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Canadian/New Zealand genotype-environment interaction trial : comparison of growth traits of Canadian… Kakwaya, Damian Saranga Muhongo 1991

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0 . CANADIAN/NEW ZEALAND GENOTYPE-ENVIRONMENT INTERACTION TRIAL COMPARISON OF GROWTH TRAITS OF CANADIAN AND NEW ZEALAND DAIRY CATTLE IN CANADA by Damian Saranga Muhongo Kakwaya B.Sc.(Agr.)/ U n i v e r s i t y o f B r i t i s h Columbia, Canada 1978 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES Department o f Animal S c i e n c e We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1991 © Damian Saranga Muhongo Kakwaya, 1991 43 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree t h a t the l i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree t h a t permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head of my department or by h i s or her r e p r e s e n t a t i v e s . I t i s understood t h a t copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n permission. Department of / \ v i m n i ~ ^C4£-^OE The U n i v e r s i t y of B r i t i s h Columbia Vancouver, Canada Date DE-6 (2/88) ABSTRACT i i T h i s study, being p a r t of a l a r g e r p r o j e c t - "Canadian/New Zealand GxE I n t e r a c t i o n T r i a l " - i s comparing Canadian and New Zealand s i r e d h e i f e r s f o r growth t r a i t s w i t h i n Canada, s i n c e d i f f e r e n c e s f o r growth t r a i t s were found i n the P o l i s h s t r a i n comparison ( J a s i o r o w s k i et a l . , 1987) and due to s e l e c t i o n programs i n the two c o u n t r i e s . Twenty Canadian H o l s t e i n and twenty New Zealand F r i e s i a n progeny t e s t e d , A.I. b u l l s were randomly mated t o over 1,000 cows i n 10 Canadian herds. 3,539 records of weight and w i t h e r height from 475 h e i f e r s ( i . e . 241 Canadian and 234 New Zealand s i r e d ) were generated. Subsets of the data f o r d i f f e r e n t stages of h e i f e r m a t u r i t y were analyzed s e p a r a t e l y . Herd and s t r a i n e f f e c t s l e a s t squares means were estimated using a n a l y s i s of v a r i a n c e . Genetic and phenotypic and c o r r e l a t i o n s and h e r i t a b i l i t y f o r weight and w i t h e r height were estimated by a D e r i v a t i v e - F r e e R e s t r i c t e d Maximum L i k e l i h o o d (DFREML) a l g o r i t h m and an animal model (AM). No d i f f e r e n c e s were found between s i r e s t r a i n s f o r weight except at 15 and 18 months where s i b groups of Canadian (CN) s i r e s were heavier than t h e i r New Zealand (NZ) contemporaries (393 vs 386 kg and 447 vs 445 kg, i i i r e s p e c t i v e l y ) . CN s i r e d h e i f e r s were t a l l e r a t a l l ages except at b i r t h , 3 and 9 months of age. At 24 months CN h e i f e r s were 136 cm w h i l e NZ h e i f e r s were 133 cm. H e r i t a b i l i t y estimates f o r weight a t b i r t h was 0.62 f o r the CN s t r a i n and 0.59 f o r the NZ s t r a i n . CN estimates (3 t o 6 months) and NZ estimates (3 t o 9 months) were c l o s e t o zero. Between 9 t o 24 months CN s t r a i n estimates ranged from 0.44 t o 0.69 while NZ estimates were 0.17 t o 0.51. The j o i n t estimates ranged from 0.10 t o 0.66. H e r i t a b i l i t y estimates f o r w i t h e r height f o r CN s t r a i n at b i r t h and between 9 t o 21 months were between 0.34 t o 0.66 and c l o s e t o zero between 3 t o 6 and at 24 months. The NZ estimates at b i r t h , 18, 21 and 24 months were between 0.36 to 0.9 3 but c l o s e t o zero between 3 t o 15 months. The j o i n t estimates ranged from 0.32 t o 0.75 between 12 t o 24 months. Genetic c o r r e l a t i o n s between weight and w i t h e r height ranged from 0.62 t o 1.0 f o r CN s t r a i n and from -0.04 t o 0.91 f o r NZ s t r a i n between 4.5 t o 21 months. At s i x months of age the gene t i c c o r r e l a t i o n f o r CN s t r a i n was -0.01 and NZ s t r a i n was 0.54. At b i r t h , both s i r e groups had a ge n e t i c c o r r e l a t i o n of 1.0. i v At 24 months NZ s t r a i n had a gen e t i c c o r r e l a t i o n of 0.84 wh i l e t h a t of the CN s t r a i n was 0. Genetic c o r r e l a t i o n s f o r the j o i n t a n a l y s i s ranged from 0.61 t o 1.0 f o r a l l ages except at 6 months (0.18). Phenotypic c o r r e l a t i o n s between weight and w i t h e r height were between 0.33 t o 0.60 f o r CN group and 0.33 t o 0.62 f o r NZ group. The j o i n t estimates were 0.36 t o 0.61. There were no d i f f e r e n c e s i n the phenotypic variances except at 9, 12 and 15 months. Genetic v a r i a n c e s were d i f f e r e n t at a l l ages except at b i r t h f o r weight. TABLE OF CONTENTS V A b s t r a c t i i L i s t of Tables v i i L i s t of Figures v i i i L i s t of Appendices i x Acknowledgements. . . x 1. General I n t r o d u c t i o n , L i t e r a t u r e Review and Objective of Thesis 1 1.1. I n t r o d u c t i o n 2 1.2. R a t i o n a l e and Objective of Thesis 8 1.2.1. R a t i o n a l e . . . . 8 1.2.2. Objec t i v e of Thesis 13 1.3. L i t e r a t u r e Review 14 1.3.1. Dairy C a t t l e Comparisons.. 15 1.3.2. T h e o r e t i c a l Considerations 25 2. Source of Data 35 2.1. I d e n t i f i c a t i o n of S i r e s 35 2.2. Experimental Herds and Animals 3 6 2.3. Feeding and Management of P r o j e c t H e i f e r s During Growth phase 38 2.4. Breeding P r o t o c o l of P r o j e c t H e i f e r s 38 2.5. Loss or Removal of H e i f e r s from P r o j e c t 38 2.6. Measurements and Data c o l l e c t i o n 39 2.7. Age 41 2.8. Observational Animals 42 2.9. C o n s t i t u t e d Data 42 Chapter One 44 Weight and Wither Height of Canadian and New Zealand s i r e d Dairy H e i f e r s 44 3.1. I n t r o d u c t i o n 45 3.2. M a t e r i a l s and Methods 50 3.2.1. Animals 50 3.2.2. Data 50 3.2.3. S t a t i s t i c a l A n a l y s i s 50 3.3. R e s u l t s and Discussion 53 3.3.1 Fixed E f f e c t s of Herd and S t r a i n 53 3.3.1.1. S i r e Group (S t r a i n ) E f f e c t s Least Squares Means 56 3.3.1.2. Herd E f f e c t s Least Squares Means 60 3.4. Conclusions ..69 v i Chapter Two 71 E s t i m a t i o n of Genetic Parameters f o r Weight and Wither Height of Canadian and New Zealand S i r e d D a i r y C a t t l e Using an Animal Model 71 4.1. I n t r o d u c t i o n 72 4.2. M a t e r i a l s and Methods 76 4.2.1. Animals and Data 76 4.2.2. S t a t i s t i c a l A n a l y s i s 79 4.3. R e s u l t s and D i s c u s s i o n 84 \ 4.3.1. V a r i a n c e Components 84 4.3.2. H e r i t a b i l i t i e s 86 4.3.3. Ge n e t i c and Phenotypic C o r r e l a t i o n s 91 4.4. Co n c l u s i o n s 94 5. General Discussion 96 6. Summary 101 Appendices 103 B i b l i o g r a p h y 118 LIST OF TABLES v i i T a b l e 1. I d e n t i f i c a t i o n of CANZ T r i a l S i r e s and O f f s p r i n g per S i r e 6 T a b l e 2. Canadian Cooperator Herds i n c l u d i n g Numbers of P r o j e c t Calves born from CN and NZ s i r e s . 3 7 Table 3. Number of Animals based on Age(months) i n each Herd 40 T a b l e 4. Number of Animals based on Age(months) i n each S i r e Group 40 T a b l e 5. Summary of the A n a l y s i s of V a r i a n c e : Weight (kg) and Wither Height (cm) 54 Table 6. Weight and Height ANOVA Degrees of Freedom..55 Table 7. Weight and Wither Height L e a s t Squares Means of Canadian and New Zealand S i r e d H o l s t e i n H e i f e r s 57 Table 8. T o t a l Number of Animals i n the Numerator R e l a t i o n s h i p M a t r i x (NRM) 77 T a b l e 9. DFREML Estimates of H e r i t a b i l i t i e s , A d d i t i v e G enetic D i r e c t and Phenotypic V a r i a n c e Components 85 Table 10. H e r i t a b i l i t y Estimates with Standard E r r o r s f o r Weight T r a i t 88 Table 11. H e r i t a b i l i t y Estimates w i t h Standard E r r o r s f o r Wither Height T r a i t 88 Table 12. G e n e t i c C o r r e l a t i o n s f o r Weight and Wither Height T r a i t s 92 Table 13. Phenotypic C o r r e l a t i o n s f o r Weight and Wither Height T r a i t s 92 F i g u r e 1. F i g u r e 2. F i g u r e 3. F i g u r e 4. F i g u r e 5. Figure 6. F i g u r e 7. F i g u r e 8. F i g u r e 9. F i g u r e 10. LIST OF FIGURES viii Comparison o f Herds: LS Means a t b i r t h . 6 1 Comparison o f Herds: LS Means a t 3 months 61 Comparison o f Herds: LS Means a t 4.5 months 62 Comparison o f Herds: LS Means a t 6 months 62 Comparison o f Herds: LS Means a t 9 months 63 Comparison o f Herds: LS Means a t 12 months 63 Comparison o f Herds: LS Means a t 15 months 64 Comparison o f Herds: LS Means a t 18 months 64 Comparison o f Herds: LS Means a t 21 months 65 Comparison o f Herds: LS Means a t 2 4 months 65 LIST OF APPENDICES i x Appendix 1: Canadian Mating Timetable 103 Appendix 2: Comparison of Growth Trends of Imported and Native Breeds i n the Tro p i c s 104 Appendix 3: Comparison of Growth Data from CANZ with OMA and USA ( i n c l u d i n g Comparative P l o t s ) 106 Appendix 4: Comparison of CANZ Weight and Height: Canada (Can) vs New Zealand (NZn) 109 Appendix 5: Comparison of Canadian and New Zealand Wither Heights 110 Appendix 6: I n d i v i d u a l Herd Weight Least Squares Means wi t h Standard E r r o r s (Both S i r e Groups) I l l Appendix 7: I n d i v i d u a l Herd Wither Height Least squares Means w i t h Standard E r r o r s (Both S i r e Groups) 113 Appendix 8: I n i t i a l H e r i t a b i l i t y Values f o r DFREML Analy s i s 115 Appendix 9: C a l c u l a t i o n of Standard E r r o r s (S.E.) of the H e r i t a b i l i t y Estimates by the Approximate Method of Swiger et a l . , (1964) 116 Appendix 10: C a l c u l a t e d F Values from the S i r e Group Variance R a t i o s f o r each Age Class 117 ACKNOWLEDGEMENTS x I wish t o express my h e a r t f e l t g r a t i t u d e t o my program Supervisor, Dr. R.G. Peterson f o r h i s understanding and academic guidance and support he has provided me throughout my masters program and i n t h i s study. Sincere thanks t o my program sup e r v i s o r y committee members, Drs. J.A. S h e l f o r d , K.M. Cheng, R. Rajamahendran f o r t h e i r i n v a l u a b l e and c r i t i c a l comments on the t h e s i s . In t h i s r e s p e c t , I p a r t i c u l a r l y thank Dr. R.G. Peterson f o r d i s c u s s i o n s and comments on e a r l i e r d r a f t s . I a l s o wish t o thank f e l l o w graduate students: Sam E. Aggrey and Ann Winkleman f o r t h e i r a s s i s t a n c e i n the a n a l y s i s and comments on t h i s t h e s i s . S p e c i a l thanks t o P a t r i c i a B o s e l l o f o r t y p i n g t h i s t h e s i s . I g r a t e f u l l y acknowledge the c o n t r i b u t i o n s of s c i e n t i s t s , t e c h n i c i a n s and o p e r a t i o n a l s t a f f a t a l l cooperating U n i v e r s i t y , College and A g r i c u l t u r e Canada Research herds i n the opera t i o n of the p r o j e c t and data c o l l e c t i o n . S p e c i a l thanks t o Dr. R.G. Peterson f o r making t h i s data a v a i l a b l e i n order t o c a r r y out t h i s study. A l s o thanks are due t o the A.I. I n d u s t r i e s of Canada and New Zealand f o r the i n i t i a t i o n of t h i s worthy p r o j e c t . Warmest and h e a r t f e l t thanks t o my f a m i l y f o r t h e i r continued support i n my academic endeavour. F i n a n c i a l a s s i s t a n c e f o r my MSc. s t u d i e s by the Vancouver Regional Branch of the B r i t i s h Columbia S o c i e t y f o r the Prevention of C r u e l t y t o Animals (BC SPCA) i s g r a t e f u l l y acknowledged. 1 1. GENERAL INTRODUCTION, LITERATURE REVIEW AND OBJECTIVE OP THESIS On the o r g a n i z a t i o n of t h i s t h e s i s : Chapters 1 and 2 are w r i t t e n i n the form of papers; each chapter c o n t a i n i n g a separate i n t r o d u c t i o n , d e s c r i p t i o n of methods and r e s u l t s and d i s c u s s i o n . 1.1. INTRODUCTION 2 The i n t e r n a t i o n a l exchange of g e n e t i c m a t e r i a l i n d a i r y c a t t l e between d i f f e r e n t c o u n t r i e s i s very important t o d a i r y breeders due t o a n t i c i p a t e d g e n e t i c and economic gains by both the importing and e x p o r t i n g c o u n t r i e s r e s p e c t i v e l y . This a c t i v i t y has been f a c i l i t a t e d by the use of a r t i f i c i a l insemination ( A . I . ) , embryo t r a n s f e r (E.T.), and the c a p a b i l i t y of long term storage and easy t r a n s p o r t of semen and embryos. Consequently, animals s e l e c t e d , r a i s e d and t e s t e d i n one environment have been used f o r breeding i n a f o r e i g n environment without p h y s i c a l l y t r a n s p o r t i n g the b u l l or dam t o t h a t environment. The attempt to increase d a i r y c a t t l e p r o d u c t i v i t y has been the c a t a l y s t i n t h i s exchange of germplasm and i n changing the genetics of the d a i r y c a t t l e . This has r e s u l t e d i n d a i r y c a t t l e p opulations w i t h high production becoming a p r e f e r r e d g e n e t i c stock. A case i n p o i n t , i s the high y i e l d of m i l k , f a t and p r o t e i n of the North American H o l s t e i n - F r i e s i a n c a t t l e which has l e d to i t s p o p u l a r i t y among d a i r y producers worldwide. The phenotype of an i n d i v i d u a l i s a f u n c t i o n of i t s genotype and environment (Pani and L a s l e y , 1972). Faced wi t h the v a s t array of c l i m a t e s , management and feeding programs, d a i r y breeders have recognized the need t o 3 evaluate and compare the gene t i c value of d i f f e r e n t s t r a i n s w i t h regard t o important productive features i n the environments where the animals w i l l perform. W i l l s i r e s or breeds t h a t rank h i g h l y i n one environment a l s o rank h i g h l y i n another? The answer t o the question asked i s a f f i r m a t i v e only i f b u l l s rank the same i n both environments based on t h e i r progeny t e s t s . In t h i s case, a GxE i n t e r a c t i o n i s very small and c l o s e t o zero or non-e x i s t e n t . I f s i g n i f i c a n t reranking of the b u l l s occurs i n the importing country, a genotype by environment (GxE) i n t e r a c t i o n e x i s t s and gene t i c merit i n the . home environment i s not a good p r e d i c t o r of performance i n the new environment. A GxE i n t e r a c t i o n i s more l i k e l y t o e x i s t when d i f f e r e n c e s between environments are l a r g e and. " f i t n e s s " i n one i s not r e l a t e d t o " f i t n e s s " i n the other (Peterson, 1988) . Concurrent with t h i s k i n d of gene t i c e v a l u a t i o n , i n the absence of a GxE i n t e r a c t i o n , i s the need t o develop r e l i a b l e conversion f a c t o r s so t h a t imported s i r e proofs can be compared t o l o c a l l y a v a i l a b l e s i r e proofs based on the system used i n the importing country (Peterson, 1988; Ron et a l . , 1987) . 4 Although H o l s t e i n - F r i e s i a n c a t t l e o r i g i n a t e d from the same place ( J a s i o r o w s k i et a l . , 1981), they have d i f f e r e d c o n s i d e r a b l y i n environmental c o n d i t i o n s as w e l l as t o v a r i o u s c r i t e r i a and methods of s e l e c t i o n i n d i f f e r e n t p a r t s of the world. Therefore, the e v a l u a t i o n of d i f f e r e n t s t r a i n s of H o l s t e i n - F r i e s i a n c a t t l e f o r p o s s i b l e GxE i n t e r a c t i o n s and s t r a i n d i f f e r e n c e s w i t h the i n t e n t i o n of seeking the best a v a i l a b l e germplasm has become very important. The genotype by environment I n t e r a c t i o n p r o j e c t i n v o l v i n g H o l s t e i n - F r i e s i a n s t r a i n s from Canada and New Zealand was p a r t of t h i s focus. I t has been documented (Peterson, 1988; Wickham et a l . , 1978) t h a t management and feeding programs of the d a i r y herds i n the two c o u n t r i e s are very d i f f e r e n t . Both c o u n t r i e s have very comprehensive s e l e c t i o n programs co n c e n t r a t i n g on the major components of income, which can be g e n e t i c a l l y improved. New Zealand has a pasture/forage based - high roughage feeding program, whi l e Canada has a concentrate - low roughage regimen. Therefore, s e l e c t i o n f o r production i n the two c o u n t r i e s may have caused the two populations t o diverge f o r t r a i t s a s s o c i a t e d w i t h adaptation t o the environmental extremes. Increased production i s the p r i n c i p a l s e l e c t i o n goal i n both c o u n t r i e s , but m i l k f a t y i e l d per cow i s the adopted 5 s e l e c t i o n c r i t e r i o n i n New Zealand w h i l e Canadian breeders have tended t o place g r e a t e r emphasis on t o t a l m i l k y i e l d . Therefore, the two populations shodld d i f f e r due t o d i f f e r e n t s e l e c t i o n goals. A p t l y c a l l e d the Canadian/New Zealand Genotype Environmental I n t e r a c t i o n T r i a l (CANZ T r i a l ) , t h i s study was i n i t i a t e d i n 1984 t o i n v e s t i g a t e the d i f f e r e n c e s between the two d a i r y p o p u l a t i o n s , provide a s e t of reference s i r e s f o r c a l c u l a t i n g conversion f a c t o r s and t o t e s t f o r the exis t e n c e of GxE e f f e c t s f o r production t r a i t s (Peterson et a l . , 1984). !! According t o Peterson (1988), the CANZ T r i a l used proven s i r e s from Canada and New Zealand as mates f o r c a t t l e i n cooperator herds of both c o u n t r i e s . In both c o u n t r i e s b u l l s were s e l e c t e d on ETA (Estimated T r a n s m i t t i n g A b i l i t y ) . These were the top b u l l s a v a i l a b l e f o r m i l k y i e l d f o r the Canadian s i r e s and m i l k f a t percent f o r New Zealand s i r e s . A l l b u l l s were widely used i n t h e i r home country and had proofs i n 1984. The planned mating design used a "random order" of s i r e s . The f i r s t cow i n heat was bred t o the f i r s t b u l l on the New Zealand l i s t and the next cow t o the f i r s t b u l l on the Canadian l i s t , w i t h the t h i r d cow mated t o the next b u l l on the New Zealand l i s t and so 6 Table lt I d e n t i f i c a t i o n of CANZ T r i a l S i r e s and Offspring per S i r e Canadian Reg. No. Semen Code Name No.Born 1. 333194 70HO150 Flin s t o n e Royal ADAM 12 2. 333860 73H0211 AQUARIUS Elevator 11 3. 322678 73H0145 Laflam ASTRONAUT 12 4. 353217 73H0393 E-Z Acres AVIATOR 13 5. 333473 70HO143 Cl i n t o n CAMP Majesty 5 6. 337679 73H0235 -Stanhope CANNONADE 13 7. 350852 73H0342 P r a i r i e - I s l e CARL 20 8. 352197 39HO107 Fairbreeze CONDUCTOR 9 9. 340909 73H0281 Cal-Clark CUTLASS 7 10. 343514 73H0332 Glenafton ENHANCER 12 11. 354682 70HO212 Lonsfarm KAY Elevator 9 12. 