Developmental patterns of plasma insulin-like growth factor-I in sheep : a thesis presented in partial fulfillment of the requirements for the degree of Master of Agricultural Science in Animal Science at Massey University

Copyright is owned by the Author of the thesis. Permission is given for

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

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DEVELOPMENTAL PATTERNS OF P LAS MA INSULIN-LIKE GROWTH FACTOR-I IN SHEEP

A thesis presented in partial fulfillment of the requirements for the degree of

Master of Agricultural Science In Animal Science

at Massey University

CHRIS TINE A ROBERTS

1989

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ACKNOWLEDGEMENTS

With graditude I thank my supervi s ors , Drs S . N. McCutcheon and H . T . Blai r , for their valuable advice and a s s i s tance throughout the

experimental work and writing up of thi s s tudy .

T o Pro f e s s or P . D . Gluckman and Dr . B . H . Breier, Developmental Phys iology Laboratory , Department of Paediatri c s , University o f Auckland Medical School, _I am grateful f or the ir extended s ource o f knowledge a s well a s for the analyses o f plasma I GF- I .

I tha nk Mr M . L . Carter, Mrs J . A . Rumba l and Mi s s M . F . S c ott of the Phys iology Laboratory, Department of Animal Science , Massey

Univers ity , f or the ir technical expertise and a s s istance both in collecting and analyz ing s ample s .

I further a cknowledge the technical a s s istance o f Miss R . A . Watson and Mr D . A . Hamilton of the Nutrition Laboratory, Department of Animal S c ie nce and Mr . W . E . Pomroy, Department o f Para s itology Laboratory in the Veterinary Pathology and Public Hea lth , for their instruction in a nalys i s of pasture digestibil ity and faecal egg counts , res pectively .

Appre c iation is expre s sed to Mr L . Willi ams for h i s watc h f ul e ye and tender c are o f my experimental animals , without which there would h a ve been nothing to a nalyse , and to my fellow graduate s tudents , Mark Carter, Peter Morgan, Leon Pi j l s , Peter Walsh , Ma chteld van Maanen and Zhen Zhong Xu f or the i r many hours of voluntary help collecting

s ample s .

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I thank Rota ry International and the many pe ople involved with Rota ry, both in the United States and New Zealand, f o r the i r f inancial and m o r a l s upp o rt . I am grateful f o r the oppo rtunity they gave me to come to New Zea land, not only fo r the a cademic studie s but als o f o r the m a n y expe riences and f r iendships which have developed . The Johannes August Ande rs on and G . O . Ansti s s Schola r s h ip s a re als o remembered fo r a s s i stance o f pe r s onal finance s . The C . Alma Bake r Trust, M a s s ey Univers ity Re s earch Fund and the Medic al Re s e a rch

Coun c il o f New Zealand a re a cknowledged for their f inancial support of thi s re s ea r c h e xpe riment .

A spec i a l thanks to Stua rt McCutcheon fo r go ing beyond the call of duty ; v i s its to the ho spital ( n o matter what the time ) , s c rap ing me off the p avement, be ing a f r iend at all times with ready a nd willing e a r s to li sten and always willing to lend a hand ( o r mind) . Thank s .

I thank the many friends, flatmates, fellow students and staff membe r s who have enc ouraged me during my studie s .

F inally, I e spe c ially tha nk my parents and family f o r thei r love and s uppo rt, Andrew Spence f o r h i s encoura gement, f a ith and love, and my Lord f o r h i s many ble s s ings .

