i t may be of no v a l u e a t a l l f o r p r e d i c t i n g i n t h e n e x t g e n e r a t i o n . B r e e d e r s a r e m a i n l y i n t e r e s t e d i n t h e c o r r e l a t i o n o f b r e e d i n g v a l u e s w h i c h i s measured by t h e g e n e t i c c o r r e l a t i o n . Thus, a s e p a r a t e d i s c u s s i o n on p h e n o t y p i c and g e n e t i c c o r r e l a t i o n s among t h e t r a i t s w i l l be p r e s e n t e d . A summary o f g e n e t i c and p h e n o t y p i c c o r r e l a t i o n s among a l l t r a i t s i s g i v e n i n T a b l e s 18 and 19, f o r groups 1 and 2 combined and Group 2 d a t a , r e s p e c t i v e l y . A summary o f e n v i r o n m e n t a l c o r r e l a t i o n s f o r b o t h combined and Group 2 i s i n Appendix T a b l e 5. The b a s i s f o r two s e p a r a t e s e t s of e s t i m a t e s was t h a t t h e e s t i m a t e s based on combined f i r s t and m u l t i p l e l a c t a t i o n cows (Groups 1 and 2) would g i v e a b e t t e r e s t i m a t e s o f the c o r r e l a t i o n s s i n c e t h i s s e t o f d a t a r e p r e s e n t s more a random p o p u l a t i o n compared w i t h m u l t i p l e l a c t a t i o n cows o n l y (Group 2 ) , wh i c h r e p r e s e n t a p o p u l a t i o n l a r g e l y s e l e c t e d f o r m i l k y i e l d . Thus, c o r r e l a t i o n s from Group 2 d a t a w i l l i n d i c a t e t h e e f f e c t o f s e l e c t i o n on c o r r e l a t i o n e s t i m a t e s . The two s e t s o f e s t i m a t e s d i f f e r e d , - 99 -and most o f t h e g e n e t i c c o r r e l a t i o n s based on combined Groups 1 and 2 were h i g h e r w i t h lower s t a n d a r d e r r o r s . The l o w e r e s t i m a t e s o f t h e g e n e t i c c o r r e l a t i o n s i n Group 2 r e f l e c t t h e e f f e c t o f s e l e c t i o n f o r f i r s t l a c t a t i o n m i l k y i e l d w h i c h p r o b a b l y reduced t h e l i n k a g e r e l a t i o n between t h i s t r a i t and l i f e t i m e p r o d u c t i o n and l o n g e v i t y . However, t h e h i g h e s t i m a t e s i n t h e combined s e t was p a r t l y due t o n a t u r e o f t h e d a t a w h i c h had about o n e - t h i r d of t h e r e c o r d s from cows c u l l e d a f t e r f i r s t l a c t a t i o n , h a v i n g i d e n t i c a l f i r s t and l a s t l a c t a t i o n y i e l d s , and l e s s v a r i a b l e l i f e t i m e y i e l d s compared t o m u l t i p l e l a c t a t i o n cows. And a l s o i n c o n s i d e r a t i o n o f t h e c o n d i t i o n s n e c e s s a r y t o comply w i t h modern b r e e d i n g t h e o r y , t h e p o p u l a t i o n o f Group 2 cows was not i d e a l because s e l e c t i v e c u l l i n g m ight have changed th e o r i g i n a l c h a r a c t e r i s t i c s o f t h e p o p u l a t i o n . Based on t h e above r e a s o n s , i t i s c o n s i d e r e d t h a t t h e combined s e t of d a t a gave more r e l i a b l e e s t i m a t e s o f c o r r e l a t i o n s . P h e n o t y p i c c o r r e l a t i o n s The c o r r e l a t i o n s o f prime i n t e r e s t i n t h i s s t u d y were t h o s e o f f i r s t l a c t a t i o n y i e l d s w i t h l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s . The s i g n i f i c a n t r e l a t i o n s h i p (r = .36) found between f i r s t l a c t a t i o n m i l k and t o t a l m i l k i s matched by Hargrove e t a l . (1969), G i l l and A l l a i r e (1976) and L i n and A l l a i r e (1978), i n d i c a t i n g t h e i n c r e a s e i n subsequent - 100 -p r o d u c t i o n w i t h t h e i n c r e a s e i n h e i f e r p r o d u c t i o n . However, t h e i n t e r p r e t a t i o n o f t h e r e l a t i o n between f i r s t l a c t a t i o n and l i f e t i m e p r o d u c t i o n i s c o m p l i c a t e d i n t h i s and o t h e r s i m i l a r s t u d i e s , s i n c e f o r cows w i t h s i n g l e l a c t a t i o n the m i l k y i e l d i n t h e f i r s t l a c t a t i o n and d u r i n g l i f e t i m e a r e e s s e n t i a l l y t h e same wh i c h w i l l b i a s the c o r r e l a t i o n upward. T h i s e s t i m a t e was lower f o r Group 2 d a t a (r = .30). F i r s t l a c t a t i o n f a t y i e l d showed a c o r r e l a t i o n of the same magnitude w i t h l i f e t i m e f a t as m i l k w i t h l i f e t i m e m i l k (Tables 18 and 19). The s t r o n g r e l a t i o n s o f f i r s t l a c t a t i o n m i l k w i t h m i l k per day (r = .77) and f i r s t l a c t a t i o n f a t y i e l d w i t h f a t y i e l d p e r day o f l i f e (r = .75) a r e s u p p o r t e d by e a r l i e r s t u d i e s summarized i n T a b l e 20. R e l a t i o n s h i p s o f f i r s t l a c t a t i o n h e r d - y e a r d e v i a t i o n m i l k and f a t w i t h l i f e t i m e p r o d u c t i o n were e s s e n t i a l l y t h e same as t h o s e f o r f i r s t l a c t a t i o n 305-day m i l k and f a t y i e l d s w i t h l i f e t i m e p r o d u c t i o n i n both t h e s e t s o f d a t a . Moreover, 3 05-day y i e l d s were v e r y h i g h l y c o r r e l a t e d w i t h h e r d - y e a r d e v i a t i o n y i e l d s (r = .98), i n d i c a t i n g t h a t t h e y a r e measures o f t h e same u n d e r l y i n g t r a i t s . The p a t t e r n o f p h e n o t y p i c c o r r e l a t i o n s i n d i c a t e d , i n g e n e r a l t h e f i r s t l a c t a t i o n y i e l d s were more h i g h l y c o r r e l a t e d w i t h y i e l d s per day o f l i f e t h a n t o t a l y i e l d d u r i n g t h e l i f e t i m e , p r o b a b l y because i n t h e former c a s e t h e e f f e c t o f v a r i a b l e c a l v i n g i n t e r v a l was e l i m i n a t e d . Table 20. Summary of phenotypic (above) and genetic (below) c o r r e l a t i o n s of f i r s t l a c t a t i o n y i e l d s with l i f e t i m e production and longevity t r a i t s . Source L i f e t i m e Production T o t a l Milk T o t a l Fat Milk/ Day T o t a l L i f e Longevity Productive L i f e Number of Lactations F i r s t L a c t a t i o n Milk Y i e l d Hargrove .et a l . (1969) G i l l and A l l a i r e (1976) Li n and A l l a i r e (1978) M i l l e r et .al. (1967) Evans .et a l . (1964) Parker et a l . (1960) Gaalaas and Plowman (1963) White and Nichols (1965) .48 . 85 .23 1.03 .43 .48 .56 1.04 ,45 ,22 ,76 ,197 .43 .76 .13 .81 ,19-.25 ,54-.77 .22 ,38 ,62 ,05 .82 I M O r-1 I ,216 F i r s t L a c t a t i o n Fat Y i e l d Hargrove et a l . (1969) G i l l and A l l a i r e (1976) Parker et a l . (1960) Gaalaas and Plowman (1963) White and Nichols (1965) .45 .94 .23 1.08 195 ,188 .40 .84 .12 .83 ,36 ,72 , 234 - 102 -The c o r r e l a t i o n s o f f i r s t l a c t a t i o n m i l k and f a t y i e l d s w i t h l o n g e v i t y t r a i t s were s i g n i f i c a n t and p o s i t i v e , r a n g i n g between .26 and .28 f o r the combined s e t o f d a t a (Table 18). T h i s p o s i t i v e a s s o c i a t i o n i n d i c a t e s t h a t h i g h p r o d u c i n g h e i f e r s a l s o s t a y e d l o n g e r i n t h e h e r d . The c o r r e l a t i o n s among l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s a r e i n T a b l e 21. Hi g h c o r r e l a t i o n s between t o t a l l i f e t i m e m i l k and f a t y i e l d s w i t h l o n g e v i t y t r a i t s (r = .96 t o .98) show t h a t h i g h y i e l d i n g cows a r e a l s o t h e l o n g e r l i v i n g cows, w h i c h was a l s o o b s e r v e d by Hargrove e t a l . (1969), who r e p o r t e d .95 as t h e c o r r e l a t i o n between l i f e t i m e m i l k and f a t y i e l d s w i t h number o f l a c t a t i o n s i n i t i a t e d . The c o n s i s t e n c y o f c o r r e l a t i o n s i n v o l v i n g t h e number of l a c t a t i o n s , l e n g t h o f p r o d u c t i v e l i f e o r c u l l i n g age w i t h one a n o t h e r o r w i t h t h e o t h e r t r a i t s seem t o i n d i c a t e t h a t a l l t h r e e measures o f l o n g e v i t y r e p r e s e n t t h e same t r a i t and one can be r e p l a c e d by the o t h e r . The e x t r e m e l y h i g h c o r r e l a t i o n (.99) between l i f e t i m e m i l k and l i f e t i m e f a t a l s o i n d i c a t e t h a t one o f t h e s e t r a i t s w i l l a d e q u a t e l y measure t h e l i f e t i m e p r o d u c t i o n . G e n e t i c c o r r e l a t i o n s Beyond t h e e s t i m a t i o n o f h e r i t a b i l i t y o f p r o d u c t i o n and l o n g e v i t y t r a i t s , t h i s s t u d y a l s o examined r e l a t i o n s h i p s among t h e s e t r a i t s , p a r t i c u l a r l y t h o s e i n v o l v i n g f i r s t Table 21. Phenotypic (above diagonal) and genetic (below diagonal) c o r r e l a t i o n s among l i f e t i m e production and longevity t r a i t s : for Groups 1 & 2 combined. Trait* 3 Milk Fat Milk Fat L L T T Milk L .90 .58 . 