B L U P -A N A L Y S IS O F G E N E T IC T R E N D S IN T H E D O H N E M E R IN O

H .C . d e K le rk an d H .J . H e y d e n ry c h *D o h n e A g r ic u ltu ra l R e s e a rc h In s titu te , S tu t te rh e im a n d ‘ U n iv e rs i ty o f S te lle n b o sc h ,

S te lle n b o sc h , R e p u b lic o f S o u th A fr ic a

S U M M A R Y

T h e D o h n e M e r in o is a S o u th A fr ic a n b re d m u tto n -w o o lle d s h e e p sp e c if ic a lly b r e d fo r th e so u r-g ra ssv e ld a re a s . A lth o u g h p h e n o ty p ic a lly w e ll d o c u m e n te d , l i t t le w a s k n o w n a b o u t its g e n e tic d e v e lo p m e n t in e co n o m ic a lly im p o r ta n t t r a i ts u n t il th e a d v e n t o f B L U P - m e th o d o lo g y . T h is p a p e r d e sc rib e s g e n e tic t r e n d s in g re asy f le e c e m a ss a n d b o d y m ass tra i ts o v e r th e w h o le d e v e lo p m e n t p e r io d a n d th re e d is tin c t p h a s e s o f d e v e lo p m e n t . G e n e t ic p ro g re s s w as s lo w b u t o b v io u s d if fe re n c e s in th e r e sp o n se g r a d ie n ts o c c u r re d in th e th re e d e v e lo p m e n ta l p h a se s . W ith in p h a se s th e d if fe re n t t r a i ts m e a s u re d r e a c te d s im ila rly .

IN T R O D U C T IO N

T h e D o h n e M e r in o is o n e o f sev e ra l S o u th A fr ic a n sh e e p b r e e d s (a ls o th e A fr in o , D o rm e r , D o rp e r , V a n d o r a n d V a n R o o y ) w h ich w e re sp e c ia lly d e v e lo p e d fo r c e r ta in h a rsh a g r ic u ltu ra l e n v iro n m e n ts , w h ile a t th e s a m e tim e sa tis fy in g sp e c if ic m a rk e t re q u ire m e n ts . T h e a im in d e v e lo p in g th e D o h n e M e rin o w as to ev o lv e a m u tto n -w o o lle d s h e e p th a t w as a d a p te d to th e c lim a tic a n d v e ld c o n d itio n s in th e so u r-g ra ssv e ld a r e a s in th e E a s te r n p a r ts o f S o u th A fr ic a (K o tz e , 1951). F u r th e r r e q u ire m e n ts w e re a h ig h fe rtil ity , a h ig h lam b g ro w th ra te , g o o d q u a li ty w o o l w ith o u t h a ir , c o lo u re d f ib re s o r k e m p , a n d th e a b ility to lam b in a u tu m n as w ell a s in sp rin g .

C o m m e n c in g in 1939 a t th e D o h n e R e se a rc h S ta tio n , G e r m a n M e r in o (p re s e n t ly S o u th A fr ic a n M u tto n M e r in o ) r a m s w e re m a te d to M e rin o e w es to p ro d u c e h a lf -b re d la m b s fro m w hich th e D o h n e M e r in o w a s d e v e lo p e d .

A lth o u g h b a se d o n o b je c tiv e m e a su re m e n ts a n d sc ien tif ic m e th o d s , th e d e v e lo p m e n t o f th e D o h n e M e r in o w a s n o t e x e c u te d as a s e le c tio n e x p e r im e n t w ith a g e n e t ic c o n tro l , b u t as a c o m p re h e n s iv e b re e d in g a n d s e le c tio n p ro c e ss , w h ile a lso c o n s id e r in g th e fu tu re a c c e p ta b ility o f th e b r e e d to th e fa rm in g in d u stry . T h e r e f o r e th e r e w a s n o sc ien tif ic p ro c e d u re a v a ila b le to m e a s u re g e n e tic p ro g re s s in th e e c o n o m ic t r a i t s o f th e b r e e d u n til B L U P -m e th o d o lo g y b e c a m e a c c ess ib le fo r g e n e ra l u se .

T h e p u rp o se o f th is p a p e r is to d iscuss so m e g e n e tic t r e n d s in th e D o h n e M e r in o a s a typ ica l e x a m p le o f th e a p p lic a t io n o f B L U P -m e th o d o lo g y to s tu d y th e g e n e t ic h is to ry o f a new fa rm a n im a l b r e e d d u r in g its in it ia l s ta g es o f d e v e lo p m e n t.

