RESPONSE TO SELECT I ON FOR OPEN FACE
AND GREASY FLEECE WEIGHT I N ROMNEY SHEEP
A thes i s presented in parti a l ful fi l ment of the requi rements for t he degree of
Doctor of Phi l osophy i n Ani mal Sc i ence at Ma s s ey Uni vers i ty
HUGH THOMAS BLA I R 1981
ABSTRACT
Sel ect i on res ponses and genet i c parameters were e s t i mated on wool , body and reproduct i ve tra i ts i n a New Zea l and Romney fl oc k . I n 1 956
the fl ock wa s d i vi ded i nto 3 sub -fl ocks , each of wh i ch has been a c l osed breed i ng group ( con s i st i ng a pproxi mate l y 80 ewes and 4 rams ) s i nce 1958 .
I n one group the mos t open - faced year l i ng s were retai ned for breed i ng , i n another , those wi th heav i es t yearl i ng fl eece we i g hts , wh i l e i n the t hird rep l a cement s were chosen at random .
Tra i ts exam i ned i ncluded post-s hear i ng l i ve wei ght ( LW ) , grea sy fl eece we i g ht ( G FW ) , cl ean fl eece we i ght ( W ) , qual i ty number ( Q N ) , c haracter grade ( CHG ) , s tapl e l ength ( SL ) , tota l cri mp number ( T CN ) , cr i mp frequency ( C F ) , cl ean scoured yi e l d ( Y ) and mean fibre d i ameter
( MFD) for the ewes and ram and ewe hoggets ; number of l ambs born ( LB ) a n d number o f l ambs reared ( LR ) per ewe j o i ned ; date -of-b i rth ( DOB ) , b i rth wei g ht ( BW ) , wean i ng wei g ht ( WW ) , medu l l ameter i ndex ( M I ) and
face-cover grade ( FC ) for the ram and ewe hoggets and the standard devi at i on of the fibre d i ameter ( SFD ) and percent medul l ated fibres
( PM F ) for the ewe hoggets .
The average i nbreed i ng c oeffi ci ent i ncreased by approx i mate l y 0 . 10 i n al l 3 fl ocks over the 21 years eva l uated . Wi thi n years , s heep wi th t he h i ghest i nbreedi ng coeffi c i ents general l y suffered a depre s s i on i n the l evel of performance .
Heri tab i l i ti es ( h2 ) and genet i c corre l ati ons ( rg ) were ca l cul ated u s i ng t he pate rnal ha l f-sib correl ati on a pproac h . Most h2 e st i mates were s i mi l a r to a l ready publ i s hed val ue s . Estimate s o f the h2 o f ram hogget GFW were s ubs tanti al l y smal l e r than correspondi ng ewe hogget val ues ( 0 . 07 to 0 . 1 5 cf 0 . 28 to 0 . 34 ) . Face-cover grade h 2 i n the face- cover fl ock a ppeared to be much reduced , suggesti ng a pos s i b l e dec l i ne i n geneti c variati on for thi s tra i t .
P henotypi c and geneti c corre l ati on s were cal cul ated amongst al l hogget tra i ts and between ewe hogget and ewe average l i fet i me
performance trai ts . Very h i g h genetic. and phenotypi c correl ati ons were found between h ogget GFW and hogget W . Ewe hogget GFW tended to be pos i ti ve l y a s s oc i ated wi th LB and L R , bot h geneti cal l y and
phenotyp i cal l y . Hogget F C was general l y u n rel ated t o other hogget and ewe tra i t s . Ewe hogget perfo rmance i n LW , G FW , W , QN , SL , T CN , Y and MFD were genera l l y moderately to strongly re l ated wi th the performan ce
i i i
of the s ame ewe i n corres pond i ng tra i ts at o l der ages . There was o ften w i de vari ati on i n the three ( one from each g roup ) genet i c correl at i on e s t i mate s for each pai r of tra i ts . Thi s vari at ion was attributed to e i ther the sma l l n umber of observati on s avai l abl e ( about 80 s i res per f l ock wi th 5 to 7 progeny per s i re ) or chan g i ng geneti c vari ance and covari ance components in the sel ect i on fl o ck s .