56 Fat L .65 - .54 . 57 Milk T .87 .75 .99 Fat T . .77 . 87 . 96 -Milk/D .93 . 48 .71 .57 Fat/D .50 .95 .59 .74 Cullage .78 .75 .98 .97 P l i f e .78 .75 .98 .97 # Lact .76 .74 .98 .97 Milk Fat Cullage P l i f e #Lact /D /D .72 .60 .51 .51 .49 .59 .72 .49 .50 . 47 .47 .43 .98 .98 . 97 .44 .47 .98 .98 . 96 - .79 .34 .34 . 33 .43 - .34 .34 . 33 .57 .57 - 1.0 .99 . 58 .57 1.0 - . 99 .55 .56 1.0 1.0 -a b Standard errors for genetic c o r r e l a t i o n s range between .014 and .086. A l l c o r r e l a t i o n s s i g n i f i c a n t l y d i f f e r e n t from zero (P < .01) - 104 -l a c t a t i o n y i e l d s , l i f e t i m e p r o d u c t i o n and l o n g e v i t y . A summary o f g e n e t i c c o r r e l a t i o n s i s i n T a b l e s 18 and 19 f o r combined and Group 2 s e t s o f d a t a , r e s p e c t i v e l y . The g e n e t i c c o r r e l a t i o n s were o f g r e a t e s t i n t e r e s t but c a u t i o n i n i n t e r p r e t i n g t h e s e c o r r e l a t i o n s i s w a r r a n t e d . The g e n e t i c c o r r e l a t i o n s were c a l c u l a t e d u s i n g h a l f - s i b a n a l y s i s and m u l t i p l i c a t i o n by a c o n s t a n t o f f o u r i n v o l v e d i n t h e c a l c u l a t i o n . S i n c e e r r o r s o f measurement were a l s o m u l t i p l i e d by t h i s f a c t o r , t h e s t a n d a r d e r r o r a s s o c i a t e d w i t h the g e n e t i c c o r r e l a t i o n was a p p r o p r i a t e l y i n f l a t e d . Thus, t h e magnitude of t h e c o r r e l a t i o n s h o u l d be judged i n r e l a t i o n t o i t s s t a n d a r d e r r o r w h i c h i s m i n i m a l and approximate i n thi<s s t u d y . F i r s t l a c t a t i o n m i l k y i e l d p o s s e s s e d s t r o n g g e n e t i c c o r r e l a t i o n s w i t h l a s t l a c t a t i o n m i l k (.83 + .04), t o t a l l i f e t i m e m i l k (.56 + .07) and m i l k per day o f p r o d u c t i v e l i f e (.93 + .02); and m o d e r a t e l y h i g h c o r r e l a t i o n s w i t h c u l l i n g age (.44 + .09), p r o d u c t i v e l i f e (.44 + .09) and number of l a c t a t i o n s completed (.41 + .09) f o r combined Groups 1 and 2. These c o r r e l a t i o n s dropped i n t h e Group 2 d a t a w i t h a c o r r e s p o n d i n g i n c r e a s e i n t h e s t a n d a r d e r r o r s (Table 19). E s t i m a t e s o f s i m i l a r n a t u r e and magnitude were a l s o o b s e r v e d between f i r s t l a c t a t i o n f a t y i e l d , l i f e t i m e f a t and l o n g e v i t y , w i t h s t r o n g e s t c o r r e l a t i o n between f i r s t l a c t a t i o n f a t y i e l d and f a t y i e l d p e r day o f p r o d u c t i v e l i f e (.93 + .02) and t h e p o o r e s t c o r r e l a t i o n between f i r s t l a c t a t i o n f a t y i e l d and t h e number of - 105 -l a c t a t i o n s c ompleted (.44 + .09) i n Groups 1 and 2 combined. Almost i d e n t i c a l c o r r e l a t i o n s were obser v e d f o r f i r s t l a c t a t i o n h e r d - y e a r d e v i a t i o n y i e l d s w i t h l i f e t i m e p r o d u c t i o n and l o n g e v i t y as t h o s e f o r f i r s t l a c t a t i o n 305-day y i e l d s w i t h l i f e t i m e p r o d u c t i o n and l o n g e v i t y (Tables 18 and 19). E s t i m a t e s o b t a i n e d i n t h i s s t u d y a r e somewhat lo w e r t h a n t h e e s t i m a t e s r e p o r t e d by o t h e r r e s e a r c h e r s (Table 2 0) . The g e n e t i c c o r r e l a t i o n s o f t o t a l l i f e t i m e y i e l d s w i t h l o n g e v i t y t r a i t s were a l l above .96, i n d i c a t i n g t h a t t h e l o n g l i v e d cows were a l s o g e n e t i c a l l y t h e h i g h p r o d u c e r s , w h i c h i s s u p p o r t e d by Hargrove e t a l . (1969) who o b t a i n e d e s t i m a t e s r a n g i n g from .95 t o .97. P e r f e c t p o s i t i v e g e n e t i c c o r r e l a t i o n (1.0 + 0.0) among l o n g e v i t y t r a i t s s u g g e s t s t h e y e s s e n t i a l l y measure t h e same u n d e r l y i n g t r a i t s and one o f t h e s e t r a i t s would be adequate as a measure of l o n g e v i t y . H i g h g e n e t i c c o r r e l a t i o n s o f f i r s t l a c t a t i o n y i e l d s w i t h y i e l d s p e r day (.93 + .02) and h i g h g e n e t i c c o r r e l a t i o n s o f y i e l d s per day w i t h t o t a l l i f e t i m e y i e l d s (.71 + .06 t o .74 + .05) suggest t h a t y i e l d p e r day would be a b e t t e r measure o f l i f e t i m e p r o d u c t i o n i n i n d i r e c t s e l e c t i o n , s i n c e y i e l d s p e r day have r e l a t i v e l y h i g h e r g e n e t i c component 2 (h = .21 t o .25) t h a n o t h e r measures o f l i f e t i m e p r o d u c t i o n 2 2 (h = .11 t o .12) and l o n g e v i t y (h = .09 t o .10). - 106 -An i m p o r t a n t l i m i t a t i o n i n i n t e r p r e t a t i o n o f t h e a n a l y s e s on l i f e t i m e t r a i t s i s t h e i n a b i l i t y t o a s s e s s c l e a r l y e f f e c t s o f s e l e c t i o n on c o r r e l a t i o n s . A c c o r d i n g t o Brown and T u r n e r (1968), s e l e c t i o n on one t r a i t , t h e o r e t i c a l l y can l e a d t o e s t i m a t e s o f g e n e t i c c o r r e l a t i o n s n e a r e r z e r o i n s e l e c t e d p o p u l a t i o n compared t o u n s e l e c t e d p o p u l a t i o n . Two s e t s o f g e n e t i c c o r r e l a t i o n e s t i m a t e s gave a chance t o l o o k a t the changes i n g e n e t i c c o r r e l a t i o n s i n more s e l e c t e d m u l t i p l e l a c t a t i o n cows (Group 2) compared t o e s t i m a t e s based on combined s i n g l e and m u l t i p l e l a c t a t i o n g roups. I n g e n e r a l , t h e drop i n t h e g e n e t i c c o r r e l a t i o n e s t i m a t e s from combined groups t o m u l t i p l e l a c t a t i o n group were h i g h e r w i t h t h o s e i n v o l v i n g f i r s t l a c t a t i o n p r o d u c t i o n ( m i l k and f a t y i e l d s ) and l i f e t i m e p r o d u c t i o n and l o n g e v i t y t h a n t h o s e i n v o l v i n g l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s . T h i s p r o v i d e s some i n d i c a t i o n t h a t dairymen were s e l e c t i n g f o r f i r s t l a c t a t i o n m i l k and f a t y i e l d s . I t was n o t c l e a r l y e v i d e n t whether they were p u t t i n g more emphasis on m i l k y i e l d than f a t y i e l d , though t h e r e was a s l i g h t r e d u c t i o n i n t h e h e r i t a b i l i t y o f f i r s t l a c t a t i o n m i l k i n t h e m u l t i p l e l a c t a t i o n group as w e l l as a drop i n t h e g e n e t i c c o r r e l a t i o n between th e two t r a i t s ; a l s o no change i n h e r i t a b i l i t y o f f a t y i e l d p r o v i d e some i n d i c a t i o n o f more s e l e c t i o n emphasis on f i r s t l a c t a t i o n m i l k . - 107 -R e l a t i o n s h i p s o f Ex p e c t e d B r e e d i n g V a l u e s f o r F i r s t  L a c t a t i o n Y i e l d s w i t h L i f e t i m e P r o d u c t i o n and L o n g e v i t y The e x p e c t e d b r e e d i n g v a l u e s (EBV) o f 138 s i r e s f o r p r o d u c t i o n and l o n g e v i t y t r a i t s were e s t i m a t e d u s i n g l e a s t square s i r e c o n s t a n t s o b t a i n e d from a n a l y s i s on combined f i r s t and m u l t i p l e l a c t a t i o n d a u g h t e r s a c c o r d i n g t o E q u a t i o n 16. The r e s u l t s a r e p r e s e n t e d i n the Appendix T a b l e The e s t i m a t e d EBV's showed l a r g e g e n e t i c d i f f e r e n c e s i n t h e t r a n s m i t t i n g a b i l i t i e s o f t h e s i r e s f o r a l l t h e p r o d u c t i o n and l o n g e v i t y t r a i t s . The EBV's f o r M i l k 1 ranged from -811 kg t o 843 kg; F a t 1, -30 kg t o 36 kg; M i l k T, -12607 kg t o 12159 kg; F a t T, -498 kg t o 475 kg; M i l k / D , -2.37 kg t o 2.22 kg; Fat/D, -.096 kg t o .093 kg; and P l i f e , -23.30 months t o 20.33 months. S i r e s were ranked d i f f e r e n t l y f o r v a r i o u s y i e l d t r a i t s and l o n g e v i t y . In g e n e r a l , t h e r e was a d i r e c t r e l a t i o n s h i p between t h e EBV's f o r f i r s t l a c t a t i o n y i e l d s , l i f e t i m e p r o d u c t i o n and l o n g e v i t y . By f o r m i n g groups of b u l l as i n T a b l e 22, i n t e r e s t i n g r e s u l t s appear. The average EBV' f o r l i f e t i m e p r o d u c t i o n and l o n g e v i t y o f s i