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M A T E R IA L A N D M E T H O D S

A ll D o h n e M e r in o sh e e p b o rn d u r in g th e d e v e lo p m e n t p e r io d 1948 to 1985 (a p p ro x im a te ly 10 000 in d iv id u a ls ) w e re in c lu d e d in th is s tu d y . D a ta in c lu d e d o b se rv a tio n s o n b o d y m ass a t b ir th , a n d a t 100 days, 180 d ay s a n d 18 m o n th s o f a g e , as w ell as g re asy f le e c e m ass a t th e l a t te r ag e .

T h e B L U P A n im a l M o d e l P ro g ra m o f th e S o u th A fr ic a n D e p a r tm e n t o f A g r ic u ltu re an d W a te r S u p p ly , as a d a p te d a n d f u r th e r d e v e lo p e d by D e lp o r t (1 9 8 9 ) w as u se d to a n a ly se th e d a ta .

A m ix e d m o d e l w a s u se d to d e sc r ib e th e o b se rv a tio n s . F o llo w in g B la ir (1 9 8 1 ) w h o w o rk e d w ith s im ila r sh e e p d a ta , a ll f irs t o rd e r in te ra c t io n s w e re e x c lu d ed fro m th e m o d e l w h ich is g iv en in th e fo llo w in g e q u a t io n .

^ i jk lm f1 + a i + b j + c k + ^1 + ^m + -e ijk lm

w h e re Y jjy m is a n in d iv id u a l p h e n o ty p ic o b se rv a tio n ,

ju is th e p o p u la t io n m e a n

aj is th e sex e f fe c t (m a le o r f e m a le )

b j is th e fixed a g e o f d a m e ffe c t ( m a tu re o r im m a tu re )

cj. is th e fixed b i r th s ta te e ffe c t (s in g le o r m u ltip le )

d j is th e fixed a v e ra g e b ir th y e a r e ffe c t, f re e f ro m g e n e tic tre n d

f™ is th e r a n d o m e f fe c t o f th e m 1*1 a n im a l in th e i1*1 y e a r (p re d ic te d b r e e d in g v a lu e ) , an d

e ijk lm ^ le r a n d o m re s id u a l e f fe c t fo r e a c h o b se rv a tio n .

A s su ch , th e m o d e l r e p re s e n ts a s in g le t r a i t a n im a l m o d e l in w hich b r e e d in g v a lu e s a re p re d ic te d fo r a ll a n im a ls .

D u e to th e la rg e n u m b e r o f e q u a t io n s in v o lv ed , i te ra t iv e p ro c e d u re s w e re e m p lo y e d . B la ir an d P o lia k (1 9 8 4 ) c o n s id e re d so lu tio n s c o n v e rg e d w h e n th e c o n v e rg e n c e c r i te r io n w as less th a n 0,0001 kg (s h e e p d a ta ) fo r b o th fix ed a n d ra n d o m e ffec ts . In th is s tu d y i te r a t io n s w e re lim ite d to 3 0 0 ro u n d s a n d th e n c o n s id e re d a s co n v e rg e d .

G e n e t ic t r e n d s w e re o b ta in e d by a v e ra g in g th e b re e d in g v a lu e s o f a n im a ls b o rn w ith in sp ec ific y e a rs (e x c lu d in g b a s e p o p u la t io n a n im a ls ) . R e g re s s io n s w e re e m p lo y e d to d e te rm in e th e g e n e tic t r e n d o v e r th e e n t i r e p e r io d as w ell a s fo r th r e e d is t in c t p h a se s . T h e s e w e re th e in itia l p h a s e (1 948 - 1955) w h e n sm a ll n u m b e rs o f c ro s sb re d a n im a ls w e re a v a ila b le , th e e x p a n s io n p h a s e (1 9 5 6 - 1975), a n d th e p e r fo rm a n c e te s tin g p h a s e (1 9 7 6 -1985) d u r in g w h ich s e le c tio n w a s p r im a r ily b a s e d o n p e r fo rm a n c e in d ices .

