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The influence of early and late breeding of dairy cows on fertility, weight changes and on milk production.. Schneider, F. (Fritz) 1980

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THE INFLUENCE OF EARLY AND LATE BREEDING OF DAIRY COWS ON FERTILITY, WEIGHT CHANGES AND ON MILK PRODUCTION OF THE PRESENT AND SUBSEQUENT LACTATION  by  FRITZ SCHNEIDER D i p l . Ing.-Agr. ETH 1977 Swiss F e d e r a l I n s t i t u t e of Technology A THESIS SUBMITTED  IN PARTIAL FULFILLMENT OF  THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES Department of 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 s t a n d a r d  THE UNIVERSITY OF BRITISH COLUMBIA June, 1980 © F r i t z S c h n e i d e r , 1980  In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make i t freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives.  It i s understood that copying or publication  of this thesis for financial gain shall not be allowed without my written permission.  Department of  ANIMAL SCIENCE  The University of British Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date  JUNE 11 , 1980  - ii -  ABSTRACT In a H o l s t e i n  herd (125 cows) the i n f l u e n c e  of e a r l y  and l a t e breeding post partum on r e p r o d u c t i o n and p r o d u c t i o n was  investigated.  At c a l v i n g the cows were  randomly a s s i g n e d to two groups. was  The  scheduled to be bred at the f i r s t  e a r l y bred group visible  f o l l o w i n g 50 days post partum which r e s u l t e d interval  The average  c o n c e p t i o n was  88 ± 33 days.  per c o n c e p t i o n .  to be bred at the f i r s t  The  first  The  cows i n the e a r l y bred of 1.50  (range: 1 to 3)  l a t e bred group was  scheduled  v i s i b l e heat f o l l o w i n g 80 days  post partum which r e s u l t e d  i n an average  i n t e r v a l of  93 ± 17 days from p a r t u r i t i o n to the f i r s t  service.  i n t e r v a l from p a r t u r i t i o n to c o n c e p t i o n was  40 days. an average The  average  i n t e r v a l from p a r t u r i t i o n to  group c o n c e i v e d a f t e r an average  average  i n an  of 73 ± 18 days from p a r t u r i t i o n to the  service.  services  heat  The 120 ±  The cows i n the l a t e bred group c o n c e i v e d a f t e r of 1.96  (range: 1 to 5) s e r v i c e s  number of s e r v i c e s  per c o n c e p t i o n was  (P£.05) h i g h e r f o r the l a t e bred  per c o n c e p t i o n . significantly  group.  The e a r l y post partum r e p r o d u c t i v e a c t i v i t y monitored w i t h m i l k progesterone a n a l y s e s . milk s t r i p p i n g s  was  was  A sample of  a n a l y s e d by a radioimmunoassay  technique every second  day from 6 days post partum u n t i l  c o n c e p t i o n o c c u r r e d or the animal was  removed from the  herd.  Cows  which  statistical estrous  to  the  post  was  heat  f i r s t  the  conceive  The  17  visible  ±  heat  Calving  which  associated delayed  in  early  but  not  bred  group  produced  the  more  between  calvings.  cows  calving  difference groups of  or  average  entire  lactation the  dry  partum traits.  the  between groups daily  period to  gained  calving  of day  and  according  to  the  this  experiment  period). reproductive  FCM  the  Calving  bred  The  late in  yield  were  group,  not  weight  no  health in  over  of  status terms the  current  early  related  than  was  lactation, and  season  gained  season  (beginning  the  sub-  calvings  calculated  subsequent  the  but  There  calving  late  pasture  between  d i f f i c u l t i e s  problems  the  calving  the  ( P ^ .05)  lactation  late  and  of  more  season.  milk  150  150  weight  non-pasture early  the in  group.  during  day  305  (PJ6.01) l e s s in  and  days  of  also  significantly  26  days  and  the  ±  f i r s t  lactation  in  48  compared  the  sequent  FCM  partum  (FCM)  in  more  progesterone  milk  and  the  f i r s t  corrected  lactation  produced  the  conception  bred  from  fat  day  Cows  post  problems  season  group  of  f i r s t  occurred  pasture  bred  305  The  days  10  excluded  length  days.  33  were  average  ± 7.5  occurred  partum.  during  not  analyses.  cycle  detected  did  to  including post production  -  TABLE  i V-  OF  CONTENTS Page  Abstract Table  i i  of  Contents  List  of  Tables  List  of  Fi gures  List  of  Appendix  iv v i i x Tables  xi  Acknowledgements  x i i  1.  INTRODUCTION  1  2.  LITERATURE  4  3.  MATERIAL  REVIEW  AND  METHODS  3.1.  A n i mal s  3.2.  Milk  3.3.  Visual  3.4.  Data  3.5.  Experimental  16  sampling heat  and m i l k  progesterone  analyses  .  detection  17 18  c o l 1 e c t i on  18  design  and s t a t i s t i c a l curve  analysis  .  Lactation  3.5.2.  Analysis  model  .  20  3.5.3.  T e s t o f i n f l u e n c e o f d a y s open on production in subsequent l a c t a t i o n  .  24  of  Correlation  computation  19  3.5.1.  3.5.4. 4.  15  variance  19  (ANOVA)  coefficients  24  RESULTS  25  4.1.  Test  for  4.2.  Reproductive 4.2.1.  4.2.2.  bias  in  the groups  25  traits  27  Influence breeding  of  Influence  of  early  versus  late 29  the  health  31  -  y  T  Page  4.3.  4.2.3.  Influence  4.2.4.  Interactions  Body w e i g h t s and body current lactation 4.3.1.  4.4.  4.7.  season  33 33  weight  changes  in  the 39  of  4.3.2.  Influence  of  health  41  4.3.3.  Influence  of  season  44  Productive  traits  early  versus  late 39  in  the  current  versus  .  .  46  of  4.4.2.  Influence  of  health  49  4.4.3.  Influence  of  season  49  Carry-over subsequent  early  lactation  Influence breeding  4.5.1.  4.6.  calving  Influence breeding  4.4.1.  4.5.  of  late 46  e f f e c t s from lactation  the  current  to  the 52  Influence breeding  of  4.5.2.  Influence  of  health  55  4.5.3.  Influence  of  season  57  Average d a i l y lactations Correlations 4.7.1.  4.7.2.  4.7.3.  milk  early  versus  late 52  production  over  the  two 59  and  regressions  Correlations traits  between  C o r r e l a t i o n s between and p r o d u c t i v e traits lactation  61 reproductive 61 reproductive of the current  C o r r e l a t i o n s between reproductive t r a i t s of the c u r r e n t and productive t r a i t s of the subsequent lactation .  63  63  - vi -  Page '4.7.4.  4.7.5.  5.  C o r r e l a t i o n s between r e p r o d u c t i v e t r a i t s and body weight changes i n the c u r r e n t and subsequent l a c t a t i o n  65  Test o f i n f l u e n c e of days open on p r o d u c t i o n i n the subsequent 1 a c t a t i on  67  DISCUSSION  69  5.1.  Onset of the e s t r o u s c y c l e v i s u a l and p r o g e s t erone d e t e c t e d heats  69  5.2.  Days from p a r t u r i t i o n t o the f i r s t s e r v i c e to c o n c e p t i o n and t o the next c a l v i n g  72  5.3.  The r e l a t i o n s h i p between r e p r o d u c t i o n , p r o d u c t i o n and body weight changes  76  6.  SUMMARY AND CONCLUSIONS  83  7.  BIBLIOGRAPHY  86  8.  APPENDIX  93  - vii LIST OF TABLES Table 1  Reasons f o r c u l l i n g of the cows from the herd the experiment  _ age p  during 16  2  Number o f o b s e r v a t i o n s  21  3  Means and standard d e v i a t i o n s of t r a i t s a t the time of c a l v i n g and i n the e a r l y post partum p e r i o d . . . . 26  4  Means and standard d e v i a t i o n s of r e p r o d u c t i v e t r a i t s and t h e i r d i f f e r e n c e s between the e a r l y bred and the l a t e bred group  30  5  Means and standard d e v i a t i o n s of r e p r o d u c t i v e t r a i t s and t h e i r d i f f e r e n c e s between the two h e a l t h codes . . 32  6  Means and standard d e v i a t i o n s of r e p r o d u c t i v e t r a i t s and t h e i r d i f f e r e n c e s between p a s t u r e season and nonp a s t u r e season  34  I n t e r a c t i o n s between groups, h e a l t h codes and seasons in reproductive t r a i t s  36  S i g n i f i c a n t g r o u p - h e a l t h code i n t e r a c t i o n s i n r e p r o d u c t i v e t r a i t s . A n a l y s i s w i t h i n the e a r l y bred broup  36  7 8  9  S i g n i f i c a n t g r o u p - h e a l t h code i n t e r a c t i o n s i n r e p r o d u c t i v e t r a i t s . A n a l y s i s w i t h i n the l a t e bred group  . 37  10  S i g n i f i c a n t group-season i n t e r a c t i o n s i n r e p r o d u c t i v e traits. A n a l y s i s w i t h i n the e a r l y bred group  37  11  S i g n i f i c a n t group-season i n t e r a c t i o n s i n r e p r o d u c t i v e traits. A n a l y s i s w i t h i n the l a t e bred group  38  12  S i g n i f i c a n t sea s o n - h e a l t h code i n t e r a c t i o n s f o r the c a l v i n g i n t e r v a l . A n a l y s i s w i t h i n seasons  38  13  Means and standard d e v i a t i o n s of body weights and body weight changes i n the c u r r e n t l a c t a t i o n and at the subsequent c a l v i n g . The d i f f e r e n c e s between e a r l y bred and l a t e bred group  40  Sex of c a l v e s  42  14  - viii  -  Table 15  Page  Group h e a l t h s t a t u s i n t e r a c t i o n f o r body weight gain (kg) between c a l v i n g s . The a n a l y s i s w i t h i n b r e e d i n g groups  42  16  Means and standard d e v i a t i o n s of body weights and body weight changes i n the c u r r e n t l a c t a t i o n and at the subsequent c a l v i n g . The d i f f e r e n c e s between heal th codes . . . .43  17  Means and standard d e v i a t i o n s o f body weight and body weight changes i n the c u r r e n t l a c t a t i o n and at the subsequent c a l v i n g . The d i f f e r e n c e s between c a l v i n g s d u r i n g the pasture season and non-pasture season  45  Means and standard d e v i a t i o n s of p r o d u c t i v e * t r a i t s i n the c u r r e n t l a c t a t i o n and the' d i f f e r e n c e s between * e a r l y bred a n d , l a t e bred group  4Z  Means and standard d e v i a t i o n s of t r a i t s i n the subsequent l a c t a t i o n and the d i f f e r e n c e s between e a r l y bred and l a t e bred group  53  Means and standard d e v i a t i o n s of t r a i t s i n the subsequent l a c t a t i o n and the d i f f e r e n c e s between the h e a l t h code groups ( h e a l t h codes o f the c u r r e n t lactation)  55  Means and standard d e v i a t i o n s of t r a i t s i n the subsequent l a c t a t i o n i n f l u e n c e d by the c a l v i n g season of the c u r r e n t l a c t a t i o n  57  Average d a i l y milk and FCM p r o d u c t i o n from the beginning of the c u r r e n t l a c t a t i o n to day 150 o f the subsequent l a c t a t i o n  60  23  C o r r e l a t i o n s between r e p r o d u c t i v e c u r r e n t post partum p e r i o d  t r a i t s of the  62  24  C o r r e l a t i o n s between r e p r o d u c t i v e t r a i t s of the c u r r e n t l a c t a t i o n  and  18  19  20  21  22  25  productive  C o r r e l a t i o n s between r e p r o d u c t i v e t r a i t s of the c u r r e n t and p r o d u c t i v e t r a i t s of the subsequent lactation  62  64  - ix -  Table  Page  26  C o r r e l a t i o n s between r e p r o d u c t i v e t r a i t s and body weight changes i n the c u r r e n t and subsequent l a c t a t i o n  66  27  R e s u l t s of the simple r e g r e s s i o n a n a l y s e s w i t h days open as independent continuous v a r i a b l e  68  - x -  LIST OF FIGURESFigure 1  2  3  4  5  6  7  Page  D e f i n i t i o n s of the f i r s t e s t r o u s c y c l e l e n g t h and the f i r s t p r o g e s t e r o n e d e t e c t e d heat on the base of milk p r o g e s t e r o n e l e v e l s i n the e a r l y post partum period  28  Mean p r o d u c t i o n and s l o p e s of e a r l y and l a t e bred group f o r f a t %, milk and f a t c o r r e c t e d m i l k on the c u r r e n t l a c t a t i o n  48  Mean p r o d u c t i o n and s l o p e s of h e a l t h code group 1 and h e a l t h code group 2 f o r f a t %, milk and f a t c o r r e c t e d milk of the c u r r e n t l a c t a t i o n  50  Mean p r o d u c t i o n and s l o p e s of cows c a l v i n g d u r i n g the pasture season versus the non-pasture season f o r f a t %, milk and f a t c o r r e c t e d milk of the current l a c t a t i o n  51  Mean p r o d u c t i o n and s l o p e s of e a r l y and l a t e bred group f o r f a t %, m i l k and f a t c o r r e c t e d m i l k o f the subsequent l a c t a t i o n (0-150 days)  54  Mean p r o d u c t i o n and s l o p e s of h e a l t h code group 1 and h e a l t h code group 2 f o r f a t %, milk and f a t c o r r e c t e d milk of the subsequent l a c t a t i o n  56  Mean p r o d u c t i o n and s l o p e s of f a t %, milk and f a t c o r r e c t e d milk of the subsequent l a c t a t i o n ( 0 150 d a y s ) . D i f f e r e n c e s due to the c a l v i n g season of the c u r r e n t l a c t a t i o n  58  - xi LIST  OF  APPENDIX  TABLES  Table .1  2 3 4  Page  Means and standard d e v i a t i o n s o f the c o v a r i a b l e s m i l k p r o d u c t i o n 0-50 days post partum, body weight changes 0-60 days post partum i n the c u r r e n t l a c t a t i o n and age of c a l v i n g a t the b e g i n n i n g of the c u r r e n t l a c t a t i o n  93  Means and standard d e v i a t i o n s o f r e p r o d u c t i v e in the c u r r e n t l a c t a t i o n  94  Means and standard d e v i a t i o n s of p r o d u c t i v e in the c u r r e n t l a c t a t i o n  traits  traits 95  Means and standard d e v i a t i o n s of body weights and body weight changes i n the c u r r e n t l a c t a t i o n and a t the subsequent c a l v i n g  96  5  Means and standard d e v i a t i o n s f o r t r a i t s subsequent l a c t a t i o n  97  6  C o r r e l a t i o n s between the body weight and the body weight changes i n the c u r r e n t l a c t a t i o n  7  C o r r e l a t i o n s between body weight and body weight changes i n the subsequent l a c t a t i o n  8  C o r r e l a t i o n s between body weight and body weight changes and m i l k p r o d u c t i o n i n the c u r r e n t l a c t a t i o n  9  i n the  C o r r e l a t i o n s between body weight and body weight changes and m i l k p r o d u c t i o n i n the subsequent 1 a c t a t i on  98 98 . 99  99  - x i i-  ACKNOWLEDGEMENTS The author would l i k e t o take t h i s o p p o r t u n i t y t o acknowledge the e f f o r t s of those people who were of prime importance  to the r e s e a r c h and p r e p a r a t i o n of t h i s  Special Animal was  thesis.  thanks to Dr. J.A. S h e l f o r d , Department of  S c i e n c e U.B.C., under whose s u p e r v i s i o n t h i s work  done and whose p a t i e n t a s s i s t a n c e i s g r e a t l y a p p r e c i a t e d . Many thanks to Dr. L . J . F i s h e r , Research  Station,  A g a s s i z f o r the p e r m i s s i o n to use the data of the d a i r y herd of the Research  S t a t i o n and h i s a d v i c e and s u g g e s t i o n s .  The author a l s o wishes  to acknowledge the help of Dr. R.G.  Peterson and Mrs. M. S t r i k e r f o r t h e i r i n v a l u a b l e a d v i c e and a s s i s t a n c e i n the a n a l y s i s of the d a t a . Thank you a l s o to the t e c h n i c i a n s i n the Department of Animal  S c i e n c e U.B.C. f o r the a n a l y s i s of the m i l k  samples. Thanks are a l s o due to the S o c i a l S c i e n c e s and Humanities  Research  C o u n c i l of Canada f o r the awards which  enabled the author to study i n Canada.  - 1 -  1.  INTRODUCTION M i l k y i e l d and r e p r o d u c t i v e performance are two  very important  f a c t o r s determining  a d a i r y herd.  On many d a i r y farms r e p r o d u c t i o n does not  f o l l o w an optimum course.  the p r o f i t a b i l i t y of  Therefore,  i t i s important  t h a t r e p r o d u c t i v e problems are t r a c e d to t h e i r  source  as r a p i d l y and e f f i c i e n t l y as p o s s i b l e . Impaired  r e p r o d u c t i o n r e s u l t s i n a decreased  d u c t i o n per day of l i f e and t h e r e f o r e h i g h e r costs.  I t i s essential  to analyse  pro-  production  and e x p l a i n as many  f a c t o r s a s s o c i a t e d w i t h r e p r o d u c t i v e f a i l u r e as p o s s i b l e and  t o q u a n t i f y the i n f l u e n c e s on p r o d u c t i o n .  used measure of f e r t i l i t y calving interval  A widely  i s the c a l v i n g i n t e r v a l .  A  of 12 to 13 months i s thought to be  i d e a l and i s p o s s i b l e i f the s e r v i c e p e r i o d i s kept w i t h i n 60 to 90 days post  partum.  From the p h y s i o l o g i c a l p o i n t o f view, a one year calving interval  i s f e a s i b l e however , c a l v i n g d i f f i c u l t i e s , 3  r e t a i n e d p l a c e n t a s , e n d o m e t r i t i s , veneral s i l e n t h e a t s , e t c . delay c o n c e p t i o n calving interval reducing to  difficult  and make an optimum  to a t t a i n .  the c a l v i n g i n t e r v a l  infections,  One step toward  i s to use m i l k  c h a r a c t e r i z e e s t r o u s c y c l e s and to i d e n t i f y  pregnant cows as e a r l y as p o s s i b l e .  The m i l k  c o n c e n t r a t i o n changes d u r i n g the course  progesterone nonprogesterone  of the e s t r o u s  - 2 -  c y c l e , being  low  markedly h i g h e r  ( 2ng/ml) d u r i n g s t a n d i n g (>5ng/ml) between heats.  heat The  and  milk  pro-  gesterone c o n c e n t r a t i o n can be determined by a r a p i d radioimmunoassay technique use progesterone in d a i r y cows.  which makes i t p o s s i b l e to  l e v e l s i n milk to monitor e s t r o u s M i l k progesterone  used i n Europe and  analyses  are  cycles  widely  North America (Heap et a l . , 1 973 ;  Hoffmann et a l . , 1 976 ; S h e l f o r d et a l . , 1 979)  to monitor  e s t r o u s c y c l e s , to e s t a b l i s h the r e p r o d u c t i v e s t a t u s of problem cows and The  purpose of the study  occurrence first and  f o r an e a r l y pregnancy check. h e r e i n was  to e s t a b l i s h the  of the f i r s t hormonal e s t r o u s c y c l e and  hormonal e s t r u s w i t h milk progesterone  the  analyses  to compare the r e s u l t s w i t h the v i s u a l l y d e t e c t e d  Reproductive  data and  p r o d u c t i v e data were a n a l y s e d  r e l a t i o n to s p e c i f i c breeding open and The  times  heats.  