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OESTROUS BEHAVIOUR AND FERTILITY IN ROilNEY MARSH EWES
A The s is presented in part ial
tulfilme nt ot the requirements for the degree of Doctor of Philosophy in An imal Scie nce
at
Ma ssey Un ive rs ity
TANG SRNG CH' ANG 1 967
ACKNOWLEDGMENTS
I w ish t o express my gra t itude for the assistance rece ived dur ing the course of th is study: to my co llea gues who in one way or anot her, unknown to me have shouldered t he burden w hich but for this Thesis, w ould have been my due; to the Massey sheep farm staff, both past and p resent, for t heir w o rk in t he ca re of the sheep flock studied herein and for t heir co-opera tion often extended bey ond the ca l l of duty; to tbe Massey L i brary staff for t he i r ever rea dy
willingness to help and to tbe Counc il of Ma ssey Univers ity for tbe oppo rtun ity a nd fa cil ities to underta ke t he present work. In add i t i on, I w i sh to acknowledge my indebtedness and appreciation to Mr. Bruce Tha tcher for h is constant
ass istance in t he collection of da ta a nd in many other ways;
to Professor A.L. Rae for h is encouragement, guidance and lasting counsel a nd to my wife, for making my work more presenta ble in her typing of t his Thesis.
I. IN'l'RODUCT ION II. SOURCE OF DATA
1 . Management of experimental animals 2. Data and da ta collect ion
�
al
Live weight cha ra cters b Oestrous behaviour c Fert il itJ of the ewe I II. METHOD OF ANALYSIS1. Est imat ion of env ironmental e ffects
2. Inte raction between s ire and year in hogget cha racte rs
3· Prel im inary analy s is of ann ua l fertil ity of the ewe
!
al
Cbi-square analy s i sb Weighted regress ion analysis
c Least-squa res regre s s ion analy sis
4 . Est imat ion ot phenotypic and genet ic parameters
�:�
Paternal ba lt- s i b analy s isCovariance analys is be tween dam and daughter ( i)
( i i) Maternal environment and weaning we1gbt Carryove r ma te rnal effect and
post weaning cha racters
(i i l) Est imat ion of heritabil ity and genetic corre lat ion
(iv) Computat ion of covariance between dam and daughter
5· Construction of select ion ind ices
IV. RESULTS AND DISCUSSION
1 . Est imates o f e nvironmental e ffects
( a ) Intera ct ion between age ot dam and
type of birt h and rea ring
( b) Est imates of environmental e ffects on bogget characters
(c) Est ima tes of environmental e ffects on fe rt il ity of the ewe
Discussion
2. Sire-year inte raction iD hogge t cha racters
1 3 3 3
5 5 6
8 10 16 18 19 22 24 26 26 30
32 36 39 41 43 48 4 8 4 8
5 1 S' 59
63
3. Pre l imina ry resu l t s ba se d on ana lysis of
a nnua l fe rt i l ity of the ewe 65
{a) Test of m u t ua l independence by ch i-squa re
a na lysis 6 6
(b) We ig hted and lea st-squa re s reg ression of annual fe rt i l ity of t he ewe on num be r
o f hogge t oestrus 6 9
4. Est imate s o f phenotyp ic corre l a t ions 73
(c)
Hogget cha ra ct e rs
Re lat ive import a nce of growth and age in the
d e termina t ion of number of hogget oestrus Hogget c ha ra ct e rs a n d fe rt i l ity o f t he ewe
73 76 79
5· Est ima tes of he r it a b i l ity a n d ge net i c corre l a t ion 83
(a) Es t ima t e s of heritability 84
(i) Hogge t c ha ra c t e rs 84
(U) Fertility of the ewe 86
6.
Discus sion
(b) Est ima t e s of gene t ic corre l a t ion
(i) Pa t e rnal ha lf-si b a na lysis
(ii) Est ima t e s of covariance between dam and daughte r
(i11) Regression o f da ughte r on dam and
covariance analysis between dam a nd d a ughter
D i s cussion
Dis cussion (Est ima tes of he rita bil ity a nd gene t i c corre l a t ion)
The s e l e c t ion ind ices
{ a) Index 1 ( I1) (b) Index 2 (I2) (c) Index 3 (I3)
(d) Properties of the selection indices
D i s c u s s io n
V. APPLICATIONS VI. SUMMARY
VII. LITERATURE CITED
88 94 95 97
98 1 02
1 07 1 1 1 1 1 2 1 1 3 114
1 1 5 1 1 7 1 21 1 27 1 33