TABLE OF CONTENTS

Page

ACKNOWLEDGEMENTS . . . i i LIST OF TABLES . . . v i i i

LIST OF FIGURES . . . ix

LIST OF ABBREVIATIONS . . . x

CHAPTER I: INTRODUCTION LIVESTOCK BREEDING P ROGRAMMES AND THE ROLE OF GENETIC MARKERS .^. . . . 1

( a ) Lean meat production ^{. . . .} . ^. . ^. . ^{. .} . . . ^. . . . ^{. .} . ^{. . . . . .. . .} . . ^. 1

( b ) Wool production ^{. . .} . ^{. .} . . ^{. . . . . . . .} . ^. . ^{. . .} . ^{. . . . . . . .} . ^. . . ^. . . ^. . 2

( c ) Milk production ^{. .. .} . . . ^{. .} . ^{. . .} . ^. . . . ^{. . . .} . ^. . ^{. . . .} . ^{. . . . .} .^{. . .} . 2

L imitations of Cur rent B reeding Programme s . ^. . ^. . ^{. . . . .} . ^. . ^{. .}. . . . ^. . 3

Genetic Markers ^{. . . . . . . . . . . . . . .. ..} . . ^{. . . . . .} . ^{. .} . ^{. ..} . ^{. . . . .} . ^{. . . . .} . . ^. 3

( a ) Enzyme p o l ymo rphi sms and enzyme a ctivity in t i s s ues ^{. . . .}4

( b ) Restriction f r agment length polymo rphisms ( RFLP s ) ^{. . . .} . ^. 5

( c ) Metabolic p a ramete rs . ^{. .} . . . ^. . ^. . ^{. . . .}. ^{. .} . ^. . . ^{. . . . .} . ^{. . . . .} . . . 6

COMPONENTS OF THE SOMATOTROPIC AXIS AS GENETIC MARKERS ^{. . . . .} . ^{. . . . . .}6

DISCOVERY AND STRUCTURE OF INSULIN-LIKE GROWTH FACTORS ( IGFs ) ^{. . ..}10

P RODUCTION OF IGF-I .^. . . ^{. .} . ^{. . .} . ^{. . . . . . . . . . . . . . . . . . .} . ^{. . . . . . . . . . . . . . .}12

IGF BINDING PROTEINS ^{. . . . .} . ^{. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .} . ^{. . . .}14

IGF RECEPTORS ^{. . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .}16

ACT IONS OF IGF-I ^{.. . . . . . . . . . ..} . ^{. . . . . . . . . . . . . .} . ^{. . . . . . . .}. ^{. . . . . . . . . . .}17 iv

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Page

FACTORS AFFECTING IGF-I LEVELS IN CIRCULATION ^{. . . . . . . . . . . . . . . . . . . .}19 Ontogenetic Development ^{. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .}19

Sex o f Animal and Gonadal Steroids .. . . . . . . . . . . . . . . . . . . . . . . . . . .2 1 Diurnal Variation ^{. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .}2 3 Nutrition ^{. . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .}2 3 Para s ites ^{. . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .}2 4

EVIDENCE FOR A GENETIC ASSOCIATION BETWEEN IGF-I AND

PRODUCTION TRAITS ^{. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .}2 5 G rowth ^{. . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .}2 5 Reproduction ^{. . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . .}2 9 Lacta t ion ^{. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .}2 9 PURPOSE AND SCOPE OF THE INVESTIGATION ^{. . . . . . . . . . . . . . . . . . . . . . . . . . .}30

CHAPTER I I: EXPERIMENTAL

P age

ABSTRACT ^{. . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . .}32

INTRODUCTION ^{. . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .}33

MATERIALS AND METHODS ^{. . . . . . . . .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .}35

Animals and Exper imental De s ign ^{. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . .}35

Live We ights and Blood Sampling ^{. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . .}36

Chemical Analys e s ^{. . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .}3 6 Faecal Egg Counts ^{. . . . . . .. . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . .}36

Pube rty in Females ^{. . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .}37

Testis Di amete r ^{. . . . . .. . .. . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .}37

Fleece We ight ^{. . . . . . . . . . .. . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .}37

Pasture Analyses ^{. . . . . . .. . . .. . . . . . . . .. . . . . . . . . . . . . . . . . . . . .. . . . .}37

Statistical Analyse s ^{. . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .}38

RESULTS ^{. . . . . . . . . . . . . . . . . . .. . . . . .. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . .}38

Live We ight ^{. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . . .}38

Pla sma IGF - I Concentrations ^{. . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . . .}39