340185 39H086 Vyecroft Centurion MAGNET 12 13. 348435 39H099 Vandyk-S Chief MYSTIC 15 14. 348114 73H0359 Provale Astronaut PAT 14 15. 351662 72H0289 Fran-Lou RENDITION 12 16. 351631 73H0356 Olmar STARMAKER 12 17. 345653 72H0274 Cherry Lane SUPERSTAR 14 18. 341252 73H0244 Skokie Elevation TELSTAR 11 19. 347045 72H0269 Maries THUNDER 16 20. 336701 73HO209 Leblanc VIBRATION 12 New Zealand Req.No Semen Code Name No.Born 1. 605261 80224 F a i r h i l l BEN GUNN 6 2. 57784 76241 Lombardi BLAIR 14 3. 604830 80243 Lyncrest Cascade BOB 10 4. 602093 79224 Beaufort C F . FABIAN 15 5. 604585 80230 Greencroft Prince GLOW 14 6. 603501 79278 Woodlea S.J. GRAHAM 15 7. 51927 74230 Clovernook L. GREGG 9 8. 603162 79247 Maniapoto A.B. IRELAND 10 9. 605601 80231 Greenfields JADE 13 10. 605197 80257 Tawa Barron JESTER 12 11. 604038 80253 Rolands Cascade KURT 14 12. 55466 62438 Charnwood LIN PETER 12 13. 56724 76226 Coldstream Majestic MAX 7 14. 601914 78229 Glengyle S t a r l i t e METEOR 13 15. 604197 80241 Kingsmill L. MOUNT batten 10 16. 603174 80209 Athol PATRICK 11 17. 603299 79274 Whiteoaks S.J. PETER 6 18. 57871 77209 Athol Famous PREFECT 18 19. 600336 78249 Pukekaraka J . ROGER 11 20. 603180 80213 Athol VALIANT 14 7 on. This design was t o ensure daughters of the Canadian and New Zealand s i r e s were born, r a i s e d and milked i n the same herds under the same environmental c o n d i t i o n s . Twenty Canadian and 20 New Zealand s i r e s (Table 1) were used i n 10 Canadian and 20 New Zealand herds. Matings i n New Zealand were confined to a s i n g l e "two-month" breeding season i n 1984, h e i f e r s were born i n 1985 and f i r s t l a c t a t i o n s were completed i n the 1987-88 season. The mating program i n Canadian herds s t a r t e d at the same time (Appendix 1) , but continued f o r a d u r a t i o n of 18 t o 20 months and as such, the p r o j e c t h e i f e r s were born over an extended p e r i o d . Age, production, body weights, heights at wi t h e r s , type, temperament, and other i n f o r m a t i o n from the daughters of these s i r e s provided the experimental observations. 1 . 2 . RATIONALE AND OBJECTIVES OF THESIS 8 1 . 2 . 1 . Rationale The g e n e t i c merit of a breed depends on the e x t e r n a l c o n d i t i o n s under which i t i s kept (Syrstad, 1976). E v a l u a t i o n of breeds i n the same environment i s necessary i n order t o detect any genet i c d i f f e r e n c e s . Due t o d i f f e r e n c e s i n c l i m a t e , feeding and management and s e l e c t i o n c r i t e r i a , the Canadian Dairy H o l s t e i n and New Zealand Dairy F r i e s i a n were p o t e n t i a l l y g e n e t i c a l l y divergent (Peterson, 1988). Genetic divergence would lead to d i f f e r e n c e s i n the phenotypic expression of the growth t r a i t s i n the two populations. The phenotypic d i f f e r e n c e s can be p a r t i t i o n e d i n t o p r o p o r t i o n s due t o environmental and g e n e t i c c o n s t r a i n t s . Genetic parameters a s s o c i a t e d w i t h these t r a i t s can be estimated. T r a d i t i o n a l l y , c a t t l e have been a major source of m i l k and meat f o r man, wit h c e r t a i n breeds h i g h l y s p e c i a l i z e d f o r mi l k or meat production. However, due t o increased demand f o r p r o t e i n sources of mil k and meat as c i t e d by Calo et a l . , ( 1 9 7 3 ) ; and Preston, ( 1 9 7 9 ) , there has been a need t o develop dual purpose c a t t l e from high m i l k producing d a i r y c a t t l e . In t h i s context, the f e a s i b i l i t y of t h i s approach depended on the genetic merits f o r beef t r a i t s among the H o l s t e i n - F r i e s i a n b u l l s which have been e s s e n t i a l l y s e l e c t e d f o r m i l k y i e l d . 9 Most growth t r a i t s of d a i r y c a t t l e have been documented i n r e l a t i o n t o m i l k production (Calo et a l . , 1973; Brum et a l . , 1969; L i n et a l . , 1985; H a r v i l l e et a l . , 1966; Hargrove et a l . , 1987). Therefore, any l o g i s t i c s i n u t i l i z i n g d a i r y c a t t l e growth t r a i t s f o r s e l e c t i o n or commercial e x p l o i t a t i o n must consider the r e l a t i o n s h i p of these t r a i t s t o m i l k production. Genetic and phenotypic 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 t o prepartum weights and weight change have been reported by L i n et a l . , (1985). The g e n e t i c c o r r e l a t i o n s between m i l k y i e l d and prepartum weights at 12, 15, 18 months of age ranged from -0.07 t o 0.40, whereas the phenotypic c o r r e l a t i o n s ranged from 0.21 t o 0.48. They concluded t h a t based on the g e n e t i c and phenotypic r e l a t i o n s h i p s of the t r a i t s , h e i f e r s w i t h l a r g e body weights prepartum had higher l a c t a t i o n y i e l d s . Brum et a l . , 1969 have reported t h a t a 25% increase i n accuracy of 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 was i n d i c a t e d f o r i n c l u s i o n of p r e c a l v i n g age body measurements on a s e l e c t i o n index. S i m i l a r s e l e c t i o n r e s t r i c t e d t o body measurements would have been 80% as e f f e c t i v e as s e l e c t i o n based on a m i l k record. H a r v i l l e et a l . , (1966) have suggested t h a t body weight could be used t o s e l e c t f o r production when no other i n f o r m a t i o n i s a v a i l a b l e . 10 According t o the study of growth i n d a i r y c a t t l e by H e i n r i c h s and Hargrove (1987), they found a p o s i t i v e phenotypic c o r r e l a t i o n of weight and height w i t h each other and w i t h average herd production. D e r i v a t i o n of growth parameters i s an a d d i t i o n a l t o o l i n the e v a l u a t i o n of d a i r y c a t t l e f o r expected performance. Knowledge of growth t r a i t s of Canadian and New Zealand d a i r y c a t t l e from animal breeding elsewhere has been documented (Peterson, 1988; J a s i o r o w s k i et a l . , 1982; Ron et a l . , 1987; and Bar-Anan et a l . , 1987). However, information on the performance of Canadian versus New Zealand s i r e d d a i r y h e i f e r s i n the Canadian environment i s l a c k i n g . Since some of the NZ s i r e s are known descendants of CN s i r e s , i t i s important t o see how t h e i r o f f s p r i n g compare with the Canadian s i r e d o f f s p r i n g . The s e l e c t i o n program i n Canada has favoured increased s i z e and s t a t u r e , w h i l e the New Zealand program has given l i t t l e emphasis t o these t r a i t s even though meat production i s an important component i n the t o t a l farm income i n New Zealand (Peterson, 1988) . Both c o u n t r i e s stand t o b e n e f i t (economically) from knowledge of growth parameters of the two pop u l a t i o n s . , Weight and height t r a i t s i n d a i r y c a t t l e can be manipulated through planned s e l e c t i o n i n order t o improve or achieve f a s t e r growth r a t e s and e a r l y 11 maturation. In t h i s way, Canada or New Zealand ( e s p e c i a l l y ) could i n c o r p o r a t e beef production i n t h e i r s e l e c t i o n programs from knowledge of the g e n e t i c c o n t r o l over the two t r a i t s . The downside of increased s t a t u r e i s t h a t animals could be too t a l l t o f i t i n m i l k i n g p a r l o u r gates and feeding s t a l l s . The increase i n s t a t u r e however, could be c o n t r o l l e d through s e l e c t i v e breeding based on i t s h e r i t a b i l i t y and c o r r e l a t i o n w i t h other t r a i t s ( i n p a r t i c u l a r weight). Knowledge of growth parameters of the two d a i r y c a t t l e populations i s t h e r e f o r e u s e f u l . Based on the afore-mentioned, i t i s hypothesized t h a t the two populations are p o s s i b l y d i f f e r e n t i n terms of weight and height due t o the s e l e c t i o n programs of the two c o u n t r i e s and t h a t i t should be p o s s i b l e t o f i n d d i f f e r e n c e s between the two genotypes based on t h e i r g e n e t i c c o n t r i b u t i o n t o body weight and s i z e ; and thereby, e s t a b l i s h a growth p a t t e r n f o r weight and height i n the Canadian and New Zealand d a i r y c a t t l e and t o estimate appropriate g e n e t i c parameters. In t h i s study, the design of the experiment u t i l i z e d 2 0 CN and 20 NZ s i r e s . Since these s i r e s were s e l e c t e d based on production and not growth t r a i t s ; they represent a random 12 sample of t h e i r home populations w i t h respect t o weight and wither height. In t h i s way conclusions drawn out of the r e s u l t s w i l l j u s t i f i a b l y apply t o whole populations. 13 1 . 2 . 2 . O b j e c t i v e of Thesis (1) To compare Canadian and New Zealand s i r e d H o l s t e i n h e i f e r s f o r s i z e and growth i n terms of absolute l i v e body weights and w i t h e r heights at v a r i o u s ages under normal Canadian feeding and management programs. (2) To estimate s i r e v a r i a n c e s , h e r i t a b i l i t i e s , g e netic and phenotypic c o r r e l a t i o n s f o r weight and wither height of Canadian and New Zealand H o l s t e i n h e i f e r s , using an animal model. 1.3. LITERATURE REVIEW 14 H i s t o r i c a l l y , s e l e c t i o n of l i v e s t o c k breeds f o r production must have begun soon a f t e r domestication of t h e i r w i l d ancestors i n the Middle East some 8,000 - 10,000 years ago (Mason et a l . , 1982) . The high y i e l d of the d a i r y cow, the high growth r a t e of beef c a t t l e breeds are a l l the r e s u l t s of s e l e c t i o n . During the l a s t 2 00 years i n Western Europe (Buvanendran et a l . , 1982), s p e c i a l i z e d and high producing breeds of d a i r y and beef c a t t l e have been formed. Before t h a t time, c a t t l e were t r i p l e - p u r p o s e i . e . draught, m i l k and meat. Each l o c a l i t y or mountain v a l l e y and each region had i t s own l o c a l breed. Serious s e l e c t i o n f o r m i l k y i e l d and f o r meat was due t o a combination of increased demand f o r these products but p r i m a r i l y due t o favourable genes and genotypic combinations t h a t l e d to genetic progress. However, i t i s only s i n c e performance recording began i n earnest t h a t a c t u a l increases i n p r o d u c t i v i t y were estimated. The above changes have been a t t r i b u t e d to the genetic p o t e n t i a l of the breeds ( e s p e c i a l l y the b lack and white breeds) and improvement i n feeding, management and disease c o n t r o l . 1 . 3 . 1 . Dairy C a t t l e Comparisons 15 Ja s i o r o w s k i et a l . , (1988) s t a t e t h a t one of the d i f f i c u l t i e s faced by breeders using imported b u l l s , or t h e i r semen, has been the absence of good in f o r m a t i o n on how t o p r e d i c t the merit of these b u l l s under c o n d i t i o n s present i n the importing country when a l l t h a t i s u s u a l l y known i s the merit of the b u l l i n the country of o r i g i n . When the d i f f e r e n c e i n the feeding and management systems i n the importing and exportin g country are l a r g e (e.g. temperate vs t r o p i c a l ) then e r r o r s i n p r e d i c t i o n are a l s o expected t o be l a r g e . I s there then a case t o be made on behalf of breeding l i v e s t o c k t h a t are b e t t e r adapted f o r production i n p a r t i c u l a r environments or regions of the world? Based on s t u d i e s of l a c t a t i o n m i l k y i e l d , i n t e r a c t i o n s appear to be of minor importance, but such i n t e r a c t i o n s may become s i g n i f i c a n t when t r a i t s such as s u r v i v a l are included (Lytton and Legates, 1966; McDowell et a l . , 1976). In t r o p i c a l and s u b t r o p i c a l environments, f i r s t generation crosses using s i r e s from temperate c o u n t r i e s w i t h high production u s u a l l y g i v e acceptable performance, but back crosses to these same s i r e s are l e s s s u c c e s s f u l due to high m o r t a l i t y , low breeding e f f i c i e n c y and short herd l i f e (McDowell et a l . , 1976) i n the backcross progeny. In t h i s context, i t seems t h a t assessment of m i l k y i e l d as w e l l as t r a i t s other than production are required to determine i f genotype x environment i n t e r a c t i o n s are important. In the Food and 16 A g r i c u l t u r e Organization of the United Nations (F.A.O.) H o l s t e i n - F r i e s i a n breed comparison i n Poland (Stolzman et a l . , 1981), s t r a i n s from 10 c o u n t r i e s ( i . e . Canada, Denmark, the German Federal Republic, B r i t a i n , I s r a e l , The Netherlands, New Zealand, Sweden, USA and Poland) were compared by inseminating P o l i s h F r i e s i a n cows w i t h semen from 4 00 young unproven s i r e s from these c o u n t r i e s and e v a l u a t i n g t h e i r progeny. The purpose of t h i s experiment was t o compare s t r a i n d i f f e r e n c e s and no i n t e r a c t i o n s of feeding or environment w i t h genotypes were reported. A l s o genetic parameters of h e r i t a b i l i t y and c o r r e l a t i o n s were not reported. In the F1 females, measures were taken f o r mi l k production as w e l l as weight. Under i n t e n s i v e c o n d i t i o n s average weights were recorded at b i r t h (35.5 kg) , 12 months (272 kg) and 18 months (369 kg) . Weights f o r F1 males were a l s o recorded under i n t e n s i v e c o n d i t i o n s . O v e r a l l average weight of FI males was 37.3 kg at b i r t h and 290 kg at 12 months. For both sexes, a l l weights v a r i a t i o n among s t r a i n s was h i g h l y s i g n i f i c a n t (P < 0.01). Comparison of these progenies was done under both i n t e n s i v e (and c o n t r o l l e d ) and f i e l d c o n d i t i o n s . The beef performance t e s t was based on sons of 218 s i r e s . R e s ults of the d a i r y performance of FI h e i f e r s from t h i s research have been f u l l y discussed by Reklewski et a l . , 17 (1984). I t was concluded t h a t the h e i f e r s of the H o l s t e i n type (from USA, Canada and I s r a e l ) were g e n e r a l l y l a r g e r than the European and New Zealand s t r a i n s . The f i r s t group produced i n general more mi l k , but w i t h a lower f a t and p r o t e i n content than the European and New Zealand s t r a i n s . The New Zealand s t r a i n had high m i l k y i e l d as w e l l but high f a t and p r o t e i n percentages. However, the New Zealand and the H o l s t e i n s t r a i n s were p r a c t i c a l l y equal w i t h regard t o f a t y i e l d and the combined f a t - p r o t e i n y i e l d . Under i n t e n s i v e feeding, the mean wither height of a l l t e s t e d cows j u s t a f t e r c a l v i n g was 127.7 cm. F1 females of Canadian and American s t r a i n s were the highest at the withers (more than 129 cm). The e f f e c t of s t r a i n on wither heights of 12 and 18 month o l d F1 b u l l s was h i g h l y s i g n i f i c a n t (P < 0.01). H o l s t e i n s from the USA, Canada and I s r a e l were the t a l l e s t . In summary, Canadian s i r e d F1 b u l l s at b i r t h , 12 and 18 months were 37.9, 304.0 and 473 kg heavy whi l e New Zealand F 1 b u l l s at the same ages were 36.8, 304.0 and 473 kg r e s p e c t i v e l y . The F1 females of Canadian s i r e s at 10 days a f t e r c a l v i n g were 476.9 kg and 129.8 cm whi l e the F 1 females of New Zealand s i r e s were 469.9 kg and 127.56 cm. 18 Although these r e s u l t s were based on unproven young s i r e s as opposed t o the CANZ t r i a l which i n v o l v e d proven s i r e s ; they i n d i c a t e d the existence of s t r a i n d i f f e r e n c e s and th e r e f o r e , formed a b a s i s f o r comparison of s i r e or d a i r y c a t t l e e v a l u a t i o n s . Considerable research has been devoted i n the genet i c e v a l u a t i o n of d a i r y breeds of c a t t l e as i n d i c a t e d by s i m i l a r e v a l u a t i o n e f f o r t s conducted i n I s r a e l (Bar-Anan et a l . , 1982), Mexico and Colombia (Abubakar et a l . , 1986); I r e l a n d and B r i t a i n ( M u l v i h i l l , 1982); and B u l g a r i a (Hinkovski et a l . , 1979).. This s h o r t l i s t does not attempt to document a l l d a i r y c a t t l e comparisons. The I s r a e l comparison (Bar-Anan et a l . , 1987) used h i g h - y i e l d proven s i r e s from the f i v e F r i e s i a n s t r a i n s which had the highest 3 05 days m i l k production i n the P o l i s h experiment, under i n t e n s i v e management. These were USA, I s r a e l , New Zealand, Canada and Sweden. This comparison i s e s p e c i a l l y important i n r e l a t i o n t o t h i s t h e s i s s i n c e i t in v o l v e d two of the same s i r e s used i n the CANZ t r i a l . Daughters of the s i r e " C l i n t o n Camp Majesty" from the Canadian group were compared among others with daughters of s i r e "Lombardi B l a i r " from the New Zealand contingency. Daughters of Canadian s i r e s were heaviest (504 kg) and daughters of New Zealand s i r e s were l i g h t e s t (462 kg). 19 Even though the number of s i r e s t e s t e d was a s m a l l , non-random sample (Bar-Anan et a l . , 1987) from the p a r t i c i p a t i n g c o u n t r i e s ; i t nevertheless i n d i c a t e d t h a t between s t r a i n d i f f e r e n c e s were l a r g e compared t o w i t h i n s t r a i n s (Heiman et a l . , 1987). In t h i s study a l s o , there was no e s t i m a t i o n of genetic parameters ( h e r i t a b i l i t y and t r a i t c o r r e l a t i o n s ) based on the s t r a i n s used. The Red and Red-and-White c a t t l e breed comparison i n B u l g a r i a (Hinkovski et a l . , 1979) compared seven s t r a i n s of Red or Red-and-White breeds based on the performance of t h e i r o f f s p r i n g as the main go a l . The experiment used 80 unproven young b u l l s (being sons of e l i t e - p r o v e n b u l l s ) from e i g h t c o u n t r i e s i . e . Canada, Denmark, F i n l a n d , Germany Federal Republic, Norway, Sweden, USSR and B u l g a r i a . The breeds used from each country were: Recessive red mutant of the H o l s t e i n - F r i e s i a n , Danish Red, F i n n i s h A y r s h i r e , RDR-Angler, Norwegian Red, Swedish Red-and-White, E s t o n i a Red and B u l g a r i a Red r e s p e c t i v e l y . B u l g a r i a cows were used as foundation females. P r e l i m i n a r y i n v e s t i g a t i o n s using backcrosses t o p r o j e c t s i r e s concluded t h a t non-additive genetic v a r i a b i l i t y (heterosis) e x i s t e d i n the F1 cross which rendered biases when fu t u r e daughter production was p r e d i c t e d from t h a t of F1 daughters. A l s o , p o s s i b l e e x i s t i n g r e l a t i o n s h i p s w i t h i n b u l l groups were ignored. 