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R E S U L T S

T h e in it ia l m e a n s a n d g e n e t ic t r e n d g ra d ie n ts o f five p ro d u c tio n t r a i ts fo r th e to ta l p e r io d o f s tu d y (1 948 to 1985) a n d fo u r t r a i ts fo r th e th re e d e v e lo p m e n ta l p h a s e s a r e sh o w n in T a b le

T a b le 1 M e a n in it ia l m ass a n d g e n e tic t r e n d g ra d ie n ts (kg)

T r a i t I n i t ia lm a s s

T o ta lp e r io d

1948 - 55 1956 - 75 1976 - 85

B irth m ass 100 d ay

3 .57 0.005 - - -

m ass 180 day

22 .79 0.045 -0.053 0 .068 0 .0 3 2

m ass 18 m o n th

29.23 0 .059 -0 .052N o t

0 .098 0 .0 4 2

m assG re a s y

44 .30 0 .059 m e a su re d 0 .017 0 .129

fle e c em ass

3 .99 0 .004 -0.006 0.015 0.001

D IS C U S S IO N

A ll fo u r tra i ts s tu d ie d , sh o w slow b u t p o sitiv e re sp o n se t r e n d s o v e r th e to ta l p e r io d o f 37 y e a rs ( a b o u t 10 g e n e ra tio n s ) . I f th e in itia l m asse s a re c o n s id e re d , th e v a lu e fo r 18 m o n th m ass a p p e a rs re la tiv e ly sm a ll c o m p a re d to th e re g re ss io n s fo r b o d y m a ss a t 100 a n d 180 days o f ag e . T h is re s u l t is h o w e v e r in a g re e m e n t w ith th e h e r i ta b i l i t ie s o f 0 .3 9 a n d 0.53 fo r 100 a n d 180 d ay m ass , c o m p a re d to 0.31 fo r 18 m o n th b o d y m ass a s fo u n d by F o u r ie (1 981) fo r th e s a m e flock . T h e t r e n d g ra d ie n ts fo r b ir th m ass a n d g re a sy f le e c e m a ss a r e m u c h sm a lle r a n d o f th e sa m e o rd e r , a s a r e a lso th e ir in it ia l v a lu e s .

G e n e t ic im p ro v e m e n t to o k p la c e a t r a te s v a ry in g fro m 0 .1 % fo r g re a sy f le e c e m a s s to 0 .2 7 % fo r 18 m o n th b o d y m ass w h ich is a b o u t o n e te n th o f th e r a te p o s s ib le in a w e ll p la n n e d s in g le t r a i t s e le c tio n sy s tem .

Such s lo w p ro g re s s in in d iv id u a l c h a ra c te ris tic s is h o w e v e r a c c e p ta b le in th e p re s e n t s i tu a t io n w h e re th e d e v e lo p m e n t o f a n e w b re e d to o k p la c e a n d w h e re th e to ta l sh e e p w as c o n s id e re d , in c lu d in g m a n y e c o n o m ica lly im p o r ta n t t r a i ts a s w e ll a s b r e e d c h a ra c te r is tic s to b e ta k e n u p in th e s ta n d a rd s o f e x ec e lle n c e o f th e n e w b re e d .

C o m p a r is o n o f th e t r e n d s o v e r th e th r e e d if fe re n t d e v e lo p m e n ta l p h a s e s a r e m o re in te re s t in g . T w o b o d y m ass tra i ts (1 0 0 a n d 180 day m a ss) a s w e ll a s g re a sy f le e c e m ass sh o w e d a n e g a tiv e t r e n d d u r in g th e in itia l p h a se (1948 - 1955) p o ss ib ly b e c a u s e o f sm a ll n u m b e rs in v o lv e d a n d th e c o n se q u e n t in b re e d in g . B o d y m a ss a t 18 m o n th s o f a g e w as n o t m e a s u re d d u r in g th is p h a se .

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D u r in g th e e x p a n s io n p h a s e (1 9 5 6 - 1975) s e le c tio n w a s p r im a rily su b je c tiv e , w ith p e r fo rm a n c e d a ta p lay in g a m in o r ro le . H o w e v e r b o th th e 100 d ay a n d 180 d a y m a ss tra its sh o w e d a g r e a te r r e s p o n s e in th e se c o n d , th a n in th e th ird (p e r fo rm a n c e te s tin g ) p h a se (1 9 7 6 - 1985). T h is r e su lt c a n p o ss ib ly b e a sc rib e d to th e fa c t th a t a l th o u g h o n a su b je c tiv e b a s is , th e s e t r a i ts w e re s e le c te d fo r d ire c tly d u r in g th e se c o n d p h a s e , w h ile th e y w e re s e le c te d fo r in d ire c tly in th e th ird p h a s e w h e n p e r fo rm a n c e d a ta an d in d ic e s w e re a v a ila b le fo r 18 m o n th m ass a n d g re a sy f le e c e m ass , w h ich th e n b e c a m e th e d ire c tly s e le c te d tra its .