Puberty in Female s ^{. . . . .. . . . . . . .. .. . . . . . . . . . . . .. . . . . . . . . . . . . . . .}3 9 Te s ti s Di amete r ^{. . . . .. . . . . . . . . . .. . . . . . . . . .. . . . .. . . . . . . . . . . . . . . .}4 7 Fleece We ight ^{. . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .}47

Pa s ture Analyse s ^{. . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .}5 1 DISCUSSION ^{. . . . . . . . . . . . . .. . .. . . . . .. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . .}5 1

v i

CHAPTER I I I : GENERAL D I SCUSSION

vii

Page GENERAL D ISCUSSI ON ^{. . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . .}55 REFERENCES ^{. . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . .}6 3

LIST OF TABLE S

Table 1 . Effects of sex, rea r ing rank, fae c al egg counts plasma non-este rified fatty a c i d c on centrations

v i i i

plas ma IGF-I concentrations on live we ight . . . 41

Table 2 . Effects of sex, re a r ing rank, faecal egg counts and pla sma non-este rified fatty a c i d c on centrations on

pla s ma IGF-I . ^. . . ^.. . . ^.. . . . ^. . . . ^. . . ^. . . . ^. . . ^. . ^. . . . 43

Table 3 . Pea r s o n intracla s s co rrelati ons for pla sma IGF-I at

nominal 115 to 490 days of age ^. . ^{. . .} . . ^{. .} . . . . .^. . ^. . . . ^{. .} . 44

Table 4 . Effects o f rearing rank, live we ight and puberty on pla sma IGF-I concentrations in female hoggets

at nominal 2 52 days of age ^. . . . ^. . ^.. . . ^{. . . . .} . . . ^.. . . ^. . ^. 47

Table 5 . Effects o f s ex, re a r ing rank, mean pla sma IGF-I concentrations and mean live we ights on total grea s y grea s y fleece weight . . . .^. . ^. . . . ^{. .} . . . ^. . . . ^. . . . 51

LIST OF FIGURES

Figure 1 . Live weight of female and male, s i ngle and twin

sheep over time . . . ^. . . . ^. . ^. . ^{. . .} . . ^{. .} . . . ^. . . . ^. . . . 40

Figure 2 . P l a sma I GF-I concentrati ons in female and ma le,

s ingl e and twin sheep ove r time . . . ^. . ^. . . . ^. . . . ^. 42

Figure 3 . Propo rtion of fema les which h a d shown fi rst o e s trus

by nominal 2 38, 252, 265 and 2 94 days of age . . . 45

Figure 4 . P l a s ma IGF-I concentrations in fema les whi ch had atta ined f i rst oestrus compa red to tho se which had

not a t nominal 252 days of a ge . ^. . . . ^. . . . ^{. .} . . 46

Figure 5 . Ave r age te s tis diamete r mea su rements in s ingle and

twin males over time . . ^. . . . ^. . . . .^. . ^. . ^{. .} . . . 48

Figure 6 . Te s t i s diamete r to live we ight ratio in s ingle and

twin males over time . . ^. . . . ^. . . . . ^. . . ^.. . . ^. . . . .^. . ^{. .} . . . ^. 4 9

Figure 7. Predicted in vivo o rganic matte r dige stibility of s amples of pa sture gra zed by experimental animals

thr o ughout the experiment .^{. . . . . . . . . . . .} . . ^{. .} . ^. . . . . ^. . . ^. . . ^. 50 ix

ANCOVA CV

FEC g

h r I GF kDa kg MAN OVA ml

NEFA ng OMD RFLP S . E . M . ST

LIST OF ABBREVIATIONS

analysis o f c o va riance coef ficient of va riation degrees Celsius

faecal egg c ounts gravitational fo rce hour

in sulin-like g rowth f acto r kilo Dalton

kilogram

multiva riate an alysis of variance millilitre

non-esterified fatty acid (s ) nanogram

o rganic matte r digestibility

restriction f ragment length polymorphism standard e r r o r about the mean

s omatotropin

X