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University Microfilms International 300 N. Zeeb Road Ann Arbor, Ml 48106 8424412 C ox, D o n n a J o RESPONSE OF FEEDLOT AND CARCASS CHARACTERISTICS TO SELECTION AND CROSSBREEDING Michigan State University University Microfilms International 300 N. Zeeb Road, Ann Arbor, Ml 48106 Ph.D. 1984 RESPONSE OF FEEDLOT AND CARCASS CHARACTERISTICS TO SELECTION AND CROSSBREEDING by Donna Jo Cox A DISSERTATION S u b m itte d to M ichig an S t a t e U n i v e r s i t y i n p a r t i a l f u l f i l l m e n t o f th e r e q u ir e m e n ts f o r t h e d e g re e of DOCTOR OF PHILOSOPHY D ep artm en t o f Animal S c ie n c e 1984 ABSTRACT RESPONSE OF FEEDLOT AND CARCASS CHARACTERISTICS TO SELECTION AND CROSSBREEDING by Donna J . Cox E f f i c i e n c y o f p r o d u c t i o n by b e e f c a t t l e p r o d u c e r s depends t o a l a r g e e x t e n t on t h e e f f e c t i v e u s e o f s e l e c t i o n and c r o s s b r e e d i n g . G e n e tic and p h e n o ty p ic c o r r e l a t i o n s and h e r i t a b i l i t i e s have been e s t i ­ m ated f o r m a rb lin g s c o r e , y i e l d g r a d e , a v e r a g e d a i l y g a i n , l o i n eye a r e a , i n t e r n a l f a t (KPH), c a r c a s s g r a d e , f a t t h i c k n e s s , f i n a l w e ig h t and y e a r l i n g w e ig h t from r e c o r d s o b t a i n e d a t t h e Lake C i t y E x p e rim en t S t a t i o n i n Lake C i t y , M ic h ig a n . The e s t i m a t e d p a r a m e t e r s can be u s e d by p r o d u c e r s a s an a i d to e f f e c t i v e l y u s i n g t h e i r r e s o u r c e s . tio n , In a d d i­ th e e f f e c t o f s e l e c t i o n was i n v e s t i g a t e d by com paring t h e p e r f o r ­ mance o f u n s e l e c t e d H e r e f o r d s t e e r s to t h e f e e d l o t and c a r c a s s t r a i t s o f H e r e f o r d s s e l e c t e d f o r y e a r l i n g w e ig h t. More d e s i r a b l e f e e d l o t g a i n s and h e a v i e r s l a u g h t e r w e ig h ts c h a r ­ a c t e r i z e d t h e s e l e c t e d H e r e f o r d s i n c o m p ariso n to th e u n s e l e c t e d group o f H e re f o rd s t e e r s . In a d d i t i o n , t h e s e l e c t e d H e r e f o r d s were more d e s i r a b l e i n t h e i r o v e r a l l m u s c lin g . When d a i r y c r o s s s t e e r s w ere compared to b e e f c r o s s b r e d s t e e r s , th e s t e e r s w ith d a i r y p e d i g r e e s o u tw e ig h ed th e t r a d i t i o n a l b e e f s t e e r f o r b o th y e a r l i n g and f i n a l w e i g h t s , a lth o u g h th e y d id n o t g a in as q u i c k l y w h ile th e y w ere i n th e f e e d l o t . Donna J . Cox A s i g n i f i c a n t im provem ent was o b s e r v e d i n t h e grow th t r a i t s and t o t a l amount o f m u s c lin g due to c r o s s b r e e d i n g . In a d d itio n , th e c r o s s b r e d s t e e r s p ro d u c e d l e a n e r c a r c a s s e s w hich r e s u l t e d i n more d e s ir a b le y ie ld grades. t ACKNOWLEDGEMENTS The a u t h o r w is h e s to th a n k Dr. W illia m T. Magee f o r h i s a d v i c e , encouragem ent and s i n c e r e s u p p o r t d u r i n g t h i s g r a d u a t e p rog ram . In a d d i t i o n , I w is h to e x p r e s s my a p p r e c i a t i o n to t h e members o f my Ph.D. g u id a n c e c o m m itte e , Dr. C. R. A n d e rso n , D r. T. A. F e r r i s , Dr. J . L. G i l l , Dr. I . L. Mao and D r. H a rla n R i t c h i e f o r t h e i r c o n t i n u a l s u p p o r t and s u g g e s t i o n s i n my g r a d u a t e e n d e a v o r . S p e c i a l th a n k s a r e e x te n d e d to t h e o t h e r f a c u l t y members o f t h e D epartm ent o f Animal S c ie n c e who gave me e n cou ragem ent and s u p p o r t d u r in g my s t u d i e s a t M ic h ig a n S t a t e U n i v e r s i t y . I n a d d i t i o n , I would l i k e to th a n k P a t Cramer f o r h e r f r i e n d s h i p and t e c h n i c a l s u p p o r t p ro v id e d me d u r in g t h e c o u r s e o f my s t u d i e s . S p e c i a l th a n k s a r e e x te n d e d to my p a r e n t s , Mr. and Mrs. W a lte r D. Cox, and s i s t e r , T r a c i f o r t h e i r u n w a iv e r in g s u p p o r t . F i n a l l y , I would l i k e to e x p r e s s my d e e p e s t th a n k s to my h u s b a n d , B. D ennis B anks, f o r h i s p e r s o n a l and p r o f e s s i o n a l en co u rag e m e n t th r o u g h o u t my g r a d u a t e program . ii TABLE OF CONTENTS Page L i s t o f T a b l e s ................................................................................................................................ v L i s t o f F i g u r e s ............................................................................................................................... v i i INTRODUCTION ................................................................. 1 LITERATURE R E V IE W .............................................................................................................................4 E f f e c t s o f S e l e c t i o n and C r o s s b r e e d in g ..................................................................... 4 Mass S e l e c t i o n - Y e a r l i n g W eight .............................................................................. 6 C r o s s b r e e d in g - F e e d l o t P e rfo rm a n c e ..................................................................... 12 C r o s s b r e e d in g - C a r c a s s C h a r a c t e r i s t i c s ............................................................ 21 P h e n o ty p ic and G e n e tic P a r a m e t e r s ......................................................................................33 H e rita b ility - G e n e ra l ................................................................................................... 33 H e rita b ility - F ee d lo t T r a i t s ................................................................................ 35 H e rita b ility - C a rc a s s T r a i t s ................................................................................ 37 P h e n o ty p ic and G e n e tic C o r r e l a t i o n s .................................................................. 37 MATERIALS AND METHODS......................................................................................................................42 Base P o p u l a t i o n ............................................................................................................................... 42 B re e d in g P r o g r a m .......................................................................................................................... 42 M a n a g e m e n t........................................................................................................................................ 44 Cows . ........................................................................................................................................ 44 R eplacem ent H e i f e r s ......................................................................................................... 45 C a l v e s .............................................................................................................................................45 S t e e r s .............................................................................................................................................46 S t a t i s t i c a l A n a l y s i s .............................................................................................................. 47 V a ria n c e Component E s t i m a t i o n iii .................................................................................. 51 Page H e r i t a b i l i t i e s and G e n o ty p ic and P h e n o ty p ic C o r r e l a t i o n s ....................... 57 RESULTS AND DISCUSSION ............................................................................................................... 60 P h e n o ty p ic C o r r e l a t i o n s ...................................................................................................... 60 H e r e f o r d s ................................................................................................................................. 60 S i m m e n t a l s ................................................................................................................................. 62 G e n e tic C o r r e l a t i o n s ............................................................................................................... 63 H e r e f o r d s ................................................................................................................................. 63 S i m m e n t a l s ................................................................................................................................. 63 H e r i t a b i l i t i e s ............................................................................................................................. 65 ................................................................................................................................. 65 S i m m e n t a l ................................................................................................................................. 70 Sample S i z e ............................................................................................................................. 70 H ereford R esponse to S e l e c t i o n .......................................................................................................... 70 D a iry C ro ss Dam v s B eef C ro s s D a m ............................................................................... 90 .......................................................................................................... 92 .......................................................................................................... 112 L i t e r a t u r e C i t e d ........................................................................................................................ 115 C r o s s b r e e d in g E f f e c t s SUMMARY AND CONCLUSION iv LIST OF TABLES B reed Group Means f o r L iv e W eights and Growth R a te s L e a s t - S q u a r e s Means o f F e e d l o t T r a i t s . . . .......................................... L e a s t - S q u a r e s Means f o r Growth by B re e d in g Group ................... 17 L e a s t - S q u a r e s Means f o r C a r c a s s T r a i t s — Age C o n s ta n t B a s is .................................................................................................................... 28 L e a s t - S q u a r e s Means f o r C a r c a s s T r a i t s — W eight C o n s ta n t B a s is ................................................................................................. 