A study of some factors affecting the post-partum oestrous interval in suckled angus cows : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University

private study only. The thesis may not be reproduced elsewhere without

the permission of the Author.

A S'I'UDY OF SOME Fi1C'l'ORS .hP:F'ECT ING 'rHE

POS'I'-PAHTUM OESTROUS INTERVAL

IN SUCKLED _ANGUS COWS

A thesis presented in partial �ul�ilment o� the requirements �or the degree of

Master o� Agricultural Science in Animal ^Science at

Massey University

Stephen Todd Morris 1976

.ABSTF..ACT

The o b j ectiv e s o� th i s study were to determine the l ength of interval from p artur ition to �irst oestrus and invest i gate �actors tha t might influenc e thi s interval . S ixty-one records w ere c ollec ted in 1975 £rom the breeding herd at M a s s ey University's No . 3 sheep farm Tuapaka ,

anotner 207 rec ords cove ring th e yea rs 1971 to 1973 and 1975 were obta ined from the herd of the Whatawhata Hill C ountry Researc h Station, Ministry of .Agriculture and Fi she r i e s , Hamilton . T h e hla s s ey herd c onsisted o f .Angus c ows a ged 4-years and older while the Vihatawhata Angus her d c onsi sted

o f cows aged 2-year s and olde r .

O e strus w a s det ected at each loc ation b y the use of c hin-b a ll m ating ha rnes se s attac hed to entire or v a secto­

mi sed bul l s . Manag ement o f the c ows followed normal N ew Z eala nd hill country practi ces witll the exc eption th a t in the Ma s sey herd p o st-c a lv ing treatments w ere imp o se d . T he s e treatments w er e :

( i ) On the hi ll throughout th e tria l ( H ) ( i i ) Removed from the p a d a t b i rth ( P B ) (i i i ) Removed from the p a d a t 20 day s ( P20 )

( iv ) Removed from the p a d at 40 days ( P40 )

.After calv ing , c ows and c a lv e s were grouped into thre e block s according t o calf age w ith treatments nested w i thin block s .

The a na lysis consi sted of a study o� the rel ationships b etween the l ength of the interval from c a lving to fir st o e strus and the nutritional treatment s , milk pro duction, c ow l ivewe ight c h ange s, and c a lf v a r i a b l e s .

The least squares mean s for post-partum interval to

�ir st o estrus were 79 .2 days and 74.5 days for the Ma ssey and Whatawhata herds , r espectiv ely . The regr e s s io n of

i i i

c a lv ing da t e s ignif ic antly ( P< 0 . 01) influenced the p o st­

p a rtum int erval in th e Ma s s ey herd, b ut the effects of

block, trea tment, age of dam and sex of c alf were non-signi­

fic ant . For the Whatawhats herd, y e a r of reco rd (P< 0 . 001 ), age o f dam ( P _<. 0 . 01 ) a nd the regre s sion of' calv ing dat e

( P _< 0 . 001) all influenced the po st-p a rtum int erval. The s i re of c a lf at fo o t and sex of c a l f were non-s ignif ic ant whil e the regression o f c ow livewe ight change p o st-c alving to ma ti ng approached signi.fic ance (0 . 05<P <0 . 10) .

Milk produc t ion of the dam f'or the Ma ssey data wa s ass e ssed by the w eigh-nurs e-we igh method . Twen ty-day milk produc tion wee s ignific antly c orrelated ( r = 0 . 25, for 59 _df, P < 0 . 05) w i th p o st-p artum int erv al t o f'irst o e strus, but 40- and 60-day milk p roduc t ion wa s no t r el a t e d to thi s int erval.

Calf' pre-weaning ga in wa s c orrela t ed ( r = 0 . 28, for 205 df',

P<0 . 05) w ith thi s interval in the Wha t a whata da t a .