in  post partum, to days  to the c a l v i n g i n t e r v a l . i n f l u e n c e of c a l v i n g a s s o c i a t e d  problems and  the i n f l u e n c e of the c a l v i n g season on  r e p r o d u c t i v e and l a c t a t i o n and  reproductive  p r o d u c t i v e performance of the  on p r o d u c t i v e performance of the  current subsequent  l a c t a t i o n was i n v e s t i g a t e d . The  o b j e c t i v e s of t h i s study were:  v i s u a l l y detected e s t r u s and  To compare  heats w i t h m i l k progesterone  detected  to t e s t whether the onset of e s t r u s was  by the c a l v i n g season, c a l v i n g a s s o c i a t e d  influenced  reproductive  - 3 -  problems and the l e v e l of p r o d u c t i o n . the  influence  To  investigate  of e a r l y and l a t e b r e e d i n g , the  of c a l v i n g a s s o c i a t e d  influence  problems and the i n f l u e n c e  c a l v i n g season on the r e p r o d u c t i v e current  l a c t a t i o n and the p r o d u c t i v e  current  and e a r l y subsequent  of the  performance i n the performance i n the  lactation.  - 4 -  2.  LITERATURE REVIEW I n e f f i c i e n t r e p r o d u c t i v e performance  i s known as  one of the major herd management problems ( R o u n s a v i l l e et al . , 1 979 ; S p a l d i n g et a l . , 1 975 ). increased mechanization  Larger herds  and  r e s u l t i n l e s s time spent per  cow  and can lead to d e c r e a s i n g r e p r o d u c t i v e success i f the management s k i l l s The to  and r e c o r d keeping are not  strengthened.  r e p r o d u c t i v e process i s very complex and very understand  and s t i l l  fully.  difficult  A g r e a t number of s t u d i e s have been  are being conducted  d e a l i n g mostly w i t h one  or  a few of the r e p r o d u c t i v e a s p e c t s or p r o d u c t i v e - r e p r o ductive relationships.  The purpose  of the f o l l o w i n g  p a r t of t h i s study i s to review some of the most i m p o r t a n t i n f o r m a t i o n and Age  of Cow.  on the pregnancy and Reed, 1961;  results. The age of the cow  has a marked e f f e c t  r a t e a f t e r the f i r s t  i n s e m i n a t i o n (Boyd  De K r u i f , 1 975 ; Rosenberg et a l . . , 1 977 ).  Most i n v e s t i g a t o r s conclude t h a t the pregnancy reduced  i n animals which  rate i s  have c a l v e d f o r the f i r s t  De K r u i f (1975) observed a d i f f e r e n c e of 5% i n the r a t e between p r i m i p a r o u s and secundiparous  cows.  time. pregnancy In cows  7 years and o l d e r the c o n c e p t i o n r a t e a f t e r the  first  i n s e m i n a t i o n i s a l s o low.  Kruif  F l o r e s (1972) and De  (1975) r e p o r t t h a t p r i m i p a r o u s cows have more days open than m u l t i p a r o u s cows.  They do not a t t r i b u t e the  reduced  - 5 -  conception  r a t e i n p r i m i parous cows to t h e i r age as such,  but to the f a c t t h a t problems a s s o c i a t e d w i t h c a l v i n g are more l i k e l y to occur a t the f i r s t c a l v i n g and d u r i n g the f i r s t t h a t these  post partum p e r i o d .  De K r u i f (1975) showed  d i f f e r e n c e s disappeared  the p r i m i p a r o u s with c a l v i n g .  when he removed a l l  cows which had some problems a s s o c i a t e d W i l t o n et al . ( 1 967 ) d i d not f i n d any  i n f l u e n c e of age on the i n t e r v a l  from c a l v i n g to con-  ception. Health of cow.  I n f e c t i o n s caused by V i b r i o f e t u s ,  T r i chomonas f e t u s , B r u c e l l a a b o r t u s , L e p t o s p i r o a , e t c . d i s t u r b the f e r t i l i t y of d a i r y c a t t l e a great d e a l . Several  of these  d i s e a s e s , .however, are under c o n t r o l , at  l e a s t i n the i n d u s t r i a l i z e d c o u n t r i e s . i n f e c t i o u s diseases disturbances  these  there are a number of n o n - i n f e c t i o u s  l i k e r e t a i n e d p l a c e n t a s , trauma to r e p r o -  d u c t i v e t r a c t and u t e r i n e i n e r t i a . can  Beside  These  disturbances  i n f l u e n c e the r e p r o d u c t i v e performance of a d a i r y  very d r a s t i c a l l y .  herd  Roberts (1971) and De K r u i f (1978)  r e l a t e d p a r t of these  disturbances  e s p e c i a l l y at the time of c a l v i n g .  to inadequate Retained  hygiene,  placenta  and e n d o m e t r i t i s are known to reduce the f e r t i 1 i t y • b y - 5 to  10% a t the f i r s t  open (Dyrendahl and  insemination  r e s u l t i n g i n more days  et a l . , 1 976 ; Morrow et a l . , 1 969 ; Roine  S a l o n i e m i , 1978; Zamet et a l . , 1979).  De K r u i f (1975)  s t r e s s e d the f a c t t h a t c a l v i n g hygiene i s p a r t i c u l a r l y  - 6 -  important  i n loose housing  systems where cows come i n t o  c l o s e r and more f r e q u e n t c o n t a c t w i t h other cows than i n s t a n c h i o n barns, r e s u l t i n g i n an i n c r e a s e d r i s k of i n f e c t i o n . C l i m a t e and season. f a c t o r a l t e r i n g conception  The c l i m a t e i s an rate in c a t t l e  High temperatures and humidity w i l l  t r o p i c s than 1962).  (Thatcher,  rate.  Early  i s b e l i e v e d to occur more o f t e n i n the  i n temperate r e g i o n s  ( S t o t t and W i l l i a m s ,  High ambient temperatures i n f l u e n c e the plasma  progesterone  level  r e s u l t i n g i n a decreased  (Rosenberg et a l . , 1 977 ; Roussel  conception  et a l . , 1 977 ).  has a very d e f i n i t e i n f l u e n c e on f e r t i l i t y In  1974).  depress b e h a v i o u r a l  e s t r u s s i g n s and with i t the c o n c e p t i o n embryonic death  important  rate  Season  in dairy c a t t l e .  temperate r e g i o n s , pregnancy r a t e s are h i g h e s t i n  s p r i n g ( M i l l e r et a l . , 1 970a; De K r u i f , 1 975 ) and are depressed  d u r i n g the w i n t e r months.  l e v e l s d u r i n g e s t r u s are lower favourable f o r conception  The plasma  progesterone  i n w i n t e r t i m e which i s  (Roussel  heat d e t e c t i o n as such i s poorer  et a l . , 1 977 ), but the  due to c o n s t a n t  confine-  ment of the cows and l e s s d a y l i g h t i n the barns (David et al.,  1971; King et a l . , 1 976 ).  David et a l . (1971) and  Mather et a l . (1978) found t h a t l i t t l e i s shown w i t h the f i r s t e s t r u s . e s t r u s behaviour visual  detection.  behavioural  During  the pasture  evidence season  i s much s t r o n g e r and more e v i d e n t f o r Francos et a l . ( 1 977)  found t h a t the  - 7 -  v o l u n t a r y feed i n t a k e i n summer i s s i g n i f i c a n t l y than  higher  i n w i n t e r and they a l s o r e l a t e d these f i n d i n g s and  the i n c r e a s e d e x e r c i s e im summer to f e r t i l i t y ' Body weight change p a t t e r n s .  as w e l l .  The body weight change  p a t t e r n of d a i r y cows and i t s r e l a t i o n to f e r t i l i t y has been s t u d i e d by many authors and  (Amir and K a l i , 1974; Huth  Smidt, 1 979 ; M i l l e r and Hooven, 1 970b; Touchberry and.  B a t r a , 1976; Youdan and K i n g , 1977).  The high e a r l y  l a c t a t i o n m i l k p r o d u c t i o n r e q u i r e s n u t r i e n t s i n excess of the d i e t a r y i n t a k e of the cow. to  T h e r e f o r e , the cow s t a r t s  m o b i l i z e body r e s e r v e s and consequently  in the f i r s t the l a c t a t i o n  l o s e s weight  p a r t (up to 50 to 70 days post partum) of (Amir and K a l i , 1974; M i l l e r and Hooven, 1970b;  Youdan and K i n g , 1977).  This weight l o s s i s dependent  on many f a c t o r s ; l e v e l of m i l k p r o d u c t i o n , m i l k plane of n u t r i t i o n , and the p r o t e i n - e n e r g y  composition,  relationship  of the d i e t being only a few of them ( B r o s t e r , 1973). There i s evidence  i n the l i t e r a t u r e  (King e t a l . , 1 976 ;  Youdan and K i n g , 1977) t h a t cows which are g a i n i n g weight d u r i n g the time of i n s e m i n a t i o n have a b e t t e r r a t e of conception  than cows l o s i n g weight.  a beneficial  Boyd (1970) demonstrated  e f f e c t of body weight gain on f e r t i l i t y  but h i s r e s u l t s were not s t a t i s t i c a l l y  significant.  f i n d i n g i n d i c a t e d t h a t e a r l y post partum breeding  rate This  (first  s e r v i c e before 60 days post partum) r e s u l t e d i n an i n f e r i o r r a t e of c o n c e p t i o n  compared to i n s e m i n a t i o n a f t e r a  - 8 -  longer r e s t period.  Herz and Graf (1976) and Roberts e t  al . ( 1 979a) r e l a t e d the d i f f i c u l t i e s pregnant with the  of g e t t i n g  cows  weight l o s s or low blood glucose l e v e l s a t  time of i n s e m i n a t i o n .  Blood glucose l e v e l s were  lower i n the e a r l y post partum p e r i o d  than i n the l a t e  pre-partum and l a t e r post partum p e r i o d . (1979b) r e l a t e d t h e i r f i n d i n g s  Roberts et al .  to the m o b i l i z a t i o n of  adipose t i s s u e due to a l a c k of s u f f i c i e n t d i e t a r y  energy  intake. Time from p a r t u r i t i o n to f i r s t discussion  insemination.  The  of the e a r l y l a c t a t i o n weight changes leads  d i r e c t l y to the d i s c u s s i o n we are d i s c u s s i n g  of the optimal  rest period.  t h i s s u b j e c t we have to s p e c i f y  If  whether  we are aiming f o r a high c o n c e p t i o n r a t e at the f i r s t i n s e m i n a t i o n post partum, a s h o r t i n t e r v a l from c a l v i n g t o c o n c e p t i o n , a maximum l a c t a t i o n milk y i e l d or a maximum life  time p r o d u c t i o n .  The c o n c e p t i o n r a t e i s r e p o r t e d to  be low i n cows i n s e m i n a t e d p r i o r to 50 days post partum (Britt,  1 975 ; Shannon e t al . , 1 952 ; Touchberry.et. a l . , 1 959 ;  Whitmore e t a l . , 1974). calving  I t i s generally  accepted t h a t a  i n t e r v a l of 12 months i s a d e s i r a b l e  et a l . , 1971; B r i t t , 1975).  (Ayalon  The 12 month c a l v i n g i n t e r v a l  i s even agreed upon by such a s t r o n g c r i t i c service  goal  a f t e r c a l v i n g as Dawson (1967).  of e a r l y  Louca and Legates  (1968) propose a c a l v i n g i n t e r v a l of 13 months f o r p r i m i parous cows and 12 months f o r m u l t i p a r o u s cows i n order  - 9 -  to a t t a i n maximum p r o d u c t i o n .  Cows must c o n c e i v e on the  average  by about 85 days post partum to a t t a i n a 12 month  calving  interval.  T h e r e f o r e , i t i s n e c e s s a r y to s t a r t  i n s e m i n a t i o n p r i o r to 60 days post partum f o r the simple reason t h a t under the best c o n d i t i o n s cows vary i n the date of appearance of heat and w a i t i n g 60 days before breedings r e s u l t s i n an average interval  c a l v i n g to f i r s t  service  much l o n g e r than 60 days (Ayalon et a l . , 1971).  Furthermore,  as d i s c u s s e d p r e v i o u s l y , e a r l y post partum  breeding r e s u l t s i n lower c o n c e p t i o n r a t e s which u n d e r l i n e s the n e c e s s i t y to s t a r t b r e e d i n g e a r l y i n o r d e r to o b t a i n a s h o r t average The  calving  interval.  r e l a t i o n s h i p between time of breeding post partum  and milk p r o d u c t i o n has been d i s c u s s e d r e p e a t e d l y throughout the years (Bar-Anan  and S o l l e r , 1979;  Louca and L e g a t e s , 1968;  Boyd,  1970;  Smith and L e g a t e s , 1962;  Trim-  b e r g e r , 1 954 ; Whitmore et a l . , 1 974 ; W i l t o n et al . , 1 967 ). Trimberger  (1954) c o n s i d e r e d e a r l y breeding as a d i s -  advantage,  e s p e c i a l l y f o r show c a t t l e , because the  l a c t a t i o n m i l k y i e l d decreases  i f cows are bred  after parturition.  Louca and Legates  from the economical  s t a n d p o i n t the y i e l d  i  early  (1968) s t a t e d t h a t per u n i t t i m e ,  milk per day or year i s more i m p o r t a n t than the t o t a l lactation production.  R i p l e y et a l . (1970) suggested  i n c l u s i o n of days open i n t o the performance d a i r y cows.  Britt  r e c o r d of  (1975) showed c l e a r l y t h a t the m i l k  the  - 10 -  production  per day of l i f e  calving intervals.  i s h i g h e s t i n cows w i t h  Menge e t a l . (1962) and Smith and  Legates (1962) r e p o r t e d on the b a s i s of t h e i r reviews  t h a t the o p i n i o n t h a t high producing  conceive  as r e a d i l y as low p r o d u c e r s ,  experimental  evidence.  t h a t high producing  short  literature cows do not  lacks conclusive  Ayalon et a l . (1971) r e p o r t e d  cows r e a c t f a v o u r a b l y to a r e s t p e r i o d  of 60 days and t h a t there are ho reasons why moderate ducing !  not  cows of good general  and r e p r o d u c t i v e h e a l t h  pro-  should  be bred a t the f i r s t e s t r u s a f t e r 45 days post partum.  Whitmore et a l . (1974) found t h a t e a r l y breeding producing  cows d i d not i n f l u e n c e the success  sequent i n s e m i n a t i o n s .  Francos and R a t t n e r  the c a l v i n g to c o n c e p t i o n with t h e i r milk y i e l d .  interval  of high  of sub(1975) compared  of high producing  cows  A l l the cows were inseminated  the f i r s t e s t r u s a f t e r 60 days post partum.  at  They found  t h a t cows y i e l d i n g 8000 kg or more i n a 305 day l a c t a t i o n on an average d i d not c o n c e i v e partum.  110 days post  Herz et a l . (1979) i n v e s t i g a t e d the p r o d u c t i o n of  r e t u r n and non-return higher production  cows and found a s i g n i f i c a n t l y  both i n m i l k y i e l d and f a t c o r r e c t e d  milk y i e l d of the r e t u r n cows. Rattner  before  N e i t h e r Francos and  ( 1 975 ) nor Herz et a l . ( 1 979)  were able to determine  whether the r e t u r n cows d i d not c o n c e i v e insemination  a f t e r the f i r s t  because they produced more m i l k or whether  they produced more milk because they d i d not conceive  - 11 -  readily.  Bar-Anan and  Soller  (1979),  in their  study  the e f f e c t s of days open on milk y i e l d , d e f i n i t e l y the accepted estimate 305  day  305  day  lactation  of the p r o d u c t i o n records  t h i s reason, lactation  y i e l d as an  ability.  rejected  unbiased  They found t h a t the  p e n a l i z e cows which c o n c e i v e  Israel  on  early.  For  i n t r o d u c e d a system which a d j u s t s  milk y i e l d f o r days open as proposed e a r l i e r  by  R i p l e y et a l . ( 1 970 ) . Heat d e t e c t i o n .  In order  to breed the cows f o r a  s h o r t e r c a l v i n g i n t e r v a l , i t i s e s s e n t i a l to employ a systematic  and  e f f i c i e n t method of e s t r u s d e t e c t i o n .  l a r g e r the herds and  The  the more mechanized the whole o p e r a t i o n  becomes, the more important e s t r u s d e t e c t i o n method.  i t i s to use a  systematic  While an unsystematic  technique  might be a p p r o p r i a t e i n small herds,  technique  becomes i n e f f i c i e n t with l a r g e r herds.  t h e r e i s no technique  as good and  o b s e r v a t i o n of the herd.  observation this  e f f i c i e n t as a  So f a r , systematic  Problems of e s t r u s d e t e c t i o n  occur e s p e c i a l l y i n the e a r l y post partum p e r i o d because s i g n s of e s t r u s are not as obvious as l a t e r on. et a l . (1971) r e p o r t e d undetected  t h a t 60% of a l l f i r s t  heats remain  because the cows are not c o n t r o l l e d and  observed p r o p e r l y .  Pelissier  detection f a i l u r e in C a l i f o r n i a delayed  David  first  s e r v i c e and  (1976) found t h a t heat was  the primary  also contributed  to the delay of the subsequent s e r v i c e s .  cause of  significantly There i s a  - 12 -  c o n s i d e r a b l e amount of i n f o r m a t i o n a v a i l a b l e on d e t e c t i o n methods and  heat d e t e c t i o n a i d s .  heat  Gartland  et  al . ( 1 976 ) measured the v a g i n a l mucus e l e c t r i c a l l y .  Kiddy  (1977) t e s t e d the use of a pedometer to measure the activity  of the cow  and  found a f o u r f o l d  activity  of cows i n e s t r u s .  observed i n a loose housing in s t a n c h i o n  The  i n c r e a s e i n the  fourfold  system.  increase  Activity  was  increases  barns as w e l l but l e s s than i n f r e e  stalls.  Foote (1975) d e s c r i b e d a whole range of mechanical d e t e c t i o n a i d s (video camera and d e t e c t o r s and markers). a t e a s e r or gomer b u l l  cow  or b u l l  for  mounted  Heat d e t e c t i o n a i d s which r e q u i r e are q u i t e expensive  r e q u i r e a f a i r amount of l a b o u r to o b t a i n results.  heat  Foote (1975) commented:  and  still  satisfactory  "There i s no s u b s t i t u t e  the eye of the s k i l l e d o b s e r v e r  and manager  who  observes h i s cows f o r e s t r u s . " Plasma and  milk progesterone  analysis.  development of radioimmunoassay techniques progesterone  l e v e l s have become one  Since  the  (RIA),  of the major hormonal  parameters used to monitor r e p r o d u c t i v e performance i n cattle.  Measurements of progesterone  made f o r a number of years Robertson and  i n plasma have been  ( S t a b e n f e l d t et a l . , 1961).  Sarda (1971) f i r s t used t h i s method to  diagnose pregnancy i n s e v e r a l domestic s p e c i e s . and  Heap (1971) found t h a t progesterone  cows was  Laing  i n the milk  c l o s e l y c o r r e l a t e d w i t h the a c t i v i t y  of the  of  - 13 -  corpus luteum and, t h e r e f o r e , suggested i t be used as an i n d i c a t o r f o r pregnancy.  Hoffmann and Hamburger  (1973)  d e s c r i b e d the p a t t e r n of milk p r o g e s t e r o n e throughout the e s t r o u s c y c l e and the i n c r e a s e i n p r o g e s t e r o n e conc e n t r a t i o n i n e a r l y pregnancy.  During s t a n d i n g heat the  m i l k p r o g e s t e r o n e c o n c e n t r a t i o n i s very low and  rises  from about the 3rd to 4th day a f t e r s t a n d i n g heat r e a c h i n g a peak between the 12th and 16th day.  The  concentration  drops again around days 17 to 20 of the 21-day c y c l e (Booth, 1979).  The development  of a r a p i d  t e c h n i q u e (Heap et a l . , 1973; Heap et a l . ,  radioimmunoassay 1976) made i t  p o s s i b l e to use milk progesterone l e v e l s f o r commercial pregnancy t e s t i n g  (Booth and H o l d s w o r t h , 1976), f o r  c o n f i r m a t i o n of e s t r u s (Hoffmann  et a l . , 1 976 ) and f o r  m o n i t o r i n g the e s t r o u s c y c l e of s u b - f e r t i l e cows (Lamming and Bulman, 1976; Braun, 1977).  