20 B i r t h weights ranged from 30.9 t o 32.3 kg f o r F 1 females w i t h an average of 31.6 kg; and 3 3.5 t o 35.0 f o r males wi t h an average of 34.1 kg. The Canadian b u l l group had an average of 32.3 and 32.9 kg f o r female and male o f f s p r i n g r e s p e c t i v e l y . L i v e weight at 3 months of age f o r females ranged from 92.2 t o 99.7 kg ( i . e . Danish Red and Angler r e p e c t i v e l y ) . The Canadian b u l l group had an average of 98.6 kg. D e t a i l s of t h i s t r i a l have been f u l l y discussed by Hinkovski et a l . , (1979). C l e a r l y , t h i s study i n d i c a t e d t h a t breed d i f f e r e n c e s e x i s t e d . The study i n Mexico and Colombia, (Abubakar et a l . , 1986) i n v e s t i g a t e d the i n t e r a c t i o n of genotype and environment f o r breeding e f f i c i e n c y and m i l k production of 17 H o l s t e i n s i r e s from USA. I t inv o l v e d : (1) e v a l u a t i o n of the r e l a t i o n s h i p of the s i r e value f o r m i l k production and herd l e v e l of m i l k y i e l d , reproductive e f f i c i e n c y and d u r a t i o n of herd l i f e f o r the progeny of those s i r e s i n the host c o u n t r i e s and (2) c o r r e l a t i o n of p r e d i c t e d s i r e values w i t h those a v a i l a b l e i n the USA. Previous t o t h i s p r o j e c t , main sources of imported s i r e s f o r both c o u n t r i e s ( i . e . Mexico and Colombia) were Canada, USA and European (to a small e x t e n t ) . R e s u l t s of t h i s study i n d i c a t e d t h a t s i r e s ranked d i f f e r e n t l y (P < 0.05) i n USA, Mexico and Colombia (Abubakar et a l . , 1986); w i t h the rank c o r r e l a t i o n i n 21 Mexico and Colombia being lowest (0.26). The low c o r r e l a t i o n s suggested genotype-environment i n t e r a c t i o n s . High temperatures were s t r e s s f u l f o r H o l s t e i n s and adversely a f f e c t e d t h e i r production throughout l i f e (Abubakar et a l . , 1986). These r e s u l t s h i g h l i g h t e d some of the c o n s i d e r a t i o n s t o be accounted f o r i n the assessment of genetic merit of high performance breeds i n suboptimal environments. The genotype-environment i n t e r a c t i o n study f o r d a i r y t r a i t s ( i . e . milk, f a t and p r o t e i n y i e l d ) between I r e l a n d and B r i t a i n ( M u l v i h i l l , 1984) suggested the presence of GxE i n t e r a c t i o n s such t h a t considerable reranking of genotype occurred i n the use of s i r e s from I r e l a n d i n B r i t a i n . J a s i o r o w s k i et a l . , (1988) f u r t h e r p o i n t out t h a t the Black and White s t r a i n s of c a t t l e - F r i e s i a n and H o l s t e i n - F r i e s i a n have become very popular i n the t r o p i c a l and s u b t r o p i c a l c o u n t r i e s p r i m a r i l y due t o t h e i r high m i l k production. In general, crosses by H o l s t e i n s i r e s have proven s u p e r i o r t o crosses from other e x o t i c breed crosses ( f o r instance, crosses using Jersey, Dairy Shorthorn and A y r s h i r e with l o c a l breeds). However, few c o u n t r i e s have d e f i n i t i v e p o l i c i e s on u t i l i z a t i o n of crossbreeding systems (McDowell, 1985). As noted by F r i s c h , (1976); and McDowell (1985) 22 production and growth r a t e s of Bos taurus breeds i s high i n temperate areas but d e c l i n e s markedly i n the t r o p i c s . Bos  i n d i c u s breeds are w e l l adapted to the t r o p i c s i n terms of s u r v i v a l but t h e i r growth r a t e and production are very low compared to temperate breeds. Consequently, crossbreeding e f f o r t s have ensued i n order t o increase growth and p r o d u c t i v i t y of Bos i n d i c u s . The most productive mix of Bos i n d i c u s and Bos taurus genes f o r a given environment, i s one which i s l e s s a f f e c t e d by environmental s t r e s s e s and expresses a s u p e r i o r a p p e t i t e to u t i l i z e a v a i l a b l e feeds and t o convert t h i s food intake i n t o productive energy. In a d d i t i o n to any improvement of crossbreds from a d d i t i v e genetic e f f e c t s , t h e i r performance l e v e l may a l s o be r e l a t e d t o an increase i n h e t e r o z y g o s i t y w i t h r e s u l t i n g h e t e r o s i s due to a favourable combination of d i f f e r e n t genotypes. According to Batra et a l . , (1983), i n an experiment i n v o l v i n g body weights and dimensions of p u r e l i n e and c r o s s l i n e h e i f e r s of the Canadian d a i r y c a t t l e , the non-additive genetic e f f e c t s from c r o s s i n g purebred H o l s t e i n s with purebred A y r s h i r e r e s u l t e d i n a 1.9 to 3.8% increase i n body measurements from b i r t h to 19 months of age. By d e f i n i t i o n , h e t e r o s i s i s a genetic i n t e r a c t i o n dependent upon the s i m i l a r i t y or v a r i a b i l i t y of the g e n e t i c make up of the two i n d i v i d u a l s mated. Wider 23 crosses e x h i b i t i n g g r e a t e r h e t e r o s i s . H e t e r o s i s i s manifested as the d i f f e r e n c e between the average performance of the crosses and the average of the parents. One of the important advantages of crossbreeding i s the m u l t i p l e t r a i t s u p e r i o r i t y of the crossbred as compared with the parents (Willham et a l . , 1985). However, Dickerson (1972) suggested t h a t i n the production of s y n t h e t i c s or F 2 populations i n order t o concentrate the p r o p o r t i o n of s u p e r i o r genes, there i s l o s s of h e t e r o s i s . Backcrossing of F1 to the best parent reduces h e t e r o s i s by h a l f . As w e l l , a d d i t i o n of a second breed (three-breed cross) has tended to deter r a t h e r than t o improve performance (McDowell, 1985). Yet, the use of s y n t h e t i c s i n the t r o p i c s has proven to be u s e f u l i n d a i r y production. Crossbreds c o n t a i n i n g 5/8 imported and 3/8 indigenous breeds have performed b e t t e r than the two-breed crosses. The 3/4 European breed cross s l i g h t l y exceeds the two-breed cross i n milk y i e l d , but reproduction i s poorer w i t h m o r t a l i t y l o s s e s i n 3/4 crosses as high as 14 t o 29% up t o 3 months (McDowell, 1985). I n t e r se matings of two-breed crosses have been d i s a p p o i n t i n g . M i l k y i e l d of 1/2 crosses of two-breed progeny has been 3 0 to 60% lower than f o r f i r s t generation two-breed crosses. Therefore, breed 24 combinations of approximately 5/8 improved and 3/8 l o c a l have been e x t e n s i v e l y u t i l i z e d . According t o (McDowell, 1985) r e p o r t s from 25 c o u n t r i e s i n the t r o p i c s (30° North and 30° South l a t i t u d e s ) i n d i c a t e d v a r i a b l e growth trends f o r two-breed crosses compared t o n a t i v e or imported breeds as shown i n Appendix 2 (A,B). On average, s u p e r i o r i t y of crossbreds has been s i m i l a r i n A f r i c a , A s i a and L a t i n America. In I n d i a , Brown Swiss-Sahiwal females have e x h i b i t e d 3.3% h e t e r o s i s f o r weight (Kiwuwa et a l . , 1983). When more than two improved breeds were used, two-breed crosses by H o l s t e i n s i r e s performed b e t t e r than crosses by A y r s h i r e , Brown Swiss, Jersey, Red P o l l or Shorthorn i n most t r a i t s (Madalena, 1981). In E t h i o p i a , i t has been shown th a t H o l s t e i n crosses exceeded Jersey crosses (Appendix 2 A) . In I n d i a , H o l s t e i n breed crosses showed higher weights at b i r t h and 12 months than the Brown Swiss crosses (Appendix 2 B). The s y n t h e t i c breeds i n d i c a t e d i n Appendix 2 C, tend t o surpass n a t i v e breeds and are equal t o or s u p e r i o r t o t h a t of two-breed crosses. These new breeds g e n e r a l l y have more mature weight than two-breed crosses due t o the gr e a t e r 25 p r o p o r t i o n of European breeding i n them. For i n s t a n c e , the Jamaica Hope has been s t a b i l i z e d at 80% Jersey, 15% Sahiwal, and 5% H o l s t e i n (Wellington et a l . , 1975). Although s e l e c t i o n programs using f o r e i g n genotypes i n the t r o p i c s f o r d a i r y c a t t l e production have i d e n t i f i e d s u i t a b l e genotypes or mixes of genotypes, c a r e f u l i n t e r p r e t a t i o n of these r e s u l t s and s p e c i f i c goals f o r breeding plans are c r u c i a l . Schaeffer (1985) has cautioned t h a t i n t e r p r e t a t i o n of r e s u l t s of i n t e r n a t i o n a l black and white d a i r y c a t t l e comparisons should take the f o l l o w i n g p o i n t s i n t o account: (1) Each t r i a l has compared a small group of b u l l s from each p a r t i c i p a t i n g country w i t h small numbers of daughters per b u l l ; (2) Among c o u n t r i e s , r a t e s of g e n e t i c change may be d i f f e r e n t and n o n - l i n e a r w i t h time. Therefore, ranking of b u l l populations f o r genetic merit today may be s i g n i f i c a n t l y d i f f e r e n t from the t r i a l r e s u l t s . 1.3.2. T h e o r e t i c a l Considerations According to Dickerson, (1962), i n the broad sense there are no "independent" genetic and environmental v a r i a t i o n s i n animal performance. Any phenotypic expression of the genotype r e q u i r e s a r e l a t i v e l y s p e c i f i c sequence of 26 environments and any environmental i n f l u e n c e i s measurable only as i t changes the expression of v i a b l e genotypes. However, d i f f e r e n c e s i n phenotypes among a s e r i e s of genotypes can remain r e l a t i v e l y constant under s e v e r a l d i f f e r i n g environments, so long as the range of both genotype and environment meet requirements f o r s u r v i v a l . In t h i s sense, one can speak of average "gene t i c " and environmental c o n t r i b u t i o n s to v a r i a t i o n due t o the j o i n t e f f e c t s of genotype and environment. Animal breeders t h e r e f o r e , t r y t o change the average genotype of a population i n ways which w i l l improve performance under the p r e v a i l i n g environmental c o n d i t i o n s . As pointed out by Dickerson, (1962) t h i s r e q u i r e s p r e d i c t i o n of the environmental fut u r e of the pop u l a t i o n as w e l l , basing s e l e c t i o n on performance under environments which permit maximum accuracy i n p r e d i c t i n g a d a p t a b i l i t y t o future environments. However, phenotypic reranking of the genotypes due to genetic-environmental i n t e r a c t i o n complicates t h i s process. Pani and Lasley (1972), have provided a very d e t a i l e d review of GxE f o r many l i v e s t o c k s p e c i e s . F r i s c h (1976) has proposed a model f o r breed d i f f e r e n c e s i n growth of c a t t l e i n the t r o p i c s . A review of GxE i n t e r a c t i o n s i n 27 d a i r y c a t t l e by Goddard (1985), a r r i v e d at the co n c l u s i o n t h a t a GxE i n t e r a c t i o n occurred when the s u p e r i o r i t y i n breeding value of one animal over another v a r i e d from one environment t o another. W h i l s t Barlow (1985) has subdivided GxE i n t e r a c t i o n s i n t o i n t e r a c t i o n of the environment w i t h a d d i t i v e genes or i n t e r a c t i o n w i t h non-a d d i t i v e genes. As w e l l , adaptation i s a c o r o l l a r y of GxE; a genotype w e l l adapted to a c e r t a i n environment has more genes s u i t e d t o t h a t environment. These same genes may be of l i t t l e value i n an environment w i t h d i f f e r e n t c o n s t r a i n t s . GxE i n t e r a c t i o n s could a l s o be manifested as a consequence of "sc a l e e f f e c t s " . For example, i f two genotypes d i f f e r i n t h e i r a b i l i t y t o consume food (appetite) then the expression of t h i s d i f f e r e n c e w i l l be grea t e r when food i s p l e n t i f u l and l e s s when food i s l i m i t e d (Barlow, 1985). Hetzel (1984) suggested t h a t i n v e s t i g a t i o n s of GxE i n animal breeding could be conducted at three l e v e l s of complexity: (a) Production t r a i t s to e s t a b l i s h whether i n t e r a c t i o n e x i t s based on the genotypes and environments i n v o l v e d ; (b) Component t r a i t s which account f o r v a r i a t i o n i n production t r a i t s ; (c) Genetic v a r i a t i o n i n bio-chemical, p h y s i o l o g i c a l and immunological processes ( e s p e c i a l l y i f these can be measured e a r l y i n the animal's l i f e ) . In subsequent reviews, Barlow (1985); Warwick (1972); and. Syrstad (1976) concluded t h a t w h i l e 28 there i s c l e a r evidence of GxE where environments d i f f e r g r e a t l y (e.g. t r o p i c a l versus temperate), the bulk of experimentation suggests l i t t l e evidence of s e r i o u s i n t e r a c t i o n when genotypes are u t i l i z e d i n environments not very d i f f e r e n t from environments i n which they were s e l e c t e d . In order to t e s t a p o s s i b l e GxE i n t e r a c t i o n , at l e a s t two d i f f e r e n t genotypes must be t e s t e d i n at l e a s t two d i f f e r e n t environments. The general v a l i d i t y of the r e s u l t s obtained may be increased by i n c r e a s i n g the number of genotypes and/or environments. S t a t i s t i c a l l y , there are at l e a s t two methods by which an i n t e r a c t i o n between genotype and environment can be t e s t e d (Pani et a l . , 1972; Syrstad, 1976). Conventionally, an a n a l y s i s of variance based on a c r o s s - c l a s s i f i e d (two-way) model i s c a r r i e d out. The appropriate s t a t i s t i c a l mixed model i s : Y ) j k = M + Aj + Bj + (AB) -- + E j j k where Y i j k represents an observation on the k t h i n d i v i d u a l of j t h genotype i n the i t h environment; fjL, f i x e d u n d e r l y i n g population mean; A,-, the f i x e d e f f e c t of the i t h environment on the j t h genotype; B j , the random e f f e c t of the j t h genotype i n the i t h environment; (AB)^- , i n t e r a c t i o n of the j t h genotype with the i t h environment; and E i j k i s the 29 d e v i a t i o n of the k t h i n d i v i d u a l from the mean of the j genotype i n the i t h environment. documented i n l i t e r a t u r e i n c l u d i n g t h a t of Pani et a l . , (1972); and Schaeffer (1984). Secondly, based on the c o n s i d e r a t i o n of the phenotype expressed i n two d i f f e r e n t environments as being two separate c h a r a c t e r s , the gene t i c c o r r e l a t i o n between the two characters i s estimated (Falconer, 1952). A genetic c o r r e l a t i o n of u n i t y means t h a t no i n t e r a c t i o n between genotype and environment e x i s t s . While zero c o r r e l a t i o n i n d i c a t e s no r e l a t i o n s h i p between the rank order of var i o u s genotypes i n the two environments. In t h i s way, one can not only f i n d whether a s i g n i f i c a n t i n t e r a c t i o n i s present, but a l s o o b t a i n a q u a n t i t a t i v e measurement of the degree of i n t e r a c t i o n . According t o Calo et a l . , (1973), the expected product-moment c o r r e l a t i o n i s obtained as: The assumptions and a p p l i c a t i o n s of t h i s model have been I I I )/ ( I 0.5 E(r) = E i = l RPT i = l RPT 1i • E RPT i = l 30 where E(r) i s the expected c o r r e l a t i o n assuming a genetic c o r r e l a t i o n of u n i t y , RPT,,- and RPT2j- are r e p e a t a b i l i t i e s f o r the i t h s i r e i n the t e s t country and the country of o r i g i n , r e s p e c t i v e l y . D e t a i l s on the a p p l i c a t i o n of t h i s formula have been discussed by Calo et a l . , (1973) ; and the s t r a i n comparison study i n I s r a e l (Heiman et a l . , 1986) i s quoted here as a t y p i c a l example based on the a p p l i c a t i o n of t h i s formula. Accurate estimates of genetic parameters ( h e r i t a b i l i t i e s and genetic c o r r e l a t i o n s between t r a i t s ) , are c r i t i c a l i n the formulation of e f f e c t i v e breeding programs. Most estimates of genetic parameters f o r production t r a i t s i n d a i r y c a t t l e have been obtained using variance components a n a l y s i s (Anderson, 1979). Components of genetic v a r i a t i o n are important because they may be used t o express phenotypic covariance between r e l a t i v e s or to i d e n t i f y sources of v a r i a t i o n s . The a d d i t i v e genetic variance can be estimated d i r e c t l y e i t h e r from p a r e n t - o f f s p r i n g covariance or from h a l f - s i b covariance; the f u l l - s i b covariance i n c l u d e s a term due t o dominance, however. An a n a l y s i s of var i a n c e (ANOVA) can take many forms, some q u i t e complex, depending on the p a r t i c u l a r experimental d e s i g n and the v a r i a n c e components to be estimated ( H a r t l , 1980). I f the t r a i t o f i n t e r e s t cannot be ev a l u a t e d d i r e c t l y from the male, an experimental d e s i g n i n v o l v i n g p a t e r n a l h a l f - s i b s i s o f t e n used as t y p i f i e d i n the study o f the CANZ p r o j e c t . Most of the g e n e t i c improvement or g a i n f o r m i l k p r o d u c t i o n i s obtained through use of stud b u l l s which i n themselves do not e x h i b i t the t r a i t p h e n o t y p i c a l l y t o render d i r e c t o b s e r v a t i o n . The t o t a l phenotypic v a r i a n c e of the female o f f s p r i n g f o r the t r a i t i n v o l v e d , i s then p a r t i t i o n e d i n t o components t h a t can be r e l a t e d t o q u a n t i t i e s o f g e n e t i c i n t e r e s t . Method 3 estimates (Henderson, 1953) are then obtained by equating the s i r e and r e s i d u a l mean squares t o t h e i r e x p e c t a t i o n s and s o l v i n g f o r the s i r e components of v a r i a n c e . Hence, s i r e v a r i a n c e ( h a l f - s i b covariance) i s equal t o a 1/4 a d d i t i v e g e n e t i c v a r i a n c e . H e r i t a b i l i t y i s then obtained as: 4 a 2 s / ( a 2 s + a 2 e ) where, a 2 s i s the s i r e v a r i a n c e and a 2 e i s the environmental v a r i a n c e (which a l s o i n c l u d e s 3/4 a d d i t i v e g e n e t i c v a r i a n c e ) . However, one disadvantage of t h i s method i s t h a t i t does not account f o r a l l r e l a t i o n s h i p s among animals. 