29 H e r i t a b i l i t y E s t i m a t e s o f F e e d l o t T r a i t s i n B eef C a t t l e 36 H e r i t a b i l i t y E s t i m a t e s o f C a r c a s s T r a i t s i n B eef C a t t l e 38 P h e n o ty p ic (P) and G e n e tic (G) C o r r e l a t i o n s Between Y e a r l i n g Weight and V a rio u s B eef C a t t l e P r o d u c t i o n T r a i t s .................................................................................................................... 41 Number o f S t e e r s W ith in B reed Group 43 ............................................... ....................... 48 R e l a t i o n s h i p M a tr ix (A f o r H erefo rd S ir e s in Group 1 ............................................................................................................... 53 A P r i o r i V a lu es o f H e r i t a b i l i t i e s and k V a lu e s Used i n th e REML A n a l y s i s .................................................................................... 58 P h e n o ty p ic C o r r e l a t i o n s o f F e e d l o t and C a r c a s s T r a i t s w ith Y e a r l i n g W eight by B reed o f S i r e .......................................... 61 G e n e tic C o r r e l a t i o n s o f F e e d l o t and C a r c a s s T r a i t s w i t h Y e a r l i n g W eight by Breed o f S i r e ........................................................ 64 S i r e and E r r o r V a r ia n c e Components and H e r i t a b i l i t i e s f o r F e e d l o t and C a r c a s s T r a i t s i n t h e H e r e f o r d B reed ................... 66 S i r e and E r r o r V a r ia n c e Components and H e r i t a b i l i t i e s f o r F e e d l o t and C a r c a s s T r a i t s i n t h e Sim m ental B reed . . . . 68 E s tim a te d Sample S iz e Needed f o r M inim al Sam pling V a ria n c e o f H e r i t a b i l i t y .......................................................................... 71 Number o f S t e e r s by Y ear and S i r e B reed Group v Table Page 18 C o n t r a s t E f f e c t s o f F e e d l o t and C a r c a s s T r a i t s Between Group 3 and Group 4 ................................................................................... 82 19 C o n t r a s t E f f e c t s o f F e e d l o t and C a r c a s s T r a i t s i n C ro s s b re d S t e e r s ...................................................................................................... 93 vi LIST OF FIGURES F ig u r e Page 1 Means o f M a rb lin g S c o re s o f U n s e l e c t e d and S e l e c t e d H e r e f o r d s , 1978-1981 2 Means o f Y i e l d G rades o f U n s e l e c t e d and S e l e c t e d H e r e f o r d s , 1978-1981 3 Means o f A verage D a ily G ain o f U n s e le c te d and S e l e c t e d H e r e f o r d s , 1978-1981 4 Means o f L o in Eye A re as o f U n s e l e c t e d and S e l e c t e d H e r e f o r d s , 1978-1981 5 Means o f I n t e r n a l F a t o f U n s e l e c t e d and S e l e c t e d H e r e f o r d s , 1978-1981 6 Means o f C a r c a s s G rades o f U n s e l e c t e d and S e l e c t e d H e r e f o r d s , 1978-1981 7 Means o f F a t T h ic k n e s s o f U n s e l e c t e d and S e l e c t e d H e r e f o r d s , 1978-1981 8 Means o f F i n a l W eight o f H e r e f o r d s , 1978-1981 9 A d ju s te d Y e a r l i n g W eight Means o f U n s e le c te d and S e l e c t e d H e r e f o r d s , 1978-1981 ............................................................................ 80 U n s e l e c t e d and S e l e c t e d 10 Means o f M a r b lin g S c o re s o f Groups 2, 3 and 4, 1978-1981 11 Means o f Y i e l d G rades o f Groups 2, 3 and 4 , 1978-1981 .................... 12 Means o f A verage D a ily G ain o f Groups 2 , 3 and 4 , 1978-1981 .......................................................................................................................... 86 13 Means o f L o in Eye A re as o f Groups 2 , 3 and 4 , 1978-1981 . . . . 14 Means o f I n t e r n a l F a t o f Groups 2, 3 and 4, 1978-1981 ..................... 88 15 Means o f C a r c a s s G rades o f Groups 2, 3 and 4 , 1978-1981 . . . . 89 16 Means o f F a t T h ic k n e s s o f Groups 2 , 3 and 4, 1978-1981 90 17 Means o f F i n a l W eight o f Groups 2, 3 and 4 , 1978-1981 ..................... 91 18 A d ju s te d Y e a r l i n g W eight Means o f Groups 2, 3 and 4 , 1978-1981 .......................................................................................................................... v ii . . . . . . . 84 85 87 92 INTRODUCTION B eef c a t t l e p r o d u c e r s i n t h e U n ite d S t a t e s a r e d i v i d e d i n t o two seg m en ts— s e e d s t o c k p r o d u c e r s and co m m ercial b e e f p r o d u c e r s w i t h th e l a t t e r c o m p ris in g a h ig h p r o p o r t i o n o f t h e b e e f c a t t l e p r o d u c e r s . Commercial c a t t l e m e n a t t e m p t to b r e e d c a t t l e i n su ch a way as to a c h ie v e th e " u l t i m a t e " g o a l o f t h e i n d u s t r y — to p ro d u c e t h e f a s t e s t grow ing c a t t l e on t h e l e a s t amcunt o f f e e d w ith c a r c a s s e s t h a t have th e g r e a t e s t amount o f e d i b l e p o r t i o n p e r u n i t o f c a r c a s s w e ig h t. In a d d i t i o n , i t i s n e c e s s a r y t h a t t h e e d i b l e p o r t i o n be p l e a s i n g to th e consum er. Two g e n e t i c t o o l s a v a i l a b l e to c o m m ercial c a t t l e m e n a r e s e l e c t i o n and c r o s s b r e e d i n g . C u n d if f (1970) a s s e r t e d i f n o n a d d i t i v e and a d d i t i v e g e n e t i c v a r i a t i o n b o th a r e i m p o r t a n t , t h e n improvement s h o u ld be maximized by com bining s y s t e m a t i c c r o s s b r e e d i n g w i t h s e l e c t i o n w i t h i n and among b r e e d s . I t i s d e s i r a b l e f o r th e b r e e d e r to h ave a r e a l i s t i c i d e a o f how q u i c k l y t h e v a r i o u s c h a r a c t e r i s t i c s o f i n t e r e s t can be changed g e n e t i ­ c a lly . Numerous e s t i m a t e s o f p o t e n t i a l p r o g r e s s from c e r t a i n s e l e c ­ t i o n program s a r e a v a i l a b l e . T hese e s t i m a t e s d e p en d , to a l a r g e d e g r e e , on th e e s t i m a t e d h e r i t a b i l i t i e s and c o r r e l a t i o n s among s e l e c t e d t r a i t s o f economic im p o r ta n c e . I t i s i m p o r t a n t to a t t e m p t to e s t i m a t e a c c u r a t e l y t h e g e n e t i c and p h e n o ty p ic p a r a m e te r s o f t r a i t s r e q u i r e d f o r a p a r t i c u l a r s e l e c t i o n program . 1 2 C ro s s b r e e d in g h a s been u sed s u c c e s s f u l l y f o r th e i n t r o d u c t i o n o f c e r t a i n d e s i r a b l e g en es i n t o a p o p u l a t i o n t h a t would have o t h e r w i s e been a b s e n t. Much o f th e c l a s s i c work w i t h c r o s s b r e e d i n g i n th e U n ite d S t a t e s was done i n th e S o u th w e s t, where Brahmans w e re c r o s s e d w ith B r i t i s h breeds o f c a t t l e . S u b s e q u e n tly , num erous European b re e d s have been u t i l i z e d f o r c r o s s b r e e d i n g p u rp o s e s i n t h e U n ite d S t a t e s . S im m en ta l numbers w i t h i n th e U n ite d S t a t e s have i n c r e a s e d r a p i d l y i n r e c e n t y e a r s and a r e now r e c o g n iz e d as an i m p o r t a n t b e e f b re e d . C o n se q u e n tly an i n c r e a s i n g l y g r e a t e r p e r c e n t a g e o f c r o s s b r e d s b o a s t some S im m e n ta l b r e e d in g . The b re e d i s w id e ly re c o g n iz e d as one t h a t p ro d u c e s a l a r g e amount o f m u s c lin g i n a m o d e ra te to l a r g e fra m e i n c o m p a riso n to th e s m a l l e r B r i t i s h b re e d s w i t h somewhat more a v e r a g e m u s c lin g . I t would be i n t e r e s t i n g to compare f e e d l o t and c a r c a s s p e rfo rm a n c e o f s t e e r s s i r e d by S im m e n ta l b u l l s to th o s e s i r e d by a t r a d i t i o n a l b eef breed, In r e c e n t y e a r s , t h e H e re f o rd . th e u se o f r e s t r i c t e d maximum l i k e l i h o o d (REML) h as g a in e d p o p u l a r i t y among d a i r y s c i e n t i s t s as a t o o l f o r e s t i m a t i n g th e v a r i a n c e com ponents n e c e s s a r y f o r e s t i m a t i o n o f h e r i t a b i l i t i e s by th e p a t e r n a l h a l f - s i b c o r r e l a t i o n method. i n th e b e e f c a t t l e f i e l d p ro c e d u re . L i t t l e work h a s been done to make u se o f t h i s r e l a t i v e l y new e s t i m a t i o n I t w ould, t h e r e f o r e , seem a p p r o p r i a t e to e s t i m a t e th e com ponents u t i l i z i n g REML m eth o d o lo g y and compare t h e s e to e s t i m a t e s p re v io u sly re p o r te d . The d a t a p r e s e n t e d i n t h i s s tu d y w ere c o l l e c t e d a t th e Lake C ity E x p e rim e n t S t a t i o n i n Lake C ity , M ich igan . They a r e a p o r t i o n o f d a t a from a l o n g - t e r m c r o s s b r e e d i n g p rogram d e s ig n e d and im p le m e n te d by W. T. Magee. The b a se cow p o p u l a t i o n c o n s i s t e d o f 200 H e re f o rd cows. B re e d in g i n th e h e rd in v o lv e d Angus, C h a r o l a i s and Sim m ental b r e e d s as w e l l a s th e H e re f o rd b r e e d . Only th e d a t a from th e s t e e r c a l v e s were u t i l i s e d in t h i s stu d y . The o b j e c t i v e s o f t h i s s tu d y w ere: 1) To compare s t e e r s s i r e d by Sim mental b u l l s s e l e c t e d on y e a r l i n g w e ig h t to s t e e r s s i r e d by H e re fo rd b u l l s a l s o s e l e c t e d on y e a r l i n g w e ig h t. 2) To compare s t e e r s s e l e c t e d f o r y e a r l i n g w e ig h t w ith th o s e u n s e l e c t e d f o r y e a r l i n g w e ig h t; b o th s i r e d by H e re fo rd b u lls. 3) To e s t i m a t e th e h e r i t a b i l i t i e s and p h e n o ty p ic and g e n e t i c c o r r e l a t i o n s o f s e l e c t e d f e e d l o t and c a r c a s s t r a i t s i n b e e f c a t t l e s e l e c t e d f o r y e a r l i n g w e ig h t. 4) To compare th e e s t i m a t e s o f h e r i t a b i l i t i e s o b t a i n e d u s i n g REML to p r e v i o u s l y r e p o r t e d e s t i m a t e s . 