Po st-c al ving l ivewe ight s of t he c ows were influenc ed by t r e a tmen t s w ith the P20 and P40 c ows be ing l ight er than th e H or PB c ows . These differenc e s in cow l ivewe ight did no t influenc e the l ength ot the p o st-p artum interv a l . Thi s r e sult indi c a t e d tha t pre-calving nutri t ion wa s m o r e important th an p o st-ca lv ing nutri tion .

The c a lv ing interva l f'or th e M a s s ey herd wa s 367 . 6 days c o mpa red wi th 365 . 1 days for th e Wha t awha ta h erd . Calving interval w a s p o si t ively and s ignif i c antly correlated w i th po s t-p artum int erva l t o first o e s t rus ( r = 0 . 29, f'or 49 _df', P<.0 . 05 , and r = 0 . 54, f'or 82 df, P<0 . 01, f'or the Ma s s ey

and Wha t a wha t a herds, respec t iv e ly) .

It wa s concl ude d fro m t hi s s t udy that i f' the int erval to f'i r s t post-partum oe s t rus in Angus cows wa s 80 d ay s , then m a t ing sho ul d c ommenc e 70 day s a ft er c a lving and co nt inue f'o r 42 day s . Young he i f'ers exp eri enc e a longer p o st-p a rtum a no e st rus and co nsequently should b e ma ted 21 day s b ef'or e the·mature he rd . Part i c ular a t tenti on needs to be given to pre-c alv ing nutr i t ion, wh i l e f'or the fir st 40-day s po st-

partum cows c an be red to maint a in liv eweight .

Adoption or th ese pract i c e s should lead to a substan­

t i al improv ement in the r eproductiv e status or a bee� b re ed­

ing herd .

ACKNOWLEDGEMENl'S

The a uthor is spec i ally indebted to his sup ervisor Mr ^{R .A .} Barton, ror his inv alua ble guidanc e and a ssistanc e in all asp ects o f the study .

V

Gratitude is also expressed to Professor h.L. Ra e for his adv i c e on statistic al matte rs and to Mr .A . B . Ple asants who g enerously gave his instruction and help in the statisti­

c al analysis and c omputer op erat i on .

Thanks ere extended to Mr ^{D .R.} Patterson who ass isted in the c ollection of most of the Massey University data and ma de many helpful c omments on the be havi our of the animals ; the Tuapaka farm staff, Mr W.M. D e ighton and Mr A.L. Harwoo d who handle d th e day-to-day management of the stock .

Mr G .K . Hi ght , Director, Wha tawhata Hill C ountry

Research Station, generously prov i ded the author with data . Sp ec i al thanks to Dr T . h . Knight and Mr G .B . Nic oll for ass istanc e in c omp iling these data , and to the tec hn i c i ans at the Whatawhata Hill C o untry Research Station for c o ll ect­

ing these rec or ds .

The staff at the Massey University C omputer Uni t were p articularly helpful , as was Mr C . J . D o dd whg assiste d w ith

computer progr amming .

Sincere thanks a re due to Mrs H i l de Godenho for the

s kilful and effic ient manner in whi c h she type d the manuscript .

The a utho r would also l ike t o thank his many c o ll eagues a nd fri ends who helped make th is study more enj oyabl e than it o therwise might have b een .

The C ombined B eef Breeders ' Res e a rc h C ommittee p rov i de d financ i a l suppo rt t o M r R . A . Barton which incl uded a grant for th is study . This contribution i

J

apprec iate d .

The author held the Hel en ^E. Aker s Scholarship and the Henry Marfell Scholarship during the course or thi s study . Thi s a s sistanc e is acknowledged wit h gratitude .