The m i l k p r o g e s t e r o n e  l e v e l s are h i g h l y c o r r e l a t e d w i t h the f a t c o n t e n t of the milk.  In o r d e r to o b t a i n r e l i a b l e r e s u l t s , i t i s i m p o r t a n t  t h a t one m i l k sampling method i s used  consistently.  S h e l f o r d et a l . ( 1 979) recommended the use of the m i l k s t r i p p i n g s , Braun  ( 1 977 ) c o r r e c t e d the samples.;to 10%  m i l k f a t and Hoffmann et a l . (1977) recommended the a n a l y s i s of the p r o g e s t e r o n e l e v e l only.  i n samples of m i l k f a t  - 14 -  The m i l k progesterone radioimmunoassay i s i n c r e a s i n being used to a s s i s t the management of d a i r y herds i n a c c o m p l i s h i n g a high l e v e l a valuable tool in  of f e r t i l i t y .  I t represents  r e q u i r e d to reach the r e p r o d u c t i v e goals  d a i r y herds s e t by De K r u i f  (1978):  1.  A pregnancy r a t e of 80% a f t e r the f i r s t  2.  An average of 1.3  3.  An average i n t e r v a l and  conception.  i n s e m i n a t i o n s per  insemination  conception.  of 85 days between  parturition  - 15 -  3.  MATERIAL AND The  METHODS  data used i n t h i s study was  d a i r y herd.  M i l k progesterone  hormonal e s t r u s .  The  c o l l e c t e d from  l e v e l s were used to d e t e c t  cows a l s o were observed  behavioural estrus signs.  for  At c a l v i n g each cow  was  domly a s s i g n e d to an e a r l y b r e e d i n g or to a l a t e group i n o r d e r to achieve an unbiased in r e l a t i o n to days from p a r t u r i t i o n (Whitmore e t a l . , 1 974).  t e s t of  ran-  breeding  fertility  to c o n c e p t i o n  H e a l t h codes were i n t r o d u c e d  to d i s t i n g u i s h between cows w i t h normal and  abnormal  c a l v i n g and e a r l y post partum h i s t o r i e s of h e a l t h A f u r t h e r d i s t i n c t i o n was  one  problems.  made between c a l v i n g i n the  p a s t u r e versus c a l v i n g i n the non-pasture  season.  The  data were s u b j e c t e d to an a n a l y s i s of v a r i a n c e to e s t i m a t e d i f f e r e n c e s due  to breeding time post partum, h e a l t h  s t a t u s and c a l v i n g season.  A general l i n e a r model  was  employed to t e s t r e p r o d u c t i o n t r a i t s of the c u r r e n t l a c t a t i o n , p r o d u c t i o n t r a i t s and body weight the c u r r e n t and subsequent l a c t a t i o n .  changes of  Sources  of un-  c o n t r o l l e d v a r i a t i o n such as age, m i l k p r o d u c t i o n i n the f i r s t 50 days post partum and body weight changes i n the f i r s t 60 days post partum were i n t r o d u c e d as c o v a r i a b l e s i n t o the s t a t i s t i c a l  model.  - 16 -  3.1.  Animals From October 1977  through May  1979  125 post p a r t u r i e n t  H o i s t e i n - F r i e s i a n cows of the d a i r y herd of the A g r i c u l t u r e Canada Research S t a t i o n i n A g a s s i z , B.C. sampled  f o r m i l k progesterone a n a l y s e s .  s t a r t e d 6 days a f t e r c a l v i n g and was day u n t i l  The  done every o t h e r  The time of t h i s t r i a l  Another  complete  14 cows were e l i m i n a t e d from the a n a l y s e s  of the subsequent  lactation.  of the cows are l i s t e d  Table 1:  removed  coincided with a  d r a s t i c herd cutback so t h a t o n l y 85 cows had data.  sampling  c o n c e p t i o n o c c u r r e d or the animal was  from the herd.  were  The reasons f o r the c u l l i n g  i n Table 1.  Reasons f o r c u l l i n g of the cows from the herd d u r i n g the experiment.  Reason  C u l l e d before conception  Culled after conception  Herd c u t b a c k , poor p r o d u c t i o n o l d age  15  5  9  4  hardware  8  1  Hard b r e e d e r s , s t e r i l e  8  M a s t i t i s , udder problems D i s p l a c e d abomasum, i n j u r y ,  Back in heat a f t e r confirmed cTotal onception,abortion  40  144  - 17 -  The A g a s s i z d a i r y herd was  housed i n a f r e e  stall  barn and the cows were m i l k e d i n a double sawtooth P a r t of the g r a i n r a t i o n was parlor.  From May  parlor.  fed d u r i n g m i l k i n g i n the  to October the cows were p a s t u r e d on  o r c h a r d grass p a s t u r e w i t h a p p r o x i m a t e l y 10% w h i t e c l o v e r . A s t r i p g r a z i n g system was  employed (the fence was  every day so t h a t the cows got a p i e c e of f r e s h each d a y ) .  In w i n t e r t i m e (November t i l l  corn s i l a g e w i t h 2 kg of hay per cow ,A11  the cows were a r t i f i c i a l l y  moved  pasture  A p r i l ) mainly  per day was  fed.  inseminated.  Possible  i n f l u e n c e s of the s e r v i c e s i r e on r e p r o d u c t i v e t r a i t s the cow  have not been taken i n t o account  in this  of  study.  S i r e s were randomly a s s i g n e d to mates i r r e s p e c t i v e of treatment on the  (e.g. e a r l y or l a t e breeding post partum) imposed  cow.  The  c o n c e p t i o n s were confirmed by r e c t a l p a l p a t i o n  2 months a f t e r i n s e m i n a t i o n . 3.2.  M i l k sampling and m i l k progesterone  analyses  Samples of the m i l k s t r i p p i n g s were taken every other day at the a f t e r n o o n m i l k i n g from 6 days post partum until  c o n c e p t i o n o c c u r r e d or the animal was  removed from  the herd.  The a n a l y s e s f o r m i l k progesterone were done  employing  the method d e s c r i b e d by S h e l f o r d et a l . (1979)  which i s a m o d i f i c a t i o n of the radioimmunoassay technique f i r s t d e s c r i b e d by Heap et a l . (1973).  - 18 -  3.3.  Visual The  heat d e t e c t i o n  cows were observed at m i l k i n g , at f e e d i n g time  and one a d d i t i o n a l o b s e r v a t i o n of the herd took p l a c e between 9:00  and 10:00  pm.  S t a n d i n g heat, i n c r e a s e d  a c t i v i t y and v a g i n a l d i s c h a r g e was  observed.  No cameras,  markers or o t h e r heat d e t e c t i o n a i d s were used.  During  the time of t h i s s t u d y , a few cows which d i d not show any v i s i b l e s i g n s of e s t r u s were observed  very c a r e f u l l y  on the b a s i s of the progesterone a n a l y s i s and  inseminated  when the progesterone l e v e l s i n d i c a t e d the cows' e s t r u s . 3.4.  Data  collection  I n f o r m a t i o n about the i n d i v i d u a l d u c t i o n , h e a l t h ) was  taken from the r e c o r d keeping  of the A g r i c u l t u r e Canada Research M i l k y i e l d was was  cows (age, r e p r o system  Station in Agassiz,  B.C.  recorded at each m i l k i n g and percent f a t  e v a l u a t e d at a p p r o x i m a t e l y 35 day i n t e r v a l s by an  official  Record of Performance  (R0P) m i l k t e s t e r .  A l l the  cows were weighed at c a l v i n g , 60 days and 80 days post par turn.  - 19 -  3.5.  Experimental  3.5.1.  design and s t a t i s t i c a l  L a c t a t i o n curve  computation  The computation of the l a c t a t i o n  curves was done on  the b a s i s of m i l k y i e l d r e c o r d i n g s taken throughout the y e a r .  The 4% f a t c o r r e c t e d milk  FCM  (kg) =  every Wednesday  A weekday was chosen to exclude a  p o s s i b l e i n f l u e n c e of weekend  following  analysis  m i l k e r s and weekend  feeders.  (FCM) was c a l c u l a t e d w i t h the  formula: M i l k (kg)  This formula was f i r s t  x  (.4 + .15 x f a t % ) .  proposed by Gaines (1928).  Slopes  and i n t e r c e p t s were c a l c u l a t e d f o r each cow u s i n g the " E q u a l i t y of Regression  Slopes T e s t " o p t i o n of the  c o v a r i a n c e a n a l y s i s which i s p a r t of the package program: A n a l y s i s of v a r i a n c e / c o v a r i a n c e  (UBC MFAV/1978).  and i n t e r c e p t s were c a l c u l a t e d f o r m i l k , FCM and f a t - p e r c e n t f o r the f o l 1 o w i n g Current  lactation:  Subsequent l a c t a t i o n :  1actation 50 150 305 100 150 305  Slopes  production intervals:  0 0 0 50 100 150  to to to to to to  days days days days days days  0 0 50 100  to 50 days to 150 days to 100 days to 150 days  These s l o p e s and i n t e r c e p t s were i n t r o d u c e d i n t o the a n a l y s i s of v a r i a n c e as dependent v a r i a b l e s .  - 20 -  3.5.2.  Analyses of v a r i a n c e (ANOVA) model  The data were s u b j e c t e d to an a n a l y s i s of v a r i a n c e . The f o l l o w i n g independent Groups:  At c a l v i n g time each cow was  to  one of two groups.  at  the f i r s t  The  v a r i a b l e s were i n t r o d u c e d : randomly a s s i g n e d  The e a r l y bred group was  inseminated  v i s i b l e heat f o l l o w i n g 50 days post partum.  l a t e bred group was  i n s e m i n a t e d at the f i r s t  visible  heat f o l l o w i n g 80 days post partum. Health s t a t u s :  A h e a l t h code was  i n t r o d u c e d to d i f -  f e r e n t i a t e between cows w i t h normal and e a r l y post partum h i s t o r i e s .  and abnormal  calving  H e a l t h code 1 r e p r e s e n t e d  a cow w i t h o u t c a l v i n g a s s o c i a t e d r e p r o d u c t i v e problems. H e a l t h code 2 r e p r e s e n t e d a cow which  had s u f f e r e d one  or  more of the f o l l o w i n g c o n d i t i o n s at c a l v i n g or w i t h i n one month a f t e r c a l v i n g : two men  calving d i f f i c u l t y  (more than  or v e t e r i n a r y a s s i s t a n c e ) , r e t a i n e d p l a c e n t a or  metritis.  Ayalon et a l . (1971) used s i m i l a r h e a l t h code  specifications. C a l v i n g season:  Since t h e r e i s evidence i n the  t h a t the c a l v i n g season  has an i n f l u e n c e on f e r t i l i t y  production in dairy c a t t l e R a t t n e r , 1975;  literature  (De K r u i f , 1975;  Francos  Roine and' S a l o n i e m i , 1978), season  and and  was  i n t r o d u c e d i n t o the general ANOVA model.  The year  d i v i d e d i n t o two seasons:  ( p a s t u r e season)  and November to A p r i l  May  to October  (non-pasture  season).  was  - 21 -  The  number of o b s e r v a t i o n s  f o r the three  v a r i a b l e s are l i s t e d  i n Table 2.  Table 2:  observations  Number of  E a r l y bred group n Health Health  code 1 code 2  Cows c a l v e d i n : Pasture season Non-pasture season  Sources of u n c o n t r o l l e d the f i r s t general  independent  Late bred group n  Total n  30 12  30 13  60  85  20 22  18 25  38] 47J  85  variation:  251  Milk production  50 days i n the l a c t a t i o n was i n t r o d u c e d  of i n the  model as c o v a r i a b l e t o account f o r the d i f f e r e n c e s  in milk p r o d u c t i o n  between the two groups.  A preliminary  a n a l y s i s of the data showed t h a t the l a t e bred group produced more milk i n t h i s p e r i o d .  The body weight change  from c a l v i n g to 60 days post partum was i n t r o d u c e d c o v a r i a b l e i n t o the model f o r the same reason: the l a t e bred group l o s t more weight i n t h i s  as  Cows i n  period.  These d i f f e r e n c e s between the two groups approached s i g n i f i c a n c e and i n d i c a t e d t h a t the two groups were not randomly a s s i g n e d  in relation  at c a l v i n g was i n t r o d u c e d  to these two t r a i t s .  as c o v a r i a b l e to account f o r  the i n f l u e n c e o f the age o f the cow on i t s f e r t i l i t y and  p r o d u c t i on.  Age  - 22 -  The f o l l o w i n g dependent v a r i a b l e s were t e s t e d i n the a n a l y s e s of v a r i a n c e : Reproductive t r a i t s : first  Occurrence of f i r s t  v i s i b l e and  p r o g e s t e r o n e d e t e c t e d heats (days post partum), f i r s t  e s t r o u s c y c l e l e n g t h ( d a y s ) , days from p a r t u r i t i o n the  first  to  s e r v i c e , number of s e r v i c e s per c o n c e p t i o n ,  days open, days from f i r s t calving interval  s e r v i c e to c o n c e p t i o n and the  (days).  Productive t r a i t s :  Slopes of l a c t a t i o n  cussed under 3.5.1.).  c u r v e s (as d i s -  M i l k p r o d u c t i o n , FCM  and f a t - p e r c e n t of the f o l l o w i n g l a c t a t i o n Current  0 0 50 100  lactation  Subsequent  lactation:  production intervals:  to 50 days to 305 days to 100 days to 150 days  50 days 0 to 50 to 100 days 100 to 150 days  In a d d i t i o n the average d a i l y m i l k p r o d u c t i o n from the b e g i n n i n g of the c u r r e n t l a c t a t i o n subsequent l a c t a t i o n was  to day 150 of the  tested.  Body w e i g h t s and body weight changes:  Calving weights,  weight of c a l v e s , body weight changes from  parturition  to 60 days and 80 days post partum i n both the c u r r e n t and the subsequent l a c t a t i o n , the body weight gain  between  c a l v i n g s and the r a t e of gain (kg/day) from 60 and 80 days post partum to the subsequent  calving.  - 23 -  The f o l l o w i n g general Y  ijkl  - /+>  +  A  i  dD l.j k•, l  where: Y^.^  B  j  +  C  k  +  A  B  i j  +  B C  jk  +  + f Fi .j k•, , + fG. .. , + l ijkl  A B C  ijk  +  6 . ., , ijkl  jAU  =  dependent v a r i a b l e ( t h e o b s e r v a t i o n of the 1-th cow) as l i s t e d above o v e r a l l mean  A.  =  the e f f e c t of the i - t h b r e e d i n g group  B. 3  =  the e f f e c t o f the j - t h h e a l t h code  C^  =  the e f f e c t o f the k - t h c a l v i n g season  D,• i k I  =  n  +  l i n e a r model was employed:  the c o v a r i a b l e milk p r o d u c t i o n 0-50 days of the 1-th cow i n the i - t h group w i t h the j - t h h e a l t h code and c a l v i n g i n the k-th season  =  J  d  =  F. .J,  the D... 1 J  =  the c o v a r i a b l e body weight changes 0-60 days post partum of the 1-th cow i n the i - t h group w i t h the j - t h h e a l t h code and c a l v i n g i n the k-th season  =  c o e f f i c i e n t a s s o c i a t e d w i t h the F... covariable  J  f  the c o e f f i c i e n t a s s o c i a t e d w i t h covariable  1 J  G. ..,  =  the c o v a r i a b l e age (mo.) o f the 1-th cow i n the i - t h group w i t h the j - t h h e a l t h code and c a l v i n g i n the k-th season  =  the c o e f f i c i e n t a s s o c i a t e d covariable  1 J  g 6...-, ' J  =  w i t h the G... 1 J  the u n e x p l a i n e d d e v i a t i o n s a s s o c i a t e d w i t h the 1-th cow. Assumed to be random w i t h a mean of zero and v a r i a n c e o f C T | .  - 24 -  For the c a l c u l a t i o n of the a n a l y s i s o f v a r i a n c e the package program UBC BMD10V (General was employed.  Linear  Hypothesis)  The t e s t s f o r s i g n i f i c a n c e were generated  with the F - t e s t on a b a s i s o f e r r o r p r o b a b i l i t i e s o f P-6 .05 and P ^ . 0 1 . analyses  In order  to e x p l a i n s i g n i f i c a n t i n t e r a c t i o n s ,  were computed w i t h i n h e a l t h codes or w i t h i n seasons  using the same general  model e x c l u d i n g  the a p p r o p r i a t e  main e f f e c t s and i n t e r a c t i o n s . 3.5.3.  Tests of i n f l u e n c e of days open on p r o d u c t i o n i n subsequent l a c t a t i o n  Days open were c h a r a c t e r i z e d by a l a r g e v a r i a t i o n and were shown by R i p l e y e t a l . (1970) to i n f l u e n c e the production analyses  i n the subsequent l a c t a t i o n .  Single  regression  w i t h days open as a c o n t i n u o u s independent v a r i a b l e  were computed to t e s t the i n f l u e n c e of days open on production  traits  s i o n analyses  i n the subsequent l a c t a t i o n .  For the r e g r e s -  the package program UBC TRP ( T r i a n g u l a r  R e g r e s s i o n Package, 1977) was used. 3.5.4.  Correlation coefficients  The c o r r e l a t i o n c o e f f i c i e n t s d i s c u s s e d simple  l a t e r are  product moments among a l l continuous v a r i a b l e s .  For the c a l c u l a t i o n o f the c o r r e l a t i o n c o e f f i c i e n t s the package program UBC TRP ( T r i a n g u l a r Regression Package, 1977) was used.  - 25 -  4. 4.1.  RESULTS Test f o r b i a s i n the groups The  t e s t f o r b i a s showed t h a t there were no  d i f f e r e n c e s between the two  groups at the time of c a l v i n g  and  i n the e a r l y post partum p e r i o d i n terms of  and  reproductive  production  traits  significant  (Table  3).  However, the  productive milk  i n the f i r s t 50 days of the l a c t a t i o n and  body weight changes (BWC)  the  from c a l v i n g to 60 days post  partum approached s i g n i f i c a n c e , t h e r e f o r e , these v a r i a b l e s were i n t r o d u c e d a n a l y s i s of  as c o v a r i a b l e s i n the main model of  variance.  the  - 26 -  Table 3:  T  r  a  i  Means and standard d e v i a t i o n s of t r a i t s a t the time of c a l v i n g and i n the e a r l y post partum p e r i o d . E a r l y bred group  t  Late bred group  x*  s.d.  x*  s.d.  44.90  20.00  46.20  22.70  number  2.45  1 .35  2. 56  1 .67  wt. (kg)  618  98  611  97  Wt. of c a l f (kg)  42.50  5. 30  43.20  5 .70  -40.80  37.10  -54.40  40. 90  M i l k 0-50 days (kg)  1520  325  1653  380  Fat % 0-50 days  3.48  .53  3. 38  .52  FCM 0-50 days (kg)  1401  31 0  1 509  416  Age of cows (mos.) Lactation Calving  BWC 0-60 days p.p. (kg)  Slope of milk  0-50 days  Slope of f a t % 0-50 days Slope of FCM 0-50 days  •Number of  observations:  .1 509  .1253  .1779  . 1 349  - .0035  .0061  .0030  .0076  .1138  .1535  .1387  .1257  42 f o r the e a r l y bred group , 43  in the l a t e bred group except f o r the weight of the c a l f (33 and 36 r e s p e c t i v e l y ) . There were no s i g n i f i c a n t  (P<£.05) d i f f e r e n c e s  between  the e a r l y bred and the l a t e bred group i n the t r a i t s above.  listed  - 27 -  4.2.  Reproductive t r a i t s The d e t a i l e d t a b l e s f o r r e p r o d u c t i v e t r a i t s of the  c u r r e n t l a c t a t i o n are shown i n the Appendix  (Tables  2a  and 2b) . The f i r s t from the f i r s t  c y c l e l e n g t h was d e f i n e d as time p e r i o d r i s e of the milk p r o g e s t e r o n e c o n c e n t r a t i o n  from 2ng/ml (the e a r l y post partum c o n c e n t r a t i o n )  to a  c o n c e n t r a t i o n above 5ng/ml and back to 2ng/ml ( F i g u r e 1 ) . The d u r a t i o n of a normal e s t r o u s c y c l e of a cow 23 days. was  The average f i r s t  found to be o n l y 17.4  from 8 days to 40 days.  i s 19 to  cycle length i n t h i s  ± 7.5  days, w i t h a wide  The f i r s t  heat was d e f i n e d as the f i r s t  experiment range  progesterone detected  drop of the m i l k p r o g e s t e r o n e  c o n c e n t r a t i o n below 2ng/ml a f t e r the c o n c e n t r a t i o n been above 5ng/ml f o r the f i r s t (Figure 1). occurred 78 days.  