4 LITERATURE REVIEW F o r s e v e r a l y e a r s germ plasm a v a i l a b l e f o r b e e f p r o d u c t i o n i n th e U n ite d S t a t e s was e s s e n t i a l l y l i m i t e d to t h r e e B r i t i s h b r e e d s and a r e p r e s e n t a t i v e o f th e Zebu b r e e d s - S h o r t h o r n , Angus, H e re f o rd and Brahman. I n th e l a t e 1 9 6 0 's and e a r l y 1 9 7 0 's i m p o r t a t i o n o f b o th a n im a ls and f r o z e n semen o f a l a r g e number o f c o n t i n e n t a l b r e e d s to N o rth America r e s u l t e d i n b r e e d e r s h a v in g a v a r i e t y o f b r e e d s from w hich to c h o o se . With th e i n i t i a t i o n o f new b lo o d i n t o t h e N o rth American p o p u l a t i o n a renewed i n t e r e s t i n c r o s s b r e e d i n g r e s u l t e d . S u b s e q u e n tl y , c o n s i d e r a b l e em phasis h a s be en p la c e d on d e v e lo p in g c r o s s b r e e d i n g sy ste m s w hich i n v o l v e d a i r y a n d / o r e x o t i c b r e e d s to meet th e p r o d u c e r 's g o a l o f more e f f i c i e n t b e e f p r o d u c t i o n . E f f e c t s o f S e l e c t i o n and C r o s s b r e e d in g C r o s s b r e e d in g i s u sed i n com m ercial p r o d u c t i o n f o r two r e a s o n s : 1) to ta k e a d v a n ta g e o f h e t e r o s i s o r h y b r id v i g o r and 2) th r o u g h b re e d c o m b in a tio n s w hich complement each o t h e r , to c r e a t e c h a r a c t e r i s t i c s n o t a v a i l a b l e i n any s i n g l e b re e d (Warwick and L e g a t e s , 1 9 7 9 ). Frahm e t a l ( 1 9S0) o b s e rv e d t h a t o v e r h a l f o f th e improvement i n p r o d u c t i o n e f f i c i e n c y o f b e e f c a t t l e r e s u l t s from u t i l i z i n g c r o s s b r e d cows. There i s e v id e n c e t h a t more h e t e r o s i s i s o b s e rv e d i n grow th p e r f o r ­ mance when c r o s s b r e d cows a r e mated to a t h i r d b re e d th a n b a c k c r o s s e d to one o f th e dam b r e e d s ( A lle n and S o u t h g a t e , 1 9 7 7 ). 5 G regory and C u n d iff ( 1 9S0) s t a t e d t h a t th e b a s i c o b j e c t i v e o f b e e f c a t t l e c r o s s b r e e d i n g sy ste m s i s to s i m u l t a n e o u s l y o p tim iz e th e u se o f b o th n o n a d d i t i v e ( h e t e r o s i s ) and a d d i t i v e (b re e d d i f f e r e n c e s ) e f f e c t s of genes. C a r tw r ig h t (1970) s u g g e s te d t h a t making u se o f b re e d c o m p le m e n ta rity a p p e a r s to be th e most e f f e c t i v e method o f u tiliz in g s e le c tio n . Breed c o m p le m e n ta rity r e f e r s to a method o f c h o o sin g a s i r e b re e d s t r o n g i n some d e s i r a b l e c h a r a c t e r i s t i c to mate to a b re e d o f dam d e s i r a b l e i n some o t h e r t r a i t b u t n o t as s t r o n g i n th e s i r e ' s d e s i r a b l e t r a i t . When b r e e d in g i n t h i s manner, i t would be e x p e c te d t h a t th e o f f s p r i n g would i n h e r i t good q u a l i t i e s f o r b o th tra its . I t i s re c o g n iz e d t h a t h y b r id v i g o r i s a o n e -tim e p r o p o s i t i o n . However, by s e l e c t i n g i n b o th th e p u re b re d and c r o s s b r e d p o p u l a t i o n s th e chances o f a d d i t i o n a l improvement a r e g r e a t e r . C o n se q u e n tly , e f f e c t s o f s e l e c t i o n and r e l a t i v e b re e d m e r i t would be fu n d a m e n tal to c ro ssb re e d in g d e c is io n s . Warwick and C a r tw r ig h t (1955) emphasized t h a t i n o r d e r to be p r o f i t a b l e , b e e f c a t t l e must have th e i n h e r e n t a b i l i t y to grow and g a i n . B i o d i n i e t a l (1968) a s s e r t e d t h a t s e l e c ­ t i o n f o r grow th r a t e s h o u ld be e f f e c t i v e n o t o n ly i n m o d ify in g grow th r a t e i t s e l f , b u t a l s o s h o u ld change a n o t h e r im p o r ta n t c h a r a c t e r , c a r c a s s c o m p o sitio n due to h ig h p h e n o ty p ic and g e n e t i c c o r r e l a t i o n s . He c i t e s v a r i o u s a u t h o r s who o b s e rv e d t h a t w h e th er a n im a ls became f a t t e r or l e a n e r was d e p en d e n t on th e s p e c i f i c c r i t e r i o n f o r s e l e c ­ tio n . Koch e t a l (1982) n o te d t h a t c a r c a s s a t t r i b u t e s a r e im p o r ta n t i n d e te r m in in g th e p o t e n t i a l v a lu e o f a l t e r n a t i v e germ plasm r e s o u r c e s f o r p r o f i t a b l e b eef p ro d u c tio n . 6 Young (1968) r a t i o n a l i z e d t h a t t o t a l e f f i c i e n c y o f b e e f p ro d u c ­ t i o n can be im p ro ved by u s e o f c o m b in a tio n s o f a v a i l a b l e germ p la sm r e s o u r c e s t h a t a r e o p t i m a l l y m atched w i t h s p e c i f i c e n v i r o n m e n t a l and management c o n d i t i o n s . V illh a m (1 9T0) p o i n t e d o u t t h a t t h e amount o f h y b r i d v i g o r depends on 1) gene f r e q u e n c y d i f f e r e n c e s and 2) d e g re e o f dom inance. C u n d if f (1970) o b s e rv e d t h a t th e a v e r a g e p e rfo rm a n c e o f th e b r e e d s would i n d i c a t e t h a t t h e r e a r e marked d i f f e r e n c e s b e tw e e n b r e e d s i n th e f r e q u e n c y o f g en es a f f e c t i n g g ro w th r a t e and c a r c a s s c o m p o s i t i o n and g ra d e . T h e r e f o r e , i t would be a r e a s o n a b l e a s s u m p tio n t h a t h e t e r o s i s i s a g r e a t e r f o r c e when h i g h l y d i v e r g e n t b r e e d s a r e crossed. Mass S e l e c t i o n - Y e a r l i n g W eight L a s le y (1972) i n d i c a t e d t h a t y e a r l i n g w e ig h t i s o f v a lu e f o r s e l e c t i o n o f b o th b u l l and h e i f e r r e p l a c e m e n t s i n th e b r e e d i n g h e rd . Y e a r l i n g w e ig h t i s a com plex c h a r a c t e r i s t i c composed o f w e an in g w e ig h t and th e r a t e o f g a i n p o s tw e a n in g . To c o m p l i c a t e m a t t e r s , McPeake (1977) p o i n t e d o u t t h a t w e an in g w e ig h t r e f l e c t s n o t o n ly th e g ro w th a b i l i t y o f th e c a l f b u t a l s o th e m a t e r n a l e n v iro n m e n t c r e a t e d by i t s dam. The c o m p l i c a t i o n a r i s e s due to th e d e s i r e to p r e d i c t y e a r l i n g w e ig h t o f th e o f f s p r i n g g iv e n d a t a from th e two p a r e n t s . C h ristia n et a l (1965) s t a t e d t h a t th e i n f l u e n c e o f w eaning w e ig h t on econom ic c h a r a c t e r s e x p r e s s e d a t o l d e r a g es coijld be due to a c a r r y - o v e r e f f e c t o f m a t e r n a l o r o t h e r e n v i r o n m e n t a l f a c t o r s o r th e i n f l u e n c e o f th e same g en es w hich a c te d p r i o r to w eaning. R e su lts in d ic a te th a t f i n a l 7 w e ig h t s h o u ld be th e s i n g l e most i m p o r ta n t t r a i t i n a s e l e c t i o n p r o ­ grammed a t im p ro v in g th e p r o d u c t i o n and c a r c a s s t r a i t s o f b e e f c a t t l e (D in k e l and B usch, 1 9 7 3 ). S h e lb y e t a l (1963) a s s e r t e d mass s e l e c t i o n s h o u ld be e f f e c t i v e f o r grow th t r a i t s . They found t h a t f i n a l w e ig h t was a s l i g h t l y s u p e r ­ i o r c r i t e r i o n f o r s e l e c t i o n th a n a v e r a g e d a i l y g a i n . Dunn e t a l (1970) s u rm is e d t h a t e s t i m a t e s o f t h e c o r r e l a t i o n betw een a s i r e ' s g e n e t i c a b i l i t y to p ro d u c e s t r a i g h t b r e d and c r o s s b r e d p ro g e n y were h i g h , i n d i c a t i n g t h a t mass s e l e c t i o n i n p u re b re d p o p u l a t i o n s c o n t r i b u ­ t i n g germ plasm to c r o s s b r e d p o p u l a t i o n s would be a p p r o x im a te ly as e f f e c t i v e i n im p ro v in g com m ercial s t r a i g h t b r e d p e rfo rm a n c e . M iquel and C a r t w r i g h t (1963) i n d i c a t e d t h a t s e l e c t i o n would be e q u a l l y e f f e c ­ t i v e i n c r o s s b r e d s and p u r e b r e d s . Koch e t a l ( 1974a) examined th e s e l e c t i o n r e s p o n s e i n H e re f o rd c a t t l e s e l e c t e d f o r 1) w eaning w e ig h t, 2) y e a r l i n g w e ig h t and 3) an in d e x o f y e a r l i n g w e ig h t and m u s c lin g s c o r e . e s t i m a t e d r e s p o n s e p e r g e n e r a t i o n was: They found th e a v e r a g e w eaning w e ig h t, 0 . 2 3 , 0 .1 7 and 0 .1 5 and y e a r l i n g w e ig h t, 0 . 3 6 , 0 .4 3 and 0.33> r e s p e c t i v e l y . s e s were r e p o r t e d i n s t a n d a r d d e v i a t i o n s . Respon­ T h e i r c o n c l u s i o n was t h a t s e l e c t i o n f o r y e a r l i n g w e ig h t may i n c r e a s e w eaning w e ig h t o r w e ig h t g a i n more th a n d i r e c t s e l e c t i o n f o r t h e s e t r a i t s . I n th e same s t u d y , Koch e t a l ( 1974a) loo ked a t th e a v e r a g e s i r e s e l e c t i o n d i f f e r e n t i a l p e r g e n e r a t i o n when s e l e c t i o n was b a se d on each o f th e t h r e e c r i t e r i o n . The s i r e d i f f e r e n t i a l s were 1 .5 1 , 1 .1 8 , 0 .8 6 s t a n d a r d d e v i a t i o n s f o r w eaning w e ig h t and 1 .4 2 , 1 .7 9 , 1 .2 2 f o r y e a r ­ l i n g w e ig h t f o r each o f th e s e l e c t i o n c r i t e r i a , re sp e c tiv e ly . They 8 d e f i n e d s e l e c t i o n d i f f e r e n t i a l a s th e d i f f e r e n c e i n mean p e rfo rm a n c e o f s e l e c t e d p a r e n t s and th e u n s e l e c t e d group from w hich th e y came. a s e p a r a t e p a p e r (Koch e t a l , In 1974b) t h e y n o te d t h a t s e l e c t i o n f o r y e a r l i n g w e ig h t may i n c r e a s e w eaning g a i n o r w e ig h t more th a n d i r e c t s e l e c t i o n f o r th e se t r a i t s . S w ig e r e t a l (1965) showed a l o s s o f 2$ i n f i n a l w e ig h t when s e l e c t i n g s t r i c t l y on y e a r l i n g w e ig h t v e r s u s an in d e x f o r w ean ing w e ig h t and d a i l y g a in . B io n d in i e t a l (1968) s e l e c t e d m ice o v e r 10 g e n e r a t i o n s f o r r a p i d g ro w th r a t e . They saw c o n c l u s i v e e v id e n c e o f c han ges i n g a in on t e s t and e f f i c i e n c y r e s u l t i n g from t h i s c r i t e r i o n o f s e l e c t i o n . T his would s u g g e s t t h a t s e l e c t i o n f o r y e a r l i n g w e ig h t i n b e e f c a t t l e would r e s u l t i n i n c r e a s e d p e rfo rm a n c e i n g ro w th t r a i t s and th e e f f i c i e n c y r e l a t e d to th o s e t r a i t s . C h e n e tte e t a l (1981) o b s e r v e d th e r e s p o n s e i n H e r e f o r d b u l l s to s e l e c t i o n f o r 1) w ean ing w e ig h t and 2 ) y e a r l i n g w e ig h t. They found t h a t t h e two t r a i t s g e n e r a l l y f o ll o w e d s i m i l a r p a t t e r n s o f r e s p o n s e . In th e group s e l e c t e d f o r y e a r l i n g w e ig h t th e y o b s e rv e d a d i r e c t re s p o n s e o f 3*27 l b / y e a r , w ean in g w e ig h t. w i t h a c o r r e l a t e d r e s p o n s e o f 1.5 l b / y e a r In a d d i t i o n , th e y r e p o r t