r e s w i t h a M i l k 1 EBV's o f 0.0 kg o r g r e a t e r was h i g h e r t h a n t h a t o f r e m a i n i n g n e g a t i v e EBV b u l l s . The average d i f f e r e n c e s were 3853 kg M i l k T, 116 kg F a t T, 1.34 kg M i l k / D , .026 kg Fat/D and 5.2 month P l i f e . S i m i l a r l y , s i r e s w i t h 0.0 kg o r b e t t e r f a t EBV's had h i g h e r EBV's f o r l i f e t i m e p r o d u c t i o n and l o n g e v i t y than n e g a t i v e f a t r a t e d b u l l s w i t h average d i f f e r e n c e s of 4764 kg M i l k T, 210 kg F a t T, .85 kg M i l k / D , .057 kg Fat/D Table 22. Differences i n average expected breeding values (EBV) for various groupings of bulls. Average expected breeding values for lifetime production and longevity — — — — - Number Milk T Fat T Milk/D Fat/D P l i f e of Sires 1. EBV Milk 1 0.0 1827.12 55.67 .6243 .0127 2.56 72 2. EBV Milk 1 0.0 -2050.52 -59.93 -.7190 -.0135 -2.62 66 Av. Difference 1 vs 2 3852.64 115.60 1.3433 .0262 5.18 — 3. EBV Fat 1 0.0 2435.65 108.46 .4181 .0295 4.06 67 4. EBV Fat 1 0.0 -2328.46 -101.60 -.4299 -.0275 -3.67 71 Av. Difference 3 vs 4 4764.11 210.06 .8480 .0570 7.73 — 5. EBV Milk 1 and EBV Fat 1 0.0 2867.09 106.69 .7477 .0285 4.29 49 6. EBV Milk 1 or EBV Fat 1 0.0 -1602.47 -58.14 -.4398 -.0154 -2.24 89 Av. Difference 5 vs 6 4469.56 164.83 1.1875 .0439 6.53 — a Units are i n kilogram except P l i f e which i s i n months. - 109 -and 7.7 months P l i f e . B u l l s w i t h 0.0 kg o r b e t t e r M i l k 1 EBV and 0.0 kg F a t 1 EBV o r b e t t e r had s u b s t a n t i a l l y h i g h e r EBV's f o r l i f e t i m e p r o d u c t i o n and l o n g e v i t y t h a n n e g a t i v e EBV M i l k 1 or F a t 1 b u l l s . Average d i f f e r e n c e between t h e s e groups were 447 0 kg, 165 kg, 1.19 kg, .04 kg and 6.5 months, r e s p e c t i v e l y , f o r t h e above t r a i t s . S c h a e f f e r and B u r n s i d e (1974) and Van V l e c k (1964) a l s o found h i g h e r s u r v i v a l r a t e o f daughters o f s i r e s w i t h p o s i t i v e m i l k p r o o f s compared t o s i r e s w i t h n e g a t i v e m i l k p r o o f s . Product-moment c o r r e l a t i o n s among the EBV's f o r p r o d u c t i o n and l o n g e v i t y o b t a i n e d i n t h i s s t u d y and b r e e d i n g v a l u e s o f s i r e s f o r Breed C l a s s Averages (BCA's) of m i l k and f a t o b t a i n e d from t h e Report (1976) on D a i r y S i r e A p p r a i s a l , D i r e c t Comparison, A g r i c u l t u r e Canada i s p r e s e n t e d i n T a b l e 23. There was a good agreement between the EBV's f o r M i l k 1 and F a t 1 w i t h c o r r e s p o n d i n g s i r e p r o o f s f o r BCA m i l k and BCA f a t (r = .91 and .92), w h i c h i s e x p e c t e d because t h e d a t a s e t used i n t h i s s t u d y i s a s u b s e t o f t h a t used by R.O.P. f o r t h e i r s i r e a p p r a i s a l . C o r r e l a t i o n s o f p a r t i c u l a r i n t e r e s t i n t h i s s t u d y were t h o s e i n v o l v i n g EBV's of f i r s t l a c t a t i o n m i l k and f a t y i e l d s w i t h EBV's f o r l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s w h i c h a r e shown i n T a b l e 24. A l l c o r r e l a t i o n s were s i g n i f i c a n t l y d i f f e r e n t from z e r o (P <. .01). The h i g h e s t c o r r e l a t i o n f o r M i l k 1 was w i t h M i l k / D (.89) and l o w e s t w i t h # L a c t (.33). S i m i l a r l y f o r F a t 1, t h e h i g h e s t c o r r e l a t i o n (.88) was w i t h Fat/D and Table 23. Product-moment c o r r e l a t i o n s 0 between breeding values of s i r e s f o r l i f e t i m e production and long e v i t y t r a i t s . a EBV b CDA BV T r a i t BCAF .65 Milk 1 .91 .59 Fat 1 .57 .92 Milk HYl .91 .58 Fat HYl .57 .92 Milk L .68 .47 Fat L .39 .71 LLL .39 .35 Milk T .47 .46 Fat T .38 .54 Milk/D .81 .52 Fat/D .42 . 84 Cullage .37 . 42 P l i f e .37 .42 « Lact .34 .40 66 .o e • 6 5 e 65 i . o e .66 75 .54 .74 45 .77 . 45 37 .33 .36 43 . 47 .48 38 .54 . 38 89 .56 . 89 48 .88 .48 36 .41 . 36 36 .41 .36 33 . 39 .33 54 76 .79 32 . 53 .48 47 .75 . 72 .48 54 . 68 . 78 .47 56 . 84 . 55 .38 88 . 58 . 8C .34 41 . 67 . 69 . 46 41 . 67 .69 . 46 39 . 64 . 67 .39 .93 . 58 .49 . 57 . 66 .60 . 98 .97 . 44 . 98 .97 .44 . 97 . 97 .42 ! h-1 O ! .51 .51 1.0 .50 .99 .99 a Breeding values of s i r e s obtained from Report (1976), A g r i c u l t u r e Canada, b Expected breeding values c a l c u l a t e d using equation 16. c A l l c o r r e l a t i o n s s i g n i f i c a n t l y d i f f e r e n t f r o . zero (P < ^ ^ d e f i n e d p a g e s 2 8 , 2 9 a n d T a b l e 4 , d BCAM and BCAF represent breed-class-average milk and f a t , r e s p e c t i v e l y . e Values > .995 have been rounded t o 1.0. Table 24. Product-moment correlations between expected breeding values (EBV) for f i r s t l a c t a t i o n y i e l d s , l i f e t i m e production and longevity. Lifetime Production , F i r s t Lactation Yields and Longevity T r a i t s Milk 1 Fat Milk L .75 .54 Fat L .45 .77 Milk T .48 .47 Fat T . 38 .54 Milk/D .89 .56 Fat/D .48 .88 Cullage .36 .41 P l i f e .36 .41 # Lact .33 .39 a A l l correlations s i g n i f i c a n t l y d i f f e r e n t from zero (P .01). b T r a i t s are defined i n pages 28, 29 and Table 4. - 112 -l o w e s t w i t h # L a c t (.39). These c o r r e l a t i o n s are s l i g h t l y l o w e r t h a n t h e c o r r e s p o n d i n g g e n e t i c c o r r e l a t i o n s o b t a i n e d f o r t h e s e t r a i t s (Table 1 8 ) . Due t o t h e l a r g e numbers of d a u g h t e r s f o r each s i r e , t h e c o r r e l a t i o n s o f EBV's a r e l a r g e l y g e n e t i c p l u s t h e e r r o r s o f e s t i m a t i o n . T a b l e 25 shows p r e d i c t i o n e q u a t i o n s o f m i l k and f a t EBV's on l i f e t i m e p r o d u c t i o n and l o n g e v i t y EBV's, and t h e p e r c e n t a g e o f v a r i a t i o n e x p l a i n e d by each r e g r e s s i o n e q u a t i o n . The s i r e EBV f o r f i r s t l a c t a t i o n m i l k and f a t y i e l d s a r e v e r y good p r e d i c t o r s o f EBV's f o r m i l k and f a t y i e l d s p e r day, r e s p e c t i v e l y a c c o u n t i n g f o r 73% o f the t o t a l v a r i a t i o n s i n each case. A d d i n g a second v a r i a b l e , f i r s t l a c t a t i o n f a t w i t h f i r s t l a c t a t i o n m i l k o r v i c e v e r s a d i d not improve t h e p r e d i c t i v e v a l u e o f t h e e q u a t i o n . F i r s t l a c t a t i o n m i l k and f a t y i e l d EBV's a r e s e p a r a t e l y e q u a l l y good p r e d i c t o r s o f EBV f o r l i f e t i m e m i l k , a c c o u n t i n g f o r 23% and 22% o f t h e t o t a l v a r i a t i o n , r e s p e c t i v e l y , and u s i n g b o t h the t r a i t s p r o v i d e s a s m a l l e x t r a r e d u c t i o n (4% and 5%) i n t h e u n e x p l a i n e d v a r i a t i o n . F i r s t l a c t a t i o n m i l k i s not as good 2 a p r e d i c t o r o f t o t a l l i f e t i m e f a t y i e l d (R = 1 4 % ) , as the 2 f i r s t l a c t a t i o n f a t y i e l d (R = 2 9 % ) , and adding f i r s t l a c t a t i o n m i l k a f t e r f i r s t l a c t a t i o n f a t does not improve t h e e f f i c i e n c y o f t h e p r e d i c t i o n . F i r s t l a c t a t i o n f a t i s a s l i g h t l y b e t t e r 2 p r e d i c t o r o f t h e l e n g t h o f p r o d u c t i v e l i f e (R = .17) t h a n 2 f i r s t l a c t a t i o n m i l k (R = .13). Table 25. Regressions of expected breeding value . (EBV) milk and/or expected breeding value f a t on expected breeding values f o r l i f e t i m e production and longevity. T r a i t Intercept b x (EBV Milk 1) + b 2 (EBV Fat 1) Variation „ Explained (R ) EBV Milk T = 22.78 -10.25 11.26 + + + 7.25 4.48 + + 178.06 104.81 23 22 27 EBV Fat T- = 1.60 .6192 .76 + + .2297 .0296 + + 8.07 7.59 14 29 29 Ebv Milk/D = .0053 .0170 .0050 + + .0024 .0025 .0386 .0022 78 32 78 EBV Fat/D = .00049 .00027 .00017 .000056 .000021 + + .0026 .0029 23 78 79 EBV P l i f e = .1316 .0879 .1088 + + .0098 .0044 + + ,2786 .2073 13 17 18 - 114 -The r e g r e s s i o n c o e f f i c i e n t s i n d i c a t e t h a t f o r each kg d i f f e r e n c e i n EBV o f s i r e f o r f i r s t l a c t a t i o n m i l k , t h e r e was a d i f f e r e n c e of more th a n 7 kg i n average EBV f o r l i f e t i m e m i l k ; and f o r each kg d i f f e r e n c e i n f i r s t l a c t a t i o n f a t , t h e r e was a d i f f e r e n c e o f more th a n 8 kg i n average EBV f o r l i f e t i m e f a t . F o r each 1000 kg d i f f e r e n c e i n EBV o f s i r e f o r f i r s t l a c t a t i o n m i l k t h e r e was a d i f f e r e n c e o f o v e r 9 months i n the l e n g t h o f p r o d u c t i v e , l i f e . - 115 -CONCLUSIONS G e n e t i c and e n v i r o n m e n t a l parameters o f l i f e t i m e p r o d u c t i o n and l o n g e v i t y o f H o l s t e i n cows i n Canadian Record o f Performance herds were e v a l u a t e d and e s t i m a t e d i n t h i s s t u d y . E s t i m a t e s o f g e n e t i c components o f v a r i a n c e and h e r i t a b i l i t i e s o f t h e i n d i v i d u a l t r a i t s were o b t a i n e d , s i n c e i n t h e absence o f g e n e t i c v a r i a t i o n no e f f e c t i v e s e l e c t i o n can be p r a c t i s e d . The s u i t a b i l i t y o f a t r a i t f o r i n c l u s i o n i n a s e l e c t i o n program was f u r t h e r e v a l u a t e d by e s t i m a t i o n o f g e n e t i c c o r r e l a t i o n s among t h e s e t r a i t s . A d d i t i o n a l l y t h e v a l u e o f s i r e p r o o f s f o r l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s , s i m i l a r t o t h o s e f o r m i l k and/or f a t y i e l d s was examined. T h i s r e p o r t i s now c o n c l u d e d w i t h t h e most s a l i e n t p o i n t s a r i s i n g from t h i s r e s e a r c h . 