The f i r s t  time a f t e r  had  parturition  progesterone detected  heat •>  33 ± 10 days post partum w i t h a range of 19 to The f i r s t  v i s i b l e heat o c c u r r e d  post partum w i t h a range of 8 to 127 days.  49 ± 26 days  - 28 F i g u r e 1:  D e f i n i t i o n s of the f i r s t e s t r o u s c y c l e l e n g t h and the f i r s t progesterone d e t e c t e d heat on the base of milk progesterone l e v e l s i n the e a r l y post partum p e r i o d .  days post  partum  A :  f i r s t r i s e of the m i l k progesterone post partum above 2ng/ml  B :  f i r s t progesterone  AB:  d u r a t i o n of the f i r s t e s t r o u s  BC:  d u r a t i o n of the second e s t r o u s c y c l e  detected  heat cycle  concentration  - 29 -  4.2.1.  I n f l u e n c e of e a r l y versus l a t e b r e e d i n g  There was  no d i f f e r e n c e between the e a r l y bred  group and the l a t e bred group i n terms of the o c c u r r e n c e of  the f i r s t v i s u a l l y : o r progesterone d e t e c t e d heats and  the l e n g t h of the f i r s t e s t r o u s c y c l e (Table 4 ) .  The  l a t e bred group had more recorded v i s i b l e heats and progesterone d e t e c t e d heats than the e a r l y bred due to a l o n g e r p e r i o d from p a r t u r i t i o n to the s e r v i c e which was  On the average  i n s e m i n a t e d 72 ± 1 8  and the l a t e bred group was parturition.  first  imposed on the cows by the treatment  ( e a r l y and l a t e b r e e d i n g ) . bred group was  group  the e a r l y  days a f t e r  parturition  i n s e m i n a t e d 93 ± 17 days a f t e r  The e a r l y bred group  had 88 ± 33 days open  w h i l e the l a t e bred group had 120 ± 40 days open which r e s u l t e d i n c a l v i n g i n t e r v a l s of 373 ± 34 versus 404 + 38 days r e s p e c t i v e l y .  The e a r l y bred group  needed  s i g n i f i c a n t l y fewer s e r v i c e s per c o n c e p t i o n (1.50; 1 to 3) than the l a t e bred group  range  (1.95; range 1 to 5 ) .  T h e r e f o r e , the e a r l y bred group a l s o had fewer days from the f i r s t  s e r v i c e to c o n c e p t i o n (16.4 versus 26.2).  of  the c o v a r i a b l e s accounted f o r a s i g n i f i c a n t amount  of  the v a r i a t i o n i n r e p r o d u c t i v e t r a i t s  (means and  s t a n d a r d d e v i a t i o n s of c o v a r i a b l e s , Appendix Significant interactions will  None  Table 1).  be d i s c u s s e d below.  - 30 -  Table 4:  Means and s t a n d a r d d e v i a t i o n s of r e p r o d u c t i v e t r a i t s and t h e i r d i f f e r e n c e s between the e a r l y bred and the l a t e bred group. E a r l y bred group  Trait  X  Late bred group  s.d.  Sign  s.d  X  1st v i s i b l e heat (d.p.p.)  50  28.5  47  25 .2  n.s.  1st prog. d e t . heat (d.p.p.)  34  10.0  33  10. 5  n.s.  Number of v i s i b l e heats  2.2  1 .0  3.0  1 .7  **  Number of prog. d e t . heats  3.1  1 .4  4.2  1 .3  **  18.4  8.6  16.6  6. 2  n.s.  72  18.2  93  17. 3  1st c y c l e l e n g t h  (days)  Days to 1 s t . s e r v i c e Number of s e r v i c e s Days from 1 s t s e r v i c e to conception Days open Calving  interval  (days)  *  1 .95  1 .50  **  1 6.40  25.0  26 . 2  39. 8  88  33.0  121  40. 6  ** **  373  34.1  404  38. 0  **  S i g n i f i c a n t d i f f e r e n c e s between groups: n.s. = not s i g n i f i c a n t .  *  P ^ . 0 5 ,  **  P  s?.01,  - 31 -  4.2.2.  Inf1uence of  The  onset of the e s t r o u s  parturition  to the f i r s t  the h e a l t h s t a t u s c y c l e was  health  slightly  (Table  c y c l e and  the days from  s e r v i c e were not 5).  shorter  The  duration  influenced of the  i n cows w i t h h e a l t h  t h i s d i f f e r e n c e , however, was  first  problems,  n o t . s i g n i f i c a n t . Cows with  h e a l t h problems needed more s e r v i c e s per c o n c e p t i o n versus 1.63), had had  a longer  more days open (113  calving interval  (400  versus 100)  versus 385  the cows w i t h o u t c a l v i n g or e a r l y post partum problems i r r e s p e c t i v e of date of b r e e d i n g . interactions will  be d i s c u s s e d  by  below.  (1.96 and  days) than reproductive  Significant  - 32 -  Table 5:  Means and standard d e v i a t i o n s of r e p r o d u c t i v e t r a i t s and t h e i r d i f f e r e n c e s between the two h e a l t h codes. Health  code  Health  code  Trait  X  S . 1d .  1st v i s i b l e heat (d.p.p.)  49  27 .6  47  25.0  n.s.  1st prog. d e t . heat (d.p.p.)  34  11 .1  34  8.2  n.s.  Number of v i s i b l e heats  2.5  1 .2  2.8  2.0  n.s.  Number of prog. d e t . heats  3.7  1 .4  3.7  1 .6  n.s.  18.1  8 .3  15.9  4.7  n.s.  82  21 .5  83  18.9  n.s.  1st c y c l e l e n g t h  (days)  Days to 1 s t . s e r v i c e Number of s e r v i c e s  1 .63  Days from 1 s t s e r v i c e t o conception  18.7  Days open Calving  interval  (days)  s.d.  X  *  1 .96 2 9 .9  27.9  40.9  **  1 00  38  113  46  **  385  35  400  47  **  S i g n i f i c a n t d i f f e r e n c e s between h e a l t h codes: * P=s ** P ^ .01, n.s. = not s i g n i f i c a n t .  The number of o b s e r v a t i o n s were 60 f o r h e a l t h code 1 and 25 f o r h e a l t h code 2, except f o r the c a l v i n g i n t e r v a l (49 and 22 o b s e r v a t i o n s r e s p e c t i v e l y ) .  - 33 -  4.2.3.  Influence  of c a l v i n g season  Pasture season versus non-pasture season the r e p r o d u c t i v e  performance very l i t t l e .  significant differences detected  influenced  There were no  i n the onset of the e s t r o u s  cycle,  h e a t s , days from p a r t u r i t i o n to the f i r s t  service  and  the number of s e r v i c e s needed per c o n c e p t i o n (Table 6 ) .  The  differences  the f i r s t interval  between the c a l v i n g season f o r days from  s e r v i c e to c o n c e p t i o n ,  days open and  reached s i g n i f i c a n c e w i t h r e l a t i v e l y  differences.  These d i f f e r e n c e s  the  calving  small  have to be e x p l a i n e d  in  r e l a t i o n to some s i g n i f i c a n t i n t e r a c t i o n s between group and  c a l v i n g season or h e a l t h  The  interactions will  4.2.4.  s t a t u s and  be d i s c u s s e d  c a l v i n g season.  below.  I n t e r a c t i ons  S i g n i f i c a n t i n t e r a c t i o n s in reproductive listed  i n Table 7.  traits  In order to e x p l a i n the s i g n i f i c a n t  i n t e r a c t i o n s , the r e s u l t s of an a n a l y s i s w i t h i n h e a l t h code and/or c a l v i n g season were used. e a r l y bred group h e a l t h not  s t a t u s and  group,  Within  the  c a l v i n g season d i d  i n f l u e n c e the number of s e r v i c e s per  Within  are  conception.  the l a t e bred group, however, cows w i t h  health  code 2 (problem cows) needed s i g n i f i c a n t l y more s e r v i c e s per c o n c e p t i o n  (2.46; range 1 to 5) versus the  cows (1.73; range 1 to 4 ) .  healthy  A s i m i l a r explanation  can  be  - 34 Table 6:  T  r  a  i  Means and s t a n d a r d d e v i a t i o n s of r e p r o d u c t i v e t r a i t s and t h e i r d i f f e r e n c e s between p a s t u r e season and non-pasture season. Pasture season  t  s.d.  X  Non-Pasture season X s .d.  Sign  28.3  48  25 .8  n. s.  32  8.6  35  11 .4  n .s .  Number of v i s i b l e heats  2. 5  1.1  2.7  1 .7  n. s.  Number of prog. d e t . heats  3.7  1 .3  3.7  1 .6  n .s .  17.4  4.5  17.6  9 .2  n. s .  83  22.8  82  18 .9  n. s .  1st  v i s i b l e heat (d.p.p.)  49  1st  prog. d e t . heat (d.p.p.)  1st c y c l e l e n g t h  (days)  Days to 1 s t s e r v i c e  :  Number of s e r v i c e s  1 .74  Days from 1 s t s e r v i c e to conception  23.0  Days open Calving interval  (days)  n. s .  1 .72 36 . 5 20.1  31 . 2  *  1 06  42  1 03  39  *  39 T  40  387  39  *  S i g n i f i c a n t d i f f e r e n c e s between p a s t u r e and non-pasture season:;: * P ^ s . 0 5 , n.s. = not s i g n i f i c a n t The number of o b s e r v a t i o n s were 38 f o r the p a s t u r e season and 49 f o r the non-pasture season.  - 35 -  given f o r the group-season i n t e r a c t i o n :  W i t h i n the e a r l y  bred group, c a l v i n g season had no i n f l u e n c e on number of s e r v i c e s per c o n c e p t i o n  (1.53  the  versus  1.42)  w h i l e w i t h i n the l a t e bred group, the cows t h a t c a l v e d d u r i n g the pasture season needed s i g n i f i c a n t l y more i n seminations  per c o n c e p t i o n than cows c a l v i n g i n the  pasture season (2.1  versus 1.8).  W i t h i n the e a r l y  nonbred  group, days open, days from the f i r s t s e r v i c e to c o n c e p t i o n and the c a l v i n g i n t e r v a l  were not s i g n i f i c a n t l y i n f l u e n c e d  by h e a l t h s t a t u s or c a l v i n g season.  However, w i t h i n the  l a t e bred group, days open and the c a l v i n g i n t e r v a l  were  s i g n i f i c a n t l y i n f l u e n c e d by h e a l t h s t a t u s ; days open and days from the f i r s t s e r v i c e to c o n c e p t i o n were i n f l u e n c e d by the c a l v i n g season (Tables 8 to 11).  The  health status  season i n t e r a c t i o n f o r the c a l v i n g i n t e r v a l was  signif-  i c a n t in the general model and w i t h i n the e a r l y bred but not w i t h i n the l a t e bred group.  group,  Health had a  s i g n i f i c a n t inf1uence on the c a l v i n g i n t e r v a l  d u r i n g the  pasture season but not d u r i n g the non-pasture  season  (Table 12). way  The  interaction  general model showed a s i g n i f i c a n t t h r e e (group-health-season)  f i r s t s e r v i c e to c o n c e p t i o n .  f o r days from  This i n t e r a c t i o n can  n e g l e c t e d because i n the pasture season i n the l a t e group, there was and t h i s animal  o n l y one  animal  w i t h h e a l t h code 2  had an extreme value (136  days).  be bred  •r  Table 7:  36 -  I n t e r a c t i o n s between g r o u p s , h e a l t h codes and seasons i n r e p r o d u c t i v e t r a i t s .  Tra i t s  Interaction Health x Season  I n t e r a c t i on Group x Season  Interact!' on Group x Health code  Number of s e r v i c e s per conception  ;n. s,  Days from 1 s t s e r v i c e to c o n c e p t i o n Calving P^  **  .05, * P •== .01 , n.s  significant  Number of s e r v i c e s per c o n c e p t i o n Days open interval  = not s i g n i f i c a n t  s .d.  Sign  12  .79  n.s.  87  12  27  n.s.  370  10  26  n.s.  n  s.d.  X  1 .53  30  . 68  1 .42  89  30  35  374  23  37  x  n.s.  n. s  S i g n i f i c a n t g r o u p - h e a l t h code i n t e r a c t i o n s i n reproductive t r a i t s . A n a l y s i s w i t h i n the e a r l y bred group. E a r l y bred group Health code 2 Health code 1  Tra i t  Calving  not  n. s  **  n.s,  interval  Table 8:  : n. s  **  Days open  n  - 37 -  Table 9:  S i g n i f i c a n t g r o u p s - h e a l t h code I n t e r a c t i o n s i n reproductive t r a i t s . A n a l y s i s w i t h i n the l a t e bred group. Late bred group H e a l t h code 2 H e a l t h code 1  Trait  n  s.d.  Sign  2.46  13  2.46  *  36  1 39  12  47  **  29  426  12  46  **  n  s. d.  X  1 .73  30  1 .48  Days open  11 3  30  Calving  394  26  X  Number of s e r v i c e s per c o n c e p t i o n  interval  Significant differences:  * P ^ .05,  ** P ^ .01  Table 10: S i g n i f i c a n t group-season i n t e r a c t i o n s i n r e p r o d u c t i v e traits. A n a l y s i s w i t h i n the e a r l y bred group. E a r l y bred group  X  Number o f s e r v i c e s per c o n c e p t i o n Days open Days from 1st s e r v i c e to concep. n.s.  Non-Pasture season  Pasture season  Trait  = not s i g n i f i c a n t  n  s.d.  X  n  s.d.  Sign.  20  .60  1 .55  22  .80  n.s.  89  20  35  87  22  32  n.s.  15.1  20  22.0  22  28.0  n.s.  1 .45  17.6  -  traits.  38  -  within  Analysis  Late  Number o f s e r v i c e s per c o n c e p t i o n  s.d.  2.06  18  1 .73  125  18  44  31 . 8  18  47  open  Days f r o m 1st s e r v i c e to c o n c e p .  Significant differences: * n.s. = not significant  Table  Non-Pasture season  n  X  Days  bred group  P a s t u r e . : season  Trai t  12:  P ^  n  s. d .  Sign  1 .88  25  1 . 45  n.s.  118  24  38  25  34  X  **  22  P ^  .01  S i g n i f i c a n t s e a s o n - h e a l t h code i n t e r a c t i o n f o r calving interval. Analysis within seasons Health  Trait Pasture  .05,  group.  1 ate bred  the  season  Non-pasture  season  Total  Significant differences: n . s . = not significant  code  1  Health  X  n  s.d.  X  382  27  37  41 2  387  22  32  397  385  49  35  400  *  P is. . 0 5 ,  **  P ^  code n  the  2  s.d.  Sign  52  *  17  47  n.s.  22  47  **  5  .01  * **  -  4.3.  39  -  Body weights and body weight changes i n the c u r r e n t 1 a c t a t i on The d e t a i l e d t a b l e s f o r body weights and body weight  changes are presented i n the Appendix 4.3.1.  (Tables 4a and 4 b ) .  I n f l u e n c e of e a r l y versus l a t e b r e e d i n g  The e a r l y post partum body weight changes were not i n f l u e n c e d by the d i v i s i o n of the herd i n t o e a r l y bred and l a t e bred groups  (Table 13).  Body weight changes were  s i g n i f i c a n t l y c o r r e l a t e d to p r o d u c t i o n (Appendix Table 8 ) . The weight of the cows at the subsequent  calving  s i g n i f i c a n t l y h i g h e r f o r cows i n the l a t e bred  was  group  (689 kg) as compared to cows i n the e a r l y bred group The body weight g a i n from c a l v i n g to c a l v i n g was significantly 45 k g ) .  h i g h e r i n the l a t e bred group  also  (67 kg versus  The average d a i l y weight gain from 60 and  days post partum r e s p e c t i v e l y to the subsequent was  a l s o h i g h e r i n the l a t e bred group.  (657 k g ) .  80  calving  The h i g h e r average  r a t e of gain i n the l a t e bred group can be e x p l a i n e d w i t h the l o n g e r dry p e r i o d of these cows. d u r i n g l a c t a t i o n was  h i g h l y c o r r e l a t e d w i t h age , (r = - . 6 6 ) ,  and the c o v a r i a b l e age accounted of the v a r i a t i o n .  The weight gain  f o r a s i g n i f i c a n t amount  - 40 -  Table  13:  Means and s t a n d a r d d e v i a t i o n s o f body w e i g h t s a n d b o d y w e i g h t c h a n g e s (BWC) i n t h e current l a c t a t i o n and at the s u b s e q u e n t c a l v i n g . The d i f f e r e n c e s between e a r l y b r e d and l a t e b r e d group. Early,bred  Trait Wt.  (kg)  at  Late  bred  group  n  s.d.  Sign  n  s.d.  611  42  97 . 0  625  43  100.7  n.s.  X  calving-(l)  group  X  BWC 0 - 6 0  d.p.p.  -41  42  37.1  -54  43  40.9  n.s.  BWC 0 - 8 0  d.p.p.  -31  42  40.1  -50  42  41 . 6  n.s.  10  40  23.0  6  40  22.5  n.s.  60 d . p . p . to ca1v i ng-(2 )  . 28  33  .16  .35  38  .14  *  80 d . p . p . to calving-(2)  .27  33  .17  .35  38  .16  *  Wt.  657  31  60.9  689  38  59.0  *  45  31  66 . 5  67  37  70.2  **  BWC 6 0 - 8 0 BWC/day  at  d.p.p. (kg/day):  calving-(2)  BWC c a l v i n g - ( 1 ) calving-(2)  '  to  Wt.  of  calf  (1)  42.0  33  4.9  43.2  36  5.8  n.s.  Wt.  of  calf  (2)  47.2  32  7.7  45.4  36  6.5  n.s.  Significant differences: significant. (1)  = current  d.p.p.  =  calving .  days  post  * P =s . 0 5 , (2) =  partum  **  P =  subsequent  .01 , n . s .  calving  =  not  - 41 -  4.3.2.  I n f l u e n c e of h e a l t h  Cows with c a l v i n g d i f f i c u l t i e s or e a r l y post partum r e p r o d u c t i v e problems had h e a v i e r c a l v e s than cows w i t h o u t problems (Table 1 6 ) . The 25 cows w i t h problems had 16 bull  c a l v e s and 9 h e i f e r c a l v e s (Table  14). B u l l  calves  tend to be h e a v i e r than h e i f e r c a l v e s and are more  likely  to cause d i f f i c u l t i e s a t c a l v i n g than h e i f e r c a l v e s ( P h i l i p s s o n , 1976).  The weight of the c a l f at the sub-  sequent c a l v i n g again was h e a v i e r f o r the cows w i t h code 2 and again  they had more b u l l  c a l v e s (14 b u l l s , 8 h e i f e r s ) .  health  c a l v e s than h e i f e r  The body weight a t the  subsequent c a l v i n g was the same f o r both h e a l t h code groups.  Cows with h e a l t h code 2 gained  more weight d u r i n g  the c u r r e n t l a c t a t i o n , the r a t e of gain (60 days and 80 days post partum r e s p e c t i v e l y to the subsequent c a l v i n g ) however was s i g n i f i c a n t l y d i f f e r e n t The group-health  (Table 1 6 ) .  s t a t u s i n t e r a c t i o n f o r body weight  gain between c a l v i n g s was s i g n i f i c a n t (P ^ .05). a n a l y s i s w i t h i n groups and h e a l t h codes (Table  The 15) demons-  t r a t e d t h a t w i t h i n the e a r l y bred group the h e a l t h code d i d not account f o r a s i g n i f i c a n t amount of the v a r i a t i o n w h i l e i t was s i g n i f i c a n t w i t h i n the l a t e bred  group.  Hence, cows w i t h c a l v i n g or e a r l y post partum problems i n the l a t e bred  group gained  the same group w i t h o u t e a r l y bred  group.  much more weight than cows of  problems or a l l the cows i n the  - 42  Table 14:  Sex  of  -  calves Current c a l v i n g bulls  Subsequent c a l v i n g  heifers  bulls  heifers  E a r l y bred group  20  22  21  12  Late bred group  23  20  13  25  H e a l t h code 1  27  33  20  29  H e a l t h code 2  16  9  14  8  Pasture season  17  21  14  18  Non-Pasture season  26  21  20  19  Table 15:  Group h e a l t h s t a t u s i n t e r a c t i o n f o r body weight gain (kg) between c a l v i n g s . The a n a l y s i s w i t h i n breedirig groups.  H e a l t h code 2 s.d. n X  Sign.  X  n  1 s.d  E a r l y bred group  42  22  62 . 1  53  9  79.4  n.s.  Late bred group  45  25  60. 3  111  12  70.5  *  Total  44  47  60. 5  86  21  78.5  *  H e a l t h code  Significant differences:  * P  •  .05,  n.s.  = not s i g n i f i c a n t  - 43 -  Table 16:  Means and standard d e v i a t i o n s of body weights and body weight changes (BWC) i n the c u r r e n t l a c t a t i o n and a t the subsequent c a l v i n g . The d i f f e r e n c e s between h e a l t h codes. H e a l t h code  T r a i t s (kg)  X  1  code • 2  Health  n  s.d.  x  n  s.d. 102.1  Sign n.s.  