e d t h a t a l l c o r r e l a t e d mea­ s u r e s o f re s p o n s e i n c o n f o r m a tio n and c o n d i t i o n were q u i t e s m a l l , w ith more p o s i t i v e change o c c u r r i n g i n th e d e g re e o f m u s c lin g r a t h e r th a n fa tn e ss. D in k e l and Busch (1973) c o n clu d e d t h a t genes c o n t r i b u t i n g to r a p i d g ro w th te n d to lo w e r tr im m a b le f a t . C u n d if f e t a l (1964) o b t a i n e d g e n e t i c c o r r e l a t i o n s w hich i n d i ­ c a te d t h a t s e l e c t i o n f o r g ro w th r a t e would be e f f e c t i v e and would le a d 9 to i n c r e a s e d m u s c u la r d e v e lo p m e n t, im prov ed c a r c a s s g ra d e and a s l i g h t in c re a se in c a rc a ss fa tn e s s . H is a n a l y s i s i s i n d i r e c t c o n t r a s t to C h e n e tte e t a l (1981) and D in k e l and Busch (1973) w hich r e p o r t n e g a ­ t i v e c o r r e l a t i o n s f o r g ro w th r a t e and c a r c a s s f a t n e s s . These r e s u l t s im p ly t h a t s e l e c t i o n f o r g ro w th r a t e would be c o m p a t ib le w i t h th e p ro d u c tio n o f d e s ir a b le c a rc a s s e s . C u n d if f e t a l (1971) e v a l u a t e d t h e e x p e c te d e f f e c t o f s e l e c t i o n f o r g ro w th r a t e on th e c o m p o s i tio n and q u a l i t y o f b e e f c a r c a s s e s . They compared t h e s e r e s u l t s to th e r e s u l t s f o r d i r e c t s e l e c t i o n o f carcass a ttr ib u te s . T h e i r c o n c l u s i o n was t h a t s e l e c t i o n f o r g ro w th r a t e c o u ld be more i n t e n s e and im p le m e n te d a t l e s s c o s t u s i n g y e a r l i n g w e ig h t o f l i v e a n im a ls t h a n d i r e c t s e l e c t i o n f o r c a r c a s s r e t a i l p r o ­ d u c t. B l a c k w e l l e t a l (1962) c o n c u r re d when th e y found e v id e n c e t h a t c a r c a s s g ra d e c o u ld be im p ro ved by s e l e c t i o n f o r s l a u g h t e r g r a d e . I t was d i s c o v e r e d t h a t g r a d e r s can a c c o u n t f o r 20-25$ o f th e v a r i a t i o n i n carcass t r a i t s (G regory e t a l , 1962). G regory e t a l (1962) c o n c lu d e d t h a t more p r e c i s e e s t i m a t e s o f c a r c a s s g ra d e s w ere needed f o r s e l e c ­ tio n of b reed in g c a t t l e . I n 1969. C u n d if f e t a l o b s e rv e d t h a t s i n g l e t r a i t s e l e c t i o n would be much more e f f e c t i v e f o r g ro w th o f r e t a i l p r o d u c t th a n f o r p r o p o r t i o n o r y i e l d o f r e t a i l p r o d u c t a t any l e v e l o f s e l e c t i o n i n t e n ­ s i t y b e c a u s e h e r i t a b i l i t y i s h i g h e r and p h e n o ty p ic v a r i a t i o n i s s i g n i ­ fic a n tly g re a ter. In a d d i t i o n , th e y a s s e r t e d t h a t s e l e c t i o n f o r g ro w th would im p ro v e o v e r a l l e f f i c i e n c y o f p r o d u c t i o n i f th e m a i n t e ­ nance r e q u i r e m e n t s o f b r e e d i n g a n i m a l s was n o t i n c r e a s e d a p r o p o r t i o n ­ a t e amount by c o r r e l a t e d c h an g e s a s s o c i a t e d w i t h t h e i r i n c r e a s e d 10 m a tu re body s i z e . L i k e w is e , t h e r e i s a s t r o n g r e l a t i o n s h i p b e tw e e n t h e a b i l i t y to make r a p i d g a in s and t h e a b i l i t y to make e f f i c i e n t g a in s i n th e f e e d l o t ( L a s le y , 1972). I n r e c e n t y e a r s , i t h a s been o f m a jo r c o n c e rn to c a t t l e b r e e d e r s to i n c r e a s e y e a r l i n g w e ig h t w h ile k e e p in g b i r t h w e ig h t c o n s t a n t . However, due to a p o s i t i v e g e n e t i c c o r r e l a t i o n b e tw e e n th e t r a i t s , we have w i t n e s s e d a p r o p o r t i o n a l i n c r e a s e i n b i r t h w e ig h ts when s e l e c t i o n i s f o r y e a r l i n g w e ig h t. D ic k e r s o n e t a l (1974) s u g g e s t t h a t t h i s does n o t have to be th e c a s e . They a d v o c a te t h a t i t i s b i o l o g i c a l l y f e a s i b l e to i n c r e a s e y e a r l i n g w e ig h t w i t h v e ry l i t t l e change i n b i r t h w e ig h t b e c a u s e th e g e n e t i c c o r r e l a t i o n i s f a r from p e r f e c t ( th e y e s t i m a t e i t to be .54). N e v erth ele ss, e v id e n c e has g e n e r a l l y s u p ­ p o r t e d an i n c r e a s e i n b i r t h w e ig h t. I n a c r o s s b r e e d i n g s t u d y a t M ich ig an S t a t e U n i v e r s i t y , McPeake (1977) found t h a t s e l e c t i o n f o r y e a r l i n g w e ig h t was th e p r i m a r y f a c t o r r e s p o n s i b l e f o r th e i n c r e a s e i n d o l l a r r e t u r n to a b e e f h e r d o v e r o u t o f-p o ck et c o sts. H is r e s u l t s i n d i c a t e d t h a t s e l e c t i o n a c c o u n te d f o r 11.4# i n c r e a s e i n a c t u a l w eaning w e ig h t. W ilso n e t a l (1976) s u g ­ g e s t e d t h a t s e l e c t i n g f o r r a p i d g ro w th s h o u ld im p ro v e b o th r a t e and e f f i c i e n c y o f g a in due to m o d e ra te h e r i t a b i l i t y o f g ro w th r a t e and th e f a v o r a b l e c o r r e l a t i o n w i t h fe e d c o n v e r s io n . S m ith and C u n d if f (1976) p r e s e n t e d r e s u l t s i n d i c a t i n g t h a t s e l e c t i o n f o r e a r l y g ro w th r a t e may be more a p p r o p r i a t e f o r m a t e r n a l s t o c k s th a n f o r t e r m i n a l s i r e b r e e d s . However, th e y n o te d t h a t th e a p p a r e n t n e g a t i v e p r e s s u r e t h a t would be p la c e d on b i r t h w e ig h t would have some m e r i t f o r s i r e b r e e d s . S w ig e r e t a l (1965) showed t h a t s e l e c t i n g f o r f i n a l w e ig h t a lo n e 11 would be 90 % a s e f f i c i e n t i n im p r o v in g t o t a l n e t m e r i t , w here n e t m e r i t i s d e f i n e d a s n e t p r o f i t , a s s e l e c t i n g f o r an in d e x i n v o l v i n g w eaning w e ig h t, p o s tw e a n in g d a i l y g a i n , f e e d c o n su m p tio n and f a t . They h y p o th e s i z e d t h a t s e l e c t i n g f o r f i n a l w e ig h t s h o u ld le a d to i n c r e a s e d n e t m e r i t th r o u g h th e p r o d u c t i o n o f enough e x t r a r e t a i l p r o d u c t to overcome th e c o s t o f p ro d u c in g e x t r a f a t . In a d d itio n , i t i s f a r s i m p l e r and l e s s e x p e n s iv e to s e l e c t f o r f i n a l w e ig h t. V inson e t a l (1969) c o n d u c te d a s t u d y w i t h mice to compare p re d ic te d resp o n ses of d iff e r e n t c r o s s b r e d s e l e c t i o n m ethods when s e le c tio n of fu tu re p a r e n t s was c o n f in e d to p u r e b r e d i n d i v i d u a l s . The t h r e e s e l e c t i o n m ethods w e re 1) mass s e l e c t i o n b a se d on i n d i v i d u a l p u re b re d p e rfo rm a n c e , 2) h a l f - s i b f a m i l y s e l e c t i o n based on p u re b re d p e rfo rm a n c e and 3) r e c i p r o c a l r e c u r r e n t s e l e c t i o n b a se d on c r o s s b r e d p e rfo rm a n c e . T r a i t s s t u d i e d i n c l u d e d b i r t h w e ig h t, w e an in g w e ig h t, p o s tw e a n in g g a i n and l i t t e r s i z e . T h e i r r e s u l t s i n d i c a t e d t h a t mass s e l e c t i o n would be e x p e c te d to y i e l d th e l a r g e s t g e n e t i c im p ro vem ent f o r a l l t r a i t s e x c e p t w e an in g w e ig h t o r l i t t e r s i z e . Many c a t t l e m e n have c o n ten d e d t h a t i t i s p o s s i b l e to s e l e c t th e f a s t e r g a i n i n g and more e f f i c i e n t a n i m a l s by p a y in g a t t e n t i o n to c o n f o r m a tio n . S e v e r a l s t u d i e s , h o w e v er, show r a t h e r c l e a r l y t h a t t h i s i s n o t th e c a s e and s e l e c t i o n f o r p e rfo rm a n c e on th e b a s i s o f c o n f o r ­ m a tio n i s i n e f f e c t i v e ( L a s le y , 1972). T a y lo r (1982) a s s e r t e d t h a t s e l e c t i o n f o r b e e f ty p e may have be en d e t r i m e n t a l to s e l e c t i o n f o r g ro w th r a t e . He q u o te d Hammond (1980) i n d e f i n i n g s e l e c t i o n o f b e e f ty p e a s s e l e c t i n g th o s e c a t t l e w i t h s h o r t e r bones and t h i c k e r m u s c le s . 12 C r o s s b r e e d in g - F e e d l o t P e rf o rm a n c e Numerous s t u d i e s h ave b een c o n d u c te d i n th e s o u t h e r n U n ite d S t a t e s e x a m in in g th e m e r i t s o f c r o s s i n g Brahman c a t t l e w i t h v a r i o u s o th e r breeds. However, due to th e sco pe o f th e p r e s e n t s tu d y , o n ly th o s e i n v e s t i g a t i o n s i n v o l v i n g b r e e d s common to th e M idw est w i l l be p re se n te d . Adams e t a l (1973) s t u d i e d th e p e rfo rm a n c e o f c r o s s e s from H e re f o rd dams b re d to s i x i m p o r te d s i r e b r e e d s and Angus and H e re f o rd b u lls. They found t h a t S im m e n ta l c r o s s e s e x c e l l e d L im o u sin and Angus by H e re f o rd c r o s s e s i n 2 0 0 -d a y w e ig h t r a t i o and p o s tw e a n in g a v e r a g e d a i l y g a in . I n t h e same s tu d y , C h a r o l a i s , S im m e n ta l, M aine-A njou, Brown S w is s and L im o u sin c r o s s e s w ere shown to e x h i b i t th e l e a s t amount o f f a t c o v e r a s com pared to Angus, H e re f o rd and L in c o ln Red cro sses. The Angus by H e r e f o r d c r o s s b r e d s w ere by f a r th e f a t t e s t . In a d d i t i o n , t h e S im m e n ta l and L im o u sin c r o s s e s had a s i g n i f i c a n t l y g r e a t e r m u scle d e v e lo p m e n t s c o r e . A lenda e t a l (1980b) c o n d u c te d an e x p e r im e n t to e s t i m a t e th e g e n e t i c e f f e c t s o f p o s tw e a n in g d a i l y g a i n , r i b e y e a r e a and f a t c o v e r. He th e n u t i l i z e d t h e s e e s t i m a t e s to a s s e s s t h e e f f e c t i v e n e s s o f c r o s s ­ b r e e d in g s y s te m s e m p lo y in g Angus, H e re f o rd and C h a r o l a i s b r e e d s . T h e i r r e s u l t s i n d i c a t e d t h a t th e sum o f th e a d d i t i v e e f f e c t s o f th e t h r e e b r e e d s d i f f e r e d (P<. 