1) The means and c o e f f i c i e n t s o f v a r i a t i o n o f l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s d e r i v e d were r e l a t i v e l y f r e e from t h e b i a s e s found i n some p r e v i o u s s t u d i e s due t o t h e n a t u r e o f r e s t r i c t i o n s w h i c h were imposed on t h e i r d a t a , such as a r e q u i r e d number o f completed l a c t a t i o n o r a s p e c i f i c age, and because a l l cows were known t o have been c u l l e d w i t h i n t h e p e r i o d s t u d i e d . 2) Herd e f f e c t was found t o be t h e most i m p o r t a n t f a c t o r a f f e c t i n g v a r i a t i o n i n p r o d u c t i o n and l o n g e v i t y t r a i t s ; i t a ccounted f o r between 5% ( f o r C u l l a g e ) and 37.6% ( f o r F a t / D ) . - 116 -Herd e f f e c t s f o r t o t a l l i f e t i m e y i e l d s and l o n g e v i t y were lower i n magnitude compared t o f i r s t l a c t a t i o n y i e l d s . Herd e f f e c t r e f l e c t e d any g e n e t i c as w e l l as t h e e n v i r o n m e n t a l d i f f e r e n c e s between h e r d s . I n d i v i d u a l e n v i r o n m e n t a l e f f e c t s c o u l d n o t be e v a l u a t e d from t h i s d a t a . Due t o t h e l a r g e number o f herds i n c l u d e d i n t h i s s t u d y and a l s o , r e c o g n i s i n g t h a t an i n t e r a c t i o n among h e r d , y e a r and season might e x i s t , t h e g e n e t i c parameters were e s t i m a t e d on t h e b a s i s o f w i t h i n h e r d - y e a r - s e a s o n s u b c l a s s e s . 3) Y e a r l y t r e n d s i n f i r s t l a c t a t i o n m i l k and f a t y i e l d s were upward i n t h i s p o p u l a t i o n w h i c h r e f l e c t e d t h e j o i n t e f f e c t s o f improved n u t r i t i o n and g e n e t i c p r o g r e s s due m a i n l y t o t h e e x t e n s i v e use o f proven b u l l s t h r o u g h a r t i f i c i a l i n semination,. There was a s l i g h t tendency f o r a r e d u c t i o n i n t h e l e n g t h o f p r o d u c t i v e l i f e and i n t h e number of l a c t a t i o n s c ompleted, i n d i c a t i n g s l i g h t l y i n c r e a s e d t u r n o v e r r a t e s d u r i n g the p e r i o d . I t i s c o n c l u d e d t h a t t h e y e a r e f f e c t s h o u l d be i n c l u d e d i n an a n a l y s i s f o r h e r i t a b i l i t y e s t i m a t e s u s i n g d a t a showing y e a r l y t r e n d . T h i s i s because t h e i n c r e a s e i n mean p r o d u c t i o n l e a d s t o an i n c r e a s e i n t h e s i r e component of v a r i a n c e a t a r a t e s l i g h t l y f a s t e r t h a n t h e i n c r e a s e i n r e s i d u a l v a r i a n c e , t h u s , i n c r e a s i n g t h e h e r i t a b i l i t y e s t i m a t e d from p a t e r n a l h a l f - s i b c o r r e l a t i o n s (Van V l e c k , 1966). A l s o the o m i s s i o n o f t h e y e a r e f f e c t from th e model might l e a d t o c o n f o u n d i n g between y e a r and s i r e e f f e c t s and t h u s c o u l d b i a s - 117 -the i n t r a c l a s s c o r r e l a t i o n upward. 4) Cows which f i r s t freshened during September to February produced more mi l k and f a t i n the f i r s t l a c t a t i o n than those which freshened f i r s t during March to August; t h i s t rend i s s i m i l a r t o the f i n d i n g s of other s t u d i e s i n the northern hemisphere. Hov/ever, l o n g e v i t y t r a i t s were not s i g n i f i c a n t l y a f f e c t e d by the season of f i r s t c a l v i n g . Due to presence of a year by season i n t e r a c t i o n f o r some of the t r a i t s under study and since herds might d i f f e r i n seasonal e f f e c t s , a herd-year-season c l a s s i f i c a t i o n was used to estimate s i r e components fr e e from the independent and j o i n t e f f e c t s of these f a c t o r s . 5) Cows which f i r s t freshened at an older age produced more milk and f a t during t h e i r l i f e t i m e and a l s o per day of productive l i f e , compared to cows f i r s t c a l v i n g younger. On the other hand, younger c a l v e r s completed more l a c t a t i o n s and stayed longer i n the herd. This may be due to the reason t h a t the l a t e c a l v e r s , having higher l a c t a t i o n y i e l d s , have longer c a l v i n g i n t e r v a l s and might have been c u l l e d more fr e q u e n t l y f o r breeding problems, thus reducing t h e i r length of productive l i f e . 6 ) High producers i n the f i r s t l a c t a t i o n w i t h i n the herd had longer c a l v i n g i n t e r v a l s than t h e i r herdmates producing l e s s m i lk. Higher t o t a l l i f e t i m e production of cows w i t h longer c a l v i n g i n t e r v a l s was due to more days i n production since production perday of l i f e was n e g a t i v e l y - 118 -c o r r e l a t e d w i t h c a l v i n g i n t e r v a l . I t appears t h a t farmers c o n s i d e r p r o d u c t i o n i n t h e c u r r e n t l a c t a t i o n , i r r e s p e c t i v e o f l a c t a t i o n l e n g t h , when making c u l l i n g d e c i s i o n s and a l s o t h a t t h e y a l l o w more chances f o r c o n c e p t i o n t o o c c u r i n h i g h y i e l d i n g cows l a t e r i n l i f e t han t h e y p e r m i t i n e a r l i e r l a c t a t i o n s . 7) G e n e t i c t r e n d s i n p r o d u c t i o n and l o n g e v i t y t r a i t s were p o s i t i v e among t h e da u g h t e r s o f s i r e s b o r n d u r i n g 1946 t h r o u g h 1960, though t h e r a t e o f p r o g r e s s p e r y e a r i n f i r s t l a c t a t i o n m i l k and f a t y i e l d s were lower t h a n o t h e r e s t i m a t e s r e c e n t l y r e p o r t e d f o r d i f f e r e n t H o l s t e i n p o p u l a t i o n s i n U.S. and Canada. These t r e n d s j u s t i f y t h e use o f s i r e groups i n s i r e e v a l u a t i o n s as w e l l as i n g e n e t i c parameter e s t i m a t e s f o r p r o d u c t i o n and l o n g e v i t y t r a i t s . G r o u p ing by y e a r o f s i r e ' s b i r t h d e f i n e s s e v e r a l s u b - p o p u l a t i o n o f s i r e s w i t h d i f f e r e n t means and a l s o removes b i a s due t o g e n e t i c t r e n d s . 8) The h e r i t a b i l i t y e s t i m a t e s o b t a i n e d f o r f i r s t l a c t a t i o n y i e l d s a r e w e l l w i t h i n t h e range o f l i t e r a t u r e v a l u e s . Due t o t h e h i g h economic v a l u e and moderate h e r i t a b i l i t y o f f i r s t l a c t a t i o n m i l k y i e l d , and s i n c e i t can be measured e a r l y i n an a n i m a l ' s l i f e , dairymen would be a d v i s e d t o c o n t i n u e s e l e c t i n g f o r h i g h f i r s t l a c t a t i o n m i l k y i e l d . T h i s w i l l l e a d t o s i m u l t a n e o u s p o s i t i v e changes i n l i f e t i m e p r o d u c t i o n and l o n g e v i t y t r a i t s . - 119 -9) S e l e c t i o n f o r t o t a l l i f e t i m e p r o d u c t i o n and l o n g e v i t y measured e i t h e r as l e n g t h o f p r o d u c t i v e l i f e o r as number o f l a c t a t i o n s , would not be e f f e c t i v e due t o t h e low h e r i t a b i l i t y o f t h e s e t r a i t s . A f u r t h e r i m p l i c a t i o n o f t h e s e r e s u l t s i s t h a t any marked improvement i n t h e o v e r a l l l o n g e v i t y o f d a i r y c a t t l e can o n l y be a c h i e v e d by improvements i n n u t r i t i o n a l , p a t h o l o g i c a l and o t h e r e n v i r o n m e n t a l f a c t o r s w h i c h e x e r t an i n f l u e n c e on t h e w e a r a b i l i t y o f cows. However, w i t h i n t h e s e major i n f l u e n c e s , t h e cows w h i c h remain l o n g e s t i n t h e h e r d w i l l n a t u r a l l y l e a v e t h e l a r g e s t number of o f f s p r i n g t h u s w i l l c r e a t i n g t h e o p p o r t u n i t y f o r a u t o m a t i c s e l e c t i o n f o r l o n g e v i t y . 