the permission of the Author.

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

a copy to be downloaded by an individual for the purpose of research and

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

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WEN G KEON G CHEON G 19 7 7

INBREED ING AND POPULATION

STRUCTURE STUDIES IN THE NEW ZEALAND ANGUS BREE D

A thesis presented in par tia l ful f ilmen t of the requirement s

fo r the degree of

Mas ter of Agr icul tural Sc ience in Animal Sc ience at

Massey Univers i ty

. -�

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'

To my Mo ther and Father

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'

iii

ABSTRACT

The breed s truc ture and genet ic his tory of the New Zealand pedigree Angus breed were analysed by Rober tson and Asker ' s ( 1951) mod if ica t io n

o f the Wright-McPhee (19 25) pedigree sampling method.

The pat tern of the breed s tructure ob tained is generally s imilar t o that found in o ther studies , but i t is both diffuse and dynamic owing to the p resent rapid expans ion of the breed . There are changes taking place in the herd composi tion o f the major breeders ' herds and many new herds have yet to f ind their l evel in the s truc ture .

Considerab le emphasis has been p laced on the use of imported

animals in the development of the breed . Of all herds registering in Volume 6 1 of the herd book, 20.5 % used imported s ires , and the percentage o f genes in the breed in 1966/67 derived from animals impor t ed since 1863 was 8 5.4.

The mos t impor tant herd in 1969 has a genetic contribution to the breed o f 21 . 9 per cen t , while the contribut ions of the four next mos t

impor tant herds wer e 8.7 2, 8 . 7 , 4 . 7 and 3 . 7 per cent . In the four

generat ion pedigrees from which these f igures were derived , the

contribut ion o f impor ted animals was 4 2 . 4% . The relat ionship between herd s i ze and impor tance of the herd was considered . Herd duration was

also discus s ed , in so f ar as i t relates to improvement of the breed . The animal with the highest rel ationship to the breed w as Blackle g (11. 6 5% in the 1900 pedigree sample) . B u t overall , the mos t impor tant animal over the period 1900-19 6 6 / 6 7 was Lancer o f Advie. Of the 3 3

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iv

s ires and 9 dams whose d irect relationships are 3 . 0% or more in any o f t h e 8 sample years , 19 s ires and 3 dams were impor ted .

The to tal inbreeding in 1966 / 6 7 (bas e year 1863) was 1 . 80% . Thi s c ompr ised 0 . 09% current inbreeding , 0 . 95% long-term inbreeding , and 0 . 76% strain inbreeding. The index of subdivis ion calculated from the non-current and long-t erm inbreeding is 1 . 79, indicating that there is onl y a slight tendency towards family format ion in the breed .

The effec tive genera tion length is approximately 5 . 6 years . Abo u t 50-56% of the animals in the 196 6 / 6 7 sample wer e sired by bulls 4 year s old or younger , while about 38% are from dams 4 years or younger .

I t is unlikel y tha t there is much genet ic var iation be tween herds . This is because bulls from maj or breeders ' herds are used widely throughout the breed while about 80 per cent of sires and 37 per cent of dams are bred in herds o ther than the one in which they were used.

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ACKNOWLEDGEMENTS

-The author wishes to thank most sincerely his supervisor, Professor A.L. Rae for his invaluable assistance and guidance throughout this study and for helpful criticism in the pre

paration of this thesis.

Appreciation is also expressed to Mr A.B. Pleasants for his advice in computing matters. The author is also grateful to Ms Raynor Ewart for typing this manuscript.

V

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"Lewontin confessed that each year he lectures on inbr eeding, and each year he reali ses tha t .he does no t yet completely unders tand it . "

Bruce Wallace , 1 9 6 8 .

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Chapter

1 2 3

4

TABLE OF CONTENTS

ABSTRACT

ACKNOWLEWEMENTS LIS T OF TABLES LIST OF FIGURES LIST OF APPENDICES INTRODUCTION

BREED EXPANSION REVIEitl OF LITERATURE

I. THE ^MEASUREMENT OF INBREEDING: S OME THEORETICAL CONSIDERATIONS

II. ALTERNATIVE APPROACHES TO INBREEDING

�

iii V

ix xi

xii

1

4 7

7 1 2

· III. COEFFICIENTS OF RELATIONSHIP 1 7

'

A. Relationship coefficients between collateral relatives

B. Direct relationships

IV. THE MEASURE!1E.NT OF INBREEDING IN COMPLEX PEDIGREES V. THE EFFECTS OF INBREEDING

1 8 1 8 1 9 2 3

A. Evidence of inbreeding depression in farm animals

24

B . Explanations of inbreeding depression and hybrid

vigour 27

VI. S TUDIES OF GENETIC CHANGES IN LIVESTOCK POPULATIONS 29

METHODS _ANDMATERIALS I. METHODS

II. DATA

33 33 37

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I

Chapter

_�

5 GENEriC ANALYSIS 40

I. THE INFLUENCE OF IMPORTATIONS 40

I I. AMOUNT OF INBREEDING 48

I I I. HOMOGENEITY OF THE BREED

56

IV. GENERATION LENGTH 65

V. ll1PORTANT HERDS 75

A.

Genetic contribution of important herds

83

B.