10) im p ly in g t h a t d i f f e r e n c e s among b re e d means w ere a s s o c i a t e d w i t h a d d i t i v e d i f f e r e n c e s . No s i g n i f i c a n t i n d i ­ v i d u a l h e t e r o t i c e f f e c t was o b s e rv e d i n any C h a r o l a i s c r o s s . Angus by H e re f o rd c r o s s p ro d u c e d 3 % i n d i v i d u a l h e t e r o s i s f o r The 13 p o s tw e a n in g d a i l y g a i n . A lle n and S o u th g a te (1977) n o te d t h a t th e h e a v i e r t h e s i r e b r e e d , th e more r a p i d th e grow th o f i t s o f f s p r i n g and th e h i g h e r th e w e ig h t a t which th e y a r e s l a u g h t e r e d . They a l s o i n d i c a t e d t h a t t h e r e i s g r e a t e r h e t e r o s i s f o r grow th p e rfo rm a n c e when c r o s s b r e d cows a r e mated to a t h i r d s i r e b re e d th a n b a c k c r o s s e d to one o f th e dam b r e e d s . For 200-day w e ig h t th e y ra n k e d f o u r b e e f b re e d s i n th e f o l l o w i n g o r d e r : C h a r o l a i s , S im m ental, H e re f o rd and Angus. Anderson e t a l (1978) examined p o s tw e a n in g d a t a on 33 c r o s s b r e d c a l v e s s i r e d by Angus, H o l s t e i n and C h ia n in a b u l l s . Those c a l v e s s i r e d by Angus b u l l s g a in e d s lo w e r i n t h e f e e d l o t and w ere l i g h t e r a t s l a u g h t e r ( P < .0 5 ) . They i n d i c a t e d t h a t when fe d to c h o ic e g r a d e , e f f i c i e n c y among s i r e g ro u p s was n o t d i f f e r e n t . B a rto n (1971) compared th e grow th c h a r a c t e r i s t i c s o f Angus, 3 e e f S h o r th o r n , M ilk in g S h o r th o r n and F r i e s i a n s t e e r s . They d e m o n s tra te d t h a t th e d a i r y s t e e r s grew f a s t e r th a n th e b e e f b r e e d s . I n a c o m p a r a tiv e f e e d l o t e x p e rim e n t w ith 53 H e re fo rd and 53 Angus s t e e r s , B u t l e r e t a l (1962) d i s c o v e r e d H e r e f o r d s t e e r s had h i g h e r g a i n s (440 l b s vs 419 l b s ) w ith somewhat b e t t e r fe e d e f f i c i e n c y (952 lb f e e d /c w t g a in vs 1035 l b f e e d /c w t g a in ) ( P < .0 5 ) . C u n d if f (1970) e x p r e s s e d th e o p i n i o n t h a t even though H e r e f o r d s e x c e l l o v e r Angus and S h o r th o r n s i n g ro w th , t h e i r below a v e r a g e m a te r ­ n a l a b i l i t y makes them no b e t t e r i n t o t a l n e t m e r i t . He a l s o o b s e rv e d t h a t h e t e r o s i s f o r p o s tw e a n in g d a t a te n d e d to d e c r e a s e w ith i n c r e a s i n g age a f t e r a p p r o x im a te ly one y e a r . G regory e t a l (1966) a l s o n o te d a d e c r e a s e i n h e t e r o s i s w ith i n c r e a s i n g a g e. C u n d if f e t a l (1981) s t u d i e d p o s tw e a n in g grow th and fe e d e f f i ­ c ie n c y f o r 798 s t e e r s r e p r e s e n t i n g H e re f o rd (H) and Angus (A) s t r a i g h t b r e d s , H erefo rd -A n g u s r e c i p r o c a l c r o s s e s (HA,AH), Red P o l l H e re fo rd (RH) and Red P o ll-A n g u s (RA) c r o s s e s , Brown Sw iss-A ngus (BA) and Brown S w is s - H e r e f o r d (BH) c r o s s e s , G e lb v ie h - H e r e f o r d (GH) and G elb vieh -A n gu s (GA) c r o s s e s , M a in e -A n jo u -H e re fo rd (MH) and M aineAnjou-Angus (MA) c r o s s e s and C h ia n in a-A n g u s (CA) and C h i a n in a - H e r e f o r d (CH) b re e d c r o s s e s . The Brown Sw iss c r o s s e s , G e lb v ie h c r o s s e s and M aine-A njou c r o s s e s e x h i b i t e d th e most r a p i d grow th r a t e s and h e a v i e s t w e ig h ts a t 424 d a y s . C o n tr a r y to p r e v i o u s r e p o r t s , th e y found t h a t th e H e refo rd -A n g u s c r o s s e s d id n o t g a i n s i g n i f i c a n t l y f a s t e r th a n th e H e re f o rd and Angus s t r a i g h t b r e d s d u r i n g th e p o s tw e a n in g p e r i o d . T ab le 1 p r e s e n t s th e b re e d means f o r grow th t r a i t s . D e u ts c h e r and S l y t e r (1978) d e te r m in e d b re e d o f s i r e to be s i g n i ­ f i c a n t f o r most f e e d l o t t r a i t s . They s u g g e s te d t h a t C h a r o l a i s s i r e d t h r e e - b r e e d c r o s s c a l v e s were h e a v i e r a t b i r t h and w e an in g , g a in e d f a s t e r i n th e f e e d l o t and had h e a v i e r f i n a l f e e d l o t and c a r c a s s w e ig h ts th a n e i t h e r Angus o r H e re f o rd s i r e d c a l v e s . T a b le 2 g i v e s th e l e a s t - s q u a r e s means th e y found f o r th e v a r i o u s f e e d l o t t r a i t s . Frahm e t a l (1980) examined t h r e e - b r e e d c a l v e s s i r e d by C h a r o l a i s and Lim ousin b u l l s . s i g n i f i c a n t l y h e av ie r a t b ir t h , A lth o u g h th e C h a r o l a i s c a l v e s were t h e d i f f e r e n c e s i n f e e d l o t p e rfo rm a n c e were n o t s i g n i f i c a n t betw een th e s i r e b r e e d s . G regory and C u n d if f (1980) n o te d t h a t , in g e n e ra l, th re e - b r e e d r o t a t i o n a l c r o s s e s showed a h i g h e r l e v e l o f h e t e r o s i s f o r most p o s t ­ w eaning c h a r a c t e r s th a n th e tw o -b r e e d r o t a t i o n a l c r o s s e s . They Table 1. Breed Croup Means fur Live Weights and Crowth Rates3 . Breed Trait No. of animals 200-day weight, kg Ini Lial weight, kg li A II 44 67 57 67 B1I BA Rli RA Breed1 Group*1 Gil GA 53 68 44 67 Mil MA 46 63 cm CIA 56 63 Avg SDC 343 455 179.2 192.8 18 6 .0d 188.7 196.3 1 9 2 . 5e 189.1 196.1 1 9 2 .6e 198.1 209.9 2 0 4 .0 f 195.8 215.9 2 0 5 .8f 194.4 213.9 2 0 4 . 2f 198.9 214.9 2 0 6 .9 f 192.0 205.7 198.9 21.1 11 A Avg 205.4 221.1 2 1 3 .2d 217.6 227.2 2 2 2 .4e 213.5 220.9 2 1 7 .2e 221.9 239.8 2 3 0 .8f 224.0 247.6 2 3 5 .8fg 225.4 250.3 2 3 7 . 8fg 227.8 245.9 2 3 6 .8fg 219.4 236.1 227.7 23.4 A Avg SE coefficients 43 60 All HA A Avg II ADC, kg llll AA II A Avg 1.046 1.007 1.026 .1836 .1522 .1074 1.074 1.019 1.047d .986 .921 . 954e 1.099 1.068 1.084fg .1530 .1500 .0972 .1763 .1482 .1234 .1703 .1540 .1300 1.134 1.098 1.1168 1.162 1.158 1 . 1 601' 1.094 1.080 1.0878 .1875 .1549 .1385 .1738 .1493 .1243 .1603 .1531 .1180 1.085 1.050 1.067 .150 .0699 .0658 .0553 3 Cundiff et al. (1981). k II = Hereford; A = Angus; R = Red Poll; B = Broun Swiss; G = Celbvieh; M = Marine Anjou; Ci = Chianina. First letter denotes sire breed and second letter denotes dam breed. c SO is square root of mean square for sires within breed. Standard error of least-squares mean can be determined by multiplying the SB coefficient x SI) of a trait. ^ Effect of heterosis in Hereford-Angus crosses (P < .05). Means for t't crosses in the same row with no common superscripts differ (P < .05). 16 T a b le 2. L e a s t - S q u a r e s Means o f F e e d l o t T r a i t s 3 B reed o f S i r e T ra it No. o f c a l v e s A d j. F i n a l F e e d l o t w t . , kg F e e d l o t ADG, k g /d a y Angus H ereford C h aro lais 77 372 .84 83 380 .88 64 420 1 .0 0 a D e u ts c h e r and S l y t e r (1978) 5 17 e s t i m a t e d t h a t a t h r e e - b r e e d r o t a t i o n s h o u ld g iv e a 20 % i n c r e a s e i n w e ig h t weaned p e r cow e x p o se d a s compared t o p u r e b r e d s , and 4.5% more th a n i n a tw o -b r e e d r o t a t i o n a l m a tin g sy ste m . I n a n e x p e r im e n t co m parin g H e r e f o r d , Angus, S h o r th o r n and a l l r e c i p r o c a l c r o s s e s , G reg o ry e t a l (1966) found t h a t d i f f e r e n c e s i n g row th r a t e and f e e d e f f i c i e n c y among s i r e s w i t h i n b r e e d w ere s i g n i f i ­ c a n t i n d i c a t i n g a l a r g e amount o f a d d i t i v e g e n e t i c v a r i a t i o n . I n th e same s t u d y , th e y found t h a t c a l v e s s i r e d by H e r e f o r d b u l l s w e re s u p e r i o r t o th e o t h e r two b r e e d s i n g row th r a t e and f e e d e f f i c i e n c y . The mean a v e r a g e d a i l y g a i n o f t h e H e r e f o r d s i r e d c a l v e s was c o n s i s t e n t l y h i g h e r i n a l l p h a s e s o f th e t r i a l a s d e m o n s t r a t e d i n T a b le 3. T a b le 3. L e a s t S q u a re s Means f o r Growth by B re e d in g Group B reed o f S i r e T ra it ADG, w eaning to 284 days ADG, 284 to 368 days ADG, 368 t o 452 days H ereford Angus S h o r th o r n 0.688 1.018 0 .8 9 0 0 .6 8 0 0 .9 4 7 0.811 0 .6 7 8 0 .9 3 3 0 .8 1 4 a G reg o ry e t a l (1966) K lo s te rm a n (1972) p o i n t e d o u t t h a t when c a t t l e a r e fe d t o a s i m i l a r d e g re e o f f i n i s h o r g r a d e , numerous e x p e r im e n ts have shown little i f any d i f f e r e n c e i n e f f i c i e n c y o f fe e d u se among t h e c a t t l e o f v a r i o u s ty p e s and s i z e s . I n c o n t r a s t , when th e y a r e f e d t o a s i m i l a r 18 w e ig h t, c ie n t. th e l a r g e r c a t t l e a r e l e a n e r , g ra d e lo w e r a n d . a r e more e f f i ­ F i n a l l y , when b e e f s t e e r s a r e f e d to t h e same ti m e , th e f a s t e r g a in in g c a t t l e are f a t t e r a t s la u g h te r. Knapp e t a l (1980) e v a l u a t e d t h r e e b re e d c r o s s e s o f H e r e f o r d , C h a r o l a i s , Angus and Brown S w is s b r e e d s on p re w e a n in g and w eaning tra its . They found t h a t c a t t l e w i t h H e re f o rd dams a lw ay s had h i g h e r means th a n th o s e from H e r e f o r d s i r e s . In c o n tr a s t, C h aro lais s ir e d c a l v e s had g r e a t e r p re w e a n in g means th a n th o s e from C h a r o l a i s dams. Koch e t a l (1982) a n a ly z e d th e g e n e t i c , e n v i r o n m e n t a l and pheno­ t y p i c r e l a t i o n s h i p s among f o u r g ro w th and 12 c a r c a s s t r a i t s o f 2453 c r o s s b r e d s t e e r s r e p r e s e n t i n g 16 d i f f e r e n t s i r e b r e e d s . b re e d s i n th e p r o j e c t w e re Angus, H e r e f o r d , The s i r e J e r s e y , S o u th Devon, S im m e n ta l, L im o u sin , C h a r o l a i s , Red P o l l , Brown S w is s , G e lb v ie h , M aine-A njou, C h ia n in a , S a h iw a l, Brahman, P in z g a u e r and T a r e n t a i s e . They s u g g e s te d t h a t s e l e c t i o n f o r i n c r e a s e d g ro w th r a t e r e s u l t e d i n l a t e r m a tu rin g le a n ty p es. c rite ria , T h e ir r e s u l t s in d ic a te d t h a t s e l e c ti o n e x c e p t g a in t o w e an in g , t h a t i n c r e a s e d r e t a i l p r o d u c t p e r ­ c e n ta g e a l s o d e c r e a s e d m a rb lx n g , b u t th e d e c lx n e was g e n e r a l l y s m a l l . K e m p ste r e t a l (1976) a s s e r t e d t h a t le a n d i s t r i b u t i o n can be ig n o r e d i n b r e e d c o m p a r is o n s . In c o n tr a s t, S w ig e r e t a l (1965) a s ­ s e r t e d d i f f e r e n c e s i n g ro w th r a t e o f l e a n was much more i m p o r t a n t th a n d i f f e r e n c e s i n q u a l i t y g ra d e when c o n s i d e r i n g a s e l e c t i o n in d e x . Z i e g l e r e t a l (1971) n o te d t h e amount o f le a n was o f u tm o s t im p o r ta n c e b e c a u s e o f th e s i m p l e eco n o m ics in v o lv e d i n fe e d c o n v e r s io n d u r in g p r o d u c t i o n and th e u l t i m a t