32 The value of an animal i s determined by many t r a i t s . The value of d a i r y c a t t l e , f o r example, i s determined i n p a r t by growth r a t e , e f f i c i e n c y of food u t i l i z a t i o n , age at f i r s t c a l v i n g , l i f e t i m e m i l k production, and t r a i t s other than production. Consequently, breeders u s u a l l y t r y to improve s e v e r a l t r a i t s of economic importance simultaneously. In t h i s regard, i t i s c r u c i a l t h a t animal breeding programs and eva l u a t i o n s take i n t o c o n s i d e r a t i o n , the nature of c o r r e l a t e d responses of some t r a i t s (to see that they are not a n t a g o n i s t i c w i t h each other and t o the d i r e c t i o n of genetic gain sought), the l e v e l of s e l e c t i o n and degree of r e l a t i o n s h i p s among animals being evaluated. Several computational models have been put forward i n attempts t o improve the accuracy of e s t i m a t i o n of var i a n c e components i n d a i r y c a t t l e s e l e c t i o n (e.g. Henderson, 1979; Uff o r d et a l . , 1979; Quaas and P o l l a k , 1981; Schaeffer and Kennedy, 1985; Meyer, 1988; Graser et a l . , 1987). According to H i l l et a l . , (1988), i f estimates are obtained using methods based on an u n c o n d i t i o n a l model ( i . e . no s e l e c t i o n and non-existence of animal r e l a t i o n s h i p s ) , they w i l l be biased s i n c e the parents are bound t o be r e l a t e d i f the p o p u l a t i o n under c o n s i d e r a t i o n i s f i n i t e ; so t h a t s i r e e f f e c t s are c o r r e l a t e d , dam e f f e c t s are c o r r e l a t e d , and 33 s i r e and dam e f f e c t s are c o r r e l a t e d w i t h each other. S i m i l a r l y , i f r e l a t i o n s h i p s among animals (on which information has been gathered f o r a n a l y s i s ) are gre a t e r than r e l a t i o n s h i p s i n the base po p u l a t i o n , any estimates thereof, w i l l be biased due t o d i f f e r e n c e s i n the degree of r e l a t i o n s h i p s i n the sampled animals and t h e i r base popu l a t i o n . In c o n t r a s t , R e s t r i c t e d Maximum L i k e l i h o o d (REML) est i m a t i o n ( H a r v i l l e , 1977) uses a l l inf o r m a t i o n a v a i l a b l e and under c e r t a i n c o n d i t i o n s , given a l l r e l e v a n t information i n which s e l e c t i o n d e c i s i o n s were based, accounts f o r s e l e c t i o n (Gianola et a l . , 1986); and even i f these c o n d i t i o n s are p a r t i a l l y met, REML estimators are oft e n considerably l e s s biased by s e l e c t i o n than t h e i r ANOVA counterparts (Meyer, 1988). REML a l s o accounts f o r the l o s s i n degrees of freedom due to f i x e d e f f e c t s i n the model of a n a l y s i s (Patterson and Thompson, 1971). Despite the t h e o r e t i c a l appeal of REML, i t s a p p l i c a t i o n has been r e s t r i c t e d by i t s rigorous computational requirements (e.g. repeated i n v e r s i o n of l a r g e c o e f f i c i e n t matrices and use of f i r s t and second d e r i v a t i v e s (Smith and Graser, 34 1986)) . As a r e s u l t , researchers have r e s o r t e d t o using v a r i a n t s of REML which are l e s s computationally demanding to o b t a i n s o l u t i o n s . According t o Meyer, (1988), the use of a d e r i v a t i v e - f r e e approach f o r REML e s t i m a t i o n of variance components was f i r s t proposed by Graser et a l . , (1987), and has provided a f l e x i b l e but powerful a l t e r n a t i v e t o REML algorithms. The l i n e a r model of a n a l y s i s envisaged f i t s an a d d i t i v e genetic e f f e c t , or breeding value f o r each animal w i t h records as w e l l as f o r any parents included i n the a n a l y s i s only through pedigree information. In a d d i t i o n , other random e f f e c t s (such as common enviromental or maternal genetic) may be f i t t e d (Meyer, 1988) . Such models which incorporate a l l information on r e l a t i o n s h i p s between animals are r e f e r r e d t o as animal models (AM). In these models, an a d d i t i v e genetic e f f e c t i s f i t t e d f o r each animal used i n the a n a l y s i s . 35 2. SOURCE OF DATA The data used i n t h i s study were ob t a i n e d from the Canada/New Zealand Genotype - Environmental I n t e r a c t i o n T r i a l (CANZ P r o j e c t ) which was i n i t i a t e d i n 1984 by the Canadian and New Zealand A.I. I n d u s t r i e s (Peterson e t a l . , 1984) . The o b j e c t i v e s o f the p r o j e c t were t o estimate d i f f e r e n c e s between p o p u l a t i o n s , t o estimate GxE i n t e r a c t i o n s and to develop f a c t o r s f o r c o n v e r t i n g s i r e p r o o f s from one country t o t h a t of another. 2.1 . I d e n t i f i c a t i o n Of S i r e s The s i r e s used i n the CANZ p r o j e c t , p r o v i d e d the g e n e t i c base t h a t was t o be ev a l u a t e d (Table 1) . S i r e s and s i r e groups were i d e n t i f i e d by the country of o r i g i n code, s i r e r e g i s t r a t i o n number, name and semen code (Table 1) . As c i t e d under s e c t i o n 1.1 of t h i s t h e s i s , these b u l l s were s e l e c t e d based on t h e i r ETA's (Peterson, 1988) as the top b u l l s i n t h e i r home c o u n t r i e s (milk y i e l d i n Canada and m i l k f a t i n New Zealand). Since s i r e s were s e l e c t e d based on p r o d u c t i o n , they represented a random sample of the a v a i l a b l e A.I. s i r e s f o r weight and w i t h e r h e i g h t t r a i t s and t h e r e f o r e should r e f l e c t p o p u l a t i o n d i f f e r e n c e s (Peterson, 1988). 36 2.2. Experimental Herds and Animals The f o u n d a t i o n female animals f o r t h i s p r o j e c t were the H o l s t e i n cows i n the v a r i o u s Canadian r e s e a r c h herds ( U n i v e r s i t y , C o l l e g e and A g r i c u l t u r e Canada) as i n d i c a t e d i n T able 2 (column 1) . These herds r e p r e s e n t e d a c r o s s s e c t i o n of herd management and farm c o n d i t i o n s i n Canada. The female cows represented a random sample of Canadian d a i r y cows. Planned matings (Peterson, 1988) u t i l i z e d f r o z e n semen which had been c o l l e c t e d from both s i r e groups ( s t r a i n s ) f o r inseminations a c r o s s a l l herds w i t h i n Canada. S i r e s w i t h i n s t r a i n were randomly a l l o c a t e d t o herds. Planned a l t e r n a t e use of s i r e s was adopted t o ensure t i e s between a l l 40 s i r e s . I f a cow t h a t was mated t o a p a r t i c u l a r s i r e d i d not conceive, a repeat mating u s i n g the same s i r e was done when the cow came i n t o heat. Otherwise, s i r e s and dams were randomly mated. ( D e t a i l s of mating d e s i g n have a l s o been c i t e d i n s e c t i o n 1.1 of t h i s t h e s i s ) . The progress of matings and normal s u c c e s s i o n of b i o l o g i c a l events i n c l u d i n g g e s t a t i o n , p a r t u r i t i o n and e v e n t u a l l y l a c t a t i o n of p r o j e c t h e i f e r s i s i n d i c a t e d i n Appendix 1. Table 2: Canadian Cooperate-r Herds inc l u d i n g Numbers of Project Calves born from CN and NZ S i r e s S i r e Groups HERDS1 CN NZ TOTAL Ag r i c u l t u r e Canada Research Station, Agassiz, B.C. (AG) 37 . 25 62 U n i v e r s i t y of Guelph, Ontario, (GU) 33 51 84 Univ e r s i t y of Manitoba, Manitoba, (MA) 23 13 36 Macdonald College, Quebec, (MD) 11 13 24 Nova Scotia A g r i c u l t u r a l College, Nova Scotia, (NS) 7 10 17 Olds A g r i c u l t u r a l College, Alberta, (OL) 11 15 26 Oyster River Research Farm, Uni v e r s i t y of B.C., (OR) 62 • 61 123 Un i v e r s i t y of Saskatchewan, Saskatchewan, (SA) 11 9 20 South Campus, Un i v e r s i t y of B.C., (SC) 22 18 40 Un i v e r s i t y of Alberta, Alberta, (UA) 24 19 43 TOTAL 241 234 475 1 According to Peterson, 1988 38 2.3. F e e d i n g And Management o f P r o j e c t H e i f e r s D u r i n g Growing Phase A l l h e i f e r s were grown under t h e "normal" f e e d i n g and management system f o r t h e h e r d s . T h i s system was c o n s i d e r e d t o be w i t h i n t h e normal range f o r w e l l managed Canadian d a i r y h e r d s and p r o v i d e d an o p p o r t u n i t y f o r adequate, i f not maximum growth r a t e , so t h a t h e i f e r s would be b r e d t o c a l v e a t two y e a r s o f age. T a r g e t w e i g h t a t f i f t e e n months o f age was 360 t o 375 kg, when h e i f e r s were t o be b r e d and t h e t a r g e t w e i g h t a t c a l v i n g was 450 t o 500 kg ( P e t e r s o n , 1984). 2 . 4 . B r e e d i n g P r o t o c o l o f P r o j e c t H e i f e r s A l l p r o j e c t a n i m a l s were managed w i t h a normal r e p r o d u c t i v e program. H e i f e r s were b r e d a t f i f t e e n months o f age o r a t t h e f i r s t o b s e r v e d h e a t . H e i f e r s were b r e d a t l e a s t t h r e e t i m e s ( i f needed) u s i n g A . I . and subsequent b r e e d i n g c o u l d use t h e " c a t c h " b u l l . A n i m a l s w h i c h d i d n o t c o n c e i v e by two hundred days a f t e r 15 months o f age were c o n s i d e r e d non-breeders and were c u l l e d ( P e t e r s o n , 1987). Any measurements t a k e n p r e v i o u s t o c u l l i n g remained p a r t o f t h e dat a b a s e . 2.5. Loss o r Removal o f h e i f e r s from P r o j e c t P r i o r t o 24 months o f age, s i c k and i n j u r e d a n i m a l s were c u l l e d i f i t was a b s o l u t e l y n e c e s s a r y and o n l y i n c o n s u l t a t i o n w i t h one of the researchers (Peterson, 1988). Henceforth, the t o t a l number of h e i f e r s w i t h i n the p r o j e c t d e c l i n e d w i t h time as r e f l e c t e d i n Table 3. In most of the age c a t e g o r i e s , daughters of both s i r e groups were almost evenly d i s t r i b u t e d on a w i t h i n herd b a s i s . 2 . 6 . Measurements and Data C o l l e c t i o n Data were recorded by t e c h n i c i a n s at the va r i o u s farms using designed data s t r u c t u r e s and codes. From b i r t h of h e i f e r s to t h e i r f i r s t c a l f , weight and wither height of p r o j e c t h e i f e r s were recorded mostly on a monthly b a s i s or date c l o s e s t t o t h i s p e r i o d . However, the design of the experiment (Peterson, 1988) req u i r e d measurements at 3 month i n t e r v a l s . A l s o , c a l v i n g ease, h e a l t h and treatment records, temperament, estrus and breeding i n f o r m a t i o n were recorded. This study u t i l i z e d data t h a t were c o l l e c t e d up to the time j u s t p r i o r to c a l v i n g . A d d i t i o n a l data were c o l l e c t e d at l e a s t through the f i r s t l a c t a t i o n but t h i s i n formation was not included i n t h i s a n a l y s i s . E s s e n t i a l l y , the database i n t h i s study was made up of repeated measurements of weight and wit h e r height on each i n d i v i d u a l animal at 3 month i n t e r v a l s . 4 0 Table 3t Number of Animals based on Age (months) i n each Herd Age Herd Group B i r t h 3 4 . 5 6 9 12 1 5 1 8 2 1 24 A G C N 37 36 36 36 36 3 6 36 36 31 24 NZ 25 23 23 23 2 3 2 3 2 3 2 3 2 1 17 GU C N 33 33 33 33 1 17 4 2 0 2 24 NZ 51 51 51 48 10 42 14 4 1 13 42 MA C N 23 23 23 23 3 22 11 20 6 15 NZ 13 13 13 13 3 13 7 12 2 7 MD C N 11 10 8 9 9 5 4 _ _ _ NZ 13 9 7 7 4 1 1 - - -NS C N 7 7 7 7 6 4 2 1 1 2 NZ 10 10 9 7 8 6 5 3 3 2 O L C N 11 8 8 7 3 _ _ _ _ _ NZ 15 13 13 12 2 - - - - -OR C N 62 57 56 56 56 57 55 5 0 46 3 1 NZ 61 60 60 59 60 60 55 57 39 48 S A C N 11 11 11 11 11 11 11 11 10 8 NZ 9 9 9 9 9 9 9 9 8 7 SC C N 22 21 21 21 21 21 21 21 21 17 NZ 18 18 18 18 18 17 17 17 16 11 U A C N 24 20 19 18 _ 14 11 2 _ 6 NZ 19 13 13 12 — 11 7 — — 4 T o t a l C N 2 4 1 2 2 6 2 2 2 2 2 1 1 4 6 187 1 5 5 1 6 1 1 1 7 1 2 7 NZ 2 3 4 2 1 9 2 1 6 2 0 8 137 1 8 2 1 3 4 1 6 2 1 0 2 1 3 8 - = not a v a i l a b l e Table 4t Number of Animals based on Age (months) i n each S i r e Group Age S t r a i n B i r t h 3 475 6 9 12 15 I I 21 24 CN NZ BOTH 2 4 1 234 4 7 5 2 2 6 2 2 2 2 2 1 146 187 155 161 117 127 2 1 9 2 1 6 2 0 8 137 1 8 2 138 1 6 2 1 0 2 138 4 4 5 4 3 8 4 2 9 2 8 3 3 6 9 2 9 3 3 2 3 2 1 9 2 6 5 41 2 . 7 . Age Analyses used i n t h i s study, i n c l u d e d weight and wither height data c o l l e c t e d a t or the observations c l o s e s t t o b i r t h , 3, 4.5, 6, 9, 12, 15, 18, 21 and 24 months. Each animal i n the database had only one record f o r weight and one f o r wither height (taken at the same ti m e ) , i f i t was present i n the herd at the s p e c i f i e d ages. The raw observations f o r each i n d i v i d u a l animal which were taken p r i o r t o or l a t e r than one month i n t e r v a l were age co r r e c t e d i n order t o ob t a i n data based on the r e q u i r e d ages of an animal i n common w i t h other animals, u s i n g the r a t e of change from previous measurements t o the current one being analyzed. For example, weight at 3 months age was adjusted based on 30.5 days i n a month as f o l l o w s : Adj. WT = WT (recorded) - B i r t h WT) x 91.5 Age (days) + B i r t h WT Wither heights were a l s o adjusted i n a s i m i l a r manner. When a previous observation was missing the average r a t e of change f o r the age group, s i r e group and herd was used t o regress the observation on an i n d i v i d u a l animal t o the appropriate age. As o b s e r v a t i o n a l changes were considered cumulative, adjustments at any other ages g r e a t e r than 3 42 months were based on a previous measurement or on b i r t h weight and number of days i n between. No c o r r e c t i o n was made f o r stage of pregnancy. 2.8. Observational Animals A v a i l a b l e animals f o r data c o l l e c t i o n at v a r i o u s ages are given i n Tables 3 and 4. A l t o g e t h e r , a t o t a l of 475 h e i f e r s were born ( i e . 241 h e i f e r s from 20 CN s i r e s and 234 h e i f e r s from 20 NZ s i r e s ) and each herd had daughters from both s t r a i n s (Table 2). Each s i r e had m u l t i p l e progenies and the s i z e of the h a l f - s i b groups ranged from f i v e t o twenty h e i f e r s with a mean of 11.9 h e i f e r s per s i b group (Table 1). 2.9. Constituted Data Data accumulated during the p e r i o d of A p r i l , 1985 t o June, 1990 formed the b a s i s of t h i s study. A t o t a l of 12,784 pa i r e d weight and wither height were recorded and these were e d i t e d t o give a database of 3,539 records of weights and wither heights. Records were removed from the database i f ( i ) date f o r record was missing and could not be p r e c i s e l y guessed at based on previous or l a t e r records; ( i i ) d u p l i c a t e observation f o r an i n d i v i d u a l animal, i . e . records' taken twice i n the same month; ( i i i ) s i n c e t h i s study r e q u i r e d measurements at 3 month i n t e r v a l s , data 43 c o l l e c t e d monthly or i n between were discarded as su r p l u s . The a v a i l a b i l i t y of the monthly measurements i n the database helped t o increase the accuracy of adjustments made to the raw data. Three c a t e g o r i e s of database were e s t a b l i s h e d based on the Canadian and New Zealand s i r e groups; as w e l l as both groups together. The database i n v o l v i n g both s i r e groups was analyzed t o represent the base p o p u l a t i o n as w e l l as mean values. CHAPTER ONE WEIGHT AND WITHER HEIGHT OF CANADIAN AND NEW ZEALAND SIRED DAIRY HEIFERS 3.1. INTRODUCTION Genetic variance i s used by breeders t o change animal populations. Since s e l e c t i o n i s the only f o r c e a v a i l a b l e to the breeder to make cumulative d i r e c t i o n a l change; development of population d i f f e r e n c e s , use of these d i f f e r e n c e s and s e l e c t i o n of stock w i t h i n populations must be optimized (Willham et a l . , 1985). For example, corresponding changes to s e l e c t i o n have been r e s p o n s i b l e f o r increases i n milk y i e l d as w e l l as s i z e and s t a t u r e i n the North American H o l s t e i n and New Zealand F r i e s i a n c a t t l e . The e v a l u a t i o n of economically important d a i r y c a t t l e t r a i t s depends upon a c a r e f u l program of keeping performance records. A l l animals of a given sex and age c l a s s must be fed and managed as n e a r l y a l i k e as p o s s i b l e so t h a t observed d i f f e r e n c e s w i l l have a maximum ge n e t i c component. Growth defined as maturation of the reproductive system, as w e l l as an increase i n body s i z e and weight (Heinrichs et a l . , 1987), i s a f f e c t e d by g e n e t i c s , n u t r i t i o n , management, housing and h e a l t h . Every animal has an inherent mature body s i z e toward which i t grows at a g e n e t i c a l l y c o n t r o l l e d r a t e (Brody, 1945), a c c e l e r a t e d or delayed by environmental f a c t o r s (Blackmore et a l . , 1958). 