Grat eful appreciation is a l so expres sed t o the a uthor ' s mo ther for her enco uragement thro ughout this and earlier studies .

vii TABLE OF CONTENTS

Chapter

ONE

TWO

.ABSTRACT

ACKNOV-�LEDG EMEN'l' S T.ABLE 0]' COl-I"'TENTS LIST OF TABLES LIST OF FIGURES INTRODUC'l'ION

REVIEV,' OF LITERATURE

A . The Phy siolo gica l Changes tha t Occur in the Post-Partum Cow

1 • Involution or the uterus

2 . Initiation of cyclic a c tivity

3 . Rel a tion to sub sequent fertility B . The Po st-Partum Interval

1 • Interval t o fir st oestrus

2 . Interva l to involution of the uterus

3. Interval to first breeding

c. Fac tors tha t may Influence the

ii

V

vii

X

xiv 1

3

3 3 7 13

1 5 1 5 17 1 9

Post-Partum Interval 23

1 • Genetic factors 23

2 . A ge and parity of cow 27

3 . Milk pro duc tion and suckling status of c ow ³⁰

4. Sex of c alf 38

5 . Nutrition of dam 40

6 . Sea son and year of c alving 46

THREE MATERIALS AND ME'rHOD 49

A. Source of Data 49

1 . Ma s sey University Da t a 49

2 ^• .Ministry of A griculture and Fisheries' D a t a

B . Metho d o f .Analy sis

51 52

Chapter 1'HREE

FOUR

1 ^• Ma ssey Univers i ty D a t a

( i ) Interval t o fir s t p o st-partum oestrus ( day s ) , m i lk produc tion of the dam (kg ) , and calving interval {day s ) ( i i ) Post-partum cow l iveweights

2 . Ministry of Agricul t ure and Fi sheri e s'

53

53 54

Data ₅₄

( i ) Interval to first p o s t-p artum oestrus 54

( i i ) · Calving interval 5 6

RESULT S AND DISCUSSION A. Ma s sey Univer s i ty Data

6 0 60 60 60 60 61 65 65 66 66 66 70 72 72 74 1 • Po s t-partum oestrous interval

( i ) Blocks ( i i ) Treatmen t s ( i i i ) Age of dam ( iv ) Sex of calf

( v ) Calving da t e

( vi ) Frequency o f o e strous act ivi ty 2 . M i lk produc t i on of dam

( i ) BloGkS ( i i ) Trea tmen t s ( i i i ) Age of dam

( iv ) Sex of calf ( v ) C alving date 3 . Cow livewei ght s

( i ) Blo cks ( i i ) Trea tment s ( i i i ) Age of dam

( iv ) Sex of c a lf ( v ) Calv ing da te

( vi ) Autumn l ivewei gh t of the cow

4. Ca lving Interva l ( i ) Blocks

( i i ) Treatmen t s ( i i i ) Age of dam ( iv ) Sex of calf

75 75 79 79 82 82 82 85 85 85 88 88

Chapter FOUR

FIVE

ix

(

^v

)

Calving date 88

(

^vi

)

Frequency of calving intervals 88

5. Correlations 88

B. Ministry of Agriculture and Fisheries' Data

93

1 • Post-partum oestrous interval

93

( 1)

Year of record

93

(

ⁱⁱ

)

Age of' dam ₉₆

(

ⁱⁱⁱ

)

Sex of' calf' 96

(

^iv

)

Calving date 96

(

^v

)

^Cow liveweight change

99

(

^vi

)

Sire of c alf 99

(

^vii

)

^Mating grOUJ?

99

(

^viii

)

Frequency of' cows showing oestrus

99

2 . Calving Interval 1 01

(

ⁱ

)

Mating group _{1 01}

(

ⁱⁱ

)

Year of' record 1 01

(

ⁱⁱⁱ

)

Age of' dam 1 04

(

^iv

)

Sex of' calf� ¹⁰⁴

(

^v

)

Sire of' calf 1 04

(

^vi

)

Calving date ^{1 04}

(

^vii

)