e r e t a i l v a lu e . In a s tu d y to e v a l u a t e h e t e r o s i s and management e f f e c t s i n p o s t - 19 w ean in g g ro w th o f Angus, H e re fo rd and r e c i p r o c a l c r o s s c a t t l e , Long and G reg ory (1975) o b s e r v e d t h a t th e c r o s s b r e d s ex ceeded th e p u r e b r e d s by 5 to 6 % f o r p o s tw e a n in g g a in and w e ig h t. Mason (1966) c o n c lu d e d t h a t i n c r o s s e s composed o f B r i t i s h b r e e d s t h e r e i s a s m a l l b u t c o n s i s t e n t amount o f h y b r i d v i g o r ( 1 - 10 $) f o r most c h a r a c t e r s o f s i z e and g ro w th . He found no g r e a t e r h y b r id v i g o r f o r a C h a r o l a i s by B r i t i s h c r o s s th a n when two B r i t i s h b r e e d s were crossed . However, t h e r e was as a d v a n ta g e i n s i z e and g ro w th r a t e o f 10^ o r more when Brahmans w ere c r o s s e s w ith B r i t i s h c a t t l e . No s i g n i f i c a n t b re e d d i f f e r e n c e s w ere found f o r b i r t h w e ig h t, w eaning w e ig h t o r s l a u g h t e r age when M c A l l i s t e r e t a l (1976) compared th e P o l l e d H e re f o rd , C h a r o l a i s , L im o u sin and S im m e n ta l b r e e d s a s s i r e s o f c ro ssb re d c alv e s. In a d d itio n , th e y found th e P o l l e d H e r e f o r d s a v e ra g e d l e s s f o r s l a u g h t e r w e ig h t p e r day o f age and more f o r f a t th ic k n e ss. I n an i n v e s t i g a t i o n c o m p a rin g c r o s s b r e d c a l v e s s i r e d by South Devon, M aine-A njou and S im m e n ta l b u l l s , Newman e t a l (1974) o b s e rv e d t h a t c a l v e s from th e M aine-A njou s i r e s were h e a v i e r when s t a r t i n g on t e s t (262 kg a s compared to 258 and 258 kg by t h e S o u th Devon and S im m e n ta l s i r e d c a l v e s , r e s p e c t i v e l y ) and g a in e d 1.42 kg p e r day w h ile on t e s t a s compared to 1.18 kg by th e S o u th Devon s i r e d c a l v e s and 1.26 kg by c a l v e s from S im m e n ta l s i r e s . O lson e t a l (1978a) c o n d u c te d an e x p e r im e n t i n v o l v i n g th e Angus, H e re f o rd and S h o r th o r n b r e e d s . They o b s e rv e d t h r e e - b r e e d c r o s s s t e e r s from c r o s s b r e d dams w ere 5-2$ h e a v i e r (P<.01) a t th e b e g in n in g b u t had no a d v a n ta g e i n p o s tw e a n in g g a in o v e r tw o - b r e e d c r o s s s t e e r s from 20 s t r a i g h t b r e d dams i n a 2 24 -d ay p o s tw e a n in g t e s t . A ll s t e e r s w ere s l a u g h t e r e d a t th e end o f th e p o s tw e a n in g f e e d i n g p e r io d i n w hich th e t h r e e - b r e e d s t e e r s a v e r a g e d 8.3 days o l d e r a t s l a u g h t e r . a l s o an i n d i c a t i o n o f i n c r e a s e d f a t i n s t e e r s from from s t r a i g h t b r e d dams. There was dams o v e r th o s e In a n o t h e r s tu d y u s i n g t h e same c a t t l e , O lson e t a l ( 1978 c) found c r o s s b r e d s s l i g h t l y more e f f i c i e n t i n p o s tw e a n in g g a i n th a n th e s t r a i g h t b r e d s . He n o te d t h e i r a d v a n ta g e i n r a t e o f g ro w th was enough to o f f s e t t h e i r h i g h e r m a in te n a n c e r e q u i r e m e n t s . S h r e f f l e r and T o u c h b e rry (1959) found th e g e n e r a l e f f e c t o f c r o s s b r e e d i n g on s k e l e t a l g ro w th i n d a i r y c a t t l e (G uernsey by H o l s t e i n ) was to o s m a l l t o be o f p r a c t i c a l o r s t a t i s t i c a l s i g n i f i ­ can ce. They found h e t e r o s i s to be o f im p o r ta n c e i n r a p i d g ro w th up to 2 y e a rs o f age. S m ith e t a l (1976) c r o s s e d H e r e f o r d and Angus dams w i t h H e r e f o r d , Angus, J e r s e y , S o uth Devon, L im o u sin , C h a r o l a i s and S im m e n ta l s i r e s . I n t h e i r s tu d y , C h a r o l a i s and S im m e n ta l c r o s s e s w ere th e l a r g e s t , f a s t e s t g a i n i n g b re e d g ro u p s . Vogt e t a l (1967) exam ined p o s tw e a n in g p e rfo rm a n c e to sla u g h te r i n Angus, H e re f o rd , S h o r th o r n and a l l r e c i p r o c a l c r o s s c a l v e s . The t w o - b r e e d c r o s s e s a v e r a g e d 40 gm more i n y e a r l i n g d a i l y g a i n th a n purebreds. They found no d i f f e r e n c e i n tw o - and t h r e e - b r e e d c r o s s e s , b u t th e b a c k c r o s s was s i g n i f i c a n t l y below th e tw o -b r e e d c r o s s . Feed­ l o t d a i l y g a in was n o t d i f f e r e n t f o r any o f t h e g ro u p s. W arwick (1968) s t a t e d t h a t i n 12 o f 13 c r o s s b r e e d i n g e x p e r im e n t s , i t was shown th e c r o s s b r e d s had a 2 - 4 $ a d v a n ta g e i n p o s tw e a n in g r a t e o f g a in w i t h a s l i g h t a d v a n ta g e i n e f f i c i e n c y . 21 F e e d l o t p e rfo rm a n c e o f pro g en y o f H e re f o rd , H e re f o rd X H o l s t e i n and H o l s t e i n cows w ere e v a l u a t e d "by W yatt e t a l (1977). They o b s e r v e d a s H o l s t e i n b r e e d i n g i n c r e a s e d l ) i n i t i a l w e ig h t i n c r e a s e d (30 to 55 kg), 2 ) s l a u g h t e r w e ig h t i n c r e a s e d (49 to 104 kg) and 3) number o f days to r e a c h c h o ic e i n c r e a s e d . C r o s s b r e e d in g - C a r c a s s C h a r a c t e r i s t i c s I n s p e c i f i c d e t a i l s t h e r e i s l a c k o f a g re e m e n t as to w hat c o n s t i ­ tu te s d e s i r a b i l i t y in b eef c arca sse s. However, t h e r e i s g e n e r a l a g re e m e n t on t h e e s s e n t i a l s - nam ely , t h a t c a r c a s s e s 3hould have 1) a maximum o f le a n combined w i t h t e n d e r n e s s and o t h e r maximum p a l a t a b i l i t y and 2) a minimum o f e x c e s s f a t (W arw ick and L e g a te s , 1979)* Of c o u r s e , due to t h e n a t u r e o f c a r c a s s c h a r a c t e r i s t i c s , an a n im a l m ust be s e l e c t e d on t h e p e r f o r m a n c e o f i t s s i b o r p ro g e n y t e s t . D eu tsch er and S l y t e r (1978) found b re e d o f s i r e most f e e d l o t t r a i t s . sig n ific a n t fo r I n an e x p e r im e n t i n v o l v i n g 77 Angus, 83 H e re fo rd and 64 C h a r o l a i s s i r e d c r o s s b r e d c a l v e s th e l e a s t - s q u a r e s means f o r v a r i o u s c a r c a s s c h a r a c t e r i s t i c s w ere: c a r c a s s w e ig h t (kg), 224, 225, 2 6 2; d r e s s i n g p e r c e n t (%), 6 1 .7 , 6 1 .6 , 6 2 .3 ; m a r b l i n g s c o r e , 4 -9, 4 . 4 9 , 4 -77 ; c a r c a s s g r a d e , 1 8 .6 , 1 8 .0 , 1 8 .4 ; f a t t h i c k n e s s (c m ), 1 .1 4 , 1 .1 7 , 0 .9 4 ; r i b e y e a r e a (c m 2 ) , 6 4 .5 , 6 5 .8 , 7 4 .2 ; k i d n e y f a t (%), 2 .9 , 2 . 6 , 3*0; c u t a b i l i t y (%), 5 0 .2 , 5 0 .4 , 5 1 .0 ; and y i e l d g r a d e , 2 .9 3 , 2.85, 2.60 f o r Angus, H e re f o rd and C h a r o l a i s s i r e d tiv e ly . For c a rc a s s grade, c a lv e s, respec­ 18 r e p r e s e n t s h ig h good and 19 i s low c h o ic e w i t h th e s c a l e i n c r e a s i n g by 1 f o r each 1/3 o f a g ra d e . The 22 m a r b lin g s c o r e i s ba se d on 4 b e in g s l i g h t and 5 s m a l l w i t h an i n c r e a s e o f 1 f o r each s t e p up i n m a rb lin g . T h e r e f o r e , i t a p p e a r s th e ra n k o f th e s i r e s f o r c a r c a s s g ra d e b ased on l e a n n e s s and m u s c lin g would be 1) C h a r o l a i s , 2) H e re f o rd and 3) Angus. C u n d if f e t a l (1971) c o n d u c te d a t r i a l i n w hich c a r c a s s w e ig h t a d j u s t e d f o r age was u sed as t h e m easu re o f g ro w th r a t e . They o b s e r v e d th e a s s o c i a t i o n b e tw ee n c u t a b i l i t y and c a r c a s s w e ig h t was more e n v i r o n m e n t a l t h a n g e n e t i c . The a n l y s i s o f g e n e t i c v a r i a t i o n w i t h i n b re e d o f s i r e - b re e d o f dam g ro u p s i n d i c a t e d t h a t s e l e c t i o n f o r r a t e o f g ro w th would be e f f e c t i v e and t h a t a s s o c i a t e d c h ang es i n c a r c a s s c o m p o s i tio n and m a r b l i n g would be g r e a t l y i n f l u e n c e d by age o r w e ig h t a t s l a u g h t e r . B ra ck e lsb erg et a l ( 197 1 ) showed t h a t c a r c a s s w e ig h t was a s i g n i f i c a n t s o u r c e o f v a r i a t i o n f o r a l l c a r c a s s t r a i t s e x c e p t m a r b l i n g and f i n a l c a r c a s s g ra d e . D ata c o l l e c t e d by Adams e t a l (1977) s u g g e s te d t h a t c a r c a s s w e ig h t would be o f v a lu e as a p r e d i c t o r o f c a r c a s s f a t n e s s w i t h i n b re e d group b u t n o t i n a p o p u l a t i o n c o m p ris e d o f s e v e r a l b r e e d s . In a t r i a l d e s ig n e d to e v a l u a t e t r a i t s i n th e U.S.D.A. y i e l d g ra d e e q u a t i o n f o r p r e d i c t i n g b e e f c a r c a s s c u t a b i l i t y i n b r e e d g ro u p s d i f f e r i n g i n ty p e , C rouse e t a l (1975) c o n c lu d e d c a r c a s s w e ig h t was a good p r e d i c t o r w i t h i n a b r e e d g rou p , b u t p o or o v e r a l l s t e e r s . They s u r m is e d f a t t h i c k n e s s was th e most u s e f u l p r e d i c t o r and l o n g i s s i m u s a r e a th e w o r s t. Koch e t a l (1982) e x p lo r e d th e w h o l e s a l e c u t c o m p o s i tio n o f 642 c a r c a s s e s o b t a i n e d from s t e e r s t h a t w ere from m a tin g s o f H e re f o rd and Angus cows to H e re f o rd , Angus, T a r e n t a i s e , P i n z g a u e r , Brahman and S a h iw a l s i r e s . They o b s e rv e d t h a t i n c r e a s e s i n w e ig h t a s s o c i a t e d w i t h 23 c o n tin u e d fe e d i n t a k e r e s u l t e d i n g r e a t e r f a t to le a n r a t i o th a n from i n c r e a s e d g e n e t i c g ro w th p o t e n t i a l . T h e i r c o n c l u s i o n was t h a t m ost o f th e v a r i a t i o n i n w h o le s a le c u t p e r c e n t a g e s and c o m p o s itio n o f c u t s was a s s o c i a t e d w i t h d i f f e r e n c e s i n t o t a l le a n and f a t y i e l d among s i r e b re e d g ro u p s. They a l s o n o te d t h a t as s i d e w e ig h t i n c r e a s e d , p e r c e n ­ ta g e o f r e t a i l p r o d u c t and b o n e - i n c u t s d e c r e a s e d w h ereas f a t t r i m in creased in a l l cu ts. C ly b u m e t a l (1961) s t u d i e d th e e f f e c t s o f b re e d and c r o s s on carcass c h a r a c te r is tic s of beef s te e rs . They o b s e rv e d Angus, P o l l e d H e re f o rd , S a n ta G e r t r u d i s and a l l two and t h r e e - w a y c r o s s 3 t e e r s . T h e ir m a jo r o b s e r v a t i o n was t h a t Angus had t h e l a r g e s t l o i n eye p e r 100 pounds o f c a r c a s s (1.95 cm^) and th e S a n ta G e r t r u d i s th e s m a l l e s t (1 .5 4 cm ^). B u t l e r e t a l (1962) compared c a r c a s s m e r i t o f 106 H e re fo rd and Angus s t e e r s . The a n a l y s i s f a v o re d th e c a r c a s s e s from th e Angus s t e e r s i n m a r b lin g s c o r e and showed a 2 / 3 g ra d e a d v a n ta g e i n f i n a l c a r c a s s g ra d e . However, i t was o b serv ed t h a t th e Angus c a t t l e had a h i g h e r p e r c e n t i n f o r e q u a r t e r w h ile th e H e r e f o r d s were s i g n i f i c a n t l y h ig h e r in h in d q u a rte r. B e e f- and d a i r y - t y p e c a t t l e w ere compared f o r c u t a b i l i t y and e a t a b i l i t y (Branaman e t a l , 1962). They n o te d th e d a i r y - t y p e a v e ra g e d 3 % l e s s i n d r e s s i n g p e r c e n t ; ho w ev er, th e y e q u a l l e d th e b e e f c a t t l e i n p e r c e n ta g e o f h i g h - p r i c e d c u t s . They d id o b s e rv e a more d e s i r a b l e a v e r a g e q u a l i t y g ra d e i n th e b e e f s t e e r s (C°) a s compared to th e d a i r y ( S t +). The o n ly p a l a t a b i l i t y a t t r i b u t e s t h a t a p p e a re d to be a s s o ­ c i a t e d w ith ty p e were th e i n t e n s i t y o f le a n f l a v o r and j u i c i n e s s . 