46 Weight i s a slower maturing ch a r a c t e r than height and consequently c a t t l e a t t a i n a higher p r o p o r t i o n of mature height than mature weight f a s t e r u n t i l both measures have reached mature values (Brody, 1945). As weight approaches height i n degree of maturity, weight t o height r a t i o i ncreases. Within l i n e and across l i n e d a i r y c a t t l e breed d i f f e r e n c e s f o r s i z e and s t a t u r e have been e x t e n s i v e l y documented i n l i t e r a t u r e (Peterson, 1988; Long et a l . , 1979; Batra et a l . , 1983; Kebede et a l . , 1982; McDowell et a l . , 1969; H e i n r i c h s et a l . , 1987; Touchberry et a l . , 1966; Donald et a l . , 1977; Lee et a l . , 1978; J a s i o r o w s k i et a l . , 1981; Hinkovski et a l . , 1982; L i n et a l . , 1985; Mason et a l . , 1982; Willham et a l . , 1985; Calo et a l . , 1973). A l s o , d i f f e r e n t breeds have d i f f e r e n t stages of maturity of the weight and height components (Long et a l . , 1979). Rapidly growing h e i f e r s may be bred at an e a r l i e r age thus reducing replacement costs and generation i n t e r v a l . Hargrove et a l . , (1987) have s t u d i e d growth patterns (wither height and heart g i r t h ) of H o l s t e i n h e i f e r s i n 163 commercial d a i r y herds i n Pennsylvania, USA i n an attempt to develop standards or "normal" weights and heights of c a t t l e from 1 t o 24 months of age. Weight and height means from t h i s study are shown i n Appendix 3. P a r t i a l r e s u l t s of a study t o chart the growth of d a i r y h e i f e r s by the 47 Ontario M i n i s t r y of A g r i c u l t u r e and Manitoba A g r i c u l t u r e (OMA), (1980-1982) are a l s o shown i n Appendix 3 t o i n d i c a t e "normal" growth r a t e s i n the Canadian d a i r y i n d u s t r y . In a subsequent review of the Ontario and Manitoba study, Murray and Kennedy (198 3) reported w i t h e r height, weight and age of replacement h e i f e r s i n terms of the mean, standard d e v i a t i o n and range as: 121.4, 12.3, 87.6 t o 144.8 cm; 348.1, 128.4, 102 to 666 kg; and 15.1, 7.0, 4.0 t o 31.6 months r e s p e c t i v e l y . R e s u l t s of the 1980-82 Eastern Ontario h e i f e r management study concluded t h a t approximately 30 t o 40 percent of the v a r i a t i o n i n both height and weight was due t o g e n e t i c d i f f e r e n c e s (Droppo, 1987). The remaining v a r i a t i o n being a t t r i b u t e d t o other non-genetic f a c t o r s mentioned e a r l i e r . In a study i n v o l v i n g p u r e l i n e and c r o s s l i n e h e i f e r s of the Canadian d a i r y c a t t l e breeding p r o j e c t , Batra et a l . , (1983) concluded t h a t l a r g e s i g n i f i c a n t d i f f e r e n c e s among experimental s t a t i o n s i n body weights and dimensions of d a i r y h e i f e r s from b i r t h to 21 months of age i n s p i t e of standardized g r a i n feeding were due to the q u a l i t y of roughages and general management. Hinkovski et a l . , (1984) reported t h a t i n the B u l g a r i a n comparison i n v o l v i n g red and white s t r a i n s of d a i r y c a t t l e , farm c o n d i t i o n s had 48 a very strong impact on l i v e weight at 3, 6, 12 and 18 months of age. Bar-Anan et a l . , (1987) have reported t h a t New Zealand s i r e d h e i f e r s were ( f o r body weight and height) s m a l l e r than Canadian s i r e d h e i f e r s i n the I s r a e l s t r a i n comparison. In the P o l i s h T r i a l , females of the F., generation weighed 3 5.5 kg at b i r t h , 227 kg at 12 months and 369 kg at 18 months (Jasiorowski et a l . , 1984). A l l weights v a r i a t i o n among s t r a i n s was s i g n i f i c a n t (P < 0.01) with the Canadian s t r a i n being heavier than the NZ s t r a i n . There i s scarce i n f o r m a t i o n f o r height measurements on the F1 females i n t h i s t r i a l . Stolzman et a l . , (1981), have reported t h a t at 29 months of age Canadian s i r e d h e i f e r s were s i g n i f i c a n t l y (P < 0.01) heavier and t a l l e r than the New Zealand s i r e d h e i f e r s (476.90 vs 469.90 kg and 129.80 cm vs 127.56 cm) r e s p e c t i v e l y . Peterson, (1988) has reported t h a t daughters of Canadian p r o j e c t s i r e s i n New Zealand were heavier than the New Zealand group (both groups having been reared i n the New Zealand environment) at each age from b i r t h t o 30 months. The Canadian group was a l s o t a l l e r at each age. Herd, group and s i r e s w i t h i n group were s i g n i f i c a n t sources of v a r i a t i o n f o r weights and heights at a l l ages. S i g n i f i c a n t d i f f e r e n c e s (P < 0.05) were found both f o r 49 weight and wither height at b i r t h , 6, 18 and 30 months (Appendix 4). This chapter deals w i t h Part (1) of the o b j e c t i v e s of t h i s study i n order t o compare Canadian and New Zealand s i r e d H o l s t e i n - F r i e s i a n h e i f e r s f o r s i z e and growth i n terms of age adjusted body weights and wither height at v a r i o u s ages under normal Canadian farm c o n d i t i o n s , feeding and management. 50 3.2. MATERIALS AND METHODS 3.2.1. Animals A v a i l a b l e animals f o r data c o l l e c t i o n at v a r i o u s ages have been described under "Source of Data" ( s e c t i o n 2.8) and given i n Tables 3 and 4. 3.2.2. Data Data u t i l i z e d i n t h i s a n a l y s i s have been described under "Source of Data" ( s e c t i o n 2.9). 3.2.3. S t a t i s t i c a l Analysis The a n a l y s i s of data was done using three c a t e g o r i e s (as explained i n s e c t i o n 2.9). The data f o r the Canadian and New Zealand s i r e groups were analyzed s e p a r a t e l y and then both combined together. Age was used t o subset the three c a t e g o r i e s . Data recorded during the ages of b i r t h , 3, 4.5, 6, 9, 12, 15, 18, 21 and 24 months p r i o r t o c a l v i n g were analyzed using l e a s t squares procedures i n order to estimate the e f f e c t s of d i f f e r e n t f a c t o r s i n the model. Two h i e r a r c h i c a l (nested) l i n e a r mixed models were used. The f i r s t mixed model i n d i c a t e d below was used t o t e s t f o r any i n t e r a c t i o n between the f i x e d e f f e c t s : Y-jkl = a + H,- + G j + K,*G.} + S(G) j k + E i j k l (1) 51 the e f f e c t s i n the model are defined as f o l l o w s : Y i j k l i s i n d i v i d u a l n t h observation on the 1 t h daughter of the k t h s i r e i n the j t h s i r e group i n the i t h herd; H i s o v e r a l l p o p u l a t i o n mean, a f i x e d e f f e c t common t o a l l observations; Hj i s the f i x e d e f f e c t of the i t h herd; Gj i s the f i x e d e f f e c t of the j t h s i r e group or s t r a i n ; Hj*Gj i s the f i x e d e f f e c t of S t r a i n x Herd i n t e r a c t i o n . E f f e c t i s common to daughters of k t h s i r e i n j t h group i n i t h herd ; S(G) J k i s a random e f f e c t of the k t h s i r e i n the j t h group common t o daughters of th a t s i r e ; E j j k l i s random e r r o r a s s o c i a t e d w i t h each observation on the 1 t h daughter of the k t h s i r e i n the j t h group i n the i t h herd, - NID (0, a2 e) . Least squares a n a l y s i s using t h i s model i n d i c a t e d t h a t herd x s t r a i n e f f e c t s were not s i g n i f i c a n t (P < 0.05) f o r a l l t r a i t s . Hence, a subsequent a n a l y s i s usinq equation (2) was c a r r i e d out. The l i n e a r model was reduced f o r comparing d i f f e r e n c e s between herds and s t r a i n as shown below: Y i J k l = H + H,. + Gj + S(G) j k + E i j k l (2) The e f f e c t s are defined as i n the previous model. Accodingly, the assumptions of t h i s model were t h a t s i r e s 52 were randomly mated t o dams, t h a t dams were un r e l a t e d and represented i n the data by only one daughter, and t h a t a l l i n t e r a c t i o n s were i n s i g n i f i c a n t . A n a l y s i s of (co)variance (ANOVA) f o r the f i x e d e f f e c t s of herd, s t r a i n and s t r a i n x herd i n t e r a c t i o n was performed using PROC GLM of SAS ( S t a t i s t i c a l A n a l y s i s System - PC Ve r s i o n 6.04, 1990). The e r r o r p r o b a b i l i t y f o r t e s t s of s i g n i f i c a n c e was set at P < 0.05. Least squares means (LS means) and standard e r r o r s (s.e.) f o r weight and wither height were generated from t h i s a n a l y s i s . M u l t i p l e Comparisons of main e f f e c t s means were performed using the Student-Neuman-Keuls t e s t (SNK). Residual p l o t s , using PROC U n i v a r i a t e of SAS (PC Version 6.04, 1990) f o r each age subclass a n a l y s i s were examined v i s u a l l y t o screen f o r o u t l i e r s and t o t e s t f o r normality of r e s i d u a l s . A p l o t of standardized r e s i d u a l s against the f i t t e d values i n d i c a t e d t h a t the l i n e a r model was appropriate, and t h a t there were no o u t l i e r s i n the database. 53 3.3 . RESULTS AND DISCUSSIONS 3.3.1. Fixed E f f e c t s of Herd and S t r a i n The herd x s t r a i n e f f e c t s i n t e r a c t i o n s were not s i g n i f i c a n t , (P < 0.05) f o r weight or wi t h e r height at any age. A summary of the r e s u l t s of the l e a s t squares a n a l y s i s of variance are presented i n Tables 5 and 6. Table 5 a l s o shows the values of R2 f o r the s t a t i s t i c a l model, th a t i s the p r o p o r t i o n of the t o t a l v a r i a t i o n i n each t r a i t t h a t was accounted f o r by f i t t i n g the model. P a r t i a l R2 values are a l s o shown f o r the i n d i v i d u a l e f f e c t s i n the model. The e f f e c t of herd was a s i g n i f i c a n t (P < 0.05) source of v a r i a t i o n f o r both t r a i t s , s i r e groups and a l l age c l a s s e s except at b i r t h and 24 months of age f o r wither height where there was no s i g n i f i c a n c e . Whereas, the e f f e c t of s t r a i n was not s i g n i f i c a n t (P < 0.05) i n a l l ages except at 15 and 18 months f o r weight; i t was s i g n i f i c a n t (P < 0.05) f o r wither height i n a l l ages except at b i r t h , 3 and 9 months. The s i r e s w i t h i n group source of v a r i a t i o n was s i g n i f i c a n t (P < 0.05) at b i r t h , 9, 12, 15, 18, 21 and 24 months f o r wither h e i g h t ; and at b i r t h , 4.5, 9, 12 and 18 months f o r weight. These d i f f e r e n c e s were a l s o reported by Peterson, (1988) i n the CANZ T r i a l i n New Zealand. 54 Table 5: Summary of the Analysis of Variance t Weight(kg) and Wither Height(cm) Weight" Age Total* Total" Herd S t r a i n H*G1 S(G) f i t t e d CSS B i r t h 0. 2980 10749 .8087 0. 0982* 0. 0071 0. 0158 0. 1712* 3 0. 2843 115949 .1044 0. 1788* 0. 0003 0. 0229 0. 0804 4.5 0. 3363 181667 .5347 0. 2122* 0. 0002 0. 0043 0. 1020* 6 0. 3496 274905 .0236 0. 2425* 0. 0009 0. 0071 0. 0809 9 0. 4420 215995 .6119 0. 2385* 0. 04E-04 0. 0126 0. 1570* 12 0. 4779 439321 .9731 0. 3085* 0. 0015 0. 0216 0. 1335* 15 0. 3525 387924 .2517 0. 1787* 0. 0063* 0. 0296 0. 1423 18 0. 3276 525225 .5791 0. 1422* 0. 0008* 0. 0082 0. 1589* 21 0. 3867 445471 .4475 0. 1496* 0. 0044 0. 0137 0. 1856 24 0. 3700 890880 .5349 0. 2051* 0. 0011 0. 0208 0. 1184 Wither Height 0 B i r t h 0. 1937 4528 .5979 0. 0313 0. 0018 0. 0312 0. 1566* 3 0. 1518 6694 .9682 0. 0685* 0. 0019 0. 0336 0. 0738 4.5 0. 1794 7142 .2090 0. 0627* 0. 0095* 0. 0122 0. 0936 6 0. 2613 9270 .5392 0. 1641* 0. 0083* 0. 0118 0. 0869 9 0. 3544 5323 .9347 0. 1491* 0. 0016 0. 0395 0. 1536* 12 0. 2787 6024 .4409 0. 0732* 0. 0346* 0. 0293 0. 1494* 15 0. 2795 4096 .7930 0. 0466* 0. 0388* 0. 0167 0. 1745* 18 0. 3547 4274 .3399 0. 0539* 0. 0610* 0. 0163 0. 1902* 21 0. 4943 3138 .3434 0. 0664* 0. 0867* 0. 0084 0. 2658* 24 0. 3838 2888 .6137 0. 0335 0. 1235* 0. 0147 0. 1899* 'Values i n t h i s column were obtained from the s t a t i s t i c a l model of Equation 1 and are not included i n "a" i n t h i s t a b l e . "Fraction of the t o t a l sums of squares (R2) accounted f o r by f i t t i n g the e f f e c t s i n the s t a t i s t i c a l model of equation (2) b T o t a l corrected sums of squares f o r weight (kg 2) and height (cm2) "Fraction of the t o t a l sums of squares ( P a r t i a l R 2)accounted f o r by each e f f e c t i n the s t a t i s t i c a l model 'Sign i f i c a n t source of v a r i a t i o n (P < 0.05) Table 6: Weight and Height ANOVA Degrees of Freedom Age TCSS Herd S t r a i n Herd*Strain 1 S l r e ( S t r a i n ) B i r t h 474 9 1 9 38 3 444 9 1 9 38 4.5 437 9 1 9 38 6 428 9 1 9 38 9 282 8 1 8 38 12 368 8 1 8 38 15 292 8 1 8 38 18 322 7 1 6 38 21 218 6 1 6 38 24 264 7 1 7 38 1Degrees of Freedom i n t h i s column were obtained from the s t a t i s t i c a l model of Equation (1) and are not included i n TCSS. 56 Since s i r e s were used w i t h i n s t r a i n across herds, herd d i f f e r e n c e s are l i k e l y t o be due t o management and environmental i n f l u e n c e s . This has been the case i n other s t u d i e s (Hinkovski et a l . , 1984; and Batra et a l . , 1986). 3.3.1.1. Sire Group (Strain) E f f e c t s Least Squares Means Group l e a s t squares means and standard e r r o r s f o r weight and wither height are presented i n Table 7 A and B. P l o t s of wither heights appear i n Appendix 5. Estimates are based on the number of animals i n each s i r e group i n each age c l a s s (Table 4). Standard erros of l e a s t squares means ranged from 0.3 to 6.2 kg f o r weight and 0.2 t o 0.5 f o r wither height i n both s t r a i n s . Weight LS means f o r the s t r a i n s were not s i g n i f i c a n t l y d i f f e r e n t (P < 0.05) at b i r t h , 3, 4.5, 6, 9, 12, 21 and 24; but at 15 and 18 months of age weight LS means were s i g n i f i c a n t l y d i f f e r e n t (P < 0.05), ( i e . 393 kg vs 386 kg and 447 kg vs 445 kg f o r CN s t r a i n vs NZ s t r a i n r e s p e c t i v e l y ) , (Table 7 A). S i g n i f i c a n t d i f f e r e n c e s between s i r e groups at b i r t h , 6 and 18 months of age have been reported by Peterson, (1988) i n New Zealand. In correspondence w i t h d i f f e r e n c e s found i n 57 Table 71 Weight and Wither Height Least squares Means of Canadian and New Zealand Sired Holstein Heifers A: Weight and Wither Height Least Squares Means with Standard Errors (S.E.), (S t r a i n Basis) S i r e Groups Canadian New Zealand Aqe (mos) Weight (kg) Height (cm) Weight (kg) Height (cm) B i r t h 42.1 ±0.3 75.8 ±0.2 41.3 ±0.3 75.5 ±0.2 3 109.7 ±1.1 91.6 ±0.3 110.3 ±1.1 91.3 ±0.3 4.5 141.7 ±1.4 97.5b ±0.3 141.1 ±1.4 96.6° ±0.3 6 186.8 ±1.7 104.8" ±0.3 188.4 ±1.8 103.9° ±0.3 9 260.3 ±2.7 114.2 ±0.5 260.4 ±2.7 113.8 ±0.4 12 335.8 ±2.6 121.6" ±0.4 332.9 ±2.7 119.9° ±0.4 15 392.6 ±3.6 126.9" ±0.4 386.2" ±3.8 125.3° ±0.4 18 447.3 ±4.9 130.7" ±0.4 444.8" ±5.2 128.7° ±0.5 21 490.5 ±5.7 133.0" ±0.4 497.4 ±5.5 130.4° ±0.4 24 543.0 ±6.2 135.5" ±0.3 538.8 ±6.2 132.9° ±0.3 Means with the same superscript within row f o r the same t r a i t are not s i g n i f i c a n t l y d i f f e r e n t (P < 0.05) - = not a v a i l a b l e B: Weight and Wither Height Least Squares Means (Both S i r e Groups) Weight (kg) Height (cm) Age (mos) Mean S.e. Mean S.e. B i r t h 41.9 0.3 75.6 0.2 3 112.6 1.1 91.8 0.3 4.5 145.4 1.4 97.3 0.3 6 193.0 1.7 104.9 0.3 9 263.3 2.7 114.0 0.5 12 334.0 2.6 120.8 0.4 15 388.8 3.6 125.9 0.4 18 439.0 4.9 129.7 0.4 21 492.5 5.7 132.2 0.4 24 528.9 6.2 134.3 0.3 58 Canada at 18 months, Canadian s i r e d daughters were heavier than New Zealand s i r e d daughters (357.10 kg vs 346.90 kg r e s p e c t i v e l y ) , as shown i n Appendix 4. However, the r e s u l t s of t h i s study at b i r t h and 6 months of age do not show any s i g n i f i c a n t d i f f e r e n c e s (P < 0.05), (42.1 kg vs 41.3 kg and 186.80 kg vs 188.40 kg r e s p e c t i v e l y ) . The New Zealand study had values of 154.0 kg vs 148.0 kg. (Appendix 4) • Daughters of the Canadian group were s i g n i f i c a n t l y (P < 0.05) t a l l e r than the daughters of New. Zealand s i r e s at a l l ages except b i r t h , 3 and 9 months (Appendix 5) . These d i f f e r e n c e s between groups are c o n s i s t e n t w i t h those found i n the t r i a l i n New Zealand (Peterson, 1988) , Appendix 4. The Canadian s t r a i n was t a l l e r than the New Zealand s t r a i n . Heights were 98.0 cm vs 97.0 cm at 6 months; and 12 0.0 cm vs 118.0 cm at 18 months r e s p e c t i v e l y (Appendix 4). The d i f f e r e n c e s of 1.0 cm and 2.0 cm i n the CANZ T r i a l i n New Zealand are s i m i l a r t o those found i n t h i s study at the same ages. The agreement between the two s t u d i e s suggests t h a t growth i n terms of height i n New Zealand i s s i m i l a r t o t h a t i n Canada. 59 In comparison of the CANZ T r i a l weight and wi t h e r height data t o the Ontario (OMA) and Pennsylvania (USA) data i n Appendix 3, at b i r t h CANZ and OMA h e i f e r s had the same weight; although, CANZ h e i f e r s were heavier than both OMA and USA h e i f e r s at 3, 4.5, 6, 9, 12 and 15 months. At 18, 21 and 24 months the OMA h e i f e r s were heavier than CANZ and USA h e i f e r s ; w h i l s t , OMA h e i f e r s were heavier than the USA h e i f e r s at a l l ages. In terms of wi t h e r h e i g h t s , the OMA h e i f e r s were the t a l l e s t at 3, 4.5, 6, 9, 12, 15, 18, 21 and 24 months; except at b i r t h when the CANZ h e i f e r s were as e q u a l l y t a l l (75.0 vs 75.6 cm r e s p e c t i v e l y ) , and the USA h e i f e r s were the s h o r t e s t at a l l corresponding ages. The OMA data f o r height seem exceedingly t a l l (at l e a s t 6 t o 10 cm t a l l e r than CANZ and USA r e s p e c t i v e l y ) between 4.5 and 24 months. The CANZ T r i a l data a l s o correspond w i t h those of Murrary and Kennedy, (1983). These r e s u l t s support the view t h a t CANZ T r i a l h e i f e r s had normal growth patterns s i m i l a r t o those expected i n the d a i r y i n d u s t r y i n Canada and the USA. 60 3.3.1.2. Herd E f f e c t s Least Squares Means Least square means and standard e r r o r s f o r herd weights and wither heights are presented i n Figures 1 t o 10 and Appendix 6 and 7 based on the number of animals i n each herd i n each age c l a s s (Table 3) . Weights and wither heights were not a v a i l a b l e f o r OL (at 12, 15, 18, 21 and 24 months); MD (at 18, 21 and 24 months) and UA (at 9 and 21 months). S i g n i f i c a n t d i f f e r e n c e s observed among herds f o r weight and wither height from b i r t h t o 24 months of age were as described below. As shown i n Figures 1 to 10 weight d i f f e r e n c e s among herds were s i g n i f i c a n t (P < 0.05) at b i r t h , 3, 4.5, 6, 12, 15, 18 and 24 months. At 9 months, MD and NS herds had the lowest weights (229.7 kg and 229.1 kg) which were s i g n i f i c a n t l y -d i f f e r e n t (P < 0.05) from the r e s t of the herds. SA had the highest weight at 21 months (541.3 kg) and a l l other herd d i f f e r e n c e s were not s i g n i f i c a n t . At b i r t h , GU, NS and SC herds had the highest weights (43.6, 43.4 and 43.2 kg) r e s p e c t i v e l y ; w h i l e OL had the lowest weight (38.8 kg). At 3, 4.5 and 6 months, GU herd had the highest weights (123.8, 158.8 and 210.7 kg) r e s p e c t i v e l y ; while OL had the highest weight at 9 months (285.5 kg). UA had the highest weights at 12, 15 and 18 Figure 1: Comparison of Herds: LS Means at Birth 61 45 42.5 W e g h t (kg) 37.5 40 35 AG W e i g h t H e i g h t 39.9 75 GU 43.6 75 • MA 41.9 75.8 MD 41.3 75.5 i NS 43.4 76.4 1 OL 38.8 74.8 H i Weight CZ3 Height OR 43.1 75.7 SA 41.5 75.3 SC 43.2 76.6 80 77.5 75 72.5 70 67.5 65 62.5 60 - 57.5 (cm) - 55 -52.5 50 UA 40 76.4 H e i g h t Herds Means with the same superscript within trait do not differ (P < 0.05) Figure 2: Comparison of Herds: LS Means at 3 Months Herds Means with the same superscript within trait do not differ (p < 0.05) Figure 3: Comparison of Herds: LS Means at 4.5 Months w e g h t (kg) 160 155 150 145 140 135 130 125 120 115 1 10 W e i g h t H e i g h t b a a • 1 I Weight E 3 Height MET AG GU 153.3158.8140 98.7 98 MA .7 98.5 MD 130 96 NS I OL 133.9148.6 96.6 96.5 1 I OR 144 96.3 SA 131 95 d c b b^ SC i UA 127.9145.8 97.8 97.4 100 98 96 94 92 90 Herds Means with the same superscript within trait do not differ (p < 0.05) Figure 4: Comparison of Herds: LS Means at 6 Months H e g h t (cm) w e i g h t (kg) 215 -| 205 195 185 175 165 155 145 W e i g h t H e i g h t i 1 1 i i Weight E D Height T AG GU 202.7210.7183.2159.2 106.5106.5104.7101.3 MA MD I NS I OL 170.1193.4 I OR 190 102.1103.5102.9102.9 SA SC 179.4183.3203.9 108 i 115 112.5 110 107.5 h 105 102.5 100 UA 105.3 H e i g h t (cm) Herds Means with the same superscript within trait do not differ (p < 0.05) Figure 5: Comparison of Herds: LS Means at 9 Months H e i g h t (cm) Herds Means with the same superscript within trait do not differ (p < 0.05) Figure 6: Comparison of Herds: LS Means at 12 