Frequency of' calving intervals 106

3. Correlations 1 06

CONCLUDING DISCUSSION 1 10

BIBLIOGRAPHY _{1 17}

LIS'l' OE' 'l'RBLES

Table Pa�

2. 1 Summaroy of' some studies reporting the

interval from paroturition to f'irst observed oestrus in various breeds of' dairy _and beef'

cattle 18

2. 2 Interv<=Jl f'rom parturition to involution o'f the uterus

2.3 Summary of' studies reporting the optimum post-partum interval required f'or maximum breeding efficiency in dairy and beef' cows

4. 1 Analysis of variance of' the main effects f'or interval to first post-partum oestrus

4. 2 Least squares means and sta ndard errors f'or post-partU@ interval to first oestrus

1+. 3 Least squares means and standard errors f'or the ef'f'ect of' treatments on post-partum interval

4.4 Cumulative frequency of' post-partum oestrual activity

4.5

4.6

4. 7

Analysis of' variance of' the main ef'f'ects f'or 20-day, 40-day and 60-day milk production

Least squares means and standard errors f'or the ef'f'ect of' blocks on milk production of' the dam

Least squares means and standard errors f'or the effect of' treatments on milk production of' the dam

20

22

62

63

64

67

68

69

71

xi

'l'abl e P age

4.8 Lea st square s means and st andard error s for the ei"fec t of age of dam, sex o.f c alf and

regression c o efficient of calving da t e on milk pro duc tion of the dam

4.9 Ana lysis of varianc e of the m ain eff'ec t s for po st-partum c ow liveweight

4.10

4.11

4.12

4.13

4.14

Lea s t squares means and st andard error s for th e effec t of blocks on c ow liveweight (ke )

Least square s means and standa rd error s for the effec t of trea tment s on c ow liveweight ( kg )

Lea st square s me ans and s t a ndard erro r s for the effec t of age of darn on c ow liveweight ( kg)

Lea s t square s means and standard erro r s ^for the eff e c t of sex of c a lf on c ow liveweight (kg)

The l e a s t square s r egre s sion c o efficient s for the effect of date of c alving and of the

a utumn liv eweight of the cow ^on her liveweight

73

76

77

80

81

83

p o st-Darturn 84

4.15

4.16

4.17

Analy sis of variance of the main effec t s for c a lving interval

Lea st square s means and s t a ndard error s ^for c alving interval

Cumul a tive frequency of c a lving interval

86

87

89

T able 4.18

4.19

Correla tions between time t o first po st-p artum oest�us (X variab le

)

and various cow and c a lf trait s (Y va ria ble s

)

Correla tions be tween c a lvin� interval

(X

^variable

)

and various c ow and calf trait s

90

(Y va r i a bles

)

⁹²

4.20 Ana ly sis of va riance of th e main effec t s for interv a l t o fir st p o st-p artum oestrus

4.21 Lea st squares me ans and st anda rd errors for t he effect of year on interval to firs t p o s t ­ partum oestr u s

4.22

4.23

4.24

4.25

4.26

4.27

Lea st squares means and st andard error s for the effect of age of dam on interval t o fir s t p o st-partum oestrus

Lea st squares mean s and st andard errors for the effect of sex of c a lf and the regre s sion c oeffic i ent s of date of calving and c ow live­

weight c hange on interv a l to first oestrus

Cumul a tive frequency of p o s t -partum oestrual a c tivity

Analy si s of varia nce of t he main effects for c alving interval

Lea st squares means and s tandar d errors for the effec t of mating gro up on c alving interv a l

Lea st squares mean s and st andard error s for the effect of year of rec ord , a ge of dam , sex of c alf and regre s sion coeffic ient of c a lving da te on calving interva l

94

95

9 7

98

100

102

103

1 05

T a ble 4.28 4.29

C um ul a tive frequency of c a lving interval

C orrela tions b etween time t o fir st po st-partum o e s trus

(A

^variable

)

and va rio us cow and c a lf t rai t s (Y va riab l e s

)

xiii

107

108

Figure

4 . 1

l..IST O:B, FIGUHES

Cow liveweight versus interval from

parturition

(

for each Block

)

⁷⁸