24 T h e r e f o r e , th e y c o n c lu d e d t h e r e was l i t t l e a d v a n ta g e f o r b e e f - t y p e from th e s t a n d p o i n t o f c a r c a s s c u t - o u t . B ass e t a l (1981) com pared c a l v e s from Angus dams s i r e d by S im m e n ta l, B londe d 'A q u ita n e , C h a r o l a i s , M aine-A njou, F r i e s i a n , J e r ­ s e y , H e re f o rd and Angus b u l l s . h e a v ie st in te r n a l fa t. p re v io u s ly re p o rte d He c o n c lu d e d d a i r y b r e e d s had th e The r e m a in in g r e s u l t s w ere c o m p a t ib le w i t h stu d ie s. A lenda e t a l (1980b) a t t e m p t e d to e s t i m a t e g e n e t i c e f f e c t s on r i b e y e a r e a and f a t c o v e r and to u t i l i z e t h e s e e s t i m a t e s to a s s e s s e f f e c t i v e n e s s o f c r o s s b r e e d i n g s y s te m s . g us, C h a r o l a i s and H e r e f o r d p a r e n ta g e . They o b s e rv e d c a t t l e o f An­ In a n aly z in g rib e y e a re a , th e y n o te d t h a t th e C h a r o l a i s a d d i t i v e e f f e c t s w ere 26$ g r e a t e r th a n e i t h e r H e re f o rd o r Angus, where th e a d d i t i v e e f f e c t o f th e i ^ c a l c u l a t e d as b re e d was n (n-1)B iii - Si ' — ♦ B3 i l - Bi d J ) --------5-------- ■ 1* w here, n i s th e number o f b r e e d s and Bi j k i s th e l e a s t s q u a r e mean f o r th e b re e d c l a s s h a v in g b r e e d i as th e s i r e , b re e d j as th e m a t e r n a l g ra n d s i r e and b re e d k a s th e m a t e r n a l g ra n d dam. In d iv id u al h e te ro - s i s ( c a l c u l a t e d as th e sum o f t h e dom inance e f f e c t and o n e - h a l f th e a d d i t i v e X a d d i t i v e e f f e c t ) was 3$ f o r th e Angus by C h a r o l a i s c r o s s e s and 2$ f o r t h e H e re f o rd by C h a r o l a i s c r o s s e s . f o r d had no s i g n i f i c a n t h e t e r o t i c e f f e c t s . The C h a r o l a i s by H ere­ M a te r n a l h e t e r o s i s was l a r g e and n e g a s iv e f o r a l l c r o s s e s , i n d i c a t i n g c r o s s b r e d dams p ro d u c e c a lv e s w ith s m a lle r rib e y e s. Angus and H e re f o rd a d d i t i v e e f f e c t s w ere more th a n 1.0 cm g r e a t e r th a n C h a r o l a i s f o r f a t co v er. Any c r o s s 25 c o n t a i n i n g C h a r o l a i s d id n o t p ro du ce i n d i v i d u a l h e t e r o s i s e f f e c t s . Fo r f u t u r e r i b e y e a r e a o f th e v a r i o u s c r o s s e s th e y p r e d i c t e d 0.1, -0 .9 and - 1.9 cm^ d e v i a t i o n s from th e mean o f th e t h r e e p u r e b r e d s f o r th e Angus X H e re f o rd and C h a r o l a i s X H e re f o rd c r o s s e s , re sp ec tiv e ly . They s u g g e s te d t h a t th e d e c r e a s e was due to l a r g e n e g a t i v e m a t e r n a l e f ­ fe c ts. No c r o s s was e x p e c te d to o u t - p e r f o r m th e p u r e b r e d C h a r o l a i s fo r rib e y e area. Koch e t a l (1976) exam ined t h e c a r c a s s c o m p o s i tio n , q u a l i t y and p a l a t a b i l i t y o f v a rio u s c ro ssb re d s. Breed o f s i r e (H e re fo rd , Angus, J e r s e y , S o uth Devon, L im o u sin , C h a r o l a i s and S im m e n ta l) was h i g h l y s ig n ific a n t fo r a ll tr a its . C h a r o l a i s - s i r e d c a l v e s had t h e h e a v i e s t c a r c a s s w e ig h ts and J e r s e y - s i r e d c a l v e s w ere t h e l i g h t e s t . p e r c e n t d id n o t d i f f e r among s i r e b r e e d s , D r e s s in g w i t h th e C h a r o l a i s and S im m e n ta l c a l v e s c a r r y i n g l e s s f a t t h a n th e o t h e r b r e e d s . K em pster e t a l (1982) exam ined d i s s e c t i o n d a t a f o r 755 s t e e r c a r c a s s e s c o m p r is in g 17 b r e e d - t y p e X f e e d i n g s y s te m g ro u p s . Breed ty p e s in c lu d e d A y r s h i r e , F r i e s i a n , F r i e s i a n X A y r s h ir e and c r o s s e s o u t o f F r i e s i a n s by Angus, C h a r o l a i s , H e r e f o r d , L im o u sin , S im m e n ta l and So uth Devon s i r e s . They a d v is e d t h a t when c a t t l e a r e s l a u g h t e r e d a t e q u a l f a t n e s s , d i f f e r e n c e s b e tw e e n b r e e d s i n th e l o n g i s s i m u s a r e a i s c l o s e l y r e l a t e d to d i f f e r e n c e s i n c a r c a s s w e ig h t. E ig h te e n hun dred p u r e b r e d and c r o s s b r e d c a l v e s pro d u ced from 1966 th r o u g h 1970 w ere in c l u d e d i n a s tu d y by H e l p h i n s t i n e and E l i n g s (1971). D ata c o l l e c t e d i n 1966 in v o lv e d o n ly s t r a i g h t b r e d H e re f o rd c alv e s. In 1967, th e f i r s t r e c i p r o c a l c r o s s e s b e tw e e n Angus and H e re fo rd w ere produced. Brown S w is s s i r e s w ere used i n i t i a l l y i n th e 26 1967 b r e e d i n g s e a s o n r e s u l t i n g i n m o s tly c r o s s b r e d c a l v e s f o r th e 1968, 1969 and 1970 c a l f c r o p s . They n o te d d i f f e r e n c e s i n d r e s s i n g p e r c e n t , r i b e y e a r e a and p e r c e n t m a jo r trim m ed c u t s due to t h e i n ­ c r e a s e i n th e number o f c r o s s b r e d c a l v e s . H e d ric k e t a l (1970) found c r o s s b r e d s a b o u t 1 % s u p e r i o r i n r i b e y e a r e a i n an e x p e r im e n t i n v o l v i n g Angus, H e re f o rd and C h a r o l a i s s t r a i g h t b r e d and c r o s s b r e d c a t t l e . No s i r e d i f f e r e n c e s w ere d e t e c t e d , w hich th e y a t t r i b u t e d to th e f a c t t h a t th e b u l l s w ere sam p led from th e b e s t o f each b re e d . In a l a t e r s tu d y i n v o l v i n g t h e same t h r e e b r e e d s , H e d ric k e t a l (1975) c o n c lu d e d C h a r o l a i s c o u ld be used w i t h a d v a n ta g e a s m a le s i n c o m b in a tio n w i t h H e r e f o r d f e m a l e s . He found c a r c a s s e s from C h a r o l a i s s i r e d c a l v e s o u tw e ig h e d H e r e f o r d s , w hich i n t u r n o u tw e ig h e d Angus. However, he n o te d t h e Angus and H e re f o rd s i r e d c a l v e s had s i g n i f i ­ c a n t l y f a t t e r c a r c a s s e s th a n th o s e from C h a r o l a i s s i r e s , w i t h th e Angus s i r e s p ro d u c in g c a l v e s w i t h th e h i g h e s t q u a l i t y g ra d e . The s t e e r s s i r e d by th e C h a r o l a i s b u l l s w ere c o n s i s t e n t l y l a r g e r i n l o i n eye a r e a . G reg ory e t a l (1966) ra n k e d t h e H e r e f o r d , th a t order fo r net m e rit of c arca ss t r a i t s . Angus and S h o r th o r n i n They found t h a t th e H e re fo rd b re e d c o n t r i b u t e d more th a n e i t h e r Angus o r S h o r th o r n b re e d to t h e a v e r a g e h e t e r o s i s e ffects. D ata w ere a n a ly z e d on s l a u g h t e r e d w e ig h t, h o t c a r c a s s w e ig h t, U.S.D.A. q u a l i t y g ra d e , a d j u s t e d f a t t h i c k n e s s a t th e 12th r i b , e sti­ m ated k id n e y and p e l v i c f a t , l o n g i s s i m u s a r e a and e s t i m a t e d c u t a b i l i t y a d j u s t e d to an a g e - c o n s t a n t b a s i s o f 453-2 days on 537 c a r c a s s e s i n a 27 f o u r - b r e e d d i a l l e l c r o s s d e s i g n i n c l u d i n g th e Red P o l l , Brown S w is s , H e re f o rd and Angus b r e e d s to e s t i m a t e h e t e r o s i s and b re e d t r a n s m i t t e d e f f e c t s on m a jo r econom ic t r a i t s o f b e e f c a t t l e (G regory e t a l , 1962). Brown S w is s ra n k e d f i r s t and Red P o l l l a s t i n b re e d t r a n s m i t ­ t e d e f f e c t s f o r c a r c a s s t r a i t s a s s o c i a t e d w i t h w e ig h t. When c a r c a s s t r a i t s w ere a d j u s t e d to a c o n s t a n t c a r c a s s w e ig h t (270.9 kg) h e t e r o s i s e f f e c t s w ere n o t i m p o r t a n t . For th e a g e -c o n s ta n t a n a ly s is , h e t e r o s i s was s i g n i f i c a n t f o r s l a u g h t e r w e ig h t, c a r c a s s w e ig h t, a d j u s t e d f a t t h i c k n e s s and e s t i m a t e d c u t a b i l i t y . The l e a s t - s q u a r e s means by b re e d o f s i r e a r e p r e s e n t e d i n T a b le 4 and T ab le 5 on an age c o n s t a n t and w e ig h t c o n s t a n t b a s i s , re sp ec tiv e ly . G e rla u g h e t a l (1951) exam ined t h e c a r c a s s m e r i t o f Angus, H ere­ f o r d and t h e i r r c i p r o c a l c r o s s e s . They found th e c r o s s b r e d s h e a v i e r w i t h a h i g h e r d r e s s i n g p e r c e n t th a n e i t h e r o f th e p u r e b r e d s . In a s i m i l a r e x p e r i m e n t , G a in es e t a l (1967) exam ined th e h e t e r o s i s e f f e c t s from c r o s s e s among Angus, H e re f o rd and S h o r th o r n s . They o b s e r v e d t h e a d j u s t e d c a r c a s s w e ig h t a v e r a g e was 9«1 kg h e a v i e r th a n s t r a i g h t b r e d s , an i n c r e a s e o f 3*1 %• The a d j u s t e d l o i n eye a r e a was 2.5 cm^ l a r g e r th a n th e mean o f s t r a i g h t b r e d s (3»6# i n c r e a s e ) . There a p p e a re d to be no h e t e r o s i s f o r c a r c a s s g r a d e , m a r b lin g s c o r e o r c a r c a s s c o n fo rm s tio n . I n a s t u d y to exam ine th e d i f f e r e n c e s i n c a r c a s s t r a i t s o f C haro­ l a i s and L im o u sin s i r e d t h r e e - b r e e d c r o s s c a l v e s , Frahm e t a l (1980) found d r e s s i n g p e r c e n t t h e - o n l y t r a i t w hich d i f f e r e d b e tw ee n b r e e d s . They o b s e rv e d a s l i g h t a d v a n ta g e f o r t h e L im o u sin s. Z i e g l e r e t a l (1971) com pared c e r t a i n c a r c a s s t r a i t s o f s e v e r a l T a b le 4. L e a s t- S q u a r e s Means f o r C arca ss T r a i t s — Age C o n sta n t B a s is 3 . Red P o l l Brown Swiss U.S.D.A. Q u a lity Grade *3 8 .7 8 .9 Adj. F a t T h ick n e ss (cm) 1 .04 E s t . Kidney & P e l v i c (%) 4 .4 L ongissim us Area (cm^) E s tim a te d C u t a b i l i t y (%) T rait 3 Gregory a l. Breed o f S i r e H e refo rd Angus Mean 8.6 9 .5 8 .9 1.22 1.29 1 . 