10) S e l e c t i o n on performance t r a i t s o f f i r s t l a c t a t i o n seems most d e s i r a b l e f o r c h a n g i n g l i f e t i m e p r o d u c t i o n s i n c e s e l e c t i o n on l i f e t i m e t r a i t s i s not p r a c t i c a l . The postponement o f s e l e c t i o n u n t i l i n f o r m a t i o n i s a v a i l a b l e on l i f e t i m e t r a i t s would g r e a t l y i n c r e a s e t h e c o s t s o f m a i n t a i n i n g p o t e n t i a l r e p l a c e m e n t s t o c k s u n t i l r e c o r d s on t h e dam o r s i r e ' s progeny a r e a v a i l a b l e , and t h u s reduce t h e g e n e t i c p r o g r e s s p e r y e a r . F o r t u n a t e l y , t h e g e n e t i c c o r r e l a t i o n s o f f i r s t l a c t a t i o n m i l k w i t h l i f e t i m e m i l k and m i l k per day o f p r o d u c t i v e l i f e a r e p o s i t i v e and h i g h r a n g i n g from .56 t o .93. S i n c e t h e h e r i t a b i l i t y o f f i r s t l a c t a t i o n m i l k y i e l d (.22) i s much h i g h e r t h a n t h e h e r i t a b i l i t y o f l i f e t i m e m i l k (.11), i n d i r e c t s e l e c t i o n f o r l i f e t i m e m i l k u s i n g f i r s t l a c t a t i o n m i l k as t h e s e l e c t i o n - 120 -c r i t e r i o n would be about 79% as a c c u r a t e as d i r e c t s e l e c t i o n f o r l i f e t i m e m i l k y i e l d - I n d i r e c t s e l e c t i o n f o r m i l k p e r day o f p r o d u c t i v e l i f e h a v i n g an e s t i m a t e o f h e r i t a b i l i t y o f s i m i l a r magnitude (.21) as t h a t o f f i r s t l a c t a t i o n m i l k would be 95% as a c c u r a t e as d i r e c t s e l e c t i o n f o r m i l k p e r day o f p r o d u c t i v e l i f e due t o t h e v e r y h i g h g e n e t i c c o r r e l a t i o n (.93) between t h e two t r a i t s . 11) The h i g h e r g e n e t i c c o r r e l a t i o n between l a s t l a c t a t i o n m i l k and t o t a l l i f e t i m e m i l k (.87) compared w i t h t h a t between f i r s t l a c t a t i o n m i l k and t o t a l l i f e t i m e m i l k (.56) su g g e s t s t h a t farmers s h o u l d pay a t t e n t i o n t o y i e l d i n t h e l a c t a t i o n i m m e d i a t e l y p r e c e d i n g when making a c u l l i n g d e c i s i o n . 12) The r e s u l t s o f t h i s s t u d y l e n d no s u p p o r t whatsoever t o s u g g e s t i o n s t h a t s e l e c t i o n based on f i r s t l a c t a t i o n m i l k y i e l d w i l l reduce t h e w o r k i n g l i f e o f d a i r y c a t t l e ; r a t h e r t h e y p o i n t c l e a r l y i n t h e o p p o s i t e d i r e c t i o n . I n t h i s p o p u l a t i o n o f H o l s t e i n cows t h e c o r r e l a t i o n between f i r s t l a c t a t i o n m i l k y i e l d and t h a t i n t h e l a s t l a c t a t i o n ( b e a r i n g i n mind t h a t we a r e c o r r e l a t i n g t h e f i r s t l a c t a t i o n w i t h i t s e l f i n o n e - t h i r d o f t h e data) i s .83, whereas between h e i f e r m i l k y i e l d and l e n g t h o f p r o d u c t i v e l i f e , i t i s .44. These r e s u l t s i n d i c a t e t h a t t h e e v a l u a t i o n of A . I . s i r e s on the b a s i s of t h e i r d a u g h t e r s f i r s t l a c t a t i o n l e v e l of m i l k p r o d u c t i o n would r e s u l t i n proven b u l l s whose d a u g h t e r s w i l l produce w e l l i n l a t e r l i f e and remain i n the h e r d l o n g e r . - 121 -13) T h i s s t u d y has shown t h a t t h e r e i s a c l o s e r e l a t i o n s h i p between the b r e e d i n g v a l u e s o f s i r e f o r f i r s t l a c t a t i o n m i l k and t o t a l l i f e t i m e m i l k (.46). T h i s means t h a t t h e d i f f e r e n c e s between s i r e s i n t h e i r h e i f e r progeny t e s t w i l l be m a i n t a i n e d i n t h e i r d a u g h t e r ' s t o t a l l i f e t i m e p r o d u c t i o n ; t h i s combines l e n g t h o f p r o d u c t i v e l i f e w i t h l e v e l o f p r o d u c t i o n p e r l a c t a t i o n . F o r each k i l o g r a m d i f f e r e n c e i n t h e b r e e d i n g v a l u e o f s i r e f o r f i r s t l a c t a t i o n m i l k , t h e r e was a d i f f e r e n c e of more than 7 kg i n t h e b r e e d i n g v a l u e f o r l i f e t i m e m i l k ; and f o r each 1000 kg d i f f e r e n c e i n b r e e d i n g v a l u e f o r f i r s t l a c t a t i o n m i l k t h e r e was a d i f f e r e n c e o f o v e r 9 months i n t h e b r e e d i n g v a l u e f o r t h e l e n g t h o f p r o d u c t i v e l i f e . These f i n d i n g s c l e a r l y i n d i c a t e t h a t t h e improvement i n l i f e t i m e p r o d u c t i o n and l o n g e v i t y o f d a u g h t e r s can be a c h i e v e d by u s i n g b u l l s w h i c h rank h i g h f o r m i l k p r o o f . G e n e t i c c o r r e l a t i o n s o f f i r s t l a c t a t i o n y i e l d s w i t h l i f e t i m e p r o d u c t i o n and l o n g e v i t y a r i s e b o t h from p l e i o t r o p y and from s e l e c t i o n f o r m i l k p r o d u c t i o n . Because of t h i s c o n f o u n d i n g , t h e g e n e t i c c o r r e l a t i o n s o b t a i n e d gave a measure o f b o t h t h e s e l e c t i o n i n t e n s i t y f o r m i l k p r o d u c t i o n and t h e g e n e t i c a s s o c i a t i o n o f m i l k p r o d u c t i o n w i t h l i f e t i m e t r a i t s . These c o r r e l a t i o n s would a l s o be dependent on the i n t e n s i t y o f i n v o l u n t a r y c u l l i n g f o r t r a i t s o t h e r t h a n m i l k p r o d u c t i o n . I f i n t e n s e s e l e c t i o n f o r m i l k p r o d u c t i o n causes a sharp i n c r e a s e i n t h e r a t e o f i n v o l u n t a r y c u l l i n g , t h e - 122 -i n t e n s i t y o f s e l e c t i o n f o r p r o d u c t i o n and a l s o t h e g e n e t i c c o r r e l a t i o n between m i l k p r o d u c t i o n and t h e l e n g t h o f h e r d l i f e would be e x p e c t e d t o d e c r e a s e i n the n e x t g e n e r a t i o n However, i t would be d i f f i c u l t t o o b t a i n t h e s e c o r r e l a t i o n s f r e e from c o n f o u n d i n g w i t h s e l e c t i o n p r e s s u r e f o r m i l k y i e l d . P o p u l a t i o n s i n which t h e r e i s no c u l l i n g f o r m i l k p r o d u c t i o n and o t h e r f a c t o r s such as udder breakdown, w h i c h e x e r t t h e i r e f f e c t s as low m i l k p r o d u c t i o n , w i l l g i v e c o r r e l a t i o n e s t i m a t e s f r e e from s e l e c t i o n e f f e c t s . S e l e c t i o n f o r l o n g p r o d u c t i v e l i f e w i l l be f e a s i b l e o n l y i f p r a c t i s e d on s i r e s o f young A . I . b u l l s , s i n c e o n l y a few s i r e s a r e needed t o c o n t r i b u t e t o t h e n e x t g e n e r a t i o n o f young s i r e s , and o n l y i f g e n e t i c a l l y v a r i a b l e p r e d i c t o r s of l o n g e v i t y w h i c h can be measured e a r l y i n l i f e a r e found. I n f o r m a t i o n on e a r l y p r o d u c t i v e and r e p r o d u c t i v e performances such as t h e p e r c e n t a g e s of a s i r e ' s d a u g h t e r s not c o m p l e t i n g t h e i r f i r s t l a c t a t i o n , and the p e r c e n t a g e s of a s i r e ' s y e a r l i d a u g h t e r s f a i l i n g t o c o n c e i v e c o u l d be measured e a r l y i n t h e d a u g h t e r ' s l i f e . These c o u l d be v a l u a b l e i f s i g n i f i c a n t d i f f e r e n c e s e x i s t i n t h e s e t r a i t s among b u l l s . 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S u r v i v a l r a t e s o f t e s t e d d a u g h t e r s o f s i r e s i n a r t i f i c i a l i n s e m i n a t i o n . J . D a i r y S c i . 57: 1394-1400. - 130 -S c h a e f f e r , L.R., M.G. Freeman and E.B. B u r n s i d e . 1975. E v a l u a t i o n o f O n t a r i o H o l s t e i n d a i r y s i r e s f o r m i l k and f a t p r o d u c t i o n . J . D a i r y S c i . 58: 109-115. Se a t h , D.M. 1940. The i n t e n s i t y and k i n d o f s e l e c t i o n a c t u a l l y p r a c t i s e d i n d a i r y h e r d s . J . D a i r y S c i . 23: 931-951. Sm i t h , J.W. and J.E. L e g a t e s . 