Wt. at c a l v i n g - ( 1 )  630  60  94.8  588  25  BWC  0-60 d.p.p.  -51  59  38.3  -39  25  41 .4  n.s.  BWC  0-80 d.p.p.  -46  59  39.8  -25  24  43.3  n.s.  BWC  60-80 d.p.p.  6  56  21 .0  14  24  26.1  n.s.  60 d.p.p. to ca1vi ng-(2 )  . 30  49  .14  .35  22  .18  n.s.  80 d.p.p. to ca1vi ng-(2 )  . 30  49  .15  .33  22  .18  n.s.  Wt. a t c a l v i n g - ( 2 )  674  48  60.8  674  21  64.9  n.s.  BWC c a l v i n g - ( l ) to calving-(2)  44  47  60.5  86  21  78. 5  *  42.1  47  4.9  43.8  22  5.9  *  45.1  46  7.2  48. 5  22  6.6  *  BWC/day (kg/day):  Wt. of c a l f  (1 )  Wt. of c a l f (2)  Significant differences: (1) = c u r r e n t c a l v i n g , d.p.p. =  * P^  .05,  n.s. = not s i g n i f i c a n t  (2) subsequent c a l v i n g  days post partum  - 44 -  4.3.3.  I n f l u e n c e of season  The season had a marked i n f l u e n c e on body weight and body weight changes  (Table 17).  The c a l v i n g weight of  the cows c a l v i n g d u r i n g the p a s t u r e season was h i g h e r than the weight of the cows c a l v i n g pasture season.  significantly  i n the non-  The cows c a l v i n g i n the p a s t u r e season  a l s o l o s t more weight i n the f i r s t 80 days of the l a c tation.  The d i f f e r e n c e between the two seasons  e s p e c i a l l y marked f o r the i n t e r v a l  was  between 60 and 80 days  post partum, where cows i n the p a s t u r e season s t i l l  were  l o s i n g weight w h i l e cows i n the non-pasture season a l r e a d y s t a r t e d to gain weight a g a i n . showed the same s i t u a t i o n : season had a s i g n i f i c a n t l y  The r a t e of gain  Cows c a l v i n g d u r i n g the p a s t u r e lower r a t e of gain from 60  days post partum to the subsequent c a l v i n g .  The same  c a l c u l a t i o n from 80 days post partum to the subsequent c a l v i n g r e v e a l e d no s i g n i f i c a n t d i f f e r e n c e s between cows c a l v i n g d u r i n g the p a s t u r e season versus cows c a l v i n g d u r i n g the non-pasture season. pasture season i n t o t a l  Cows c a l v i n g i n the non-  gained more weight d u r i n g the  l a c t a t i o n up to the subsequent c a l v i n g .  At the  subsequent  c a l v i n g , t h e r e were no d i f f e r e n c e s between the two seasons i n terms of the body weight of the cow and the calf.  - 45 -  Table 17:  Trait  Means and s t a n d a r d d e v i a t i o n s of body weight and body weight changes (BWC) i n the c u r r e n t l a c t a t i o n and at the subsequent c a l v i n g . The d i f f e r e n c e s between c a l v i n g s d u r i n g the p a s t u r e season and non-pasture season.  (kg)  Pasture season n  X  Non-Pasture season s .d.  X  n  s.d.  Sign  Wt.  at c a l v i n g - ( l )  648  38  90 . 7  595  47  98.9  *  BWC  0-60  d.p.p.  -53  38  31 .2  -43  47  45.1  n.s.  BWC  0-80  d.p.p.  -56  37  26 .8  -28  47  47 .1  **  BWC  60-80 d.p.p.  - 2  35  21 . 3  45  20 . 7  **  683  32  55 .8  667  37  66 . 2  n.s.  .25  33  • •  14  .37  38  .1 5  *  .26  33  •  16  .34  38  .17  n.s.  BWC c a l v i n g - ( l ) to calving-(2)  26  31  61 . 2  80  37  65.8  **  Wt.  of c a l f  (1)  44  31  5 .8  41  38  4.6  *  Wt.  of c a l f  (2)  47  31  8 .3  46  37  6.0  n.s.  Wt. at c a l v i n g - ( 2 )  16  BWC/day ( k g / d a y ) : 60 d . p . p . - c a l v i n g -(2) 80 d.p.p . - c a l v i ng -(2)  Significant differences: significant. (1) c u r r e n t c a l v i n g , d.p.p.  =  *P  . 05, ** p £.01 , n.s. = not  (2) subsequent  days post partum  calving  - 46 -  .4.4.  Productive t r a i t s  in. the c u r r e n t  lactation  The d e t a i l e d t a b l e s f o r p r o d u c t i v e current lactation  are presented  t r a i t s of the  i n the Appendix  (Tables  3a and 3b). The c o v a r i a b l e m i l k p r o d u c t i o n as expected, variation  4.4.1.  0-50 days post  partum  accounted f o r a s i g n i f i c a n t amount of the  i n most p r o d u c t i o n  traits.  I n f l u e n c e of e a r l y versus  The cows i n the l a t e bred in the 305 day l a c t a t i o n milk (FCM) (Table 18).  late  breeding  group produced more milk  and a l s o more f a t c o r r e c t e d The slopes f o r the p e r i o d from  150 days to 305 days of the l a c t a t i o n were a l s o s i g n i f i c a n t l y d i f f e r e n t .  f o r m i l k and FCM  Cows i n the l a t e  group had a g r e a t e r p e r s i s t e n c y i n the l a t t e r p a r t of the l a c t a t i o n  (Figure 2).  bred  - 47 -  Table 18:  Means and s t a n d a r d d e v i a t i o n s of p r o d u c t i v e t r a i t s i n the c u r r e n t l a c t a t i o n and the d i f f e r e n c e s between e a r l y bred and l a t e bred group  Trait  E a r l y bred group x s.d.  Late bred group x s.d.  Sign.  FCM 0-50 days (kg)  1401  31 0  1 509  416  n.s.  FCM 50-100 days (kg)  1386  285  1412  612  n.s.  FCM 100-150 days (kg)  1 284  233  1 31 3  303  n.s.  FCM 305 days (kg)  7276  1 565  7995  2304  *  M i l k 305 days (kg)  7595  1659  8550  2484  *  Fat % 305 days  3.71  .47  3. 57  .38  n.s.  Slope milk 0-150 days  -.0271  .0366  --.0372  .0639  n.s.  Slope f a t % 0-150 days  -.0013  .0034  -.0016  .0036  n.s.  Slope FCM 0-150 days  -.0290  .0420  -.0405  .0648  n.s.  Slope milk 150-305 days  -.1178  .0487  -.0955  .0448  **  .0009  .0008  .0010  .0119  n.s.  -.1059  .0430  -. 0825  .0419  **  Slope f a t % 150-305 days Slope FCM 150-305 days  S i g n i f i c a n t d i f f e r e n c e s between groups: n.s. = not s i g n i f i c a n t .  * P ^ . 05, ** P ^  .C  - 48 -  F i g u r e 2:  Mean p r o d u c t i o n and slopes of e a r l y and l a t e bred group f o r f a t %, m i l k and f a t c o r r e c t e d m i l k (FCM) of the c u r r e n t l a c t a t i o n .  E a r l y bred group Late bred group  days of c u r r e n t  lactation  - 49 -  4.4.2.  I n f l u e n c e of h e a l t h  The  grouping  of the herd a c c o r d i n g  to h e a l t h codes  d i d not i n f l u e n c e the p r o d u c t i v e performance of the cows. None of the analysed lactation two  production  t r a i t s of the  current  showed a s i g n i f i c a n t d i f f e r e n c e between the  h e a l t h code groups.  Figure 3 shows t h a t there were  small d i f f e r e n c e s i n the f a t % i n the m i l k ; cows w i t h e a r l y post partum r e p r o d u c t i v e d i s o r d e r s produced l e s s f a t than the heal thy. cows.(Fi gure 3 ) . or FCM  In terms of milk  p r o d u c t i o n , there were no s i g n i f i c a n t d i f f e r e n c e s  in the f i r s t p a r t of the l a c t a t i o n . production  M i l k or  FCM  i n the l a t t e r p a r t of the l a c t a t i o n was  exactly  the same f o r both of the h e a l t h code groups ( F i g u r e 3 ) .  4.4.3.  I n f l u e n c e of season  The  i n f l u e n c e of the c a l v i n g season on p r o d u c t i o n  the c u r r e n t l a c t a t i o n was  not s u b s t a n t i a l ( F i g u r e 4 ) .  Cows c a l v i n g i n the pasture  season had  a significantly  ( P 6 . 0 5 ) higher f a t t e s t up to 150  days i n the  (3.51% ± .48% versus  and  ficantly kg ± 2011  3.25%  ( P * . 0 5 ) more FCM kg versus  milk y i e l d was  ± .36%)  i n the t o t a l l a c t a t i o n  7507 kg ± 1992  FCM  kg).  production  The  (7880  uncorrected The  slopes  d i d 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 between the two (Figure 4).  lactation  produced s i g n i -  not s i g n i f i c a n t l y d i f f e r e n t .  of f a t %, milk and  in  c a l v i n g seasons  -  3:  50  -  Mean p r o d u c t i o n and s l o p e s o f h e a l t h code group 1 and h e a l t h code group 2 f o r f a t %, milk and f a t c o r r e c t e d milk (FCM) of the current l a c t a t i o n .  days of c u r r e n t  H e a l t h code group  1  Health  2  lactation  code group  - 51 -  F i g u r e 4:  Mean p r o d u c t i o n and s l o p e s of cows c a l v i n g d u r i n g the pasture season versus the nonpasture season f o r f a t %, milk and f a t c o r r e c t e d m i l k (FCM) of the c u r r e n t l a c t a t i o n . —• —  0  50  100  150  days of c u r r e n t  Pasture season Non-Pasture season  200 lactation  250  305  - 52 -  4.5.  Carry-over e f f e c t s sequent  lactation  The d e t a i l e d  tables for t r a i t s  l a c t a t i o n are presented  4.5.1.  from the c u r r e n t to the sub-  i n the subsequent  i n the Appendix (Tables 5a and 5b).  I n f l u e n c e of e a r l y versus l a t e  breeding  The body weight changes i n the e a r l y post  partum  p e r i o d of the subsequent l a c t a t i o n were not s i g n i f i c a n t l y different  between  the two groups (Table 19).  There were  some s i g n i f i c a n t d i f f e r e n c e s i n terms of m i l k p r o d u c t i o n : Cows i n the l a t e bred group produced s i g n i f i c a n t l y more f a t c o r r e c t e d milk (FCM)  i n the p e r i o d s 50 to 100 and  100 to 150 days post partum.  Mean p r o d u c t i o n and s l o p e s  of f a t %, m i l k and FCM of the subsequent l a c t a t i o n presented  i n F i g u r e 5.  are  The common s l o p e s f o r m i l k and  FCM f o r the p e r i o d 0-150  days of the two groups were  significantly different.  However, the s l o p e s of the  different  segments  of the l a c t a t i o n  s i g n i f i c a n t d i f f e r e n c e s (Figure 5).  d i d not show any  - 53 -  Table 19:  Means and standard d e v i a t i o n s of t r a i t s i n the subsequent l a c t a t i o n and the d i f f e r e n c e s between e a r l y and l a t e bred groups. E a r l y bred group X s.d.  Trait  Late bred group x s.d.  Si  0-60 d.p.p. (kg)  -55  33.0  -66  39.4  n.  BWC 0-80 d.p.p. (kg)  -32  45.9  -54  43.9  n.  18  22.5  8  27 .9  n.  FCM 0-50 days p.p. (kg)  1 540  40.6  1745  253  n.  FCM 50-100 days p.p. (kg)  1 554  160  1689  21 2  *  FCM 1 00-1 50 days p .p.(kg)  1351  161  1479  188  *  Slope m i l k 0-150 d.p.p.  0640  .0353  -.0318  .0361  **  Slope f a t % 0-150 d.p.p. -. 0025  . 0055  -.0036  .0054  n.  0709  .0302  -.0492  .0390  *  BWC  BWC  60-80 d.p.p. (kg)  Slope FCM 0-150 d.p.p.  SE-  . 01 , n. s. = not  Number of o b s e r v a t i o n s were 25 f o r the e a r l y 27 f o r the l a t e bred group.  bred group and  Significant differences: significant  BWC  = body weight  changes,  *  05, ** P  d.p.p . = days post partum  - 54 -  F i g u r e 5:  Mean p r o d u c t i o n and s l o p e s of e a r l y and l a t e bred group f o r f a t %, m i l k and f a t c o r r e c t e d milk (FCM) of the subsequent l a c t a t i o n ( 0 150 days ) .  E a r l y bred group Late bred group  I  0  1 50  1 100  days of subsequent  1—„ 150 lactation  - 55 -  4.5.2.  Influence  of h e a l t h  Among the p r o d u c t i o n  t r a i t s , the only  significant  d i f f e r e n c e between the two h e a l t h code groups was the f a t % t e s t i n the milk of the f i r s t 50 days of the subsequent lactation higher  (Table  20).  The cows i n h e a l t h code 1 had the  f a t t e s t (3.84% versus 3.62%).  Cows i n h e a l t h  code group 2 l o s t more weight i n the e a r l y post partum p e r i o d of the c u r r e n t  l a c t a t i o n and they a l s o l o s t more  weight i n the subsequent e a r l y post partum p e r i o d . terms of mean p r o d u c t i o n  In  and the s l o p e s f o r f a t %, milk  and FCM, no d i f f e r e n c e s between h e a l t h code groups reached a significant ( P & . 0 5 ) level  Table 20:  (Figure 6).  Means and standard d e v i a t i o n s of t r a i t s i n the subsequent l a c t a t i o n and the d i f f e r e n c e s between the h e a l t h code groups ( h e a l t h codes of the current 1 a c t a t i on). Health  H e a l t h code 2 Si s.d. n X  Tra i t  X  code 1 s.d. n  BWC c a l v i n g - ( l ) to c a l v i n g - ( 2 ) (kg)  44  47  60.5  86  22  78.5  Wt. at c a l v i n g (2) (kg)  674  47  61  674  21  65  n.  BWC 0-60 days p.p. (kg)  -56  38  33.4  -71  16  42.6  n.  BWC 0-80 days p.p. (kg)  -36  38  47.5  -63  1 6 35 .2  17  38  26.6  8  16  22.3  3.84  38  3. 62  18  .53  BWC 60-80 d.p.p. (kg) Fat % 0-50 d.p.p.  S i g n i f i c a n t d i f f e r e n c e s : * P - .05, ;  (1) c u r r e n t c a l v i ng ,  . 56  *  * n.  *  n . s. = not s i g n i f i c a n t  (2) subsequent c a l v i n g  - 56 -  F i g u r e 6:  Mean p r o d u c t i o n and slopes of h e a l t h code group 1 and h e a l t h code group 2 f o r f a t %, milk and f a t c o r r e c t e d m i l k (FCM) of the subsequent 1 a c t a t i on (0-150 days ) . ' H e a l t h code H e a l t h code  0  50  100  days of subsequent  150 lactation  1 2  - 57 -  4.5.3.  I n f l u e n c e of season  The c a l v i n g season of the c u r r e n t l a c t a t i o n i n f l u e n c e d the onset of the l a c t a t i o n lactation  (Table 21, F i g u r e 7 ) .  The milk p r o d u c t i o n of  the cows c a l v i n g d u r i n g the pasture lactation  i n the subsequent  season i n the c u r r e n t  i n c r e a s e d f a s t e r than the p r o d u c t i o n  of cows  c a l v i n g d u r i n g the non-pasture season i n the c u r r e n t lactation. production  In terms of t o t a l i n the f i r s t  milk p r o d u c t i o n  or FCM  150 days of the subsequent l a c -  t a t i o n , there were no s i g n i f i c a n t (P> .05) d i f f e r e n c e s between the two seasons.  Table 21:  Means and standard d e v i a t i o n s of t r a i t s i n the subsequent l a c t a t i o n i n f l u e n c e d by the c a l v i n g season of the c u r r e n t l a c t a t i o n . Pasture  Trai t  Non nPasture season s.d. x n  season  Sign  x  n  s.d  2125  26  .1108  .1115  31  .1921  **  Slope f a t % 0-50 d.p.p.  0090  23  .0135  .0042  29  .0100  n.s  Slope FCM 0-50 d.p.p.  1679  23  .1187  .0939  29  .1813  *  Slope milk d.p.p.  0-50  Significant differences: n.s. = not s i g n i f i c a n t d.p.p.  =  days post  * P & . 0 5 , **  partum  P*.01  <- 58 -  F i g u r e 7:  Mean p r o d u c t i o n and s l o p e s of f a t %, m i l k and f a t c o r r e c t e d m i l k (FCM) of the subsequent l a c t a t i o n (0-150 d a y s ) . D i f f e r e n c e s due to the c a l v i n g season of the c u r r e n t l a c t a t i o n .  P a s t u r e season Non-Pasture season  0  50  100  days of subsequent  150  lactation  - 59 -  4.6.  Average d a i l y m i l k p r o d u c t i o n over the two The  a n a l y s e s of the m i l k p r o d u c t i o n showed t h a t the  l a t e bred cows produced more m i l k and c u r r e n t and The  lactations  FCM  i n both  the b e g i n n i n g of the subsequent  longer i n t e r v a l  from p a r t u r i t i o n  the l a t e bred group a l s o r e s u l t e d  the  lactation.  to c o n c e p t i o n  of  i n a l o n g e r dry p e r i o d .  In order to compare the d a i l y m i l k p r o d u c t i o n of the early and  and the l a t e bred group, the h e a l t h s t a t u s groups  the groups a c c o r d i n g to the c a l v i n g  season,  the  average d a i l y milk p r o d u c t i o n from the b e g i n n i n g of the c u r r e n t to day calculated.  150 of the subsequent l a c t a t i o n  The  results  of t h i s c a l c u l a t i o n  was  showed t h a t  t h e r e were no d i f f e r e n c e s i n the average d a i l y m i l k FCM  p r o d u c t i o n between e a r l y  and  l a t e bred groups,  s t a t u s groups or groups a c c o r d i n g to c a l v i n g (Table 22).  These r e s u l t s  no s u p e r i o r i t y  taken  health  season  demonstrated t h a t t h e r e  was  of the l a t e bred group i n terms of m i l k  production.when the l o n g e r dry p e r i o d (due open) was  and  into  account.  to more days  - 60 -  Table 22:  Average d a i l y m i l k and FCM p r o d u c t i o n from b e g i n n i n g of the c u r r e n t l a c t a t i o n to day 1 of the subsequent l a c t a t i o n .  Late bred group  E a r l y bred group  Trait  x  n  s.d  5.07  22.79  38  5.65  5.64  20.63  38  6.00  Health code group 1  Health  x  n  s.d  m i l k (kg)  22.11  133  FCM (kg)  20.69  33  code group 2  n  s.d.  x  n  s.d.  milk (kg)  22.66  49  5.15  22.05  22  5 .90  FCM (kg)  20.68  49  5.96  20.62  22  5.54  Non-Pasture  season  Pasture  season  x  n  s.d.  x  n  s.d.  milk (kg)  23.73  32  5.00  21.44  39  5.49  FCM (kg)  21.64  32  6.15  19.86  39  5.44  n.s.  =  not s i g n i f i c a n t  (P>.05)  - 61 -  4.7.  C o r r e l a t i o n s and The  regressions  complete c o r r e l a t i o n t a b l e s are presented  the Appendix (Tables  4.7.1 .  6 to 9 ) .  C o r r e l a t i o n s between r e p r o d u c t i v e  The  f i r s t v i s u a l l y detected  the f i r s t  progesterone  detected  from p a r t u r i t i o n to the f i r s t first  progesterone  detected  traits  heat was  c o r r e l a t e d with  heat and w i t h the days  s e r v i c e (Table 23).  heat was  progesterone  heat was  The  later  the  d e t e c t e d , the l o n g e r was  d u r a t i o n of the f i r s t e s t r o u s c y c l e . progesterone  The  highly c o r r e l a t e d with  the d u r a t i o n of the f i r s t e s t r o u s c y c l e . first  in  the  In terms of milk  l e v e l s , t h i s i n d i c a t e d t h a t milk  progesterone  l e v e l s were high f o r a long time p r i o r to a l a t e d e t e c t i o n of the f i r s t progesterone  heat (see d e f i n i t i o n of d u r a t i o n  of f i r s t e s t r o u s c y c l e , page 27). l e n g t h was detected listed  The  first  not c o r r e l a t e d w i t h the f i r s t  heat.  The  remaining  visually  significant correlations  i n Table 23 were cause r e l a t i o n s :  days to  s e r v i c e were c o r r e l a t e d w i t h days open and interval.  The  cycle  the c a l v i n g  number of s e r v i c e s per c o n c e p t i o n  c o r r e l a t e d to days open, to the i n t e r v a l s e r v i c e to c o n c e p t i o n  and  first  were  from the  to the c a l v i n g i n t e r v a l .  first  - 62 Table 23:  C o r r e l a t i o n s between r e p r o d u c t i v e , t r a i t s of the c u r r e n t post partum p e r i o d . 1st 1st vi si bl e prog, heat heat  1st cycle 1ength  number .'days days of to 1st •open service services  Days 1st service to conception  1st v i s i b l e heat  1.00  1st prog, heat  .32*  1.00  1st cycle length  .19  .62*  1.00  Days 1st service  .33*  .03  .04  1.00  # of services  -.11  -.01  -.07  .05  1.00  .06  -.01  -.04  .55*  .77*  1.00  Days to 1st serv. to conception  -.13  -.01  -.06  .05  .90*  .86*  1.00  Calving interval  .07  .03  -.01  .59*  .69*  .96*  .80*  Days open  *Significant correlation  Table 2.4:  (P&  .01)  C o r r e l a t i o n s between r e p r o d u c t i v e and p r o d u c t i v e t r a i t s of the c u r r e n t l a c t a t i o n . _to number calving days 1st c y c l e days of "1st i nterva open .