Months w e i g h t (kg) 375 360 H 345 330 315 300 285 270 W e i g h t H e i g h t c b b • i AG c b c a b • I 120.8 GU 121.7 i 1 I MA MD 353.5350.8320.9036.2293.1 121.4120.4118.4 NS OL Weight CZl Height 314.8 120 SC 338 326.7375.3 120.3123.4120.3 125 h 122.5 120 h 117.5 115 h 112.5 110 UA H e i g h t (cm) Herds Means with the same superscript within trait do not differ (p < 0.05) Figure 7: Comparison of Herds: LS Means at 15 Months 430 420 410 400 390 380 370 (kg) 360 350 W e g h t W e i g h t H e i g h t i AG I GU 125.6126.2126.9 I MA 408.7-392.6376.1384.6367.1 I MD 128 NS 125.9 OL Weight E~3 Height T OR SA 125.4126.4 SC 376.4398.2374.9425.7 127 130 - 127.5 125 122.5 UA 123.7 H e i g h t 120 Herds Means with the same superscript within trait do not differ (p < 0.05) Figure 8: Comparison of Herds: LS Means at 18 Months 500 480 W 460 e i g h t 440 420 (kg) 400 380 W e i g h t H e i g h t 1 AG GU 462.2J431.2434.1 130.1129.3130.2 MA MD 1 NS 404.71 127.6 Herds 1 OL i i I Weight IZ3 Height OR SA 1424.8469.6440 128.9130.5131.6 SC I UA 7501 2 129.7 132.5 130 - 127.5 H e i g h t (cm) 125 Means with the same superscript within trait do not differ (p < 0.05) Figure 9: Comparison of Herds: LS Means at 21 Months 540 -525 -W 510 e g 495 h t (kg) 480 -] 465 450 Weight Height AG 132.6 GU 504.1462.2461.5 131.1 MA 130.3 MD NS 508.7 129.2 OL r 135 132.5 H e i g h t 127.5 (em) 130 125 Herds Means with the same superscript within trait do not differ (p < 0.05) Figure 10: Comparison of Herds: LS Means at 24 Months w e i 9 h t (kg) 620 600 580 560 540 520 500 480 Weight Height Weight • Height T AG 135.1 GU 552.9531.8545.1 MA 134.1134.5 MD OL OR i SC 497.2 617.1 519.8539.4 134.2135.1135.6134.1 I UA 136 134.5 - 133 131.5 H e i g h t (cm) 130 Herds Means with the same superscript within trait do not differ (p < 0.05) 66 months (375.3, 425.7 and 501.2 kg) r e s p e c t i v e l y . SA had the highest weights at 21 (541.3 kg) and 24 months (617.1 kg) . I t i s evident t h a t the d i f f e r e n t herds provided d i f f e r e n t environmental c o n d i t i o n s (such as c l i m a t e , housing and r e l a t i v e n u t r i t i o n ) which i n f l u e n c e d weight from herd t o herd. Since s i r e groups were e q u a l l y and randomly mated across herds, these herd i n f l u e n c e s were expected to be common to both s i r e groups i n the same herd and any d i f f e r e n c e s a r i s i n g w i t h i n herd would be a r e f l e c t i o n of genetic merit of s i r e groups. D i f f e r e n c e s i n weight among herds i s t h e r e f o r e , an i n d i c a t i o n of herds' environmental i n f l u e n c e s (e.g. n u t r i t i o n ) . As presented i n Figures 1 t o 10, wither height d i f f e r e n c e s among herds were not s i g n i f i c a n t (P < 0.05) at b i r t h , 15 and 18 months. S i g n i f i c a n t d i f f e r e n c e s (P < 0.05) among herds occurred at 3, 4.5, 6, 9, 12 and 21 months. At 24 months, NS had the lowest wither heights (131.1 cm) which were s i g n i f i c a n t l y d i f f e r e n t (P < 0.05) from a l l other herds. At b i r t h , OL had the lowest wither height (74.8 cm) while SC had the highest (76.6 cm). At 3 months, NS and OL herds had the lowest wither height measurements (90.8 and 89.4 cm r e s p e c t i v e l y ) , while AG (93.3 cm), GU (92.5 cm) and SC (92.7 cm) were the highest. At 4.5 months, SA had the 67 lowest wither height (95.0 cm), whi l e AG, GU, MA and SC had the highest (98.7, 98.0, 98.5 and 97.8 cm r e s p e c t i v e l y ) . MD had the lowest wither height (101.3 cm) at 6 months, whil e SC had the highest (108.7 cm). At 15 months, MD wit h e r height (128.0 cm) was the highest, w h i l e UA (123.7 cm) was the lowest. At 9, 12, 18 and 21 months, NS had the lowest wither heights (111.0, 118.4, 127.6, 129.2 r e s p e c t i v e l y ) w h i l e SC had the highest (118.0, 123.4, 131.6, 134.0 r e s p e c t i v e l y ) . A l s o , SC had the highest wither height at 24 months. Again, . these r e s u l t s suggest t h a t the d i f f e r e n t herds i n f l u e n c e d the expression of the wither height t r a i t d i f f e r e n t l y . That i s , d i f f e r e n c e s among herds were due t o herd environment or management as has been p r e v i o u s l y suggested by Hinkovski et a l . , (1984); and Batra et a l . , (1983). S i g n i f i c a n t d i f f e r e n c e s among herds f o r b i r t h weights but not wither heights suggest t h a t environmental i n f l u e n c e s ( n u t r i t i o n a l s t a t u s of the dams and management) had a s i g n i f i c a n t impact on body weight more than w i t h e r heights. 68 GU (from b i r t h t o 6 months), OL (at 9 months), UA (from 12 to 18 months) and SA (between 21 t o 24 months) provided the most favourable environmental c o n d i t i o n s f o r body weight i n c r e a s e s ; w h i l e GU, AG and SC (from b i r t h t o 3 months), SC (between 6 to 24 months except at 15 months) and MD (at 15 months) most advantageously i n f l u e n c e d w i t h er height development. 3.4. CONCLUSIONS While the o f f s p r i n g of Canadian s i r e s had equal weights t o those of the New Zealand s i r e s ; the former were t a l l e r than the l a t t e r . These r e s u l t s l i k e l y do represent s i m i l a r i t i e s or d i f f e r e n c e s i n the Canadian and New Zealand populations s i n c e the s i r e s were s e l e c t e d at random wi t h respect t o these t r a i t s . These r e s u l t s p a r t l y confirm what has been suggested p r e v i o u s l y . That Canadian o f f s p r i n g are t a l l e r than New Zealand o f f s p r i n g (Jasiorowski et a l . , 1981; Bar-Anan et a l . , 1987; Peterson, 1988). C o n c l u s i v e l y , the s e l e c t i o n program i n Canada has favoured increased s t a t u r e , while the New Zealand program has given l i t t l e emphasis t o t h i s t r a i t (Peterson, 1988). S i z e and s t a t u r e are important i n s e l e c t i o n regimens which emphasize both m i l k and meat production from d a i r y c a t t l e . The r e s u l t s a l s o suggest t h a t under Canadian feeding regimes, New Zealand o f f s p r i n g have the gene t i c p o t e n t i a l to grow to weights equal t o Canadian o f f s p r i n g . The s e l e c t i o n program i n New Zealand has not s e l e c t e d against t r a i t s f o r the e f f i c i e n t metabolic u t i l i z a t i o n of low-roughage d i e t s as evident from the weight comparisons. 70 The feeding regimen i n Canada f o s t e r e d an equal amount of genetic expression f o r the weight t r a i t i n both s t r a i n s . This i s a p o s s i b l e e x p l a n a t i o n f o r the apparent disagreement of the weight r e s u l t s i n t h i s study w i t h other s t u d i e s (Peterson, 1988; J a s i o r o w s k i , 1981; Bar-Anan, 1984). Any i n d i v i d u a l d i f f e r e n c e s between sib-groups were probably due t o i n d i v i d u a l s i r e d i f f e r e n c e s i n t h e i r o v e r a l l genetic merit. The comparison of growth r a t e s achieved i n New Zealand w i t h those a t t a i n e d i n Canada w i t h i n the CANZ T r i a l (Appendix 4 ) , i n d i c a t e s t h a t the former were l i g h t e r than the l a t t e r ; which would p o s s i b l y be a r e f l e c t i o n of the i n f l u e n c e of feeding regime. Growth trends a t t a i n e d i n the CANZ T r i a l i n Canada are w i t h i n "normal" growth trends reported i n l i t e r a t u r e ( p l o t s i n Appendix 3) . 71 CHAPTER TWO ESTIMATION OF GENETIC PARAMETERS FOR WEIGHT AND WITHER HEIGHT OF CANADIAN AND NEW ZEALAND SIRED DAIRY CATTLE USING AN ANIMAL MODEL 72 4.1. INTRODUCTION Breeders face problems of improving p o t e n t i a l performance of t h e i r stock not only i n a v a r i e t y of t r a i t s , but a l s o under a v a r i e t y of environments. Development and r e a l i z a t i o n of animal breeding plans r e q u i r e knowledge of the g e n e t i c c h a r a c t e r i s t i c s of a population with respect to the t r a i t s of concern (Swalve et a l . , 1987; Meyer, 1988). The amount of emphasis i n s e l e c t i o n t h a t i s j u s t i f i e d f o r any t r a i t depends upon the p o t e n t i a l c o n t r i b u t i o n t o improvement i n o v e r a l l performance, and i s governed by i t s economic importance, v a r i a b i l i t y , h e r i t a b i l i t y , plus g e n e t i c and phenotypic c o r r e l a t i o n with other t r a i t s under s e l e c t i o n (Dickerson, 1962); and the r e l a t i v e need f o r improvement i n the t r a i t s of concern. Estimation of genetic parameters i n v o l v e s p a r t i t i o n i n g of o b s e r v a t i o n a l components, i e . phenotypic covariances between r e l a t i v e s i n t o causal components (Falconer, 1981). As pointed out (Meyer, 1988; Henderson, 1979), most animal breeding data comes from s e l e c t i o n experiments or f i e l d l i v e s t o c k improvement schemes. 73 However, phenotypic and gene t i c covariances have been estimated using a n a l y s i s of (co)variance (ANOVA) or analogous procedures based on an u n c o n d i t i o n a l model; t h a t i s , any s e l e c t i o n t h a t has occurred i n the po p u l a t i o n from which the data were obtained f o r e s t i m a t i o n i s ignored and random e f f e c t s are considered u n c o r r e l a t e d (Henderson, 1979). In t h i s case, estimates would be biased. A l s o , when records or information on which s e l e c t i o n was based are ignored or not included i n the a n a l y s i s , estimates are l i k e l y to be biased (Meyer, 1988) . For example, i f cows are c u l l e d on conformation as w e l l as y i e l d ; and conformation i s c o r r e l a t e d t o production; estimates of breeding value f o r production based on y i e l d data alone may be biased; the l e v e l of b i a s depending on the degree of c o r r e l a t i o n between conformation and production and i n t e n s i t y of s e l e c t i o n t h a t i s placed upon conformation ( H i l l et a l . , 1988). In d a i r y c a t t l e breeding, a d d i t i v e g e n e t i c v a r i a n c e has been j u d i c i o u s l y used t o obta i n p u r e l i n e breeds (Willham et a l . , 1985). A l s o , s t r a i n d i f f e r e n c e s (or gen e t i c variance) among breeds have been used t o replace l e s s productive breeds with high producing crossbreds or s y n t h e t i c s . 74 Therefore, accurate estimates of h e r i t a b i l i t y (which i s the p r o p o r t i o n of t o t a l phenotypic variance a s s o c i a t e d w i t h a d d i t i v e g e n e t i c variance (Falconer, 1981)) and the degree of genetic c o r r e l a t i o n s between t r a i t s are t h e r e f o r e e s s e n t i a l i n the formulation and e v a l u a t i o n of breeding plans. The importance of genetic parameters i s f u r t h e r underscored by numerous c i t a t i o n s i n l i t e r a t u r e as noted below. Murray et a l . , (1983) have reported the h e r i t a b i l i t y of height as 0.43 ± 0.16 and f o r weight as 0.32 ± 0.14 at 15 months of age based on 565 H o l s t e i n replacement h e i f e r s s i r e d by 102 s i r e s i n 18 herds i n Eastern Ontario. Genetic c o r r e l a t i o n s between height and weight were 0.64 and the phenotypic c o r r e l a t i o n s were 0.43. H e i n r i c h s and Hargrove (1987) e s t a b l i s h e d growth patterns (wither height and heart g i r t h (body weight)) f o r H o l s t e i n females from 1 to 24 months i n 163 Pennsylvania commercial d a i r y herds. Weights and heights had a p o s i t i v e phenotypic c o r r e l a t i o n w i t h each other (0.40) and with average herd production (0.34 and 0.41); corresponding c o r r e l a t i o n s w i t h age at f i r s t p a r t u r i t i o n were: -0.30, -0.17, and -0.22. In beef c a t t l e , i n d i v i d u a l weights at v a r i o u s ages to weaning have moderate h e r i t a b i l i t i e s , 0.35 t o 0.60 (Bushra et a l . , 1989); Flock et a l . , (1962) found phenotypic c o r r e l a t i o n of 0.60 f o r 75 b i r t h weight and wither height. In I s r a e l , S o l l e r et a l . , (1966) found h e r i t a b i l i t i e s f o r weights of 0.30 ( d a i l y g a i n to 12 months), 0.30 ( l i v e weight f o r age), and 0.50 (365 days weight). M a r t i n et a l . , (1962) found phenotypic c o r r e l a t i o n s i n H o l s t e i n calves f o r b i r t h weight, 2, 6 and 12 months gains to be p o s i t i v e l y c o r r e l a t e d w i t h m i l k y i e l d (0.09 to 0.30). For H o l s t e i n replacement h e i f e r s between 4.0 t o 31.6 months of age, Murray et a l . , (1962) found h e r i t a b i l i t i e s of weight and height of 0.32 and 0.43 and geneti c and phenotypic c o r r e l a t i o n s of 0.64 and 0.43. These parameters are needed t o evaluate the breeding p l a n i t s e l f as w e l l as f o r p r e d i c t i o n of breeding values and r e l a t i o n s h i p s among t r a i t s . This chapter deals w i t h p a r t (2) of the o b j e c t i v e s i n t h i s study i n order to estimate s i r e v a r i a n c e s , h e r i t a b i l i t i e s , g e netic and phenotypic c o r r e l a t i o n s f o r weight and wither height of Canadian and New Zealand H o l s t e i n h e i f e r s using DFREML and AM with one random e f f e c t . 76 4.2. MATERIALS AND METHODS 4.2.1. Animals and Data The database used i n t h i s a n a l y s i s has been described i n the "Source of Data" (sections 2 . 8 and 2 . 9 ) and i s the same database employed i n the f i r s t chapter of t h i s t h e s i s . In t h i s a n a l y s i s the pedigree of the p r o j e c t animals was e s t a b l i s h e d . The pedigree was constructed such t h a t i t contained: ( i ) p r o j e c t h e i f e r s ; ( i i ) p r o j e c t s i r e s and dams (as p a r e n t s ) ; ( i i i ) maternal grand s i r e s (MGS) through the p r o j e c t dams' s i d e ; (iv) p a t e r n a l grand s i r e s (PGS) through the p r o j e c t s i r e s ' s i d e ; (v) p a t e r n a l grand dams (PGD) a l s o through the p r o j e c t s i r e s ' s i d e ; and ( v i ) maternal grand s i r e s of p r o j e c t s i r e s (MGS of s i r e s ) . A l l r e l a t i o n s h i p s f o r p r o j e c t h e i f e r s , dams, s i r e s and t h e i r ancestors were constructed through one numerator r e l a t i o n s h i p matrix (NRM). In the NRM, a Canadian s i r e - "Roybrook S t a r l i t e " ( r e g i s t r a t i o n no. 308691) - who was not p a r t of the p r o j e c t s i r e s , was however, the s i r e of "Stanhope Cannonade", "Glenafton Enhancer", "Cherry Lane Superstar" and "Maries Thunder" ( i n the Canadian s i r e group); and of "Glengyle S t a r l i t e Meteor" i n the New Zealand group. 77 Table 8: T o t a l Number of Animals 1 i n the Numerator Relationship Matrix (NRM) S i r e Groups AGE(mos) BOTH CN NZ B i r t h 1180 880 873 3 1150 865 858 4.5 1143 861 855 6 1134 860 847 9 988 785 776 12 1074 826 821 15 998 794 777 18 1028 800 801 21 924 756 741 24 970 766 777 1 number of animals with records i n the matrix appear i n Table 4 i 78 The r e l a t i o n s h i p s between these four Canadian s i r e s and the New Zealand s i r e were ignored; and the two populations were considered u n r e l a t e d . Table 8 presents the t o t a l number of animals i n the r e l a t i o n s h i p matrix. Animals which have records i n the r e l a t i o n s h i p matrix are shown i n Table 4 at each age category. F i r s t l y , the data were prepared such t h a t the l e v e l s of each f i x e d e f f e c t (herd and s t r a i n ) and the random (animal) e f f e c t s were numbered c o n s e c u t i v e l y . This included i n d i v i d u a l s i n the pedigree which d i d not have any records. I f a parent was unknown, i t was coded as zero. The f i n a l record layout contained an animal i d e n t i f i c a t i o n (e.g. a p r o j e c t h e i f e r ) , s i r e i d e n t i f i c a t i o n , dam i d e n t i f i c a t i o n , f i x e d e f f e c t and t r a i t measurement i n t h a t order according to Meyer, ( 1 9 8 8 ) . 79 4.2.2. S t a t i s t i c a l Analysis Weights and wither heights were analyzed i n order t o estimate h e r i t a b i l i t i e s and d i r e c t a d d i t i v e g e n e t i c e f f e c t s f o r each s i r e group (Canadian, New Zealand and both s i r e groups together) w i t h ages at b i r t h , 3, 4.5, 6, 9, 12, 18, 21 and 24 month as subsets. The a n a l y s i s was done on a UNIX operating system u t i l i z i n g SUN OS Version 4.1; and Meyer's DFREML programs (Meyer, 1988). The DFREML algorithm i n t h i s a n a l y s i s u t i l i z e d a u n i v a r i a t e model f o r the e s t i m a t i o n of variance components according to Meyer, (1988). The method u t i l i z e d a d e r i v a t i v e - f r e e o p t i m i z a t i o n procedure t o evaluate the l o g - l i k e l i h o o d e x p l i c i t l y and l o c a t e the maximum. Residual e r r o r s , a d d i t i v e genetic e f f e c t s were considered t o be the random e f f e c t s and s t r a i n and herd as f i x e d e f f e c t s i n the model as shown below: Y = X/3 + Zu + e (3) where Y i s a v e c t o r of N observations of weight or wither height records; j3 i s a vec t o r of herd and s t r a i n f i x e d 80 e f f e c t s of length(p + q) and X'X i s d i a g o n a l ; p i s the number of herds and q i s the number of s i r e groups; u i s a v e c t o r of unknown random a d d i t i v e g e n e t i c e f f e c t s of i n d i v i d u a l animals; e i s a v e c t o r of N random r e s i d u a l e f f e c t s ; X and Z are known incidence matrices f o r f i x e d and random e f f e c t s . The assumptions of (co)variance between gene t i c and r e s i d u a l e f f e c t s i n t h i s model are: V ( u ) = Aa u 2 = G, v ( e ) = l a e 2 = R Cov ( u, e') = 0 Where, I i s an i d e n t i t y matrix and a2 u i s the a d d i t i v e g enetic v a r i a n c e ; a2 e i s the e r r o r v a r i a n c e ; and A i s the numerator r e l a t i o n s h i p matrix. Let Zu = (Z, 0 ) | u, j where u, represents animals w i t h progeny or animals w i t h records i n y, and u 2 represents r e l a t i v e s of i n d i v i d u a l s i n u, t h a t were needed t o compute A and which had no value i n y; (e.g. Y. = 0 f o r a MGS or s i r e ) . Then V(Y) = ZGZ• + R 81 As o u t l i n e d (Meyer, 1988), the n a t u r a l l o g of the l i k e l i h o o d f u n c t i o n t o be maximized i s : - 2 Log L = Const + Log|R| + Log|G| + Log|c| = Y'Py (4) where C i s the c o e f f i c i e n t matrix i n the mixed model equations (MME) p e r t a i n i n g t o equation (3) (or a f u l l rank submatrix t h e r e o f ) , and P i s a matrix, P = V"1 - V"1 X (X'V 1 X)" X'V"1 = V"1 - V"1 X (X'V"1 X)"1 X'V"1 Algorithms t o l o c a t e the maximum of (4) have been f u l l y discussed by Meyer, (1988). The program t o perform the i t e r a t i o n s , r e q u i r e s i n i t i a l estimates of h e r i t a b i l i t i e s or p r i o r s . These were de r i v e d from the L.S. analyses i n Chapter 1 using Henderson's Method 3 (Henderson, 1953) and are presented i n Appendix 8. The convergence c r i t e r i o n used was the minimum variance of the l i k e l i h o o d f u n c t i o n (-2 Log L) values w i t h i n each round of i t e r a t i o n . The program was run u n t i l a convergence c r i t e r i o n of 1 x 10"9 was reached. The maximum number of i t e r a t e s was set at 50 but, a l l analyses converged w i t h 20 or l e s s i t e r a t i o n s . The i t e r a t i o n s stopped when the 82 estimated h e r i t a b i l i t y d i d not change i n the f i r s t two decimal p o i n t s a f t e r rounding. The a d d i t i v e g e n e t i c ( d i r e c t ) , phenotypic and r e s i d u a l v a r iances and h e r i t a b i l i t i e s were estimated as the outcome of the a n a l y s i s . The a d d i t i v e g e n e t i c variance was estimated as the variance of animals' a d d i t i v e g e n e t i c merit instead of, f o r example, four times the variance between s i r e s or twice the covariance between parents and o f f s p r i n g ( H i l l and Meyer, 1988). Genetic and phenotypic c o r r e l a t i o n s were c a l c u l a t e d using the i d e n t i t y : V(A+B) = V ( A ) + V ( B ) + 2 COV ( A , B ) (5) The covariance and variance components i n the above formula ( l e t t i n g A represent weight w h i l e B represents wither height) are defined as f o l l o w s : V(A+B) i s the s i r e v ariance component of the sum of A and B; V(A) i s the s i r e component of variance of A; V(B) i s the s i r e component of variance of B and COV(A,B) i s the s i r e component of covariance between A and B. Where, Phenotypic Covariance, a ( p 1 p 2 =1/2 ( <J 2 ( p 1 + p 2 )-a 2 p 1-a 2J P2 Genetic Covariance, a ( g 1 g 2 =1/2 ( o\gUg2)-o2gro2J Phenotypic C o r r e l a t i o n , r = a p "(p1,p2) / 2 2 s 1/2 1 ( ° pi X ° p2> 83 G e n o t y p i c C o r r e l a t i o n , r g = r j ( g 1 2 ) , M a 9 i x a g 2 ) ' In the above formulae : a 2 p and a 2 g r e f e r t o p h e n o t y p i c and g e n o t y p i c v a r i a n c e s r e s p e c t i v e l y . 