B o d y m a ss a t 18 m o n th s w a s th e on ly t r a i t m e a su re d , w h ich sh o w e d a h ig h e r r e sp o n se d u r in g th e p e r fo rm a n c e te s tin g p h a s e th a n d u r in g th e e x p a n s io n p h a se . S tu d ie d o n its ow n, th is r e s u l t is q u ite p r e d ic ta b le b e c a u s e o f th e o b jec tiv e , p e r fo rm a n c e b a s e d s e le c tio n in th e th ird p h a se . O n th e o th e r h a n d g re a sy f le e c e m ass, th e o th e r t r a i t s u b je c te d to d ire c t o b je c tiv e s e le c tio n d u r in g th e th ir d p h a s e , r e a c te d v ery m u c h lik e 100 a n d 180 d a y b o d y m a ss in th a t i t sh o w e d a m u c h lo w e r r e sp o n se d u r in g th e th ird th a n in th e s e c o n d p h a se . T h is w as p o ss ib ly d u e to th e m o re d isc r im in a tin g se le c tio n fo r w o o l q u a lity w h ich a c c o m p a n ie d s e le c tio n fo r g re a sy f le e c e m ass d u r in g th e p e r fo rm a n c e te s tin g p h a s e . F o r in s ta n c e , m u c h g r e a te r e m p h a s is w a s p la c e d o n w o o l f in e n e ss a n d 23 m ic ro n s w as th e m a x im u m c u t o f f lim it d u r in g th is p h a se .

A n o th e r a sp e c t to b e c o n s id e re d w ith re g a rd to th e d is sa p o in tin g re s p o n s e d u r in g th e p e r fo rm a n c e te s tin g p h a s e is t h a t s o m e "u n re la te d " o u ts id e ra m s f ro m c o -o p e ra tin g flocks w e re u se d in th e s tu d d u r in g 1978, 1980, 1981 a n d 1982. G ra p h ic r e p re s e n ta t io n o f th e d a ta sh o w e d c o n s id e ra b ly h ig h e r v a r ia b il i ty in b re e d in g v a lu e s d u r in g th e th ird p h a s e , w h ich in d ic a te d th a t w h ile so m e o u ts id e ra m s w e re o f a h ig h e r g e n e tic m e r i t th a n th e h o m e b re d ra m s , o th e r s w e re o f a lo w e r s ta n d a rd . A ll in d ic a tio n s a re th a t th e b r e e d h a s n o t y e t re a c h e d a g e n e tic p la te a u a n d a B L U P -a n a ly s is a t a la te r s ta g e m ig h t v e ry w e ll in d ic a te a fu th e r su rg e o f g e n e tic r e sp o n se . I f f u r th e r n e w b re e d s w e re to b e d e v e lo p e d a t th is p o in t in tim e , o n e w o u ld h a v e b e e n in a m u c h b e t t e r p o s it io n to m a k e g o o d u s e o f p e r fo rm a n c e te s tin g a n d to m o n ito r its d e v e lo p m e n t by th e u se o f B L U P -te c h n o lo g y .

R E F E R E N C E S

B L A IR , H .T ., 1981. P h . D . D is s e r ta t io n . M assey U n iv ., N e w Z e a la n d

B L A IR , H .T . an d P O L L A K , E .J ., 1984. J . A n im . Sci. 58: 1090 - 1096

D E L P O R T , G .J ., 1989. P h . D . D is s e r ta tio n , U n iv . o f th e O ra n g e F re e S ta te , B lo e m fo n te in , R e p u b lic o f S o u th A frica .

F O U R IE , A .J ., 1981. M .Sc. A g ric . T h e s is . U n iv . o f S te lle n b o sc h , R e p u b lic o f S o u th A frica .

K O T Z E , J .J .J ., 1951. F a rm in g in S o u th A fric a , A p ril, 1951.

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