1962. R e l a t i o n o f days open and days d r y t o l a c t a t i o n m i l k and f a t y i e l d s . J . D a i r y S c i . 45: 1192-1198. Spooner, R.L. 1978. Reasons f o r c u l l i n g i n d a i r y h e r d s . P r o c . of B r i t i s h C a t t l e B r e e d e r ' s c l u b m e e t i n g , Cambridge, J a n u a r y 197 8; pp. 4 3-4 8. S w i g e r , L.A., W.R. Harvey, D.O. E v e r s o n and K.E. Gregory. 1964. The v a r i a n c e o f i n t r a c l a s s c o r r e l a t i o n i n v o l v i n g group w i t h one o b s e r v a t i o n . B i o m e t r i c s 20: 818-826. T a l l i s , G.M. 1959. Sampling e r r o r s o f g e n e t i c c o r r e l a t i o n c o e f f i c i e n t s c a l c u l a t e d from a n a l y s i s o f v a r i a n c e and c o v a r i a n c e . A u s t . J . S t a t . 1: 35-43. T r i m b e r g e r , G.W. and M.G. F i n c h e r . 1956. R e g u l a r i t y o f e s t r u s , o v a r i a n f u n c t i o n and c o n c e p t i o n r a t e s i n d a i r y c a t t l e . New York Agr. E x p t . S t a . , B u l l . 911. TRP. 1977. T r i a n g u l a r R e g r e s s i o n Package. Computing C e n t r e , U n i v e r s i t y o f B r i t i s h C o lumbia, Vancouver. Van V l e c k , L.D. 1964. F i r s t l a c t a t i o n performance and h e r d l i f e . J . D a i r y S c i . 47: 1000-1004. Van V l e c k , L.D. 1964. G e n e t i c parameters of f i v e - m o n t h l a c t a t i o n r e c o r d s . J . D a i r y S c i . 47: 421-425. Van V l e c k , L.D. 1966. Change i n v a r i a n c e components a s s o c i a t e d w i t h m i l k r e c o r d s w i t h t i m e and i n c r e a s e i n mean p r o d u c t i o n . J . D a i r y S c i . 49: 36-40. Van V l e c k , L.D. , L.H. W a d d e l l and C R . Henderson. 1961. Components o f v a r i a n c e a s s o c i a t e d w i t h m i l k and f a t r e c o r d s o f a r t i f i c i a l l y s i r e d H o l s t e i n d a u g h t e r s . J . Anim. S c i . 20: 812-816. Van V l e c k , L.D. and G.E. B r a d f o r d . 1965. Comparison of h e r i t a b i l i t y e s t i m a t e s f o r daughter dam r e g r e s s i o n and p a t e r n a l h a l f - s i b c o r r e l a t i o n . J . D a i r y S c i . 48: 1372-1375. - 131 -Verde, O.G., C.J. W i l c o x , F.G. M a r t i n and C.W. Reeves. 1972. G e n e t i c t r e n d s i n m i l k p r o d u c t i o n i n F l o r i d a D a i r y Herd Improvement' A s s o c i a t i o n h e r d s . J . D a i r y S c i . 55: 1010-1012. Whi t e , J.M. and J.R. N i c h o l s . 1965. R e l a t i o n s h i p s between f i r s t l a c t a t i o n , l a t e r performance, and l e n g t h o f he r d l i f e i n H o l s t e i n - F r i e s i a n c a t t l e . J . D a i r y S c i . 48: 468-474. W i l c o x , C . J . , S.N. Gaunt and B.R. F a r t h i n g . 1971. G e n e t i c -i n t e r r e l a t i o n s h i p s o f m i l k c o m p o s i t i o n and y i e l d . S o u t h e r n C o o p e r a t i v e S e r i e s B u l l . 515. A g r i c . Exp. S t a t . U n i v e r s i t y o f F l o r i d a , G a i n s v i l l e , F l o r i d a . W i l c o x , C.J., K.O. P f a u and J.W. B a r t l e t t . 1957. An i n v e s t i g a t i o n o f the i n h e r i t a n c e o f female r e p r o d u c t i v e performance and l o n g e v i t y , and t h e i r i n t e r r e l a t i o n s h i p s w i t h i n a H o l s t e i n - F r i e s i a n h e r d . J . D a i r y S c i . 40: 942-947. W i l t o n , J.W., E.B. B u r n s i d e and J.C. Rennie. 1967. The e f f e c t s o f days d r y and days open on t h e m i l k and b u t t e r f a t p r o d u c t i o n of H o l s t e i n - F r i e s i a n c a t t l e . Can. J . Anim. S c i . 47: 85-90. Wunder, W.W. and L.D. M c G i l l i a r d . 1967. Seasons o f c a l v i n g and t h e i r i n t e r a c t i o n s w i t h age f o r l a c t a t i o n a l m i l k y i e l d . J . D a i r y S c i . ( A b s t r . ) 50: 986. 5, Appendix 1. Year l e a s t square means f o r Group 1 cows. Least Square Means + SE m „ 2 T r a i t 1958 1959 1960 1961 1962 1963 1964 1965 O v e r a l l No.of obs. 2482 2311 2751 2850 3075 3307 3617 2625 23018 Milk 1 4286+23 4272+23 4253+22 4372+22 4533+21 4575+21 4627+21 4728+22 4456+16 Fat 1 158+.9 159+.9 158+.8 164+.8 168+.8 170+.8 173+.8 176+.8 166+.6 Milk HYl -954+18 -933+19 -997+17 -992+17 -996+16 -1013+16 -1040+15 -1019+17 -989+8 Fat HYl -35+.3 -34+.7 -37+.6 -36+.6 -36+.6 -38+.6 -39+.6 -39+.6 -37+.3 LLL 340+1.6 341+1.7 340+1.6 344+1.5 345+1.5 346+1.4 347+1.4 355+1.6 345+.8 1 Milk T 4691+33 4674+34 4659+32 4824+31 5010+30 5071+30 5118+29 5318+32 4921+20 M Fat T 174+1.3 175+1.3 175+1.2 182+1.2 187+1.2 190+1.1 193+1.1 200+1.2 184+.8 C O N J Milk/D 13.8+.07 13.7+.07 13.7+.07 14.0+.07 14.5+.06 14.6+.06 14.7+.06 15.0+.07 14.3+.05 1 Fat/D .51+.003 .51+.003 .51+.003 .53+.003 .54+.003 .55+.003 .55+.003 .56+.003 .53+.002 Cullage 40.9+.05 40.9+.06 40.9+.05 41.0+.05 41.0+.05 41.1+.05 41.1+.05 41.3+.05 41.0+.03 P l i f e 11.2+.05 11.2+.06 11.2+.05 11.3+.05 11.3+.05 11.4+.05 11.4+.05 11.7+.05 11.3+.03 1 Year of f i r s t c a l v i n g . 2 Units are i n kg, -except Cullage, P l i f e are i n months and LLL i s i n days. Appendix 2. Year l e a s t square means f o r Group 2 cows. Least Square Means +SE T r a i t 2 1958 1959 1960 1961 1962 1963 1964 1965 O v e r a l l No.of obs. 1907 2424 3196 3759 4228 4694 4678 3695 28581 Milk 1 4768+25 4706+23 4707+22 4810+22 4938+21 5052+20 5123+21 5180+21 4911+18 Fat 1 176+1.0 175+.9 176+.9 181+.8 184+.8 188+.8 192+.8 194+.8 183+.7 Milk HYl -485+19 -515+17 -558+15 -596+14 -588+14 -579+13 -606+13 -605+14 -567+8 Eat HYl -17+.7 -19+.6 -20+.6 -21+.5 -22+.5 -22+.5 -23+. 5 — 23+.5 -21+.3 Milk L 5592+35 5640+32 5687+30 5753+29 5839+28 5923+27 5953+27 6006+28 5799+22 Fat L 209+1.4 211+1.3 213+1.2 216+1.1 219+1.1 222+1.1 225+1.1 226+1.1 217.5+.9 LLL 337+2.0 338+1.7 336+1.6 341+1.5 340+1.4 342+1.3 343+1.3 343+1.4 340+.7 Milk T 25853+420 25563+370 24770+337 25379+317 25551+299 26925+282 26129+286 25436+300 25701+174 Fat T 970+16 961+14 937+13 960+12 964+11 1016+11 992+11 962+11 97 0+7 Milk/D 14.4+.07 14.6+.07 14.8+.07 15.0+.06 15. 3+-. 06 15.6+.06 15.7+.06 15.7+.06 15.1+,05 Fat/D .54+.003 .55+.003 .56+.003 .57+.002 .57+.002 .59+.002 .59+.002 .59+.002 .57+.002 Cullage 86.9+.77 85.2+.68 82.9+.62 83.6+.58 83.2+.55 84.9+.51 83.2+.52 81.2+.55 83.9+.31 P l i f e 57.7+.78 56.0+.68 53.7+.62 54.4+.58 53.9+.55 55.7+.51 54.0+.52 52.0+.55 54 .7+%31 # Lact 4.4+.055- 4.3+.048 4.1+.044 4.1+.042 4.1+.039 4.2+.036 4.1+.037 4.0+.039 4.2+.022 1 2 Year of f i r s t c a l v i n g . U n i t s are i n kg except Cullage, P l i f e i n months, LLL i n days and # Lact i n numbers. Appendix 3. .. Season'1' l e a s t square means f o r Group 1 and Group 2 cows. • Least Square Mean + SE GROUP 1 GROUP 2 T r a i t Season 1 Season 2 O v e r a l l Season 1 Season 2 O v e r . i l l No.of obs. 8062 14956 23018 9165 19416 285B1 Mi l k 1 4354+17 4558+16 4456+16 4800+19 5021+18 4911+18 Fa t 1 162+.7 169+.6 166+.6 179+.7 187+.7 183+.7 Milk HYl -1069+11 -909+9 -989+8 • -656+10 -477+9 -567+8 Fat HYl -39+.4 -34+.4 -37+.3 -24+.4 -18+.3 -21+.3 1 Milk L NA NA NA 5781+24 5817+22 5799+22 M Fat L NA NA NA 217+.9 218+.9 217.5+.9 LO •» LLL 343+1.0 347+0.9 345+0.8 342+1.0 339+0.8 340+0.7 1 Milk T 4814+23 5027+21 4921+20 25636+222 25766+185 2570i+174 Fat T 181+.9 188+.8 184.5+.8 970+.8 970+.7 970+.7 Milk/D 14.0+.05 14.5+.05 14.3+.05 15.0±-05 15.3+.05 15.1+.05 Fat/D .53+.002 .54+.001 .53+.002 .56+.002 .57+.002 .57+.002 Cullage 41.0+.03 41.0+.03 41.0+.03 84.1+.40 83.7+.33 83.9+.31 P l i f e 11.3+.03 11.4+.03 11.3+.03 54.9+.4 54.5+.33 54.7+.31 # Lact NA NA NA 4.2+.029 4.2+.023 4.2+.022 1 2 Season 1 (March-August) and season 2 (September-February) of f i r s t c a l v i n g . U n i t s are i n kg except Cullage, P l i f e i n months, LLL i n days and $ Lact i n numbers. - 135 -Appendix 4. S i r e and e r r o r components of variance and covariance. Variance or Covariance Groups 1 and 2 Combined Group 2 T r a i t 3 S i r e E r r o r S i r e E r r o r a M i l k 1 Mil k 1 Fat 1 Mil k HYl Fat HYl M i l k L Fat L LLL Mi l k T Fat T Milk/D Fat/D Cullage P l i f e # Lact Fat 1 Fat 1 Milk HYl Fat HYl Mil k L Fat L LLL M i l k T Fat T Milk/D Fat/D Cullage P l i f e # Lact Milk HYl Mil k HYl Fat.HYl M i l k L Fat L LLL Mi l k T Fat T Milk/D Fat/D Cullage P l i f e # Lact (b) 27053 534 27224 539 29169 540 795 242642 7106 70.60 1.13 333 338 21.76 (b) (b) 43.65 536 43.77 667 50 24.27 8289 409 1.35 0.1235 13.77 13.92 0.9354 27389 541 29454 545 787 247634 7277 71.22 1.14 342 346 22.44 471748 14796 467832 14650 423269 13357 9705 3733298 131382 1034.98 31.42 5456 5508 369.03 661.02 14698 656.84 13309 608 328.16 129725 5301 31.24 1.4855 203.52 205.35 13.8818 481258 15180 420880 13312 9728 3724256 131214 1029.10 31.33 5442 5491 368.01 21653 346 21936 355 18384 122 604.24 144380 2935 55.82 .5739 115.58 116.59 6.10 38.57 361 39.12 280 37.42 21.66 4397 290 .8686 .1086 5.99. 