Real i zed heri tabi l i ty ( hf) esti mates for FC and hogget G FW ranged between 0 . 39 to 0 . 54 and 0 . 06 to 0 . 19 , res pe ct i vel y . The hf e s t i mates of hogget GFW were i n good agreement wi th the paternal hal f- s i b
correl at i on esti ma te s of h2 deri ved from t h e ram hogget data but were marked l y l ess t han equi val ent estimates obt a i ned from the ewe hogget
data . The h
�
esti mates of FC were genera l l y hi gher than paternal hal f- s i b e s t i mates , but were i n good. agreement wi th e s t i mates deri ved by other workers .I n the face-cover fl ock corre l ated res pon ses were general l y smal l . Pos i ti ve co rrel ated respon ses o f a bout 1 0% were recorded i n LB a nd LR over the 2 1 yea rs eva l uated . I n the fl eece we i ght g roup the components contri buti ng toward i n creased G FW al l showed pos iti ve correl a ted
respon ses . Lamb prod ucti on ( LB a nd LR ) of t he fl eece we i ght group showed a n i ncrease of a bout 30% , rel ati ve to the contro l fl oc k , over the 21 yea rs stud i ed .
AC KNOWLEDGEMENTS
I woul d l ike to thank my supervi sors , Or G . A . Wi ckham and
Profes s or A . L . Rae , for the excel l ent gu i dance they have prov i ded dur i ng the cou rs e of my stud i e s . The i r wi l l i ngness to p ro vi de counsel wheneve r requ i red was great l y apprec i ated .
V
Profe s sor R . D . Ande rson provi ded s t i mul ati ng and rewa rd i ng d i s cu s s i on i n the fi e l d of s tat i sti cal analys i s and h i s hel p i s grateful l y acknowl edged .
T he worki ng envi ronment provi ded by the Department of Sheep Hus bandry staff and post-graduate students wa s a valuabl e source of moti va t i on .
In p arti cu l a r , the s es s i ons wi th Mr Stuart McCutcheon were a l ways reward i ng .
My g ra t i tude i s a l so extended to the farm and techn i ca l s taff , espec i a l l y Mr Bruce Thatcher , who col l ected the i nformati on upon whi ch th i s thes i s i s based ; and to the Computer Uni t staff who assi s ted me i n understand i n g "Betsy" .
A s pec i a l thank you i s due to Mrs A . F . Barton for her ski l ful typi ng of t h i s thes i s wi thi n the restri cted time a va i l a bl e .
T o my wi fe , Al an a , your support and en couragement pl ayed a n i mportant rol e i n enabl i ng me to compl ete what often a ppea red a daun ti ng task .
F i na l l y , to al l of my fri ends who suffered my depre s s i ons and s h a red in my " h i g h s " , thank you .