1 and 2 r e f e r t o t r a i t s 1 (weight) and 2 (wi ther h e i g h t ) . The DFREML t e c h n i q u e used i n t h i s a n a l y s i s d i d not g i v e S t a n d a r d e r r o r s f o r the e s t i m a t e s . T h e r e f o r e , S t a n d a r d e r r o r s o f the h e r i t a b i l i t y e s t i m a t e s were c a l c u l a t e d by the approximate method o f Swiger e t a l . , (1964) when n o r m a l i t y of the i n t r a c l a s s c o r r e l a t i o n , t , i s assumed (Appendix 9) . Homogeneity o f the g e n e t i c and p h e n o t y p i c v a r i a n c e s due t o the s i r e groups f o r each t r a i t was t e s t e d u s i n g the " v a r i a n c e r a t i o t e s t " : F = S, 2 / S 2 2 where, F i s the t e s t s t a t i s t i c , S, 2 and S 2 2 are the v a r i a n c e s c o r r e s p o n d i n g t o each s i r e g r o u p . C a l c u l a t e d F v a l u e s were compared w i t h c r i t i c a l F v a l u e s o f the F d i s t r i b u t i o n from S t a n d a r d T a b l e s ( Z a r , 1974; H i c k s , 1982). The c r i t i c a l r e g i o n was s e t a t F > F 0 9 5 ( l ) ( n ^ l ) , (n 2 ~l) and a = 0 .05; where (n-1) are the degrees o f freedom dependent on the number o f o b s e r v a t i o n s o f each s i r e group i n each age c l a s s and (1) denotes the a p p l i c a t i o n o f a o n e - s i d e d t e s t i n o r d e r t o show whether one v a r i a n c e i s g r e a t e r o r l e s s t h a n a n o t h e r . 84 4.3. RESULTS AND DISCUSSION 4.3.1. Variance Components Estimates of the a d d i t i v e ( d i r e c t ) g e n e t i c and t o t a l phenotypic variances f o r the two t r a i t s w i t h i n s t r a i n are presented i n Table 9. C a l c u l a t e d F values (using v a r i a n c e r a t i o s ) f o r t e s t i n g the hornoscedasticity of variances are presented i n Appendix 10. Based on the variance r a t i o s i n Appendix 10, weight phenotypic variance estimates due t o s i r e groups were not d i f f e r e n t at a l l ages. Wither height phenotypic variances due to s i r e groups were a l s o not d i f f e r e n t f o r a l l ages except at 9, 12 and 15 months where estimates f o r NZ s i r e group were smaller than the CN s i r e group estimates (Table 9). P o s s i b l e cause of the smaller NZ s i r e group estimates could be due t o sampling e r r o r . Where estimates are not d i f f e r e n t , the pooled phenotypic variances at the v a r i o u s ages provide the best estimate of the two s i r e group phenotypic variances f o r each t r a i t . I t can be deduced from these r e s u l t s t h a t there was a s i m i l a r environmental i n f l u e n c e on both s i r e groups f o r the phenotypic expression of weight and height except at 9, 12 and 15 months f o r the 85 Table 9t DFREML Estimates of H e r i t a b i l i t i e s , A d d i t ive Genetic Di r e c t and Phenotypic Variance Components Weight Height Age St r a i n h a o».(kg') ° a p(kg J) h* a*.(cm2) o» p(cm 2) B i r t h CN 0.62 12.84 20.72 0.57 5.63 9.91 NZ 0.59 12.07 20.58 0.36 3.25 9.08 BOTH 0.66 13.74 20.92 0.45 4.33 9.60 3 CN 0.22 45.63 205.09 0.00 0.30E-03 15.18 NZ 0.00 0.10E-02 213.85 0.28 3.63 13.09 BOTH 0.10 20.77 212.98 0.05 0.73 14.24 4.5 CN 0.31 109.87 350.17 0.08 1.29 15.46 NZ 0.05 15.25 308.81 0.19 2.88 15.58 BOTH 0.20 64.49 326.52 0.13 2.03 15.33 6 CN 0.21 110.62 536.32 0.02 0.45 19.05 NZ 0.08 33.31 436.88 0.08 1.40 18.01 BOTH 0.16 75.94 482.17 0.03 0.52 18.32 9 CN 0.66 425.82 647.02 0.36 6.53 17.93 NZ 0.28 141.56 500.64 0. 10E-03 0.62E-03 12.22 BOTH 0.48 272.38 568.67 0.20 3.16 15.69 12 CN 0.69 584.88 844.13 0.53 9.32 17.56 NZ 0.44 339.72 767.30 0.20 2.35 11.69 BOTH 0.50 404.90 809.39 0.32 4.68 14.72 15 CN 0.45 491.23 1089.19 0.34 5.24 15.39 NZ 0.17 183.32 1066.60 0. 90E-03 0.95E-02 10.45 BOTH 0.36 388.52 1090.96 0.31 4.03 13.08 18 CN 0.45 657.18 1445.14 0.43 5.01 11.59 NZ 0.51 716.69 1405.28 0.39 4.36 11.17 BOTH 0.47 658.71 1409.00 0.39 4.50 11.42 21 CN NZ BOTH 0.44 0.34 0.39 695.41 637.88 659.81 1572.88 1871.31 1700.00 0.66 0.84 0.75 8.21 8.87 8.72 12.51 10.60 11.57 24 CN 0.52 1401.06 2964.34 0.10E-03 0.80E-03 9.52 NZ 0.07 189.63 2615.65 0.93 8.59 9.24 BOTH 0.12 306.78 2610.89 0.54 4.97 9.25 86 height t r a i t . A d d i t i v e g e n e t i c variances due t o the two s i r e groups f o r weight, were not s i g n i f i c a n t l y d i f f e r e n t (P < 0.05) at b i r t h , 12, 18 and 21 months. Between 3 t o 9 months; 15 and 24 months, weight a d d i t i v e g e n e t i c variances due t o CN s i r e group were higher than those due t o the NZ s i r e group. Wither height a d d i t i v e g e n e t i c variances due to the two s i r e groups were not d i f f e r e n t at b i r t h and 18 months. However, between 3 to 6 months; and at 24 months, NZ s i r e group a d d i t i v e genetic variances were higher than those due to the CN s i r e group. From 9 to 12 months, wither height a d d i t i v e genetic variances due t o the CN s i r e group were higher than those due t o the NZ s i r e group. These values are q u i t e e r r a t i c and t h e r e f o r e , do not render a c l e a r i n t e r p r e t a t i o n . Such i n c o n s i s t e n c i e s could be due to sampling e r r o r , small s i z e of data set and management c o n d i t i o n s which i n f l u e n c e d the expression of the g e n e t i c p o t e n t i a l of these t r a i t s i n u n p r e d i c t a b l e ways. Peterson, (1988) reported f o r the CANZ T r i a l i n New Zealand t h a t s i r e variances from BLUP analyses f o r weight and height at 3 0 months of age were 134.62 kg 2 and 1.99 cm2 r e s p e c t i v e l y . The proportions are i n agreement wi t h t h i s study even though the r e s u l t s were based on a much l a t e r age. 87 In a study i n v o l v i n g H o s t e i n - F r i e s i a n b u l l s , Calo et a l . , (1973) found t h a t s i r e c o n t r i b u t i o n t o variances i n weight v a r i e d c onsiderably w i t h age of o f f s p r i n g . The s i r e v a r i a n c e component f o r body weight was n i l at 9 months; peaked to 24% between 18 to 30 months but l a t e r d e c l i n e d t o 16% at 60 months of age. 4.3.2. H e r i t a b i l i t i e s H e r i t a b i l i t y estimates f o r weight and height at w i t h e r s are presented i n Tables 10 and 11. Standard erros f o r these estimates ranged from 0.18 t o 0.34 and 0.13 t o 0.38 ( f o r the CN s i r e group) and from 0.13 t o 0.37 and 0.18 t o 0.43 ( f o r the NZ s i r e group) f o r weight and height t r a i t s a c c o r d i n g l y . Standard e r r o r s f o r the combined groups were lower (0.11 to 0.24 and 0.10 to 0.28 ( f o r weight and height r e s p e c t i v e l y ) . H e r i t a b i l i t y estimates f o r weight f o r the CN s t r a i n as analyzed s e p a r a t e l y , at b i r t h , 9, 12, 15, 18, 21 and 24 months of age were high (0.44 t o 0.69); but low and c l o s e to zero f o r 3, 4.5 and 6 months (0.21 t o 0.31) due to the l a r g e standard e r r o r s (0.18 t o 0.21). H e r i t a b i l i t y estimates f o r weight f o r the NZ s t r a i n were a l l lower than the CN s t r a i n at b i r t h , 3, 12, 15, 21 and 24 months of age (0.17 t o 0.59) except at 18 months of age where the NZ s t r a i n estimate was higher (0.51 vs 0.45) 88 Table 10: H e r i t a b i l i t y Estimates with Standard Errors f o r Weight T r a i t S i r e Groups AGE(mos) BOTH CN NZ B i r t h 0.66 ±0.19 0.62 ±0.26 0.59 ±0.26 3 0.10 ±0.11 0.22 ±0.18 0.00 ±0.13 4.5 0.20 ±0.13 0.31 ±0.21 0.05 ±0.14 6 0.16 ±0.12 0.21 ±0.18 0.08 ±0.16 9 0.48 ±0.21 0.66 ±0.33 0.28 ±0.28 12 0.50 ±0.19 0.69 ±0.30 0.44 ±0.26 15 0.36 ±0.19 0.45 ±0.29 0.17 ±0.26 18 0.47 ±0.20 0.45 ±0.28 0.51 ±0.29 21 0.39 ±0.24 0.44 ±0.34 0.34 ±0.37 24 0.12 ±0.17 0.52 ±0.34 0.07 ±0.23 Table 11: H e r i t a b i l i t y Estimates with Standard Errors for Wither Height T r a i t S i r e Groups AGE (mos) BOTH CN NZ B i r t h 0.45 ±0.16 0.57 ±0.25 0.36 ±0.21 3 0.05 ±0.10 0.00 ±0.13 0.28 ±0.20 4.5 0.13 ±0.11 0.08 ±0.15 0.19 ±0.18 6 0.03 ±0.10 0.02 ±0.13 0.08 ±0.16 9 0.20 ±0.18 0.36 ±0.28 0.1E-03±0.22 12 0.32 ±0.16 0.53 ±0.27 0.20 ±0.21 15 0.31 ±0.19 0.34 ±0.27 0.9E-03±0.22 18 0.39 ±0.19 0.43 ±0.28 0.39 ±0.27 21 0.75 ±0.28 0.66 ±0.38 0.84 ±0.43 24 0.54 ±0.23 0.1E-03±0.24 0.93 ±0.38 89 r e s p e c t i v e l y . Between 3 t o 9 months, NZ s t r a i n estimates were c l o s e t o zero and had l a r g e standard e r r o r s (0.13 t o 0.28). The j o i n t estimates of h e r i t a b i l i t y f o r weight ranged from 0.3 6 t o 0.66 between 9 t o 12 months and at b i r t h ; while at 3, 4.5, 6 and 24 months, estimates had l a r g e standard e r r o r s and were c l o s e t o zero. H e r i t a b i l i t y estimates f o r wither height followed a s i m i l a r p a t t e r n . CN estimates were high at b i r t h , 9, 12, 15, 18 and 21 months of age (0.34 to 0.66) but c l o s e t o zero at 3, 4.5, 6 and 24 months of age (0.0 t o 0.08). The NZ estimates were a l s o high f o r b i r t h , 18, 21 and 24 months of age (0.36 to 0.93) but c l o s e t o zero at 3, 4.5, 6, 9, 12 and 15 months of age (0.0 to 0.28). The j o i n t estimates of h e r i t a b i l i t y f o r wither height were c l o s e t o zero between 3 to 9 months; but high (0.31 t o 0.75), at b i r t h and between the ages of 12 t o 24 months. H e r i t a b i l i t y estimates reported by Peterson, (1988) f o r the t r i a l i n New Zealand i n d i c a t e values of 0.62 f o r weight and 0.68 f o r wither height at 3 0 months. These values are w i t h i n range of those found i n t h i s study d e s p i t e the age d i f f e r e n c e . S i m i l a r values f o r weight and w i t h e r height f o r H o l s t e i n type d a i r y c a t t l e have been reported i n 90 l i t e r a t u r e (Bushra et a l . , 1989; L i n et a l . , 1985; Murray et a l . , 1983). Brum et a l . , (1969) have reported t h a t h e r i t a b i l i t i e s f o r p a t e r n a l - s i s t e r body measurements at three, s i x and twelve months of age v a r i e d from 0.10 t o 0.52. S i m i l a r estimates from r e g r e s s i o n of daughters on dams ranged from -0.06 t o +0.61. H e r i t a b i l i t y estimates based on the Canadian s i r e group were higher f o r weight than f o r wither height except at 21 months when the estimates f o r height were higher. H e r i t a b i l i t y estimates based on the New Zealand s i r e group were higher f o r weight than f o r w i t h e r height at b i r t h , 9, 12 and 18 months of age; and l e s s at 3, 4.5, 21 and 24 months of age. A high estimate of h e r i t a b i l i t y f o r a t r a i t i n d i c a t e s a genetic component and emphasizes a p o s s i b l e value i n genetic e v a l u a t i o n or improvement. 91 4.3.3. Genetic and Phenotypic Correlations Genetic and phenotypic c o r r e l a t i o n estimates are i n Tables 12 and 13. Genetic c o r r e l a t i o n s between weight and wi t h e r height were higher f o r the CN s t r a i n (0.62 t o 1.0) than f o r the NZ s t r a i n (-0.04 to 0.91) at 4.5, 9, 12, 15, 18 and 21 months of age. At s i x months of age the gene t i c c o r r e l a t i o n f o r CN s t r a i n was lower than the NZ s t r a i n (-0.01 vs 0.54) r e s p e c t i v e l y . At b i r t h , both CN and NZ s i r e groups had a genetic c o r r e l a t i o n of 1.0. At 24 months of age, the CN s t r a i n showed no genetic c o r r e l a t i o n , w h i l e the NZ s t r a i n showed a genetic c o r r e l a t i o n of 0.84. Genetic c o r r e l a t i o n s f o r the j o i n t a n a l y s i s were a l l high ranging from 0.61 t o 1.0 f o r a l l ages except at 6 months (0.18). A high g e n e t i c c o r r e l a t i o n i n d i c a t e s t h a t a genetic gain i n one t r a i t w i l l lead to an increase i n the other. In other words, a genetic trend i n one t r a i t w i l l be s t r o n g l y accompanied by a s i m i l a r genetic trend i n the c o r r e l a t e d t r a i t . Phenotypic c o r r e l a t i o n s between weight and wi t h e r height f o r both s t r a i n s were r e l a t i v e l y high at a l l ages (0.33 t o 0.60 f o r CN group and 0.33 to 0.62 f o r NZ group). The j o i n t estimates f o r phenotypic c o r r e l a t i o n s were a l s o high Table 12: Genetic Correlations For Weight and Wither Height T r a i t s S i r e Groups AGE(mos.) BOTH CN NZ B i r t h 1.00 1.00 1.00 3 0.79 0.00 0.00 4.5 0.61 1.00 -0.04 6 0.18 -0.01 0.54 9 1.00 1.00 0.00 12 1.00 1.00 0.67 15 0.81 0.62 0.48 18 0.92 0.86 0.37 21 1.00 1.00 0.91 24 0.89 0.00 0.84 Table 13: Phenotypic Correlations f o r Weight and Wither Height T r a i t s S i r e Groups AGE(mos.) BOTH CN NZ B i r t h 0.61 0.60 0.62 3 0.51 0.59 0.42 4.5 0.54 0.60 0.49 6 0.54 0.55 0.55 9 0.38 0.37 0.38 12 0.36 0.43 0.26 15 0.37 0.33 0.38 18 0.41 0.45 0.33 21 0.41 0.40 0.41 24 0.39 0.40 0.39 93 at a l l ages (0.36 t o 0.61). A l l three category estimates were c l o s e l y i n agreement w i t h each other and denoted t h a t weight and wither height are h i g h l y c o r r e l a t e d . Both t r a i t s are l i k e l y t o be s i m i l a r l y i n f l u e n c e d by environmental parameters. The occurrence of a negative g e n e t i c c o r r e l a t i o n at 6 months (-0.01) f o r Canadian s i r e s and at 4.5 months (-0.04) f o r the New Zealand s i r e s , p o s s i b l y represents c o r r e l a t e d environmental e f f e c t s as suggested by Bushra et a l . , (1989) i n a s i m i l a r study. 94 4.4. CONCLUSIONS Lack of d i f f e r e n c e s i n the estimates of phenotypic variances due t o the s i r e groups w i t h i n t r a i t s i m p l i e s t h a t these variances can be pooled. The pooled v a r i a n c e s being the best estimate of the un d e r l y i n g p o p u l a t i o n v a r i a n c e s . As w e l l , l a c k of d i f f e r e n c e s i m p l i e s t h a t environmental c o n d i t i o n s had a s i m i l a r s t i m u l a t i n g e f f e c t on the phenotypic expression of weight and height i n both s i r e groups. Otherwise, d i f f e r e n c e s i n phenotypic variances between s t r a i n s w i t h i n t r a i t could be due t o sampling e r r o r . Smaller genetic variances f o r weight due t o the New Zealand s i r e group imply t h a t there are s m a l l e r g e n e t i c d i f f e r e n c e s among b u l l s i n t h a t group and t h e r e f o r e , l e s s v a r i a b i l i t y f o r f u r t h e r improvement. The high h e r i t a b i l i t y estimates i n t h i s study may be the outcome of i n c l u d i n g r e l a t i o n s h i p s among animals i n the a n a l y s i s . Furthermore, due t o the u t i l i z a t i o n of a s i n g l e t r a i t model, these h e r i t a b i l i t y estimates are independent of other t r a i t s and could vary i f a m u l t i - t r a i t model i s used. 95 The c o n s i s t e n t occurrence of lower h e r i t a b i l i t i e s f o r weight (at 3, 4.5, 6, 9, 12, 15, 21 and 24 months of age) f o r the NZ s t r a i n as compared t o the CN s t r a i n p o i n t s t o a p o s s i b l e genotype environmental (GxE) i n t e r a c t i o n f o r t h i s t r a i t . Sampling e r r o r may a l s o have c o n t r i b u t e d t o the low h e r i t a b i l i t e s . The CN s t r a i n h e r i t a b i l i t i e s f o r t h i s t r a i t correspond w i t h the estimates of the j o i n t a n a l y s i s , (which i s considered here as the base population) , except at 24 months of age. H e r i t a b i l i t i e s f o r the NZ s t r a i n w i t h e r height a l s o suggest the existence of a GxE i n t e r a c t i o n . There was c l e a r l y a l a c k of s i g n i f i c a n t d i f f e r e n c e s i n the phenotypic expression of the weight t r a i t (even though the CN h e i f e r s were recorded as being heavier than t h e i r NZ c o u n t e r p a r t s ) . The high genetic c o r r e l a t i o n between weight and wither height leads t o the c o n c l u s i o n t h a t s e l e c t i n g f o r increased weights should be accompanied by high c o r r e l a t e d responses i n wither heights i n both the Canadian and New Zealand s t r a i n s . The i n c l u s i o n of l a r g e r numbers of o f f s p r i n g per s i r e from the two s t r a i n s would improve the e s t i m a t i o n of these g e n e t i c parameters. 