Important animals

87

6 BREED STRUCTURE 9 3

7 REGIS·rRATION PRACTICES 99

I. HERD SIZE 1 01

I I. THE USE OF IMPORTED STOCK BY NEW-ZEALAND HERDS 1 05

I I I. THE USE OF BULLS FROM PROMINENT NEW ZEAL.AND HERDS 1 07

IV. HERD DDRATION 1 1 0

8

DISCUSSION 1 1 3

BIBLIOGRAPHY

1 22

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ix

LIST OF TABLES

Table _�

2 . 1

3 · 3 3 · 4

5 . 3

5 - 4

5 - 5 5 . 6

5 - 7

5 . 9

5 . 1 0 5 . 1 1

5 . 1 2

Proportionate increases in number of females registered per

^annum

and number of herds during seven periods of

time .

The effect of inbreeding on body-weight and milk yield.

Inbreeding and subdivision of the pure breeds of live s tock .

Proportion o f the registrations included in each sample .

Numbers of AngQs cattle imported into New Zealand during ten-year periods from 1 863 to 1 975 .

�ngus importations 1 863-1 976 distributed according to country of origin and year of entry into New Zealand.

The effect of the different importations on the breed at ten yearly intervals .

The extent o f current inbreeding in eight sample years for the New Zealand pedigree AngQs .

Extent of current inbreeding in other cattle breeds . Amount of total inbreeding in eight sample years for the pedigree Angus in New Zealand.

Inter se relationship and non-current inbreeding, subdivided into long-term and strain inbreeding in eight sa�ple years for the Ne}'l Zeala.nd pedigree Angus .

Contributions by imported animals to the non-current

inbreeding and inter se relationship ties in the New Zealand pedigree Angus .

Number of inter se relationship ties contributed by �he seven most often appearing imported animals and the three most often appearing New Zealand herds in eight samp le years for the New Zealand pedigree Angus .

Average length of interval between generations .

Parent-offspring intervals and average generation length for pedigree Angus cattle in New Zealand.

Differences between the various parent-offspring intervals ( years ) for the New Zealand pedigree Angus.

6 25

30

39

42

43 44

49 51

53

58

62

67

72

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Table

5. 1 4

5 1 5

7 . 4

7 . 5

'

Herds in order of importance for each of the three methods of analysis used to determine the important herds of the

X

New Zealand pedigree Angus. 77

Years of origin and dispersal of the most important pedigree

Angus herds in New Zealand in 1 900, 1 9 30 and 1 966/67.

.

79 Distribution of herds supplying the sires in the four

generation pedigrees of samples of females born in 1 900 , 1 930

and 1 966/67. 82

Genetic contribution of Imported and the nine major herds

to a sample of pedigree Angus females born 1 966/67. 85

Percentage direct relationship for animals important to the

breed in eight sample years. 88

Herd types and registration practice s of herds registering

in volume 61 of the New Zealand Aberdeen Angus Herd Book. 1 00 Analysis of Breeders ' Herds ( 1 ) , ( 2) , ( 3) and ( 4 ) by numbers

of females registered in volume 61 of the New Zealand Aberdeen

Angus Herd Book. 1 02

Numbers and percentages of herds in each stratum using

imported sires and dams. 1 06

Numbers of herds in each stratum using bulls from B.H. ( 1 )

herds. 1 08

Percentages of sires and dams bred in herds other than the one

in

which they were used, in eight samples of the pedigree Angus

breed in New Zealand. 1 09

Percentage dis tribution of Angus breeders distributed according

to duration of breeding effort. 1 1 1

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xi

LIST OF FIGURES

Figure Page

2 . 1

5-3 5-4

5-5

5. 6

6. 1

Growth of the Angus breed in New Zealand: number of male and female regi strations in each volume of the New Zealand Angus Herd Book since 1 91 7 .

The 1 6 possible tie s in an eight-line pedigree.

An actual pedigree drawn according to Robertson and Asker ' s ( 1 951 ) modification of Wright ' s "Short Method".

Angus importations 1 863-1 976.

The genetic contribution of foundation s to ck and impor

tations since 1 863 to eight samples of pedigree Angus females.

Current inbreeding for each of the 8 sample years.

Non-current inbreeding subdivided into long-tem and strain inbreeding.

Distribution of the sire-son and sire-daughter intervals in the New Zealand p edigree Angus for the 8 sample years.

Distribution of the dam-son and dam-daughter intervals in the New Zealand pedigree Angus for the 8 sample years.

Diagrammatic representation of breed structure based on regis tration data in volume 6 1 of the New Zealand Aberdeen Angus Herd Book.

5 34

36 41

45

50

52

68

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Appendix I II III

IV V

VI

VII VIII

'

LIST OF APPENDICES

Number of male and female registrations in each volume of the New Zealand AngQs Herd Book .

Number of female registrations and number of herds in each of the eight 1 0-year periods ( 1 900- 1 970 ) .

An example of the use of Wright ' s ( 1 922 ) formula for the computation of the coefficient of inbreeding.

An example of the use of coancestry for computing ipbreeding coefficients .

Number of male and female pedigree Angus cattle imported into New Zealand since 1 86 3 .

List of importations

(

^{1 863-1976}

)

^.

Parent-offspring intervals of the New Zealand pedigree Angus for eight sample years .

Prominent animals from studi es of various cattle breeds .

xii

128 129 130 131

134 136

152 160