6.03 .3738 22223 370 18962 146.15 617 156387 3413 57.28 .6379 133.76 135.02 7.43 410766 12439 406638 12282 259502 7170 7120.04 2806065 93380 868.05 25.1422 3169.84 3168.26 202.57 572.77 12330 568.04 7303 378.57 242.59 92601 3978 24.9327 1.2290 119.25 119.00 7.7292 418779 12760 257789 7134.67 7033 2808380 93666 864.26 25.0889 3178.34 3175.28 203.60 Cont'd - 136 -T r a i t S i r e E r r o r S i r e E r r o r Fat HYl Fat HYl M i l k L Fat L LLL M i l k T Fat T Milk/D Fat/D Cullage P l i f e # Lact M i l k L Mil k L Fat L LLL Milk T Fat T Milk/D Fat/D Cullage P l i f e # Lact Fat L Fat L LLL Mi l k T Fat T Milk/D Fat/D Cullage P l i f e # Lact LLL LLL Milk T Fat T Milk/D Fat/D Cullage P l i f e # Lact (b) 43.87 678 50.26 24.12 8507 416.49 1.3765 .1240 14.13 14.29 .9633 (b) 46124 1238 1345 492391 16842 92.4 5 2.18 771 778 52.18 (b) 78.94 44.07 17566 791 1.98 .1695 30.49 30.74 2.10 (b) 80.64 16336 605.04 2.52 .0822 27.21 27. 44 1.75 £79.34 13233 606.26 329.63 129925 5315.39 31.0347 1.4819 203.96 205.69 13.9203 1281499 45103 27465 9990406 367824 1604 53.19 16779 16948 1164.66 1928.18 1003.95 363312 14392 52.15 2.4266 628.72 635.12 43.64 4991.48 186725 7071.30 22.03 . 8729 313.58 312.86 9.81 39.64 300.30 38.30 22.09 4814 306.68 .9196 .1111 6.60 6.64 .4181 31212 661 1077 364642 11706 74.76 1.53 488 489 31.88 61.17 37.61 12246 636 1.29 .1519 20. 07 20.11 1.35 85.90 16689 640.62 2.60 .0992 25.81 25.84 1.60 588.48 7244.61 377.46 239.68 93218 4009.82 24.8318 1.2280 120.48 120.18 7.8451 1120792 38701 32833 6989656 251243 1423.83 46.45 10009 10023 648.56 1717.07 1222.30 241882 9957 44.95 2.1773 364.58 364.93 23.46 5138.57 281266 10628.11 30.29 1.1758 476.73 477.47 21.13 Cont'd - 137 -T r a i t S i r e E r r o r S i r e E r r o r Milk T Milk T (b) 6895357 238364462 5976508 .216881820 Fat T 258369 8946578 223141 8104100 Milk/D 859.53 14148.41 786.68 15066.57 Fat/D 31.03 514.48 27.37 533.74 Cullage 11857 443989 9574 390128 P l i f e 11931 446865 9554 390507 # Lact 824.25 31936.28 652.87 27579.59 Fat T Fat T (bl 10420 341654 9474 310425 Milk/D 27.09 505.72 23.56 531.33 Fat/D 1.51 20.95 1.49 22.00 Cullage 455.23 16781.99 374.80 14733.07 P l i f e 457.96 16890.28 373.91 14746.69 # Lact 31.75 1206.15 25.68 1040.70 Milk/D Miik/D (b) .2146 3.9402 .2014 3.5783 Fat/D .0040 .1253 . 0037 .1131 Cullage 1.22 19.37 .9262 19.2611 P l i f e 1.23 19.44 .9275 19.2386 # Lact .0820 1.3621 .0589 1.3275 Fat/D Fat/D (b) .00040567 .00608623 .00041307 .00546823 Cullage .0524 .7544 . 0421 .7365 P l i f e .0529 .7573 .0421 .7353 # Lact .0036 . 0529 .0028 . 0506 Cullage Cullage (b) 21.13 865.51 16.55 745.74 P l i f e 21.25 871.07 16.50 746.22 # Lact 1.47 62.25 1.14 52.70 P l i f e P l i f e (b) 21.38 877.16 16.46 747.26 # Lact 1.48 62.67 1.14 52.74 # Lact # Lact (b) .1035 4.5771 .0794 3.8460 a U n i t s are kg , except C u l l a g e , P l i f e i n month and LLL i n days . b Values are components of var i a n c e . Appendix 5. Environmental c o r r e l a t i o n s f o r Groups 1 and 2 combined (above diagonal) and Group 2 (below diagonal) cows. T r a i t s M i l k 1 Fat 1 M i l k HYl Fat HYl Milk L Fat L LLL Milk T Fat T Milk/D Fat/D Cullage P l i f e « La( Milk 1 .92 .98 .89 . 50 .46 . 17 .33 .32 .73 .64 .25 .25 .24 Fat 1 .91 .90 .98 .46 .48 .16 .31 .32 .65 .69 .25 .25 .23 Milk HYl .98 .89 .92 .49 .45 .17 .32 .31 .71 .63 .25 .25 .23 Fat HYl .88 .97 .91 .45 .47 .16 .30 .31 .63 .68 .24 .24 .23 Milk L .34 .30 . 33 .29 .94 .32 .54 .53 .68 .63 .48 .48 .47 Fat L . 30 .32 .29 .31 .93 .31 .51 .53 .62 .67 .46 .46 .44 LLL .13 .12 .13 .12 .42 .41 .14 '.14 . 12 . 13 .12 .12 .03 Milk T .29 .26 .28 .26 .41 .37 .24 .99 .43 . 41 .98 .98 .97 Fat T .27 .27 .27 .27 .40 .39 .24 .99 .42 .42 .98 .98 .97 Milk/D .69 .61 . 68 .59 .69 .61 .19 .52 .50 .89 .31 .30 .30 Fat/D .61 .65 .60 .64 .64 .68 .19 .49 .51 .91 .30 .30 .29 Cullage .18 .18 .18 .18 . 32 .30 .22 .97 .97 .36 . 36 1.00 .99 P l i f e .18 .18 .18 .18 .32 .29 .22 .97 .97 .36 .35 1.0 .99 # Lact .17 .16 .16 .16 .29 .26 .12 .96 .96 .35 .34 .98 .98 Appendix 6. Expected breeding values (EBV) of s i r e s f o r production and longevity t r a i t s . T r a i t s S i r e No. of I.D. Daughters Milk 1 Fat 1 Milk T Fat T Milk/D Fat/D P l i f e # Lact 197003 135 75.31 -4.82 197782 74 -649.20 -17.78 198507 120 -72.99 4.74 199659 87 61.21 -16.94 205583 300 -424.47 -3.80 205597 245 52.22 6.53 207873 150 -268.02 -11.10 212300 92 -810.53 -17.70 212665 32 -145.84 -7.04 212878 51 -529.44 -24.82 213155 373 -354.63 -22.83 213459 52 128.76 -11.97 2137*9 786 -114.49 -14.51 214469 350 351.77 35.62 214704 87 38.47 -8.85 215077 120 -645.61 -9.10 217549 174 -251.92 -5.4) 218036 654 180.70 -2.69 218115 106 -255.10 3.80 219120 101 520.06 29.26 220731 241 -159.05 6.83 221015 173 -589.15 -17.3* 227079 618 108.61 0.46 228078 121 57.36 6.40 229203 397 105.09 2.90 229512 1017 -68.73 15.81 230488 118 319.2 6 22.43 231300 199 -64.20 2.27 2)3108 49 -173.28 -20.5* 233528 962 488.28 10.00 236866 151 184.95 13.17 236937 166 268.94 -*.49 3566.61 -7404.72 945.89 -4366.87 -9916.21 4326.35 212.69 -2568.47 -1582.65 r8748.2 ) -6438.59 3766.48 5880.78 -838. 07 3925.58 -7479.14 1488.74 -61.52 -3098.27 6049.15 4885.82 -7959.94 -4632.40 -179.02 2033.87 7101.90 1967.79 -923.33 -1359.36 -426.83 7066.91 -7059.72 98.99 -257.92 73.26 -236.11 -329.38 172.26 -3.38 -47.18 -44.91 -35). 30 -272.55 108.83 177.86 41.12 126.71 -236.49 68.88 -38.88 -72.14 235.47 261.08 -303.68 -191.77 3.28 75.11 352.21 66.03 -15.6* -99.94 -54.1* 291.4* -30*.5* 0.1253 -1.1125 -0.37*1 0.2037 -1.501* 1.07*9 -0.7*71 -1.8331 -0.**90 -1.2971 -1.395* 0.4913 0.1*52 0.6591 0.2827 -2.3657 -0.8925 0.5751 -0.3899 1.7123 -0.6*63 -2.26*5 0.0562 -0.3915 0.0*19 0.5*61 0.90*4 -0.3901 -0.0995 1.0708 1.0195 -0.1331 -0.0232 -0.0268 0.0088 -0.0505 -0.0254 0.0494 -0.0317 -0.0272 -0.0152 -0.0704 -0.0853 -0.0266 -0.0237 0.0864 -0.0102 -0.0436 -0.0259 -0.0076 0.0256 0.0649 0.0205 -0.0724 -0.0092 -0.0082 -0.0017 0.0802 0.0512 0.0009 -0.0533 0.0123 0.0618 -0.0453 7.8184 -14.6979 3.492fir -8.3686 -17.0079 5.0081 I. 2729 -2.5372 -5.3717 -14.5088 -11.7525 6.5489 12.3800 -2.4207 7.9115 -11.3617 4.9950 -1.911* -6.0609 4.7932 9.7723 -10.9026 -8.5647 -0.77*1 4.4214 11.8512 1.4860 -2.7704 -0.6894 -2.4409 I I . 7488 -12.6813 0.5160 -1.0042 0.3299 -0.6960 -1.1326 0.2334 0.1562 -0.0821 -0.3864 -1.0550 -0.8399 0.4819 0.8476 -0.1563 0.4577 -0.6640 0.4)57 -0.2544 -0.41)6 0.2498 0.6182 -0.6985 -0.6600 -0.0467 0.3316 0.8768 0.1682 -0.1590 0.0336 -0.2560 0.8299 -1.0011 Cont'd T r a i t s 3 S i r e No. of I.D. Daughters M i l k 1 Fat 1 M i l k T Fat T 237136 1053 109.92 16.80 -6*3.58 2*. 51 237445 473 276.97 28.22 7748.00 370.41 237674 198 -142.45 -14.98 3010.01 82.94 238433 116 843.33 34.10 -9083.49 -373.09 239301 446 453.92 0.72 5157.86 113.11 23974* 109 -418.03 -30.46 -8426.75 -366.13 240227 101 -83.79 -7.88 -12607.29 -497.88 2*1377 263 -454.80 -6.51 -2301.23 -59.6* 241845 93 336.41 8.39 1110.37 50.38 241933 380 220.52 7.30 5113.76 178.*l 241947 64 •189.80 -2.15 -3926.59 -138.60 241954 96 274.15 10.17 2.55 -7.19 2*203) 53 22.83 -13.67 -49.43 -40.43 242423 201 283.41 0. 78 6054.92 176.46 2*2 865 43 60.56 2*.)9 -1123.49 15.70 243319 201 72.77 7.1* 404.44 32.03 243527 101 11.38 -*.*6 818.05 0.76 244044 143 -139.11 -18.00 -2454.72 -126.13 244211 39 -227.03 -1.46 1069.25 80. 84 2**468 258 -301.52 -10.97 -4423.90 -164.42 244626 269 181.39 -6.48 2456.96 16. 19 2*519* 1*7 -127.9* 2.83 -3*9.51 23.91 245 302 34 350.53 -10.26 -3050.56 -184.24 245456 11*2 -139.8* -3.76 -3085.12 -99.29 245551 59 -302.20 -15.74 -875.46 -47.95 246338 499 443.11 -0.47 4342.40 91.75 246359 243 353.46 5.58 597.53 9.36 246610 180 -799.71 -28.62 -10894.63 -403.56 248207 65 153.43 5.67 1373.49 71.81 248598 141 -352.81 1.23 4016.80 210.24 248997 37* -289.38 -28.46 -115.88 -71.67 249631 118 -8.86 -0.75 -4260. 76 -154.04 2*9838 167 -567.1* -6.8* 866.80 120.55 250051 101 - 108.56 8.65 -5907.50 -189.01 250585 77 -*36.68 -4.99 -1878.5* -56.61 250 735 562 -31.02 16.51 6936.99 351.38 Milk/D Fat/D P l i f e # Lact -0.1870 0.8536 -0.6599 1.0926 0.7675 -1.1726 -0.1*72 -1.6692 0.7208 0.538* -0.8552 0.2519 0.2643 1.5009 0.4)88 -0.2821 0.7201 -0.*185 -0.8768 -0.4407 0.7541 -0.3057 0. 5989 -0. 3*01 -0.7*73 1. )78) 0.6769 -1.7570 0.1996 -1.1654 -0.1942 -0.3826 -1.0937 0.2560 -0.07)9 0.6172 0.03)1 0.0889 -0.0*85 0.0326 -0.0238 -0.0960 -0.0262 -0.0352 0.0221 0.0211 -0.0227 0.0103 -0.02*9 0.0213 0.0870 0.0032 0.0093 -0.0488 -0.0087 -0.0150 -0.0219 0.0188 -0.0451 -0.0043 -0.0397 -0.0032 0.0051 -0.0667 0.0203 0.0002 -0.0611 -0.0090 0.0131 0.0406 0.03*) 0.0849 0.1901 13.5771 8.6150 -17.6157 10.1920 -15.3176 -23.3002 0.1593 0.6096 9.1113 -6.2746 -1.8393 -0.0478 8.4021 -2.0744 0.9598 -1.3202 -3.8227 4.)889 -8.6781 3.0675 0.8667 -8.1075 -4.8)35 0.6465 5.231) -0.8483 -19.7661 3.8876 11.9898 0.8616 -6.8075 3.4592 -13.7175 - ) . 