Cha pter
ONE
TWO
ABSTRACT
ACKNOWL EDGEMENTS L I ST OF TABL ES L I ST OF F IGURES
I NTRODUCT I ON
TABLE OF CONTE NTS
REV I EW OF L I TE RATURE 2 . 1 Introduct i on 2 . 2 Fl eece we i ght
2 . 2 . 1 I ntroduct i on
2 . 2 . 2 Sel ect i on cri te ri a
2 . 2 . 3 Ana l ys i s of di rect res ponse to sel ec ti on for cl ean fl eece we i g ht
2 . 2 . 4 Ana l ys i s of correl ated res ponse s to s e l ecti on fo r c l ean fl eece we i g ht 2 . 2 . 5 Di rect res ponse to sel ect i on for cl ean
fl eece we i ght
2 . 2 . 6 Components through wh i ch di rect res pon se occu rs �
2 . 2 . 7 Correl ated res ponses to sel ection for cl ean fl eece weight
2 . 3 Fa ce cove r
i i
V
i x x i
1
4 4 4 4 5
5
9
1 0
1 6
1 7 1 9
Chapter TWO
THREE
2 . 4 The e s t i mati on of d i rect respon se to sel ecti on
i n domesti c a n i ma l s 24
2 . 4 . 1 I ntroducti on 24
2 . 4 . 2 Sel ecti on i n one direct i on wi thout
a control 26
2 . 4 . 3 Sel ect i on i n one directi on wi th a
control 28
2 . 4 . 4 Di vergent sel e ction 33
2 . 4 . 5 Errors associ ated wi th estimati ng geneti c
res pon se to sel ecti on 33
MATER IALS AND METHODS 3 . 1 Mater i a l s
3 . 1 . 1 T he sheep and their environment 3 . 1 . 2 T he data
3 . 2 Stati s t i cal methods 3 . 2 . 1 I ntroducti on
3 . 2 . 2 The effect of i nbreed i ng
3 . 2 . 3 P henotypi c s tandard dev i ati ons and
4 1 4 1 4 1 46 5 1 5 1 5 3
corre l at i on s 5 3
3 . 2 . 4 Lea st sq uare s e s t imates of the genet i c
response 54
3 . 2 . 5 E s t i mat i on o f g enetic correl ati ons and
her i tabi l i t i es 54
3 . 2 . 6 The use of mi xed model equat i ons to esti mate geneti c respon se
3 . 2 . 7 Cal cul ati on of real i zed responses
6 1 6 2
v i i
C hapter FOUR
F IVE
S I X
SEVEN
E IG HT
N I N E
NON-GENET I C E F FECTS AND T H E E FFECT O F I NBRE ED I NG 4 . 1 Introducti on
Page 6 5 65 4 . 2 The effect of dam age and b i rth / reari ng ra n k 6 5 4 . 3 The effect o f i n breed i ng o n pe rformance 69
PHENOTY P I C AND GENET I C CORRELAT I ONS , HERITAB I L I T I ES AND PHENOTYP I C STANDARD DEV IAT I ONS
5 . 1 Phenotypi c standard devi at i on s 5 . 2 Phenotypi c correl a t i on s
5 . 3 Geneti c corre l at i on s 5 . 4 Heri tabi l i t i e s
THE USE O F T H E I NVERSE OF THE RELAT I ONSHIP MATR I X I N M IXED MODE L EQUAT IONS
D I RECT RESPON SES TO SELECT I ON
74 74 82 86 94
1 00
1 03
7 . 1 Introduct i on 1 03
7 . 2 Di rect res ponse to se l ect i on for open face 105 7 . 3 Di rect response to sel e cti on for h i gh hogget
greasy fl eece we i g ht 1 1 2
CORRELATED RESPONSES TO SEL ECT I ON 120
8 . 1 Introduct i on 120
8 . 2 Correl ated re sponses to sel ect i on for open face 120 8 . 3 Correl ated res ponses to se l ect i on for h i gh
hogget g reasy fl eece we i g ht 123
C ON CL US I ONS 130
B I BL I OGRAPHY 136
L I ST OF TABLES
Tabl e
2 . 1 Sel ecti on cri teri a for the vari ous c l ean fl eece
wei ght sel ect i on experiments 6
2 . 2 N umbers of ewe s and rams u sed i n the various cl ean
f l eece weight sel ect i on experi ments 1 1
2 . 3 Di rect respon ses to sel ect i on for h i gh c l ean fl eece
we i ght 12
2 . 4 C orrel ated res ponses to sel ect i on for h i gh c l ean
f l eece wei ght 18
2 . 5 An i ndi cati on of the s i z e o f genet i c correl ati on
e s t i mates between c l ean fl eece weight and other tra i ts 20 2 . 6 An i ndi cati on of the s i ze o f geneti c correl ati on
e s t imates between greasy fl eece wei ght and other t ra i ts 2 1 2 . 7 Avai l a bl e esti mates of the heri tabi l i ty of face-cover
grade 2 5
2 . 8 Approx imate vari ance equa t i on s for the estimators of