-length service . services . 26**  .15  .18  .15  .13  FCM 50-100 days  .24*  . 20  .21*  .1 9  .18  M i l k 305 days  .17  .36**  . 34**  . 39**  .36**  FCM 305 days  .18  . 30**  . 37**  .37**  . 37**  . 04  .1 3  2g**  . 32**  .36**  .04  .13  2 9**  . 32**  . 37**  FCM 0-50  days  Slope milk  305 d,.  Slope FCM 305 d.  S i g n i f i c a n t c o r r e l a t i o n s * P ^ .05,  ** p  .01  - 63 -  4.7.2.  C o r r e l a t i o n s betweeen r e p r o d u c t i v e and t r a i t s of the c u r r e n t  The the FCM  current lactation  FCM  p o s i t i v e l y c o r r e l a t e d with  of the f i r s t and (Table 2 4 ) .  to f i r s t s e r v i c e was m i l k and  lactation  f i r s t c y c l e l e n g t h was production  The  production  FCM  second 50 days of interval  of the c u r r e n t l a c t a t i o n .  production  was  the  from c a l v i n g  p o s i t i v e l y c o r r e l a t e d w i t h the  number of s e r v i c e s per c o n c e p t i o n w i t h milk and  productive  total The  positively correlated  f o r the p e r i o d 50-100 days,  the e n t i r e l a c t a t i o n , as 'well as w i t h the s l o p e s f o r milk and  FCM  production  of the e n t i r e l a c t a t i o n .  number of s e r v i c e s per c o n c e p t i o n ,  The  days open and  the  c a l v i n g i n t e r v a l were p o s i t i v e l y c o r r e l a t e d w i t h the  total  milk and  with  FCM  production  of the c u r r e n t l a c t a t i o n  the s l o p e s of the 305 day milk and  FCM  and  production.  c o r r e l a t i o n s i n d i c a t e d t h a t the l a t e r the cows  These  conceived,  the more they produced or v i c e - v e r s a .  4.7.3.  The  C o r r e l a t i o n s between r e p r o d u c t i v e t r a i t s of the c u r r e n t and p r o d u c t i v e t r a i t s of the subsequent lactation f i r s t progesterone detected  i c a n t l y c o r r e l a t e d w i t h the FCM 100  heats were s i g n i f -  production  days p e r i o d of the subsequent l a c t a t i o n  slope of the f a t t e s t of the. f i r s t  150  sequent l a c t a t i o n  first  (Table 25).  The  l e n g t h i n the c u r r e n t l a c t a t i o n was  of the 50 and w i t h  to the  days i n the subestrous  cycle  s i g n i f i c a n t l y cor-  - 64 -  related  w i t h the f a t t e s t i n the f i r s t 50 days of the  subsequent l a c t a t i o n and w i t h the s l o p e of the f a t t e s t and the FCM p r o d u c t i o n i n the f i r s t subsequent l a c t a t i o n . service,  150 days o f the  Days from p a r t u r i t i o n  days open and the c a l v i n g  to f i r s t  i n t e r v a l were  correlated  w i t h s e v e r a l p r o d u c t i o n t r a i t s i n the subsequent l a c t a t i o n . In o r d e r to e x p l a i n these c o r r e l a t i o n s , analysis  was conducted, the r e s u l t s  discussed  of which w i l l  be  below.  Table 25:  C o r r e l a t i o n s between r e p r o d u c t i v e t r a i t s of the c u r r e n t and p r o d u c t i v e t r a i t s of the subsequent l a c t a t i o n . 1st prog. heat  Trait Fat  a regression  % 0-50 days  1st cycle length  days to 1 s t service -.12  days "" / J  o p e n  -.06  calving interval interval  .18  .41**  -.07  FCM 50-100 days  .33**  .25  .32**  .43**  .28*  FCM 100-150 days  .13  .11  .29*  .40**  .34**  SI ope mi 1k days  .06  -.21  .37**  .39**  .35**  0-150  Slope f a t % 0150 days Slope FCM days Significant  -.34**  -.34**  -.23  -.54**  -.04  -.14  -.10  .23  .22  0-150 correlations:  * P * .05,  .30* ** P ^  .01  - 65 -  4.7.4.  C o r r e l a t i o n s between r e p r o d u c t i v e t r a i t s and body weight changes i n the c u r r e n t and subsequent 1 a c t a t i on  The f i r s t  v i s i b l e heat and the f i r s t  progesterone  d e t e c t e d heat were both p o s i t i v e l y c o r r e l a t e d w i t h the body weight changes i n the f i r s t t i v e l y of the c u r r e n t l a c t a t i o n  60 and 80 days r e s p e c (Table 26).  The n e g a t i v e  c o r r e l a t i o n c o e f f i c i e n t i n d i c a t e d t h a t the more weight a cow  l o s t i n the e a r l y post partum p e r i o d the l a t e r the  onset of e s t r u s and the l a t e r the cow estrus behaviour.  S i n c e l a t e onset of e s t r u s and e s t r u s  behaviour delayed the f i r s t was  showed a v i s i b l e  s e r v i c e , days to f i r s t  c o r r e l a t e d w i t h the e a r l y l a c t a t i o n  changes i n the same manner as the f i r s t the f i r s t v i s u a l l y d e t e c t e d heat. calving interval  body weight progesterone  Days open and  and  the  were not c o r r e l a t e d w i t h body weight  changes i n e i t h e r l a c t a t i o n .  The f i r s t  d e t e c t e d heat and the days to the f i r s t n e g a t i v e l y c o r r e l a t e d w i t h the 0-60 the subsequent  service  progesterone s e r v i c e were both  day weight changes i n  l a c t a t i o n , i n d i c a t i n g t h a t the l a t e r  the  onset of progesterone d e t e c t e d e s t r u s and the l a t e r the first  i n s e m i n a t i o n took p l a c e , the more weight the cows  l o s t i n the e a r l y p o r t i o n of the subsequent  lactation.  E a r l y post partum body weight changes were c o r r e l a t e d w i t h production t r a i t s  (Appendix Table 9 ) .  C o r r e l a t i o n s with  p r o d u c t i o n t r a i t s and body weight changes can be e x p l a i n e d b e t t e r i f the c o r r e l a t i o n s between body weight changes and p r o d u c t i o n are taken i n t o  account.  - 66 -  Table 26:  C o r r e l a t i o n s between r e p r o d u c t i v e t r a i t s and body weight changes (BWC) i n the c u r r e n t and subsequent 1actation . 1st 1st days to (kg) visible prog. 1st heat heat service d  Trait  Current l a c t a t i o n : BWC 0-60 days p.p.  .24*  -.24**  -.20  -.19  BCW  0-80 days p.p.  .26**  -.19  - .24*  -.15  BWC  60-80 days p.p.  .06  -.01  .06  .05  .19  -.13  .01  .01  -.26*  -.25*  -.17 -.03  BWC 1st c a l v i n g to 2nd c a l v i n g Subsequent l a c t a t i o n BWC  0-60  days p.p.  .07  BWC  0-80 days p.p.  -.03  -.21  -.21  BWC  60-80 days p.p.  .08  .00  .03  Significant correlations: * P ^ d.p.p. = days post partum  .05,  ** P ^. .01  - .05  - 67 -  4.7.5.  Test of i n f l u e n c e of days open on p r o d u c t i o n i n the subsequent l a c t a t i o n  The a n a l y s i s of v a r i a n c e showed t h a t the groups ( e a r l y and l a t e b r e e d i n g ) d i d not have a marked i n f l u e n c e on the p r o d u c t i o n and body weight changes of the e a r l y subsequent l a c t a t i o n .  The h y p o t h e s i s  than the days from p a r t u r i t i o n  i s that f a c t o r s other  to the f i r s t  service, like  days open or the c a l v i n g i n t e r v a l , have a g r e a t e r i n f l u e n c e on the subsequent l a c t a t i o n .  In order to show  these i n f l u e n c e s , a simple r e g r e s s i o n a n a l y s i s was computed w i t h days open as independent c o n t i n u o u s  variable.  This a n a l y s i s r e s u l t e d i n the f o l l o w i n g o b s e r v a t i o n s : Days open c o n t r i b u t e d s i g n i f i c a n t l y to the p r e d i c t i o n of m i l k and FCM p r o d u c t i o n i n the f i r s t  lactation  (Table 2 7 ) .  In the subsequent l a c t a t i o n days open of the c u r r e n t lactation  i n f l u e n c e d the weight of the c a l f i n the  subsequent l a c t a t i o n  but not the body weight changes i n  the e a r l y post partum p e r i o d o f the subsequent l a c t a t i o n . The c o n t r i b u t i o n of days open to the p r e d i c t i o n of production  traits  i n the e a r l y subsequent l a c t a t i o n  moderate.  Days open i n f l u e n c e d the s l o p e of the m i l k  p r o d u c t i o n curve i n the f i r s t  was  150 days but n e i t h e r the  slope of f a t % or FCM p r o d u c t i o n was i n f l u e n c e d . r e g r e s s i o n of milk p r o d u c t i o n d u r i n g the f i r s t  The  50 days  versus days open was not s i g n i f i c a n t , the r e g r e s s i o n of days open on FCM p r o d u c t i o n from 1 00-1 50 days, however, was  significant.  - 68 -  Table 27:  R e s u l t s of the simple r e g r e s s i o n a n a l y s e s w i t h days open as independent c o n t i n u o u s variable.  Dependent  variables  Regression coefficient  C o e f f i c i ent of d e t e r mination R  Current  Sign  2  lactation:  M i l k 305 days  19.3376  .19  FCM 305 days (kg)  14.2039  .14  Wei ght of ca1f (kg)  - . 07694  . 57  Weight change d.p.p. (kg)  -.31395  .03  n.s.  Weight change 60-80 d.p.p. (kg)  .07309  .00  n.s.  M i l k 0-50 days (kg)  1 . 77031  .05  n.s,  FCM 100-150 days  2.0541 1  .16  . 000420  .15  *  - .000021  .02  n. s  .000230  .05  n.s  Subsequent  lactation:  0-60  SI ope m i l k 0-150  days  Slope f a t % 0-150 Slope FCM 0-150  days  days  * S i g n i f i c a n t c o n t r i b u t i o n to the r e g r e s s i o n e q u a t i o n (P*.01). n.s. BWC  = ' not s i g n i f i c a n t =  body weight changes,  d.p.p.  days post partum  - 69 -  5.  DISCUSSION  5.1.  The onset of the e s t r o u s c y c l e , v i s u a l  and  progesterone d e t e c t e d heat The i n v o l u t i o n of the bovine u t e r u s a f t e r  parturition  takes a p p r o x i m a t e l y 30 days (Lamming , 1 978 ; R o b e r t s , 1971). The f i r s t to  p r o g e s t e r o n e r i s e was r e p o r t e d by Lamming (1978)  occur 25 ± 10 days post partum.  study i n d i c a t e d t h a t the f i r s t  The r e s u l t s of t h i s  p r o g e s t e r o n e d e t e c t e d heat  o c c u r r e d 33 ± 10 days w i t h a range from 19 to 78 days post partum and are comparable w i t h the f i n d i n g s of Morrow et  al.  (1969).  He r e p o r t e d t h a t the f i r s t  estrus  between 30 and 76 days post partum, and t h a t  was  follicular  development s t a r t e d between 16 and 21 days post partum. In  i n d i c a t i n g i t h e wide range from 30 to 76 days Morrow e t  al . ( 1 969 ) s t r e s s e d the importance of the i n d i v i d u a l The wide range i n the onset of the f i r s t  cow.  p r o g e s t e r o n e heat  a l s o showed t h a t the wide range o f the d e t e c t i o n o f the first of  v i s i b l e heat (8 to 127 days) was not o n l y a r e s u l t  inadequate o b s e r v a t i o n of the cows but t h a t there  a c t u a l l y was a l a r g e v a r i a t i o n between cows.  De  (1978) i n c l u d e d chance i n h h i s l i s t  influencing  the  f e r t i l i t y o f d a i r y herds.  small  of f a c t o r s  Kruif  He c o n c l u d e d t h a t i n  herds (up to a p p r o x i m a t e l y 40 cows) due to the  l a r g e v a r i a t i o n between  individual  chance ( f o r no apparent reason) may i n t e r v a l s to the f i r s t  cows the f e r t i l i t y be i m p a i r e d .  by  Different  e s t r u s have been r e p o r t e d by King  - 70 -  et a l . ( 1 976 ) w i t h 19.5 21 days and Wagner and  days, Mather et a l . ( 1 978) Hansel  (1969) w i t h 14 days.  time d i f f e r e n c e between the f i r s t heat and  the f i r s t  most of the f i r s t behavioural  heats were s i l e n t or w i t h  progesterone  the herds c o n t i n u o u s l y and between the occurrence  were r e p o r t e d  undetected  visual  The  to  1971;  time from  detected  estrus  to the f i n d i n g s of C a l l a h a n et a l .  King et a l . (1976).  the f i r s t  little  (Davi>d et a l . ,  King et a l . , 1976).  to the f i r s t  (33 days)-was s i m i l a r  and  that  E a r l y post partum heats are r e p o r t e d  Morrow et a l . , 1969;  (1971) and  The  detected  t h e r e f o r e , they remained  be d i f f i c u l t to d e t e c t v i s u a l l y  parturition  progesterone  v i s i b l e heat (16 days) i n d i c a t e d  evidence,  by the herdsmen.  with  These workers observed  d i d not f i n d any d i f f e r e n c e  of the f i r s t detected  progesterone  heats.  detected  F i r s t estrous  to vary c o n s i d e r a b l y i n l e n g t h and  cycles  very  o f t e n were s h o r t e r than 21 days (Mather et a l . , 1978; B r i t t , 1980), t h e r e f o r e the average d u r a t i o n of 17 days found in t h i s experiment can  be c o n s i d e r e d  normal.  though B r i t t (1980) excluded  a l l the cows w i t h  Al-  calving  a s s o c i a t e d r e p r o d u c t i v e d i s o r d e r s , he found an average first  c y c l e l e n g t h of 17 days as w e l l .  the f i r s t progesterone correlated  ( r = .62)  l a t e r the f i r s t the l o n g e r was  detected  study  heats were s i g n i f i c a n t l y  w i t h the f i r s t  progesterone  In t h i s  cycle lengths.  detected  estrus  the d u r a t i o n of the preceeding  The  occurred, estrous  - 71  c y c l e (see d e f i n i t i o n of f i r s t  estrous  c y c l e , page 27)  Mather et a l . (1978) found a p o s i t i v e c o r r e l a t i o n between the f i r s t  progesterone peak l e v e l  d u r a t i o n of the f i r s t c y c l e . in  post partum and the  He a l s o found an i n c r e a s e  the peak progesterone c o n c e n t r a t i o n  l e n g t h over the f i r s t  and i n the c y c l e  three c y c l e s before  the system  was back to steady progesterone c y c l e s and normal c y c l e lengths.^ 21.1  Britt  (1980) r e p o r t e d  average c y c l e l e n g t h s of  and 21.4 days f o r subsequent c y c l e s which  a first  followed  c y c l e l e n g t h of 17 days.  C a l v i n g problems o r c a l v i n g a s s o c i a t e d e a r l y post partum r e p r o d u c t i v e  problems d i d not i n f l u e n c e the onset  of the progesterone d e t e c t e d  estrous cycles in t h i s  B a i e r e t a l . (1973) r e p o r t e d  t h a t a l a t e r onset of the  estrous  c y c l e i n cows w i t h c a l v i n g a s s o c i a t e d  was mostly r e l a t e d to a slower  problems  i n v o l u t i o n o f the u t e r u s .  B a i e r e t a l . (1973) observed the cows f o r e s t r u s and  used r e c t a l  and  follicular The  estrous  study.  signs  p a l p a t i o n s to check u t e r i n e i n v o l u t i o n development.  c a l v i n g season d i d not i n f l u e n c e the onset of the c y c l e or the f i r s t  cycle length.  S t o t t and  1 The p a t t e r n of the m i l k progesterone c o n c e n t r a t i o n of the f i r s t and subsequent e s t r o u s c y c l e s of the same cows i n the same experiment are being s t u d i e d i n a d i f f e r e n t Master of Science p r o j e c t by W.L. S l a c k , Department of Animal S c i e n c e , U n i v e r s i t y of B r i t i s h Columbia, Vancouver, B.C.  - 72 -  W i l l i a m s (1962) showed t h a t cows exposed to high tempe r a t u r e s i n the summer months had depressed They r e l a t e d the lower f e r t i l i t y cycles.  The  fertility.  to very long e s t r o u s  pasture season temperatures  i n the temperate  F r a s e r V a l l e y c l i m a t e a p p a r e n t l y were not high enough to i n f l u e n c e the c y c l e l e n g t h s of the cows.  The  fact that  n e i t h e r c a l v i n g a s s o c i a t e d r e p r o d u c t i v e problems, the c a l v i n g season, 0-50  nor' the c o v a r i a b l e s (age, m i l k p r o d u c t i o n  days, body weight  changes 0-60  days) accounted  a s i g n i f i c a n t p a r t of the v a r i a t i o n of the onset e s t r u s was  an obvious  of  e x p r e s s i o n of the l a r g e i n e x p l a i n -  able v a r i a t i o n between i n d i v i d u a l  5.2.  for  cows.  Days from p a r t u r i t i o n to the f i r s t s e r v i c e , number of s e r v i c e s per c o n c e p t i o n , days open and the calving interval The  e a r l y bred group s c o n c e i v i r i g - 8 8 days post partum  a f t e r 1.50  s e r v i c e s per c o n c e p t i o n as opposed to the  bred group c o n c e i v i n g 120 days post partum a f t e r  late  1.96  s e r v i c e s per c o n c e p t i o n showed a p o s i t i v e e f f e c t of the e a r l i e r breeding on f e r t i l i t y of cows scheduled  i n t h i s herd.  to be bred at the f i r s t  A number  visible  heat  f o l l o w i n g 50 days post partum d i d not show any  visible  heat u n t i l  interval  much l a t e r .  from the scheduled  T h e r e f o r e , the average  breeding to the a c t u a l breeding  was  l o n g e r i n the e a r l y bred group (50 to 73 days = 23 days) than i n the l a t e bred group (80 to 93 days = 13 d a y s ) .  - 73 -  In comparison to the l i t e r a t u r e , i n t e r v a l s from c a l v i n g to the f i r s t  s e r v i c e of 73 days and  from c a l v i n g to  c o n c e p t i o n of 88 days were not c o n s i d e r e d  s h o r t and  were  necessary to a c h i e v e a one  year c a l v i n g i n t e r v a l (Ayalon  et a l . , 1971;  S o l l e r , 1979;  Kali,  Bar-Anan and  Machnai  1971). Many authors have r e p o r t e d  t h a t the c o n c e p t i o n  from s e r v i c e s p r i o r to 40 days post partum was c o n c e p t i o n from s e r v i c e s between 50 and in  and  the post partum p e r i o d  1975).  The  lower than  70 days or  ( K r a u s s l i c h , 1974;  same workers a l s o r e p o r t e d  rate  later  Kupferschmid,  t h a t there  was  no d i f f e r e n c e i n c o n c e p t i o n r a t e of i n s e m i n a t i o n s  between  50 and -70 days as compared to s e r v i c e s l a t e r i n the partum p e r i o d .  S i g n i f i c a n t l y increased  post  numbers of  s e r v i c e s per c o n c e p t i o n 80 days post partum or l a t e r , o  found i n t h i s experiment, have not been r e p o r t e d previously.  The  bred group and  s i g n i f i c a n t d i f f e r e n c e between the  early  the l a t e bred group i n terms of number of  s e r v i c e s per c o n c e p t i o n and c o n c e p t i o n was  as  eliminated  days from f i r s t  service  when cows w i t h c a l v i n g  problems were excluded from the a n a l y s i s .  This  to  associated analysis  showed t h a t cows i n the e a r l y bred group c o n c e i v e d a f t e r 1.53  s e r v i c e s and  t h a t cows i n the l a t e bred group  c o n c e i v e d a f t e r 1.73 better f e r t i l i t y f e r e n c e was  services.  This  still  showed a  i n the e a r l y bred group but  no longer  significant.  the  dif-  Problem cows i n the  - 74 -  e a r l y bred group c o n c e i v e d as r e a d i l y as the h e a l t h y cows (1.42 versus 1.53  s e r v i c e s per c o n c e p t i o n ) .  