5. GENERAL DISCUSSION The breeding value of an i n d i v i d u a l or informat i o n about i t s genotype may be obtained from i t s own phenotype or t h a t of i t s r e l a t i v e s . The choice of inf o r m a t i o n source depends on the degree of r e l a t i o n s h i p between the phenotype and genotype (e.g. h2) f o r a p a r t i c u l a r c h a r a c t e r , whether expression of the character i s s p e c i f i c t o females only (e.g. milk production) and stage i n animal's l i f e a t which the character i s expressed. The phenotype, as already noted, i s fashioned from a s t a t e d genotype and i n f l u e n c e d by environmental f a c t o r s . For t h i s reason, i n s e l e c t i n g and e v a l u a t i n g the characters t h a t make up the animal's phenotype, account should be taken of the environmental parameters i n which the animals are r a i s e d . Furthermore, i t i s necessary to provide a f u l l s t a n d a r d i z a t i o n ( c r i t e r i a ) with respect to e v a l u a t i o n techniques (accuracy, a n a l y t i c a l and s t a t i s t i c a l methods) i n order t o estimate genetic and non-genetic causes of v a r i a t i o n , on a wider s c a l e or populations. The establishment of conversion f a c t o r s i s a l s o necessary t o be able t o make comparison of d i f f e r e n t s i r e proofs from v a r i o u s c o u n t r i e s . I n c i d e n t a l l y , i t i s sometimes d i f f i c u l t t o account f o r a l l f a c t o r s i n f l u e n c i n g a p a r t i c u l a r record. As documented i n 97 t h i s study, growth ( i n terms of weight and height) i s i n f l u e n c e d by g e n e t i c s , n u t r i t i o n , management, housing and h e a l t h . However, gi v e n a p p r o p r i a t e f a m i l y s t r u c t u r e s or r e l a t i o n s h i p s among animals i n the p o p u l a t i o n of i n t e r e s t , p r e v i o u s s e l e c t i o n programs and c r i t e r i a f o r s e l e c t i o n (as used i n t h i s s t u d y ) , we can o b t a i n w i t h some c o n s i d e r a b l e degree of accuracy, unbiased estimates and comparisons of g e n e t i c merit of i n d i v i d u a l s or groups of animals. As c i t e d i n the l i t e r a t u r e review i n t h i s t h e s i s e v a l u a t i o n s or comparisons of d a i r y c a t t l e are v e r y important, due t o the d i f f e r e n t i a l performance of d i f f e r e n t breeds a c c o r d i n g t o the environment. As such, temperate as w e l l as t r o p i c a l d a i r y c a t t l e improvements or s e l e c t i o n programs have sought t o secure the b e s t s u i t e d p e d i g r e e s t o c k or c r o s s b r e d s f o r a p a r t i c u l a r environment. In t h i s regard, the H o l s t e i n - F r i e s i a n breeds have o f f e r e d t h i s g e n e t i c p o t e n t i a l ; which u n d e r l i n e s t h e i r c o n t i n u e d g e n e t i c e v a l u a t i o n . The CANZ T r i a l was aimed a t comparing the performance of Canadian H o l s t e i n s i r e s with New Zealand F r i e s i a n s i r e s w i t h i n the Canadian environment (the c o o p e r a t i n g d a i r y h e r d s ) , as w e l l as t o compare the two s t r a i n s of s i r e s i n the New Zealand environment ( c o o p e r a t i n g d a i r y herds) i n 98 order t o d e t e c t any g e n e t i c d i f f e r e n c e s due t o management and s e l e c t i o n programs, i f any, under the assumption t h a t t h e r e may be a GxE i n t e r a c t i o n . The b a s i s of t h i s study was t o compare o f f s p r i n g of both Canadian and New Zealand s i r e s i n Canada f o r weight and w i t h e r h e i g h t t r a i t s . U n l i k e p r e v i o u s s t u d i e s t h a t were conducted i n Poland ( J a s i o r o w s k i e t a l . , 1981); I s r a e l (Bar-Anan et a l . , 1982); Mexico and Colombia (Abubakar e t a l . , 1986); i n t h i s study, h e r i t a b i l i t i e s , g e n e t i c and phenotypic v a r i a n c e s have been estimated i n order t o document the comparative g e n e t i c p o t e n t i a l of the two p o p u l a t i o n s . Knowledge of the k i n d and amount of g e n e t i c v a r i a n c e and i t s d i s t r i b u t i o n i n the two p o p u l a t i o n s c o u l d l e a d t o the d e s i g n of optimum breeding p l a n s which c l e a r l y take i n t o c o n s i d e r a t i o n weight and h e i g h t t r a i t s . The i n c l u s i o n of a n c e s t o r s i n the numerator r e l a t i o n s h i p matrix may have c o n t r i b u t e d t o the h i g h h e r i t a b i l i t y e s timates obtained i n t h i s study (as suggested i n another study by Carabano e t a l . , 1989). 99 As has been documented (Peterson, 1988; J a s i o r o w s k i , 1984; Bar-Anan et a l . , 1987), New Zealand s i r e d o f f s p r i n g have been l i g h t e r than the Canadian s i r e d o f f s p r i n g . However, under Canadian feeding and management regimes, New Zealand s i r e d o f f s p r i n g had the opportunity t o express t h e i r g e n e t i c p o t e n t i a l and t h e r e f o r e , grew t o the same s i z e as the Canadian o f f s p r i n g as r e f l e c t e d i n t h e i r weights. This outcome suggests a genotype - environmental i n t e r a c t i o n f o r the New Zealand s i r e d o f f s p r i n g . Since the Canadian s i r e d o f f s p r i n g were heavier i n New Zealand (Peterson, 1988) but maintained equal weight t o the New Zealand s i r e d o f f s p r i n g i n Canada; suggests t h a t the Canadian d a i r y i n d u s t r y may increase forage l e v e l s i n t h e i r feeding regimen and s t i l l m aintain higher or equivalent growth r a t e s w i t h those of New Zealand. The e f f e c t of t h i s on mi l k production and o v e r a l l performance w i l l have to be taken i n t o c o n s i d e r a t i o n ; s i n c e growth i n New Zealand was l e s s than t h a t i n Canada and p o s s i b l y r e f l e c t i n g the i n f l u e n c e of feeding and management schemes. Both s t r a i n s d i s p l a y e d a high degree of 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 f o r the weight t r a i t , but the ge n e t i c v a r i a n c e f o r the height t r a i t was sm a l l . A high l e v e l of gene t i c variance suggests t h a t animals w i l l respond t o gene t i c improvement through s e l e c t i o n . 100 H e r i t a b i l i t i e s f o r weight and height at w i t h e r s ranged from low t o high i n both s t r a i n s . Since the c o e f f i c i e n t of gen e t i c determination, h 2, i n d i c a t e s the degree of response to s e l e c t i o n t h a t may be expected from a t r a i t ; these r e s u l t s suggest t h a t weight and height are h i g h l y h e r i t a b l e and t h e r e f o r e , should respond t o s e l e c t i o n . However, w i t h i n s t r a i n h e r i t a b i l i t y estimates have been accompanied by l a r g e standard e r r o r s compared t o those obtained when s i r e groups were analyzed together. This b i a s i n the i n d i v i d u a l s t r a i n estimates was due t o the sma l l e r o f f s p r i n g numbers. Therefore, i n c l u s i o n of more o f f s p r i n g (per s i r e ) w i t h i n group would enhance the e s t i m a t i o n of h e r i t a b i l i t i e s . Phenotypic and genetic c o r r e l a t i o n s (between weight and wither height) i n t h i s study were high. This was i n d i c a t e d f o r both s i r e groups. The genetic c o r r e l a t i o n s were higher than those c i t e d i n l i t e r a t u r e . These estimates may be i n f l a t e d due t o sampling e r r o r . However, a high 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 i n d i c a t e s t h a t s e l e c t i o n f o r one t r a i t w i l l i n d i r e c t l y lead t o s e l e c t i o n f o r the other. A high phenotypic c o r r e l a t i o n i m p l i e s t h a t the two t r a i t s are s i m i l a r l y i n f l u e n c e d by environmental f a c t o r s . 101 6. SUMMARY (1) O f f s p r i n g of Canadian and New Zealand s i r e s were e q u a l l y heavy at a l l ages wi t h the exception of the 15 and 18 month weights where the Canadian h e i f e r s were heavier than the New Zealand h e i f e r s . (2) Canadian s i r e d h e i f e r s were t a l l e r a t the withers than New Zealand s i r e d h e i f e r s at a l l ages except at b i r t h , 3 and 9 months when they were equal i n height. (3) Both Canadian and New Zealand s i r e groups e x h i b i t e d equal phenotypic variances f o r weight and wither height t r a i t s , except at 9, 12 and 15 months when Canadian s i r e group variances were higher. (4) The high degree of a d d i t i v e g e n e t i c variance f o r the weight t r a i t i n d i c a t e s t h a t there i s s t i l l o pportunity f o r improvement. Weight and height are h i g h l y h e r i t a b l e and subject to responding t o s e l e c t i o n . (5) Weight and height are h i g h l y g e n e t i c a l l y c o r r e l a t e d . S e l e c t i n g f o r one w i l l i n d i r e c t l y s e l e c t f o r the other. 102 In the o v e r a l l context, knowledge of p o p u l a t i o n d i f f e r e n c e s and t h e i r g e n e t i c parameters could lead t o s e l e c t i o n methods based on h e r i t a b i l i t y and gene t i c v a r i a t i o n of the cha r a c t e r s , g e n e t i c c o r r e l a t i o n between them and t h e i r r e l a t i v e economic values. The i n t e r r e l a t i o n s h i p of the genetic make-up of an animal and the environment i n which the animal i s producing or being t e s t e d must be considered i n a s e l e c t i o n or breeding plan. Only when a GxE i n t e r a c t i o n i s i n s i g n i f i c a n t , can the e v a l u a t i o n of an animal i n one environment, be of relevance (or a p p l i c a b l e ) i n another f o r e i g n environment. In which case, r e l i a b l e conversion f a c t o r s are re q u i r e d f o r comparison of va r i o u s e v a l u a t i o n methods. 103 Appendix Is Canadian Mating Timetablet Event Occurrence Comments Matings July '84 - June '86 B i r t h of Project Calves A p r i l '85 - March '87 B i r t h weights and TOP* F i r s t Lactation - s t a r t A p r i l '87 - March '89 (Project dams) - end A p r i l '88 - March '90 Heifer growth Spring 1989 Weight and Wither Height records F i r s t Lactation (Heifers) Spring 1990 Weight and Wither Height records, Production t r a i t s , TOP t According to Peterson (1985) # " T r a i t s other than Production" Appendix 2 : Comparison of Growth Trends of Imported and Native Breeds i n the Tropics A. Least squares means f o r l o c a l breeds and two-breed or 3/4 crossbreds i n research stations of Ethiopia (Source: Kiwuwa et a l . , 1983) Native 2-breed 3/4 crosses T r a i t Arsi(A) Zebu(Z) JxA HxA HXZ HxHA HxHZ JxJA No. cows 62 94 39 154 60 66 37 70 B i r t h wt. (kg) 21.5 23.0 21.9 24.4 27.1 25.5 27.2 24.1 Postpartum wt. (kg) 236 309 269 307 328 324 325 306 J=Jersey , H=Holstein B. Performance of two-breed or three-breed and 3/4 crosses of Brown Swiss (B), Holstein (H), or Jersey (J) with Tharparkar (T) at the National Dairy Research Centre, Karnal, India (Source: Mason, 1982) Native 2-Breed 3-Breed 3/4 Cross T r a i t T HxT BxT JxT HxBT HxJT HxHT No. Cows 176 118 69 74 32 43 58 B i r t h wt. (kg) 21.0 27.2 26.9 21.6 30.0 25.4 29.8 12 mo. wt. (kg) 124 199 167 172 155 154 163 C. Performance of Synthetic Breeds or Strains of T r o p i c a l o r i g i n (Source: Schneeberger et a l . , 1982) JH l PR2 AMZ3 KS4 Sibovey 5 O r i g i n Jamaica B r a z i l A u s t r a l i a India Cuba Body Wt. (kg) 394 422 386 368 430 Age (mo.) 34.5 34.7 31.0 36.3 31.3 1 Jamaica Hope (Jersey and Sahiwal) 2Pitanguei-Ras (5/8 Red Poll-3/8 Zebu) A u s t r a l i a n Milking Zebu (Jersey-Sahiwal or Red Sindhi) 4Karan - Swiss (1/2-5/8 Brown Swiss and Sahiwal or Red Sindhi) 5Sibovey (5/8 Holstein, 3/8 Zebu) Appendix 3s Comparison of Growth Data from CANZ with OMA and USA (including comparative plo t s ) Weight (kg) Age ( m o s ) CANZ OMA1 USA2 B i r t h 4 1 . 9 4 2 . 0 3 0 . 5 3 1 1 2 . 6 1 0 0 . 0 9 9 . 0 4 . 5 1 4 5 . 4 1 4 0 . 5 1 3 3 . 4 6 1 9 3 . 0 1 8 2 . 0 1 6 8 . 6 9 2 6 3 . 3 2 5 7 . 5 2 3 1 . 4 12 3 3 4 . 0 3 2 3 . 0 3 0 2 . 5 15 3 8 8 . 8 3 8 7 . 0 3 6 8 . 4 18 4 3 9 . 0 4 5 0 . 0 4 1 9 . 8 21 4 9 2 . 5 5 0 6 . 5 4 7 7 . 5 24 5 2 8 . 9 5 7 5 . 0 5 1 5 . 5 Wither Height (cm) B i r t h 7 5 . 6 7 5 . 0 7 3 . 6 3 9 1 . 8 9 3 . 0 8 9 . 7 4 . 5 9 7 . 3 1 0 3 . 0 9 5 . 2 6 1 0 4 . 9 1 1 2 . 0 1 0 1 . 1 9 1 1 4 . 0 1 2 0 . 5 1 1 0 . 6 12 1 2 0 . 8 1 2 7 . 0 1 1 7 . 9 15 1 2 5 . 9 1 3 1 . 5 1 2 2 . 7 18 1 2 9 . 7 1 3 6 . 0 1 2 7 . 2 21 1 3 2 . 2 1 3 9 . 5 1 3 0 . 7 24 1 3 4 . 3 1 4 2 . 0 1 3 2 . 1 ' O n t a r i o M i n i s t r y o f A g r i c u l t u r e a n d M a n i t o b a A g r i c u l t u r e G r o w t h G u i d e s ( 1 9 8 0 - 1 9 8 2 ) ' P e n n s y l v a n i a , U S A , S t a n d a r d s o f W e i g h t a n d H e i g h t ( H a r g r o v e e t a l . , 1 9 8 7 ) Appendix 3: CANZ vs OMA and USA Weight Plots Appendix 3: CANZ vs OMA and USA Wither Height Plots 9 12 15 Age (Months) Appendix 4: Comparison of CANZ Weight and Height: Canada (Can) vs New Zealand (NZn) Weight (kg) Age(mos) CN(Can) NZ(Can) CN(NZn) NZ(NZn) B i r t h 42.1* 41.3* 37.6° 36.1° 6 186.8* 188.4* 154.0° 148.0° 18 447.3* 444.8" 357.0C 347.0° 30 - - 394.0° 381.0° Wither Height (cm) 6 104.8* 103.9b 98.0° 97.0° 18 130.7* 128.7b 120.0° 118.0° 30 - - 130.0° 127.0° Means with the same superscript i n a row f o r the same t r a i t between countries are not d i f f e r e n t (P < 0.05) - = not a v a i l a b l e A p p e n d i x 5 : C o m p a r i s o n o f C a n a d i a n a n d N e w Z e a l a n d W i t h e r H e i g h t s Birth 3 4.5 6 9 12 15 18 21 24 Age (months) Means with the same supersc r ip t wi th in age do not d i f fer (P<0.05) I l l Appendix 6: Individual Herd Weight Least Squares Means with Standard Errors (Both S i r e Groups) Age(months) Herd B i r t h 3.0 4.5 6.0 9.0 AG 39.9"'° ±0.6 118.1"'b ±2.0 153.3"'b ±2.4 202.7"'b ±2.9 277.3 ±3.1 GU 43.6' ±0.5 123.8" ±1.6 158.8" ±2.0 210.7" ±2.5 266.3 ±7.4 MA 41.9"'b ±0.7 109.1b'° ±2.5 1 4 0 > 7 . . d . o ±3.1 183.2°-d'" ±3.8 260.0 ±9.8 MD 41.3*-" ±0.9 102.4° ±3.5 130.0*-d ±4.8 159.2* • ±5.7 229.7" ±7.0 NS 43.4" ±1.0 106.6° ±3.7 133.9*'d ±4.6 170.1* ±6.1 229.1" ±6.5 OL 38.8° ±0.9 111.2b'° ±3.3 148.6"'"'° ±4.0 193.4"'b-° ±5.3 285.5 ±11.0 OR 43.1" ±0.4 111.2b'° ±1.4 144.0b'd'° ±1.7 190.0b'°'d ±2.1 258.2 ±2.3 SA 41.5"-b ±1.0 104.3° ±3.4 131.0" ±4.2 179.4d'" ±5.1 258.4 ±5.6 SC 43. 2" ±0.7 100.6° ±2.4 127.9" ±2.9 183.3°'d'" ±3.6 278.6 ±3.8 UA 40.0b'c ±0.7 112.7b'° ±2.6 145.8b'd'° ±3.2 203.9"'b ±4.1 -Means with the same superscript i n the same column are not s i g n i f i c a n t l y d i f f e r e n t (P < 0.05) - = not a v a i l a b l e 112 Appendix 6 (con't)t Individual Herd Weight Least Squares Means with Standard Errors (Both S i r e Groups) Age(months) Herd 12.0 15.0 18.0 21.0 24.0 AG 353.5b ±3.7 408.7*'b ±4.4 462.2*'b ±4.9 504.l b ±6.0 552.9b ±8.6 GU 350.8b'c ±3.7 392.6b'°'d ± 8.2 431.2b'° ±4.9 462.2b ±,12.0 531.8b'° ±6.7 MA 320.9*'d ±4.9 376.1b-°-d ±8.0 434.1b'° ±6.9 461.5b ±16.0 545.1b'° ±12.0 MD 336.2c'd'• ±12.0 384.6c'd ±16.0 - - -NS 293.1£ ±9.0 367.l d ±13.0 404.7° ±20.0 508.7b ±23.0 524.3b'° ±28.0 OL - - - - -OR 314.8° ±2.6 376.4b-c'd ±3.3 424.8b'° ±3.7 482.8b ±4.7 497.2° ±6.0 SA 338.0b'c'd ±6.4 398.3*-b-° ±7.8 469.6*'b ±8.6 541.3* ±11.0 617.1* ±15.0 SC 326.7°'d'* ±4.6 374.9b'c-d ±5.5 440.7b'° ±6.2 497.l b ±7.1 519.8b'° ±10.0 UA 375.3* ±5.6 425.7* ±8.0 501.2* ±28.0 - 539.4b'° ±17.0 Means with the same superscript i n the same column are not s i g n i f i c a n t l y d i f f e r e n t (P < 0.05) - = not a v a i l a b l e 113 Appendix 7> Individual Herd Hither Heights Least Squares Means with Standard Errors (Both S i r e Groups) Age(months) Herd B i r t h 3.0 4.5 6.0 9.0 AG 75.0 ±0.4 93.3*'° ±0.5 98.7'-b ±0.5 106.5*'b ±0.6 113.9*'b'° ±0.5 GU 75.0 ±0.3 92.5* ±0.4 98.0* ±0.4 106.5*'b ±0.5 112.1° ±1.0 MA 75.8 ±0.5 91.7*'" ±0.7 98.5* ±0.7 104.7*'b-e ±0.7 116.6* ±2.0 MD 75.5 ±0.6 91.8*-b ±0.9 96.0*'b ±1.0 101.3d ±1.0 113.7*'"' = ±1.0 NS 76.4 ±0.7 90.8*'b ±1.0 96.6*'b ±1.0 102.l d ±1.0 111.0= ±1.0 OL 74.8 ±0.6 89.4" ±0.9 96.5*'b ±0.9 103.5b'°'d ±1.0 114.2*'" ±2.0 OR 75.7 ±0.3 91.1*'b ±0.4 96.3*'b ±0.4 102.9°'d ±0.4 113.5*'"'=. ±0.4 SA 75.3 ±0.7 89. 6b ±0.9 95. 0 b ±0.9 102.9c-d ±1.0 112.7"'° ±0.9 SC 76.6 ±0.5 92.7* ±0.6 97.8* ±0.6 108.0* ±0.7 118.0* ±0.7 UA 76.4 ±0.5 91.5*'b ±0.7 97.4*'b ±0.7 105.3*'b'c ±0.8 -Means with the same superscript i n the same column are not s i g n i f i c a n t l y d i f f e r e n t (P < 0.05) - = not a v a i l a b l e 114 Appendix 7 ( c o n ' t ) t Individual Herd Wither Height Least Squares Means with Standard Errors (Both S i r e Groups) Age(months) Herd 12.0 15.0 18.0 21.0 24.0 AG 120. 8"'"'° 125.6 130.1 132.6" 135.1 ±0.5 ±0.5 ±0.4 ±0.5 ±0.5 GU 121.7*'b'c 126.2 129.3 131.l b 134.1 ±0.5 ±0.9 ±0.4 ±0.9 ±0.4 MA 121.4"'b 126.9 130.2 130.3"'b 134.5 ±0.7 ±0.9 ±0.6 ±1.0 ±0.7 MD 120.4*'b'c 128.0 _ ±2.0 ±1.7 NS 118.4° 125.9 127.6 129.2" 131.1 ±1.0 ±2.0 ±2.0 ±2.0 ±2.0 OL - - - — -OR 120.0b'° 125.4 128.9 131.6"'" 134.2 ±0.4 ±0.4 ±0.3 ±0.4 ±0.3 SA 1 2 0 > 3 . , b , c 126.4 130.5 133.1" 135.1 ±0.9 ±0.8 ±0.8 ±0.8 ±0.8 SC 123.4* 127.0 131.6 134.0" 135.6 ±1.0 ±0.6 ±0.5 ±0.5 ±0.6 UA 120.3"'b'° 123.7 129.7 134.1 ±0.8 ±0.9 ±2.5 ±1.0 Means with the same superscript i n the same column are not s i g n i f i c a n t l y d i f f e r e n t (P < 0.05) - = not a v a i l a b l e 115 Appendix 8s I n i t i a l H e r i t a b i l i t y Values 1 f o r DFREML Analysis Age Weight Wither (Weight Height and Height) B i r t h 0.52 0.37 0.4 3 0.06 0.04 0.05 4.5 0.20 0.06 0.2 6 0.09 0.06 0.07 9 0.39 0.26 0.30 12 0.46 0.31 0.35 15 0.22 0.29 0.25 18 0.34 0.51 0.40 21 0.27 0.84 0.50 24 0.05 0.43 0.24 Values were derived from Least squares analyses i n equation (1) based on a s i r e models h 2 = 4o2. / o2. + a 2, where, h 2 i s h e r i t a b i l i t y , a 2, i s s i r e variance and cr2. i s e r r o r variance. 116 Appendix 9: Calculation of Standard Errors (S.E.) of the H e r i t a b i l i t y Estimates by the Approximate Method of Swiger et a l . , (1964): S.E. (h2) =4 2(n.-l) ( l - c ) 2 ( l - r ( ^ 1 - l ) t) Kx2 (n. -s) (s-1) where n. i s the t o t a l number of o f f s p r i n g f o r a l l f a m i l i e s ( s i r e s ) per s i r e group i n each age c l a s s ( t a b l e 4 ) ; S i s the number of s i r e s per s i r e group; t i s the 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: t = a 2, / (a 2, + a2.) i n each age c l a s s ; K x i s the weighted number of progeny per s i r e i n each s i r e group, i n each age category (as i n d i c a t e d below). A c c o r d i n g t o Becker (1984), K x f o r unequal s u b c l a s s ( f a m i l y ) numbers (unbalanced design) i s o b t a i n e d as: Kx = [n. - (2 2 n ^ / n . J / d f i j where df i s the s i r e degrees of freedom per s i r e group i n each age c l a s s . Kx Values generated by ANOVA: Age(mos) S i r e Group BOTH1 CANADIAN2 NEW ZEALAND3 B i r t h 11.614 11.56 11.234 3 10.867 10.801 10.503 4.5 10.694 10.621 10.339 6 10.466 10.548 9.9516 9 6.8417 6.836 6.4578 12 8.9815 8.9043 8.6783 15 7.067 7.2894 6.4489 18 7.8417 7.6288 7.7438 21 5.2629 5.4877 4.736 24 6.3926 5.8969 6.5137 JS = 40, 2S = 20, JS = 20 f o r a l l ages 117 Appendix 10i Calculated F values from the S i r e Group Variance Ratios f o r each Age c l a s s . Weight (kg) Age(mos) a 2. (F value) 1 a 2 p (F va l u e ) 2 B i r t h 1.06 1.01 3 45630.00* 1.04 4.5 7.20* 1.13 6 3.30* 1.22 9 3.00* 1.29 12 1.72 1.10 15 2.68* 1.02 18 1.09 1.02 21 1.09 1.19 24 7.38* 1.13 Wither Height (cm) Age(mos) a 2. 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