geneti c respon se 37
2 . 9 Formu l a for the cal cul ati on o f a
�
and a� 382 . 1 0 A compari son of h4/MNC• h4/2M0 and h 2 / L 39
3 . 1 Some p hys i ca l a s pects of the two areas u pon whi ch the
experi menta l fl ocks were carri ed 42
3 . 2 Si z e o f ewe mat i ng fl ocks and the i r age c ompos i ti on 44 3 . 3 Number of ram and ewe hoggets recorded i n each sub-fl ock 47 3 . 4 Tra i t abbrev i ati on s and years of col l ecti on 48
3 . 5 Sys tem of gradi ng for face cover 5 1
3 . 6 The combi nati on of dam age , bi rth rank and reari ng rank
to gi ve one fi xed effect 52
4 . 1 T he effect of dam age and b i rth/reari ng rank on the
performance of ewe hoggets 66
4 . 2 T he e ffect of reari ng rank on t he performan ce of ram
hoggets 67
4 . 3 The e ffect of dam age and b i rth/reari ng rank on ewe
average l i fet ime performan ce 68
i x
Tabl e
4 . 4 . The n umber of s i res represented by at l east one son
i n t he fol l owi ng generati on 7 1
4 . 5 The effect of 1 0% i nbreedi ng on performance 73 5 . 1 Phenotypi c and genet i c corre l ati ons and phenotypi c
standard dev i a t i ons from t he ewe hogget data 75-76 5 . 2 P henotypi c and geneti c corre l ati ons and phenotypi c
standard dev i ati ons from the ram hogget data 77- 78 5 . 3 Genet i c correl ati ons between ewe hogget and ewe
a verage l i feti me performance tra i ts 79-80 5 . 4 Phenotypi c corre l ati ons between ewe hogget and ewe
average l i feti me performan ce tra i ts and ewe average
l i fe t i me performan ce phenotypi c standard devi a t i ons 8 1 5 . 5 A compari s on of two methods of der i v i ng standard
errors for geneti c corre l ati ons usi ng control ewe
hogget i n formati on 8 7
5 . 6 A c ompari son o f two methods of deri v i ng s tandard e rrors for heri tabi l i ti es u s i ng control ewe hogget
i nformati on 95
5 . 7 Esti mates of her i tabi l i ty and thei r standard erro rs
from the ewe hogget data 96
5 .8 Est i mates of heri tabi l i ty and the i r standard errors
from t he ram hogget data 97
5 . 9 E s t i mates of heri tabi l i ty and thei r standard errors
from the ewe average l i fetime performance data 98 6 . 1 Average yearl y s i re breedi ng val ue esti mates for ewe
hogget greasy fl eece wei ght wi th the i nc l u s i on of the i nverse of the rel at i ons h i p matri x i n t he mi xed model
equa t i ons 102
7 . 1 The effect of t he magni tude of the cr�/cr� ratio o n
sol uti ons t o t h e mi xed model equat i ons 1 04 7 . 2 Esti mates of rea l i zed heri tabi l i ties and thei r s tandard
errors for face-cover grade 1 09
7 . 3 Esti mates of rea l i zed heri tabi l i ti es and thei r s tandard
errors for greasy fl eece wei ght 1 1 5
7 . 4 F l o ck average c umul ated sel ecti on d i ffe renti al s ( FACSD )
for each sex i n the two sel ecti on fl ocks 1 1 9 8 . 1 Corre l ated respon ses to sel ecti on for open face and
t he i r standard errors 1 2 1
8 . 2 Corre l ated responses to sel ect i on for greasy fl eece
we i ght and the i r standard errors 1 24
Figure
4 . 1
7 . 1
7 . 2
7 . 3
7 . 4
L I ST OF F I GURES
The average rate of i ncrease i n i nbreed i ng i n each of the three s u b-fl ocks
E s t i mated and predi cted rates of res ponse to sel ecti on for ewe hogget face-cover grade
E s t i mated and predi cted rates of res ponse to s e l ecti on for ram hogget face-cover grade
E s t i mated and predi cted rates of res ponse to sel ecti on for ewe hogget greasy fl eece wei ght
E s t i mated and predi cted rates of respon se to s e l ecti on for ram hogget greasy fl eece wei ght
xi
70 1 06
1 07
1 1 3 1 14