Problem  cows i n the l a t e bred group r e q u i r e d s i g n i f i c a n t l y more s e r v i c e s per c o n c e p t i o n than h e a l t h y cows i n the same group (2.46  versus 1.73)  and a l s o r e q u i r e d more s e r v i c e s  per c o n c e p t i o n than a l l o t h e r cows i n the (2.46  versus 1.60).  These f a c t s can not be  experiment readily  e x p l a i n e d i n the c o n t e x t of t h i s study and need f u r t h e r investigation.  P o s s i b l e reasons were:  the s e v e r i t y of  the d i s o r d e r s of the a f f e c t e d cows might have been d i f f e r e n t i n the two groups; or treatment and  treatment  e f f e c t s might have been d i f f e r e n t . Onset of e s t r u s , l e n g t h of the f i r s t e s t r o u s c y c l e and the number of v i s u a l l y and progesterone  detected  were the same f o r normal and problem  These f a c t s  cows.  i n d i c a t e d t h a t the reason f o r delayed c o n c e p t i o n not due was  to o v a r i a n i n a c t i v i t y .  heats  was  More l i k e l y the u t e r u s  not ready f o r the i m p l a n t a t i o n of the f e r t i l i z e d . - o v u m  a t the time of the u n s u c c e s s f u l i n s e m i n a t i o n s .  Morrow  et a l . ( 1 969 ) r e p o r t e d t h a t o v a r i a n a c t i v i t y . a f t e r p a r t u r i t i o n n o r m a l l y resumed before u t e r i n e i n v o l u t i o n was  completed.  B a i e r et a l . (1973) r e p o r t e d t h a t c a l v i n g  d i f f i c u l t i e s delayed u t e r i n e i n v o l u t i o n .  Retained  p l a c e n t a and m e t r i t i s a l s o are known to be adverse  to  the i m p l a n t a t i o n of the embryo (Roine and S a l o n i e m i , 1978).  - 75 -  The seasonal i n f l u e n c e s on f e r t i l i t y s i g n i f i c a n t w i t h i n the l a t e bred group.  were only Cows which  c a l v e d i n the p a s t u r e season had a decreased  fertility.  These f i n d i n g s again showed t h a t i n the l a t e bred group the  apparent o p t i m a l time f o r i n s e m i n a t i o n was passed  so t h a t i n f l u e n c e s l i k e season and h e a l t h became s i g n i f i c a n t . the  fertility  problems  Braun (1977) was a b l e to improve  i n problem herds by b r e e d i n g a l l cows i n  those herds as soon as they showed normal e s t r o u s c y c l e s . Braun  (1977) monitored the c y c l e s w i t h m i l k p r o g e s t e r o n e  analysis.  Z e r o b i n (1979) recommended b r e e d i n g problem  cows as soon as they show e s t r u s ( e i t h e r v i s u a l progesterone d e t e c t e d ones).  H i s recommendation  based on the b e l i e f t h a t an u n s u c c e s s f u l did  or: : was  insemination  not i n f l u e n c e the c o n c e p t i o n r a t e of subsequent  breedings. A low f e r t i l i t y  r a t e d u r i n g l a t e summer and f a l l  months was r e p o r t e d by Hewett (1968) and De K r u i f (1975). The lower f e r t i l i t y  i n the p a s t u r e season a l s o might  have been a s s o c i a t e d w i t h the body weight changes e a r l y post partum p e r i o d . p a s t u r e season s t i l l  i n the  Cows which<calved 'in•the  l o s t weight between 60 and 80 days  post partum w h i l e cows which c a l v e d i n the non-pasture season were a l r e a d y g a i n i n g weight i n the same p e r i o d . K i n g r e t a l . ( 1 976) and Youdan and King ( 1 977 ) r e p o r t e d  - 76 -  a beneficial  i n f l u e n c e of body weight gain on  fertility  at time of i n s e m i n a t i o n . The goal of a one year c a l v i n g i n t e r v a l  was  achieved  in the e a r l y bred group (373 days) but not i n the l a t e bred group (404 d a y s ) .  These f i n d i n g s support the  statement of Ayalon et a l . (1977) t h a t i n order to a c h i e v e a 365 day c a l v i n g i n t e r v a l , i t i s necessary to s t a r t breeding the cows not l a t e r than 50 days post partum.  5.3.  The r e l a t i o n s h i p between r e p r o d u c t i o n , p r o d u c t i o n and body weight changes The d a i r y herd of the A g r i c u l t u r e Canada  S t a t i o n i n A g a s s i z i s a high y i e l d i n g H o l s t e i n (average p r o d u c t i o n of the 85 cows i n t h i s 8084 kg m i l k , 7644 kg FCM).  Research herd  experiment:  S i m i l a r s t u d i e s dated 10 to  20 y e a r s ago d e a l t with p r o d u c t i o n l e v e l s which were s u b s t a n t i a l l y lower (Smith and L e g a t e s , 1962; W i l t o n et al . 1 967 ).  More r e c e n t s t u d i e s , e s p e c i a l l y from  Israel,  have i n v o l v e d milk p r o d u c t i o n l e v e l s comparable w i t h the p r o d u c t i o n of the A g a s s i z herd. Beside the g e n e t i c improvement of the herds, and management have been improved  s u b s t a n t i a l l y to  increase milk production, yet r e s u l t i n g on the cows.  nutrition  i n more s t r e s s  For t h i s reason the r e s u l t s in t h i s  study  of r e p r o d u c t i o n - p r o d u c t i o n r e l a t i o n s h i p s have been compared to r e s e a r c h r e s u l t s from  Israel.  S i g n i f i c a n t c o r r e l a t i o n s i n the range of r =  .30  - 77 -  between milk p r o d u c t i o n  and  reproduction  traits  (number of  s e r v i c e s per c o n c e p t i o n , days open, c a l v i n g i n t e r v a l ) have been r e p o r t e d Francos and  p r e v i o u s l y (Bar-Anan and  R a t t n e r , 1975;  Soller,  Hewett, 1968).  These c o r r e l a -  t i o n s o f f e r an e x p l a n a t i o n f o r the h i g h e r 305 y i e l d of the l a t e bred group.  The  1979;  day  milk  fact that early l a c t a -  t i o n milk y i e l d s were not s i g n i f i c a n t l y c o r r e l a t e d with reproduction  t r a i t s but the s l o p e s f o r m i l k p r o d u c t i o n  of  the l a t t e r p a r t of the c u r r e n t l a c t a t i o n of cows i n the l a t e bred group showed a g r e a t e r p e r s i s t e n c y i n d i c a t e d t h a t the d i f f e r e n c e s i n milk y i e l d were mainly  due  the l a c t a t i o n .  concluded  groups  to the d i f f e r e n c e s i n the l a t t e r p a r t of These f i n d i n g s are i n agreement w i t h  f i n d i n g s of Erb et a l . (1952) and who  between the two  Smith and  the  Legates (1962)  t h a t g e s t a t i o n d i d not m a t e r i a l l y a f f e c t  milk y i e l d u n t i l milk p r o d u c t i o n  the 5th month a f t e r c o n c e p t i o n . i n the l a t e bred  group was  The  higher  not accompanied  by a g r e a t e r body weight l o s s i n the e a r l y post partum period.  The  tendency to a h i g h e r 305 day m i l k  of cows c a l v i n g d u r i n g the pasture by s i g n i f i c a n t l y and  season was  production accompanied  (P6.01) h i g h e r body weights at c a l v i n g  body weight changes i n the e a r l y post partum p e r i o d  as w e l l as w i t h a lower f e r t i l i t y  (P^.05).  These  sit-  u a t i o n s i n d i c a t e d t h a t high m i l k y i e l d s were not n e c e s s a r i l y r e l a t e d to high body weight l o s s e s i n the e a r l y post partum p e r i o d .  However, high body weight  - 78 -  l o s s e s o f t e n were r e l a t e d to high m i l k y i e l d s and depressed  with  fertility.  S i m i l a r f i n d i n g s and  the r e p e a t e d l y  reported  negative  i n f l u e n c e of e a r l y post partum body weight l o s s e s on fertility  (Amir and  K a l i , 1974;  B r o s t e r , 1973;  and  K i n g , 1977)  and  Roberts et a l . (1979a) (1979b).  did  not f i n d t h a t blood  on f e r t i l i t y .  i n i t i a t e d the work of Herz and  glucose  Herz and  l e v e l s had  Graf  of f a t t y a c i d s from adipose partum p e r i o d ) and  (due  Graf  any  influence  to the m o b i l i z a t i o n  fertility.  The  f i n d i n g s of Roberts f o r lower  of cows which c a l v e d d u r i n g the pasture  fertility  season and  l o s i n g weight i n the p e r i o d 60 to 80 days  non-pasture season had  weight between 60 and  season and were a l r e a d y  e f f e c t of body weight gain on f e r t i l i t y Smidt (1979) and  the  than cows which  80 days post partum.  Hodges (1976), Huth and  took  Cows which c a l v e d d u r i n g  a better f e r t i l i t y  c a l v e d d u r i n g the pasture  were  post  On the average, the f i r s t i n s e m i n a t i o n  p l a c e 83 days post partum.  (1977).  (1976)  t i s s u e i n the e a r l y post  et a l . ( 1 979a) o f f e r e d an e x p l a n a t i o n  partum.  (1976)  Roberts et a l . (1979a) found a s i g n i f i c a n t  r e l a t i o n s h i p between f a t t y l i v e r  still  Youdan  was  gaining  A positive reported  Youdan and  A f u r t h e r e x p l a n a t i o n f o r the b e t t e r  by King  fertility  of cows c a l v i n g i n the w i n t e r months (non-pasture season) i s the r e p o r t e d  lower  progesterone  l e v e l s during  estrus  in the w i n t e r months which were r e l a t e d to i n c r e a s e d  - 79 -  c o n c e p t i o n r a t e s (Rosenberg et a l . 1977). The  l o n g e r r e s t p e r i o d post partum of the l a t e  group r e s u l t e d h i g h e r weight  i n a l o n g e r dry p e r i o d and  therefore in a  gain between c a l v i n g s , a higher body  at the subsequent c a l v i n g , . a n d a bred group a l s o gained weight  bred  heavier c a l f .  weight  The  late  at a h i g h e r d a i l y r a t e  (from 60 and 80 days post partum r e s p e c t i v e l y to the subsequent c a l v i n g ) than the e a r l y bred group.  The  weight  gain between c a l v i n g s i s e s p e c i a l l y important f o r h e i f e r s , t h e r e f o r e , s e v e r a l authors  recommended a l o n g e r  p e r i o d f o r h e i f e r s than f o r cows (Louca  rest  and Legates  1 968 ;  Bar-Anan and S o l l e r , 1979). C a l v i n g a s s o c i a t e d d i s o r d e r s were not  significantly  r e l a t e d to p r o d u c t i o n t r a i t s , the s l i g h t l y h i g h e r FCM  p r o d u c t i o n observed  i n a f f e c t e d cows can be e x p l a i n e d  with t h e i r longer i n t e r v a l  from c a l v i n g to c o n c e p t i o n  ( c o r r e l a t i o n between days open and 305 day f o r a l l cows i n the experiment The  (PA.10)  FCM  production  r = .37).  c a r r y o v e r e f f e c t s o f the c u r r e n t l a c t a t i o n to the  subsequent l a c t a t i o n were moderate.  The  greater p e r s i s t -  ency of m i l k p r o d u c t i o n i n the f i r s t 150 days of the subsequent l a c t a t i o n f o r the l a t e bred group can be r e l a t e d to the l o n g e r dry p e r i o d of t h i s group. cows i n the experiment  A l l the  were d r i e d o f f at 305 days which  r e s u l t e d i n a l o n g e r dry p e r i o d f o r the l a t e bred  group.  Wood (1977) showed t h a t the dry p e r i o d i n f l u e n c e d the  - 80 -  onset of m i l k p r o d u c t i o n to  i n the f o l l o w i n g l a c t a t i o n .  the l o n g e r dry p e r i o d of the l a t e bred  average d a i l y milk and  FCM  yields  Due  group the  ( c a l c u l a t e d over both  l a c t a t i o n s ) were the same f o r both the e a r l y and  the  late  bred group.  per  day  Economically  of p r o d u c t i v e  life  lactation yields.  the average p r o d u c t i o n  i s more important Therefore,  than the 305  as mentioned b e f o r e ,  i n t r o d u c e d a system which a d j u s t s l a c t a t i o n milk for  days open (Bar-Anan and The  problems ( h e a l t h code group 2) had There was  Israel  yields  S o l l e r , 1979).  cows w i t h c a l v i n g a s s o c i a t e d  calvings.  day  reproductive  h e a v i e r c a l v e s at both  no d i f f e r e n c e i n body weights at  c a l v i n g s between the two  h e a l t h code groups.  Philipsson  (1976) found t h a t the d i f f e r e n t weights of c a l v e s from cows w i t h equal due  body weights ( w i t h i n the same breed) were  to a) the age  of the cow  and  b) g e n e t i c s .  The  i n c i d e n c e of c a l v i n g a s s o c i a t e d r e p r o d u c t i v e problems of the 71 cows c a l v i n g a second time w i t h i n t h i s was  very low  experiment  (5 o b s e r v a t i o n s ) ; too low to i n c l u d e i t  i n t o the s t a t i s t i c a l  analysis.  This low i n c i d e n c e of  c a l v i n g a s s o c i a t e d problems might be due  to the f a c t t h a t  at the subsequent c a l v i n g s t h e r e were no h e i f e r s c a l v i n g because new  cows were not i n t r o d u c e d  into this  experiment.  At the c u r r e n t c a l v i n g there were 10 h e i f e r s , which represented Philipsson  40% of the cows w i t h c a l v i n g a s s o c i a t e d problems. (1976) showed t h a t the i n c i d e n c e of d y s t o c i a  - 81  was higher i n p r i m i p a r o u s Swedish d a i r y breeds.  than i n m u l t i p a r o u s  Cows i n h e a l t h code group 2 had  a lower f a t t e s t i n the f i r s t lactation.  cows i n  50 days o f the subsequent  T h e i r f a t t e s t tended t o be lower  i n the  c u r r e n t l a c t a t i o n as w e l l ; however, the d i f f e r e n c e was not s i g n i f i c a n t .  Whether t h i s d i f f e r e n c e i n the f a t t e s t  was g e n e t i c a l l y determined or was r e l a t e d to the r e p r o d u c t i v e d i s o r d e r s cannot be decided  i n the c o n t e x t of t h i s  s tudy. Cows which c a l v e d d u r i n g the pasture beginning  of the c u r r e n t l a c t a t i o n  of the d a i l y m i l k y i e l d a lower  showed a f a s t e r i n c r e a s e  ( s l o p e f o r m i l k 0-50 days) and  f a t t e s t i n the f i r s t  lactation.  season a t the  50 days of the subsequent  Since 90% of the cows c a l v e d i n the same  season a t the subsequent c a l v i n g as a t the c u r r e n t c a l v i n g , these  d i f f e r e n c e s can be a s s o c i a t e d with the c a l v i n g  season.  Wood (1969) showed t h a t the p r o d u c t i o n  of cows  which c a l v e d i n s p r i n g and e a r l y summer i n c r e a s e d f a s t e r than f o r cows which c a l v e d i n other seasons. (1964) and Waite e t a l . (1959) r e p o r t e d milk f a t depression pasture.  t h a t a marked  e s p e c i a l l y during spring  A l l these workers d e a l t w i t h s p r i n g and e a r l y  summer c a l v i n g s . however, covered October.  occurred  Huber e t a l .  The pasture  season i n t h i s  the complete pasture  experiment,  season, May to  Hence, the f i n d i n g s of Wood (1969), Huber e t a l .  (1964) and Waite e t a l . (1959) do not c o n c l u s i v e l y e x p l a i n  - 82  -  the r e s u l t s i n t h i s experiment. The r e g r e s s i o n e q u a t i o n s  to p r e d i c t body weight  changes and p r o d u c t i o n i n the e a r l y subsequent did  not r e v e a l any new r e l a t i o n s h i p s .  lactation  Days open was a  s u i t a b l e parameter to p r e d i c t the weight of the c a l f of 9  the subsequent c a l v i n g (R  = .57).  p r e d i c t i o n s of p r o d u c t i o n t r a i t s  In o t h e r  equations,  i n the subsequent  l a c t a t i o n , w i t h days open as independent v a r i a b l e ; the c o e f f i c i e n t of d e t e r m i n a t i o n was very low.  (R ) although  significant,  The r e s u l t s of the r e g r e s s i o n a n a l y s i s  showed again t h a t the r e l a t i o n s h i p between  reproductive  t r a i t s of the c u r r e n t l a c t a t i o n and p r o d u c t i v e t r a i t s of the subsequent l a c t a t i o n were not s u b s t a n t i a l .  - 83 -  6.  SUMMARY AND CONCLUSIONS In  a H o l s t e i n d a i r y h e r d , the i n f l u e n c e of e a r l y and  l a t e b r e e d i n g post partum on r e p r o d u c t i o n was i n v e s t i gated.  The e a r l y post partum r e p r o d u c t i v e a c t i v i t y was  monitored w i t h m i l k progesterone The  large v a r i a t i o n  analysis.  i n the onset of the f i r s t  estrus,  (both progesterone and v i s u a l l y d e t e c t e d ones) c o u l d not be e x p l a i n e d by age, m i l k p r o d u c t i o n , body weight  losses  d u r i n g the e a r l y post partum p e r i o d , c a l v i n g a s s o c i a t e d r e p r o d u c t i v e d i s o r d e r s , or c a l v i n g season.  The l a t e r  d e t e c t i o n of the f i r s t v i s i b l e heat as compared to the first  progesterone d e t e c t e d heat i n d i c a t e d t h a t most cows  showed l i t t l e  or no b e h a v i o u r a l evidence of f i r s t  estrus,  t h e r e f o r e they were not d e t e c t e d by the herdsmen. Cows bred e a r l y (73 ± 18 days post partum) c o n c e i v e d a f t e r fewer s e r v i c e s per c o n c e p t i o n than cows bred  late  (93 ± 17 days post partum).  group  W i t h i n the e a r l y bred  cows w i t h c a l v i n g a s s o c i a t e d r e p r o d u c t i v e problems  con-  c e i v e d as r e a d i l y as u n a f f e c t e d cows, w h i l e a f f e c t e d cows in the l a t e bred group r e q u i r e d s i g n i f i c a n t l y more s e r v i c e s per c o n c e p t i o n . to  A s i m i l a r s i t u a t i o n was found i n r e l a t i o n  the c a l v i n g season:  C a l v i n g d u r i n g the p a s t u r e season  delayed c o n c e p t i o n i n the l a t e bred group but d i d not i n f l u e n c e c o n c e p t i o n i n the e a r l y bred  group.  The cows i n the l a t e bred group produced in  more FCM  the 305 day l a c t a t i o n and i n the b e g i n n i n g of the  - 84  subsequent l a c t a t i o n .  -  There was no d i f f e r e n c e i n the  average d a i l y milk p r o d u c t i o n from the beginning sequent l a c t a t i o n .  c a l c u l a t e d ov/er the p e r i o d  o f the c u r r e n t to day 150 of the subDays open and days d r y become  important  f a c t o r s i f more emphasis i s placed on average milk per day of p r o d u c t i v e  life  yields  r a t h e r than on 305 day l a c t a t i o n  yields. High m i l k p r o d u c t i o n  had a n e g a t i v e  i n f l u e n c e on  r e p r o d u c t i o n o n l y when r e l a t e d to s u b s t a n t i a l body weight l o s s e s i n the same time p e r i o d .  There was no marked  e f f e c t of c a l v i n g a s s o c i a t e d problems or c a l v i n g season on p r o d u c t i o n subsequent  i n the c u r r e n t or the b e g i n n i n g  of the  lactation.  