2 ) ) 6 11.2272 -0.0809 0.9329 0.50*5 -1.3315 0.7479 -1.1076 -1.5912 0.1123 0.1168 0.6119 -0.4401 -0.2181 0.0149 0.6017 -0.1132 0.0827 -0.0881 -0.2217 0.3)07 -0.5623 0.1685 0.1832 -0.6530 - 0 . ) 7 l l 0.0540 0.33)1 -0.1203 -1.3240 0.1322 0.8682 0.0102 -0.5453 0.2873 -0.8634 -0.163) 0.6524 Cont'd T r a i t s 3 S i r e No. of Fat T I.D. Daughters M i l k 1 Fat 1 Milk T 251054 46 -243.28 -5.81 -5283.66 -164.85 251 647 154 141.42 1.14 3300.87 112.31 251671 382 215.53 -8.67 92.60 -67.90 252189 32 443.17 13.35 6846.71 274.95 252334 116 -309.76 -9.32 25.92 -1.48 252697 210 442.66 10.21 5581.74 19).87 254196 49 -285.99 -23.51 -2555.76 -151.43 254293 456 -23.08 -10.34 -1445.86 -89.76 254339 186 -377.97 9.31 -1006.59 31.99 254 3 55 349 -482.15 11.67 -6720.33 -151.84 25444) 494 328.31 23.99 1953.75 113.48 254568 275 123.57 -2.91 -3359.61 -120.73 255055 64 108.88 3.01 -3296.28 -134.06 259163 252 -299.75 13.58 8095.22 439.16 255164 85 437.10 9.01 2247.32 47.88 255165 161 16.67 -0.84 -6441.40 -242.11 255184 245 122.01 -0.26 1369.25 32.82 255362 571 -273.93 3.14 -8231.83 -260.00 255835 157 192.53 0.01 5164. 14 177.12 255838 109 102.82 -11.22 -1329.61 -87.83 255034 155 187.04 -5.45 -1543.24 -111.74 256075 179 333.05 10.12 319).18 120.77 256451 205 -707.29 -28.12 -5415.10 -222.93 256645 183 -165.62 -5.60 775.26 31.38 256 960 93 -107.31 -9.97 -9713.21 -389.57 257451 62 5.32 -9.77 -8607.17 -390.82 257571 104 267.84 5.68 -2462.80 -117.63 258319 81 -172.31 -12.32 -10031.78 -456.86 258330 85 -509.50 -4.29 956.85 79.88 258920 167 -70.38 -9.44 1122.58 23.81 259176 187 41.90 -1.44 4174.77 169.12 259214 93 -201.88 -17.90 -11136.98 -460.74 259542 211 -122.88 4.10 859.74 72.54 259958 353 443.95 15.27 12159.46 474.56 260 0 7 6 83 -219.85 -16.30 2675.52 88.68 260293 313 -289.95 -9.09 -7940.86 -287.64 Milk/D Fat/D P l i f e t Lact -0.711) -0.1230 0.8350 2.0993 -1.1005 1.4858 0.5952 0.2016 -1.0755 -1.8675 0.6128 0.2386 -0.6887 -0.1504 0.5)67 0.2724 0.5417 -0.8708 1.2521 -0.2757 0.1349 1.2919 -1.8034 -0.2727 -0.1250 -0.0886 0.2919 -0.9176 -0.9847 -0.3292 0.7)55 -0.3792 -1.1314 1.5173 -0.6886 -1.4324 -0.0091 -0.0198 -0.0229 0.0825 -0.0311 0.0)85 -0.0104 -0.0220 0.0210 0.0262 0.0611 -0.0064 -0.0333 0.0839 -0.0147 0.0049 0.0014 0.0127 0.0316 -0.0504 -0.0363 0.04)8 -0.0707 -0.0124 -0.0244 -0.0492 -0.0023 -0.0560 0.0063 -0.0282 0.029) -0.0481 -0.0138 0.0577 -0.0307 -0.0376 -9.2757 6.1514 -1.8603 10.1281 2.9714 8.6644 -4.6955 -3.9817 0.4084 -8.0185 3.9296 -6.3766 -5.1216 15.3919 4.9958 -11.2 640 1.7296 -14.2376 6.8050 -0.3570 -2.7294 2.8303 -7.9902 0.7973 -19.7817 -17.3281 -4.9975 -17.2086 3.8119 3.1888 7.3152 -20.6640 3.)622 20.3350 6.7233 -11.4387 -0.7667 0.3487 -0.1469 0.7182 0.2138 0.6298 -0.2824 -0. )16) -0.0545 -0.5909 0.2085 -0.4069 -0.3080 1.0589 0.)7)) -0.8337 0.1)75 -1.0313 0.4939 0.0309 -0.2512 0.1604 -0.5454 0.1385 -1.3554 -1.0932 -0.3740 -1.3076 0.3664 0.0227 0.4202 -1.4071 0.1922 1.2915 0.5022 -0.7836 I I Cont' d T r a i t s 3 S i r e No. of I.D. Daughters Mi l k 1 Fat 1 Milk T Fat T Milk/D Fat/D P l i f e # Lact 250315 96 -145.84 9.77 260599 521 525.43 1.36 261345 148 -296.2 7 -6.93 261442 168 723.41 20.83 261481 182 401.89 17.64 261594 70 71.33 2.75 261992 125 171.18 6.00 262153 111 -640.00 -26.01 262208 265 69.41 -7.53 262241 97 625.27 29.15 262612 254 548.25 9.38 262688 210 -53.98 -7.82 263002 81 -559.25 -17.48 2630)8 244 -85.99 14.15 263332 267 211.45 8.84 26)475 262 393.52 2.66 264804 485 -769.24 -4.18 265)01 311 -331.91 11.43 266128 67 177.77 14.80 266752 88 40.90 5.58 267150 844 422.90 9.77 267260 154 281.65 12.98 267701 140 -17.75 -2.16 268043 335 -218.02 10.44 2686)0 11) 503.82 9.93 271386 118 55.20 -11.27 272170 190 626.64 21.71 272270 67 318.53 9.47 273372 136 -270.10 -11.77 274043 82 41.87 -0.71 274514 80 23.75 -11.96 274558 183 -199.50 -4.86 275932 141 746.30 31.72 278746 246 96.64 17.24 5891.37 10768.28 2486.55 6627.18 1991.40 753.49 4523.82 -9735.54 -2829.83 3824.69 -7671.55 -3647.38 2687.01 8023.93 9329.89 9568.40 -5981.13 306.53 3829.99 - 3806.08 8595.09 9906.30 2615.95 874.50 4038.60 4293.32 5422.99 -88.20 -384.01 2899.11 -1941.37 -270.18 4320.97 1784.16 335.99 329.52 118.65 209.65 84.10 36.68 175.68 -372.34 -153.94 157.02 -325.07 -156.95" 118.38 376.54 363.47 301.82 -141.40 98.61 182.20 -127.58 286.74 387. 72 82.54 100.58 134.33 124.45 188.31 -23.87 -22.52 96.47 -106.58 -15.14 189.21 103.84 -0.10/5 1.6544 -0.4555 2.2201 0.5269 -0.1979 0.5892 -1.7027 0.488) 1.7502 0.8259 -0.6535 -0.6453 -0.4268 -0.0310 0.9554 -2.2472 -0.9433 0.3420 0.5)7) 1.5245 0.901) -0.3928 -0.1967 0.4539 0.3570 1.4783 0.6143 -0. 3248 -0.1139 -0.0775 0.1818 1.6301 -0.1425 0.0458 0.0126 -0.0034 0.0546 0.0227 0.0011 0.0267 -0.0763 -0.0177 0.0930 0.0049 -0.0438 -0.0138 0.0423 0.0021 -0.0050 -0.0095 0.0316 0.0348 0.0299 0.0436 0.0425 -0.0160 0.0502 -0.0014 -0.0237 0.0463 0.0136 -0.0141 -0.0174 -0.0423 0.0156 0.0741 0.0269 13.4921 16.4117 4.0853 9.4141 1.5307 1.8736 8.6523 -16.1687 -5.5324 3.5919 -15.5597 -6.3093 6.2376 18.4281 19.8826 17.7008 -6.9092 3.8296 9.4304 -7.1328 12.9490 16.2694 6.8734 2.2274 7.5595 8.9457 8.2085 -0.8970 -0.5158 6.4608 -3.1814 -0.3885 4.9519 3.7632 1.0012 1.0866 0.3964 0.6745 0.0507 0.1914 0.5438 -1.0674 -0.4752 0.2093 -1.1606 -0.5500 0.4203 1.2562 1.3212 1.3081 -0.4577 0.1762 0.6937 -0.4525 1.0170 1.3209 0.4224 0.2282 0.5458 0.7140 0.6545 -0.1297 0.0299 0.3776 -0.1725 0.0275 0.2900 0.1956 Units are kg, except P l i f e i n months and # Lact i n numbers. PUBLICATIONS Hoque, M. 1968. Repeatability of semen characteristics of yearling beef bul ls. An. S c i . J . of Pakistan 1:34. Hoque, M. and R.J. Cooper. 1968. Relationship between growth rate and semen characteristics in young bulls. An. Sc i . J . of Pakistan. 1:58. Hoque, M. 1968. Heritability of semen characteristics of yearling beef bulls. Presented in 20th All Pakistan Science Conference. Proceedings, Section A, Pg. 132. Hoque, M., M.A. Hashem and Q.M.F. Rahim. 1970. A study on the sea-sonal variation in semen characteristics of Lohi ram under local environmental conditions of Bangladesh Agricultural University sheep farm. Bangladesh J . of An. S c i . 3:1. Huq, M.A., M. Hoque and Q.M.F. Rahim. 1971. A comparative study of l i v a b i l i t y , growth rate, age and weight at sexual maturity of the 4th generation graded Deshi x White Leghorn, Oeshi x New Hampshire and Deshi x White Cornish. Bangladesh J . of An. S c i . 4:13. Rahman, A.M.M., M. Hoque, W.O. Graves and M.A. Lat i f . 1968. Cost of producing broilers up to 12 weeks of age. An. S c i . J . of Pakistan 1:10?. Rahman, M.M., Q.M.F. Rahim and M. Hoque. 1968. A comparative study of the fleece y ie ld , staple length, percentages of different types of wool fibres and fineness of wool in Local x Lohi grade 1 and East Pakistan Indigenous sheep. An. S c i . J . of Pakistan. 1:52. Rahman, M.M., Q.M.F. Rahim and M. Hoque. 1971. A comparative study of wool quality of Local x Lohi grade 1 and grade 2. Bangladesh J . of An. S c i . 4:9. Huq, M.A., M. Hoque, Q.M.F. Rahim and M.A. Lat i f . 1968. A compara-tive study of egg production, egg size, f e r t i l i t y and hatchability of the 3rd generation graded Deshi x White Leghorn, Deshi x New Hampshire, and Deshi x White Cornish. An. S c i . J . of Pakistan. 1:105. J a l i l , M.A., Q.M.F. Rahim and M. Hoque. 1971. Statistical study of some economical traits of cattle in Bangladesh. Bangladesh J . of An. Sci . 4:52. A l i , S .Z . , M. Hoque and M.A. Hasnath. 1 973. A study of the growth and reproductive performance of Black Bengal goats under farm con-di t ions. Indian Vet. J . 50:438. A l i . S.Z. and M. Hoque. 1974. Preservation of bovine semen at room temperature. Bangladesh J . of Agr i . S c i . 1. A l i , M.A. and M. Hoque. 1975. Heritabil ity of body weight and shank length at 8 weeks of age in New Hampshire and R.I.R. chicks. Bangladesh J . of An. S c i . 5:71.. Hoque, M. and John Hodges. 1979. Genetic and phenotypic parameters of lifetime production traits in Holstein cows. Presented at the 74th Annual Meeting of the American Dairy Science Association, June 24-27, 1979, Utah State University, Logan, Utah. J . Dairy S c i . 62 (Abstract): 108. Hoque, M. and John Hodges. 1980. Genetic and phenotypic parameters of lifetime production traits in Holstein cows. Submitted for publication in J . Dairy S c i . Nov. 1979. Hoque, M. and John Hodges. 1980. Lifetime production and longevity of cows related to their s i re 's breeding values. Submitted for publication In J . Dairy S c i . Nov. 1979. 

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