In s h o r t , the c o n c l u s i o n s from t h i s study a r e : The  onset of e s t r u s showed a l a r g e i n e x p l a i n a b l e  indi vi dua1 vari ati on . E a r l y breeding o  versus  l a t e breeding  resulted in less  i  s e r v i c e s per c o n c e p t i o n  f o r the e a r l y bred  Cows w i t h r e p r o d u c t i v e problems conceived  cows. r e a d i l y when  bred e a r l y but r e q u i r e d more s e r v i c e s per c o n c e p t i o n when bred The  late.  i n f l u e n c e of c a l v i n g a s s o c i a t e d d i s o r d e r s and the  c a l v i n g season was more d i s t i n c t i n the l a t e group than i n the e a r l y bred  bred  group.  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F e r t i l i t y i n New York a r t i f i c i a l l y inseminated H o l s t e i n herds i n d a i r y herd improvement. J . D a i r y S c i . 8: 718723. S t a b e n f e l d t , G. H. , E d q v i s t , L. E., K i n d a h l , H., G u s t a f s s o n , B. and Bane, A. 1961. P r a c t i c a l i m p l i c a t i o n s of r e c e n t p h y s i o l o g i c f i n d i n g s f o r r e p r o d u c t i v e e f f i c i e n c y i n cows, mares, sows and ewes. J . Am. v e t . med. A s s . 172: 667-675 S t o t t , G. H. and W i l l i a m s , R. J . 1962. Causes of low breeding e f f i c i e n c y i n d a i r y c a t t l e a s s o c i a t e d w i t h seasonal high temperatures. J . D a i r y S c i . 45: 1369-1375. T h a t c h e r , W. W. 1974. E f f e c t s o f season, c l i m a t e and temperature on r e p r o d u c t i o n and l a c t a t i o n . J . Dairy S c i . 57: 360-368. Touchberry, R. W., R o t t e n s t e i n , K. and Andersen, H. 1959. A s s o c i a t i o n s between s e r v i c e i n t e r v a l , i n t e r v a l from f i r s t s e r v i c e to c o n c e p t i o n , number of s e r v i c e s per c o n c e p t i o n and l e v e l of b u t t e r f a t p r o d u c t i o n . J . Dairy S c i . 42: 1157-1170. Touchberry, R. W. and B a t r a , T. R. 1976. Body weight changes i n l a c t a t i n g purebred and c r o s s b r e d d a i r y c a t t l e . J . Dai ry S c i . 59: 733-743. T r i m b e r g e r , G. W. 1954. Conception r a t e s i n d a i r y c a t t l e from s e r v i c e s at v a r i o u s i n t e r v a l s a f t e r p a r t u r i t i o n . J. D a i r y S c i . 37: 1042-1049. Wagner, W. C. and H a n s e l , W. 1969. R e p r o d u c t i v e p h y s i o l o g y of the post partum cow. 1. c l i n i c a l and h i s t o l o g i c a l findings. J . Reprod. F e r t . 18: 493-501. Waite, R., C a s t l e , M. E. and Watson, J . N. 1959. The e f f e c t on m i l k c o m p o s i t i o n of f e e d i n g s p r i n g grass to cows. J . D a i r y Res. 26: 173-181.  - 92 -  Whitmore, H. L., T y l e r , W. J . and C a s i d a , L. E. 1974. E f f e c t s of e a r l y post partum breeding i n d a i r y c a t t l e . J. of Anim. S c i . 38: 339-347. W i l t o n , J . W., B u r n s i d e , E. B. and Rennie, J. C. 1967. The e f f e c t s of days dry and days open on the m i l k and b u t t e r f a t p r o d u c t i o n of H o i s t e i n - F r i e s i a n c a t t l e . Can. J . An. S c i . 47: 85-90. Wood, P. D. P. 1969. F a c t o r s a f f e c t i n g t h e shape o f the l a c t a t i o n curve i n c a t t l e . Anim. Prod. 11: 307-316. Wood, P. D. P. 1977. The e f f e c t of the d r y p e r i o d on the subsequent l a c t a t i o n i n t h r e e h a l f - s i b groups o f British Friesians. J . a g r i c . S c i . Camb. 89: 737-741. Youdan, P. G. and K i n g , J . 0. 1977. The e f f e c t o f body weight changes on f e r t i l i t y d u r i n g t h e post partum p e r i o d i n d a i r y cows. B r i t . v e t . J . 133: 635-641. Zamet, C. H., C o l e n b r a n d e r , V. F., E r b , R. E., C a l l a h a n , C. J . , Chew, B. P. and M o e l l e r , N. J . 1979. V a r i a b l e s a s s o c i a t e d w i t h p e r i p a r t u m t r a i t s i n d a i r y cows. Theriogenology. 11: 229-272. Z e r o b i n , K. 1979. Personal communications. F a c u l t y of Veterinary Medicine. Zurich.  - 93 -  8.  APPENDIX  Table 1:  Means and s t a n d a r d d e v i a t i o n s of the c o v a r i a b l e s m i l k p r o d u c t i o n 0-50 days post partum, body weight changes (BWC) 0-60 days post partum i n the c u r r e n t l a c t a t i o n and age of c a l v i n g at the b e g i n n i n g of the c u r r e n t l a c t a t i o n . Mi 1 k P r o d u c t i on 0-50 d.p.p. (kg)  Cows i n:  Body Weight Changes 0-60 d.p.p. (kg) s.d  Age (mb . )  s.d  X  s.d.  X  1 520  326  -40.8  37 .1  44.9  20. 0  1653  380  -54.4  40. 9  46.2  22 .7  Health code 1  1619  360  -40 .8  37. 1  45 .1  17. 3  Health code 2  1511  351  -54.4  40 .8  46 .6  29 .2  Pasture season  1649  336  -53.3  31 .2  47.3  20. 9  Non-pasture season 1 543  374  -43.9  44. 9  44.4  21 . 5  1587  358  -47.6  39. 4  45 .5  21 . 3  E a r l y bred Late bred  Total  group group  •  X  •  Table  2:  Means  and  standard  deviations  a)  E a r l y and l a t e b r e d the c a l v i n g season  b)  Interactions  and  of  groups,  reproductive health  a)  early  Trait  s .d.  to  Health  late  bred  X  s. d.  status  normal S i gn  (H)  Calving  abnormal  X  s.d.  X  pasture  season  (S)  non-pasture  s.d.  Sign  X  s.d.  X  s.d.  Sign  49  27.6  47  25.0  n.s.  49  28.3  48  25.8  n.s.  33  10. . 5  34  11.1  34  8.2  n.s.  32  8.6  35  n.s.  3.0  1 .. 7  **  11.4  1 .0  2.5  1.2  2.8  2.0  n.s.  2.5  1.1  1.7  n.s.  1 .4  4.2  1 .3  **  2.7  3.1  3.7  1.4  3.7  1.6  n.s.  3.7  1.3  3.7  1.6  n.s.  18.4  8. 6  16.6  6 .2  n.s.  18.1  8.3  15.9  4.7  n.s. 17.4  4.5  17.6  9.2  n.s.  72  18. 2  93  17 . 3  82  21.5  83  18.9  22.8  82  18.9  n.s.  Number o f prog. d e t . heats  34  10;0  2.2  Days to 1 s t . s e r v i c e  1.50  Days from 1 s t s e r v i c e to conception  accordinq  n.s.  heats  Number of s e r v i c e s  groups  lactatic  n.s.  28. 5  (d.p.p. )  (days)  and  current  25 . 2  50  1st v i s i b l e heat (d.p.p.)  1st c y c l e length  group  the  (G)  bred  X  Number of v i s i b l e  status  in  covariables Groups  1st prog. d e t . heat  traits  ** *  1 .95  1.63  26.2  39 . 8  **  88  33. 0  121  40 .6  **  100  38  373  34. 1  404  38 . 0  **  385  35  Days open  18.7  29.9  27.9 113 400  n.s. *  1.96  25. 0  16.40  C a l v i n g I n t e r v a l (days)  47  83 1.74  1.72  IO  n.s.  40.9  **  23.0  36.5  20.1  31.2  *  46  **  106  42  103  39  *  47  **  387  40  391  39  *  b)  I n t e r a c t i ons  Covariables  Trait G x Number 1st  of  cycle  Number  of  prog. length  heats  (days)  services  Days from 1st conception Days  det.  service  to  open  Calving  interval  (days)  H  G  x  S  x  S  G  x  H  x  S  age (mo.)  mi 1 k 0-50  d.p.p.(tg)  BWC 0-60 d.p.p.m)  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  .01011  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  *  *  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  -.00451  * ** n. s  significant (P* significant (P* not s i g n i f i c a n t  BWC  body  1  weight  .05) .01)  changes,  •[ r a i t s l i s t e d in i n t e r a c t i o n s and Table 2b.  d.p.p.  = days  T a b l e 2a w i t h o u t c o v a r i a b l e s were  any not  post  partum  significant l i s t e d in  Table 3:  Means and standard deviations of productive t r a i t s in the current lactation a)  Early and late bred groups, health status group and groups according to the calving season  b) Covariables  1  Groups (G) early bred  Trait  FCM 0-50 days (kg) FCM 50-100 days (kg)  late bred  s.d.  X  1401 1386  Health status (H)  X  1509  310  1412  285  X  s.d.  n. s.  1495  354  612  n. s.  1453  n. s,  1302  416  abnormal  normal  s.d. Sign.  Cal vi ng season (S)  X  s.d.  pasture Sign.  X  non- pasture  s.d.  X  s.d.  Si gn  1362  371  n .s.  1532  33~5  1404  385  n.s.  331  1269  709  n, s.  1458  335  1361  565  n.s.  274  1293  265  n,. s.  1322  292  1288  251  1284  233  1313  303  FCM 305 days (kg)  7276  1565  7995  2304  *  7708  1974  7492  2089  *  7880  2012  7506  1992  Milk 305 days (kg)  7595  1659  8550  2484  *  8084  2058  8084  2438  n. s.  8202  2082  8039  2250  n.s.  Fat I 305 days  3.71  .47  3.57  .38  n. s.  3.68  .42  3.55  .44  n. s.  3.74  .46  3.57  .40  n.s.  Slope milk 0-150 days  -.0271  .0366  -.0372  .0639  n. s. -.0383  .0410  .0175  .0712  n.. s. -.0411  .0379  -.0249  .0609  n.s.  Slope fat X 0-150 days  -.0013  .0034  -.0016  .0036  n. s. -.0013  .0032  .0019  .0041  n.. 5 .  -.0012  .0035  -.0019  .0035  n.s.  Slope FCM 0-150 days  -.0290  .0420  -.0405  .0648  n.  s. -.0398  .0446  .0230  .0733  n.. S . -.1433  .0413  -.0287  .0632  n.s.  Slope milk 150-305 days •-.1178  .0487  -.0955  .0448  **  -.1073  .0490  .1052  .0457  n.. s. -.1045  .0547  -.1079  .0419  n.s.  Slope fat t 150-305 days  .0008  .0010  .0119  n. s. -.0010  .0011  .0010  .0009  n,. s. -.0009  .0011  .0010  .0010  n.s.  .0419  **  .0447  .0907  .0419  n.. s. -.0948  .0521  -.0362  .0362  n.s.  FCM 100-150 days (kg)  Slope FCM 150-305 days  .0009 -.1059  -.0825  .0430  -.0956  b) Covari ables Trait'  Age (mo.)  Milk 050 d.p.p. (H)  BWC 060 d.p (tg)  2.09701  .79563  n.s.  FCM 50-100 days (kg)  n.s.  58840  n.s.  FCM 100-150 days (kg)  n.s.  4001 3  n.s.  FCM 305 days (kg)  n.s.  3.68808 .  n.s.  Milk 305 days (kg)  n.s.  4. 35779  n.s.  Slope milk 0-150 days  n.s.  - . 00006  .00017  Slope FCM 0-150 days  n.s.  - . 00007  n.s.  -.00071  n.s.  n.s.  Slope fat t 1 50-305 days -.00002  n.s.  n.s.  -.00077  n.s.  n.s.  FCM 0-50 days (kg)  Slope milk 150-305 days  Slope FCM 150-305 days  **  n.s.  significant (P* .05) significant (P* .01 ) not significant BWC  body weight changes, d.p.p. = days post partum  1  No interactions of traits listed in Table 3a were significant.  2  Traits listed in Table 3a without any significant covariables were not listed in Table 3b.  n.s.  *  cn  Table  4-  Means and s t a n d a r d d e v i a t i o n s o f body w e i g h t s and body w e i g h t i n the c u r r e n t l a c t a t i o n and a t the s u b s e q u e n t calving. a)  Early the  b)  and  late  calving  Interactions  bred  groups,  and  early  Wt.  at  calving-(l)  BWC  0-60  d.p.p.  BWC  0-80  d.p.p.  BWC  60-80  BWC/day  d.p.p.  to  late  bred  61 1  42  97 . 0  62b  43  -41  42  37 . 1  -54  43  X  s.d. 100.7 40.9  (H)  Calving  a bnormal  normal  bred  n  s. d.  status  Sign.  X  n  s.d.  X  n.s.  630  60  94.8  588  25  102.1  n.s.  n.s.  -51  59  38.3  -39  25  41  .4  Si gn.  (S)  non - p a s t u r e  pasture s.d.  n  season  X  n  s.d.  Sign  90 .7  595  47  98.9  *  38  31 . 2  -43  47  45.1  n.s.  -56  37  26 . 8  -28  47  47.1  **  35  21 . 3  16  45  20.7  **  33  .  .37  38  .15  n  s. d.  648  38  n.s.  -53  x  -31  42  40 . 1  -50  42  41 . 6  n.s.  -46  59  39.8  -25  24  43.3  n.s.  10  40  23 . 0  6  40  22.5  n.s.  6  56  21 . 0  14  24  26.1  n.s.  -  33  .16  .35  38  .14  .30  49  .14  . 35  22  .18  n.s.  .25  .28  .30  49  .15  .33  22  .18  n.s. n.s.  2  to  d.p.p.  to .27  33  .17  .35  38  .16  Wt.  at  657  31  60.9  689  38  59.0  BWC  calving-(l)  calving-(2)  calf  *  (1)  674  44  to  calving-(2) of  according  Health  calving-(2)  Wt.  groups  (kg/day):  d.p.p.  calving-(2) 80  and  (G)  n  X  group  covariables  Group  Trait  status  (BWC)  season  a)  60  health  changes  45  31  66.5  67  37  70.2  42.0  33  4.9  43.2  36  5.8  n.s.  42.1  .26  14  33  .16  .34  38  • 17  n.s.  683  32  55.8  667  37  66.2  n.s.  48  60.8  674  21  64.9  47  60. 5  86  21  78.5  26  31  61 . 2  80  37  65.8  47  4.9  43.8  22  5.9  44  31  5.8  41  38  4.6  b) C o v a r i a b l es  Interactions Trait G  n.s.  n.s.  n.s.  n.s.  Age (mo. ) 3 .64819  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  60 d . p . p . - c a l v i n g -(2)  n.s.  n.s.  80 d . p . p . - c a 1 v i ng -(2)  n.s.  Wt.  Wt.  at  BWC  0-80  BWC  60-80  at  calving-(l ) d.p.p. d.p.p.  calving-(2)  BWC c a l v i n g - t i ) calving-(2) Wt.  of  calf  (1)  x  H  G  x  S  H  x  S  G  x  H x  S  Milk 0-50 d . p . p .u«>  BWC 0 - 6 0 d.p. p  .2491 6  -.53863  n.s.  n ..s.  .70976  n.s.  n.s.  n.s.  n.s.  n.s.  - .00998  n.s.  n.s.  n.s.  0 .01001  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  n.s.  *  n.s.  n.s.  n.s.  -.2821 5 n.s.  n.s.  n.s.  .26688  n.s.  .04057  .79207  n.s.  .01140  n.s.  s i g n i f i c a n t (P & . 0 5 ) significant (Pfe.Ol ) not s i g n i f i c a n t  BWC  body  **  weight  changes,  d.p.p.  = days  post  partum  to -3 .59641 n.s.  1  Traits listed in i n t e r a c t i o n s and Table 4b.  T a b l e 4a w i t h o u t c o v a r i a b l e s were  any not  significant listed in  Table 5:  Means and standard deviations for traits in the subsequent lactation. a)  Early and late bred groups, health status group and groups according to the calving season  b)  Interactions and covariables  a)  Health status (H)  Groups (G)  Trait  x 657  Calving weight (kg)  s.d.  s.d.  X  97.0  Si gn. *  X  Calving season (S)  abnormal  normal  late bred  early bred  s.d.  Pasture  s.d.  X  675  60.8  675  64.9  689  100.7  n. s .  45  7.2  48  6.4  Non -Pasture  Sign.  X  s.d.  X  s.d.  Sign  n.s.  683  55.8  667  64.4  n. s.  *  47  5.3  45  5.8  47  8.3  46  6.0  n. s.  BWC 0-60 d.p.p. (kg)  -55  33.0  -66  39.4  n. s.  -56  33.1  -71  42.6  n.s.  -55  31.8  -64  40.5  n. s.  BWC 0-80 d.p.p. (kg)  -32  45.9  -54  43.9  n. s.  -36  47.5  -63  35.2  n.s.  -40  45.7  -49  47.0  n. s.  BWC 60-80 d.p.p.(kg)  18  22.5  8  27,9  n. s .  20  26.3  8  22.2  n.s.  13  23.1  14  30.1  n. s.  1620  409  1803  250  1701  360  1739  322  n.s.  1756  290  1672  385  n. s.  Weight of calf (kg)  M1lk 0-50 days (kg) Fat t 0-50 days FCM 0-50 days (kg) Slope milk 0-50 days Slope fat 0-50 days  3.73 1540  .48  3.80  .64  253  1745  40.6  n. s. n. s. n. s .  .56  3.62  .54  *  3.69  .63  3.84  .47  *  1648  367  1636  315  n.s.  1663  260  1624  410  n. s.  .1945  .1472  n.s.  2125  .1108  .1115  .1921  **  3.84  1444  .1701  . 1702  .1702  n. s.  .1399  1771  -. 0059  .0113  0069  .0069  n. s.  -.0064  0125  - .0063  .0106  n.s.  0090  .0136  .0042  .0100  n. s.  .1111  1720  .1617  .1316  n.s.  1679  .1187  .0939  .1813  *  n. s.  1170  .1589  •1376  .1376  n. s.  Slope milk 0-150 da.  -. 0640  .0353  -. 0318  .0361  **  -.0467  ,0317  - .0522  .0421  n.s.  0508  .0364  -.0468  .0404  Slope f a t I 0-150 da.  -. 0025  .0055  -. 0036  .0054  n. s.  -.0026  0048  - .0039  .0067  n.s.  0026  .0057  -.0032  .0053  n. s.  Slope FCM 0-150 days  -. ,0709  .0302  0492  .0390  *  -.0570  0373  .0672  .0338  n.s.  -.0607  .0378  n. s.  Slope FCM 0-50 days  0585  .0342  b) Covariables  Interactions Trait  •  1  H  Milk 0-50 BWC 0-60 d.p.p.(n) d., p . p .(»»> .26688 n., s.  G xH  G x S  S xH  Calving weight (kg)  n.s.  n.s.  n.s.  n . s.  Age (mo. ) n.s.  BWC 0-60 d.p.p. (kg)  n .s.  n.s.  n.s.  n . s.  2.22134  -.10406  n.. s.  BWC 0-80 d.p.p. (kg)  *  n.s.  n.s.  n . s.  n. s.  -.12510  n,. s.  M1lk 0-50 days (kg)  n.s.  n.s.  n.s.  Gx 1 xS  n . s.  n. s.  .60117  n,. s.  .42136  n,. s.  FCM 0-50 days (kg)  n . s.  n.s.  n.s.  n . s.  n. s.  Slope milk 0-50 days  n . s.  n.s.  n.s.  n . s.  n. s .  -.00018  - .00072  Slope FCM 0-50 days  n . s.  n.s.  n.s.  n . s.  n. s.  -.00019  .00067  Slope milk 0-150 da.  n . s.  n.s.  n.s.  n . s.  n. s.  -.00005  n.s.  Slope FCM 0-150 days  n . s.  n.s.  n.s.  n . s.  n. s .  -.00005  n.s.  * **  n.s.  significant (P* .05) significant ( P * .01) not significant  BWC = body weight changes, d. p.p. = days post partum  1  Traits listed in Table 5a without any significant i nteracti ons and covariables were not listed In Table 5b.  - 98 -  Table  6:  Correlations (BWC) i n the  between current  Calving weight (1)  Trait  Calving Weight  weight of  (1)  calf  body w e i g h t lactation.  Weight of calf(l)  .33**  0-60  d.p.p.  -.63**  -.18  BWC  0-80  d.p.p.  -.65**  -.23  BWC  60-80  -.13  -.14  BWC  calving  -.78**  -.09  calving  (2)  Calving  weight  Table  = days  7:  (2)  post  .72**  BWC calving (1 ) - calving (2)  Weight  of  calf  .84**  .67**  (2) = * P6  -.27*  1.00  .67**  .10  1.00  -.08  -.10  -.29*  between body w e i g h t and subsequent l a c t a t i o n . Calving w e i gh t (2)  Weight of calf(2)  body  weight  BWC 0-60 dpp(2)  changes  BWC 0-80 dpp(2)  1 .00 (2)  -.10  (2)  -.06  1 .00 .33**  1 .00  d.p.p.(2)  -.25  -.19  .11  BWC  0-80  d.p.p.(2)  -.25  -.17  .03  BWC  60-80  -.17  .00  .10  d.p.p.(2)  (1) = c u r r e n t l a c t a t i o n , (2) = ** S i g n i f i c a n t correlation: P ^ days  .37**  subsequent lactation .05, * * P & .01  0-60  =  1.00  -.17  BWC  d.p.p.  BWC calv.(l)calv.(2)  1.00  .72**  BWC c a l v . (1 ) -calv.(2)  weight  BWC 60-80 dpp  partum  Correlations (BWC) i n the  Trai t  Calving  BWC 0-80 dpp  changes  -  (1) = c u r r e n t l a c t a t i o n Significant correlations d.p.p.  weight  1.00  BWC  (1)  BWC 0-60 dpp  body  1.00  (1)  d.p.p.  and  post  partum  subsequent .01  1 .00 .76** -.02  lactation  1 .00 .45**  - 99 -  Table  8:  C o r r e l a t i o n s (BWC)  and  between  m i l k  body  C a l v i n g w e i g h t  T r a i t  (1) FCM  0-50  FCM  50-100  FCM  100-150  FCM  305  Fat  %  M i l k  and  the  body  c u r r e n t  weight  changes  l a c t a t i o n .  BWC  BWC  0-60  0-80  c a l v i n g  dpp  dpp  c a l v i n g  BWC  - . 6 6 * *  - . 6 6 * *  - . 6 4 * *  .  4 4 * *  - . 2 9 *  - . 3 0 *  - . 5 6 * *  .  6 5 * *  - . 4 5 * *  - . 4 5 * *  - . 5 1 * *  . 5 8 * *  - . 4 5 * *  -  - . 5 0 * *  .03  - . 0 8  - . 0 6  - . 0 5  . 5 6 * *  - . 4 2 * *  - . 4 3 * *  - . 4 6 * *  - . 4 5 * *  . 4 6 * *  . 4 8 * *  • . 4 1 * *  days days  days days  305  in  . 8 3 * *  days  305  w e i g h t s  p r o d u c t i o n  days  . 4 5 * *  Slope  FCM  0-150  Slope  FCM  150-305  .01  - . 2 6  .00  . 2 9 *  Slope  FCM  0-305  .  - .  . 3 6 * *  . 4 7 * *  (1)  c u r r e n t  =  S i g n i f i c a n t d . p . p .  Table  =  l a c t a t i o n ,  (2)  =  *  P A  c o r r e l a t i o n s :  days  9:  3 4 * *  post  and  between  m i l k  . 0 5 ,  t  * *  l a c t a t i o n P  .01  w e i g h t  and  in  subsequent  the  body  w e i g h t  C a l v i n g  BWC 0-60  0-80  (2)  dpp(2)  dpp(2)  -.10  .13  - . 0 6  -.16  -.01  . 4 0 * *  - . 2 3  - . 3 2 *  . 3 7 * *  - . 0 0  -.07 .17  (1)  - c a l v . ( 2 )  ght  BWC  FCM  0-50  FCM  50-100  FCM  100-150  days  - . 3 0 *  Fat  %  days  .09  -.19  .05  days  - . 2 3  -.07  - . 0 3  .04  da.  .16  .24  .13  .21  .20  days  0-150  Slope  M i l k  0-150  Slope  Fat  %  Slope  FCM  0-150  0-150  days  -.12  (1) = c u r r e n t l a c t a t i o n , S i g n i f i c a n t c o r r e l a t i o n s : d . p . p .  =  days  post  changes  l a c t a t i o n .  wei  c a l v .  days  body  p r o d u c t i o n BWC  T r a i  subsequent  partum  C o r r e l a t i o n s (BWC)  5 4 * *  partum  .00 -.10  (2) = subsequent l a c t a t i o n * P & . 0 5 , * * P 4 .01  

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