1 0 + .02 3 .7 3 .3 3.7 3 .8 + .05 66.6 74.4 66.2 68.4 6 8.9 ± - 45 5 4 .8 5 7 .3 5 5 .1 54.2 5 5 .3 ± -I* .83 (1 9 6 2 ). k 8 = a v e ra g e good; 9 = h ig h good; 10 = low c h o ic e ; 11 = a v e ra g e c h o i c e . + .10 T able 5. L e a s t- S q u a re s Means f o r C a rc a ss T r a i t s — Weight C o n sta n t B a s is a T ra it Red P o l l U.S.D.A. Q u a lity Grade^ 8.8 A d j. Fat T h ick n e ss (cm) 1.05 E s t. Kidney and P e l v i c F a t (%) 4 .4 Longissim us Area (cm^) E s tim a te d C u t a b i l i t y (%) Brown Swiss Breed o f S i r e H e re fo rd Angus Mean 8.6 9 .6 8.8 1 .1 8 1.2 6 1 .0 7 + .02 3 .6 3 .3 3.7 3.7 + .05 6 7 .2 71.2 66.0 67.2 6 7 .9 + .43 54.7 57.4 5 5 .3 54.3 5 5.4 + .15 8 .4 .79 a Gregory e t a l . (1 96 2 ). 8 = a v e ra g e good; 9 = h ig h good; 10 = low c h o ic e ; 11 = a v e ra g e c h o ic e . + .10 50 b re e d s and c r o s s e s . T h e i r r e s u l t s i n d i c a t e d th e C h a r o l a i s and H ol­ s t e i n s t e e r gro u p s had a s i g n i f i c a n t l y g r e a t e r (P<.01) c u t a b i l i t y th a n any o t h e r b re e d g ro u p ( C h a r o l a i s (C), H e re f o rd (He), H o l s t e i n (Ho), S h o r t h o r n , Angus ( a ) , A by A-Ho, He b y A-Ho, P o l l e d He by A-Ho). a d d itio n , In th e Angus and S h o r th o r n s t e e r s had s i g n i f i c a n t l y g r e a t e r m a r b lin g s c o r e s th a n th e o t h e r b re e d g ro u p s . The C h a r o l a i s , H o l s t e i n and P o l l e d He by A-Ho s t e e r g ro up s w ere lo w e r i n t o t a l a c c e p t a b i l i t y . Young e t a l (1978) a t t e m p t e d to c h a r a c t e r i z e v a r i o u s ty p e s o f th re e -b re e d cross c a t t l e fo r c a rc a ss t r a i t s . T h e i r t r i a l i n c l u d e d 282 s t e e r s w ith c a r c a s s d a t a c o l l e c t e d on 275 p ro d u c e d by a r t i f i c i a l l y i n s e m i n a t i n g y e a r l i n g h e i f e r s o f 12 c r o s s b r e d g ro u p s (H e re fo rd -A n g u s r e c ip r o c a l c ro s se s p lu s c r o s s e s p rod u ced by m a tin g J e r s e y , S ou th Devon, S im m e n ta l, L im o u sin and C h a r o l a i s s i r e s t o H e re f o rd and Angus cows) to H e r e f o r d , Angus, Brahman, S o u th Devon and H o l s t e i n b u l l s . When age was h e ld c o n s t a n t b re e d o f s i r e was s i g n i f i c a n t f o r a l l t r a i t s e x c e p t l o i n eye a r e a and m a t u r i t y . Breed o f s i r e o f cow was a s i g n i f i c a n t s o u rc e o f v a r i a t i o n f o r f a t t h i c k n e s s , lo n g issim u s a re a , e s t i m a t e d p e r c e n t a g e k id n e y , h e a r t and p e l v i c f a t , y i e l d g ra d e and c o n f o r m a tio n . te r tra it. Breed o f dam o f cow was n o t s i g n i f i c a n t f o r any s l a u g h ­ H o l s t e i n s i r e d s t e e r s had t h e l e a s t amount o f f a t o v e r th e l o n g i s s i m u s , w hich r e s u l t e d i n th e b e s t y i e l d g ra d e f o r any s i r e b re e d . When w e ig h t was h e ld c o n s t a n t , b re e d o f s i r e was s i g n i f i c a n t f o r th e same t r a i t s as when age was c o n s t a n t . I n a d d i t i o n , b re e d o f s i r e o f cow was s i g n i f i c a n t f o r a l l c a r c a s s t r a i t s e x c e p t s l a u g h t e r w e ig h t, m a t u r i t y and q u a l i t y g ra d e . W yatt e t a l (1977) a n a ly z e d th e c a r c a s s t r a i t s o f p ro g e n y from 31 H e re fo rd , H e re f o rd X H o l s t e i n and H o l s t e i n cows b re d to C h a r o la i s b u lls. As p e r c e n t H o l s t e i n b r e e d in g i n c r e a s e d : in creased , 2) r i b e y e a r e a was l a r g e r , 1) C a rc a s s w e ig h t 3) c u t a b i l i t y d e c r e a s e d and 4) c o n f o r m a tio n s c o r e s w ere lo w e r. In a s tu d y to a p p r a i s e g e n e t i c p a r a m e t e r s o f c a r c a s s c h a r a c t e r i s ­ t i c s from prog en y o f P o l l e d H e re fo rd s i r e s and H o ls te in -A n g u s cows, W ilso n e t a l (1976) found th e f a s t e r g ro w in g c a t t l e ten d ed to have lo w e r m a rb lin g s c o r e s . M a rb lin g s c o r e o n ly a c c o u n te d f o r 7.3 % o f th e v a ria n c e in sh e a r score. Warwick (1968) f a i l e d to f i n d any h e t e r o t i c e f f e c t s . A lthough th e t h r e e - b r e e d B r i t i s h c r o s s n e v e r exceeded th e p u re b re d s i n a s i n g l e tra it, i n t o t a l n e t m e r i t c r o s s e s u s u a l l y ex ceeded th e b e s t p u re b re d . They showed C h a r o l a i s s i r e d c a lv e s w ere s u p e r i o r i n l e a n n e s s o f c a r ­ c a s s , b u t w ere 1/3 to 2 /3 lo w e r i n c a r c a s s g ra d e th a n B r i t i s h s i r e d c a lv e s a t th e same w e ig h t. Temple e t a l (1960) c o n t r a s t e d th e c a r c a s s q u a l i t y o f c r o s s b r e d s t e e r s s i r e d by s i x b re e d s o f b u l l s . They ran k ed th e b re e d s : h orn , H e re fo rd , Angus, Brahman, Brangus and C h a r o l a i s . S h o rt­ However, th e range o f g ra d e s was o n ly from low good to low c h o ic e i n d i c a t i n g s m a l l d i f f e r e n c e s i n q u a l i t y due to s i r e b re e d . In th e th e C h a r o la i s s i r e d c a l v e s had th e l a r g e s t r i b e y e s tu d y , th e y found a r e a o f th e s i x b reeds. I n an i n v e s t i g a t i o n o f th e c a r c a s s c h a r a c t e r i s t i c s and meat q u a l i t y o f H e re fo rd and F r i e s i a n s t e e r s , T a y lo r (1982) found a d e f i ­ n i t e a d v a n ta g e f o r th e b re e d i n d r e s s i n g p e r c e n t (P<.01), a lth o u g h t h e r e were no d i f f e r e n c e s i n l i v e w e ig h t. As i m p l i e d by th e l a r g e r 32 d r e s s i n g p e r c e n t , t h e H e re f o rd s t e e r s w ere f a t t e r , e a r l y m a tu r in g c h a r a c t e r i s t i c . d iff e r e n c e s in te n d ern ess, d e n o tin g t h e i r However, he was u n a b le to show any ju ic in e s s or fla v o r. O lson e t a l (1978b) o b s e r v e d m a t e r n a l h e t e r o s i s was n o n s i g n i f i ­ c a n t f o r c a r c a s s t r a i t s o f s t e e r s when s l a u g h t e r age was i n c l u d e d a s l i n e a r and q u a d r a t i c c o v a r i a b l e s . L a s le y e t a l (1971) c o n c u r r e d when th e y , to o , i n d i c a t e d t h a t h e t e r o s i s may n o t be i m p o r t a n t f o r c a r c a s s tra its . Newman e t a l (1974) compared p r o d u c t i o n t r a i t s o f s t e e r s by South Devon, M aine-A njou and S im m e n ta l s i r e s . They found t h e b re e d o f s i r e d i f f e r e n c e s i n s l a u g h t e r a g e, l o i n eye a r e a and c a r c a s s w e ig h t w ere n o t s i g n i f i c a n t . They d id f i n d t h a t th e S o u th Devon b re e d was f a t t e r p e r 100 kg o f c a r c a s s r e s u l t i n g i n a more d e s i r a b l e m a r b lin g score. C a r c a s s q u a l i t y and f a t , l e a n and bone d i s t r i b u t i o n w ere a n a ly z e d from B r i t i s h and C o n t i n e n t a l s i r e d (P. H e re f o rd , and S im m e n ta l) c r o s s b r e d s t e e r s . C h aro lais, L im o u sin The P o l l e d H e re f o rd c a l v e s a v e r a g e d l e s s f o r s l a u g h t e r w e ig h t, l o i n eye a r e a and p e r c e n t trim m ed l o i n p e r day o f age. A ltho ug h th e C h a r o l a i s and L im o u sin s i r e d c a l v e s had h e a v i e r (P<.01) c a r c a s s w e i g h t s , th e S im m e n ta l c a l v e s had a g r e a t e r (P < .0 5 ) p e r c e n t h i n d q u a r t e r . Long and G reg ory (1975) c o n t r a s t e d th e c a r c a s s t r a i t s o f Angus, H e re f o rd and r e c i p r o c a l c r o s s c a t t l e w i t h h o t c a r c a s s w e ig h t a s a c o v a ria te . They c o n c lu d e d c a t t l e w i t h Angus s i r e s o r dams p rod uced h e a v ie r c a rc a ss e s w ith h ig h e r d re s s in g p e rc e n ta g e s, co n fo rm atio n s c o r e s , m a r b lin g s c o r e s and f i n a l g r a d e s . N e v e r t h e l e s s , th e y w ere 33 f a t t e r w ith lo w er c u t a b i l i t y . The a u t h o r s o b s e rv e d h e t e r o s i s e f f e c t s f o r l o i n eye a r e a and f a t t h i c k n e s s . P h e n o ty p ic and G e n e tic P a ra m e te r s G e n e tic change th ro u g h s e l e c t i o n i s d e p en d e n t on th e g e n e t i c v a r i a b i l i t y found i n th e p o p u l a t i o n . S h e lb y e t a l . (1963) n o te d th e p h e n o ty p ic and g e n e t i c r e l a t i o n s h i p s e x i s t i n g betw een and w i t h i n v a r ­ io u s t r a i t s used as c r i t e r i a f o r s e l e c t i o n must be known to maximize th e r a t e o f p r o g r e s s i n a s e l e c t i o n program . I t h a s been shown i n swine t h a t th e amount o f v a r i a t i o n e x p l a i n e d by g e n e t i c s i s d i f f e r e n t from one b re e d to th e n e x t (B lunn and B a k e r, 1 94 7 ). Alenda e t a l . ( 1980a) s u g g e s te d t h a t h a v in g e s t i m a t e s o f th e g e n e t i c and m a te r n a l e f f e c t s , th e m ag n itu d e o f b o th mean and v a r i a n c e can be p r e d i c t e d a n d / o r c o n t r o l l e d by s e l e c t i o n o f b r e e d s e n t e r i n g i n t o o r by c h an g in g th e o r d e r o f b re e d s i n t h e r o t a t i o n . H e r i t a b i l i t y - G e n era l S e l e c t i o n i s based on th e p h e n o ty p ic v a lu e o f b r e e d in g a n im a ls and a t tim es on th o s e o f t h e i r r e l a t i v e s . These p h e n o ty p ic v a lu e s a r e used to o b t a i n an e x p e c te d b r e e d in g v a lu e a s an i n i t i a l s t e p in th e s e le c tio n process. The r e l a t i v e a g re em e n t betw een phen otyp e and b r e e d in g v a lu e i s m easured by th e c o e f f i c i e n t o f h e r i t a b i l i t y o r sim p ly h e r i t a b i l i t y ( h ^ ) . Lush (1945) p o in te d o u t th e im p o rta n c e o f h e r i t a b i l i t y and empha­ 34 s i z e d i t s r o l e i n p r e d i c t i n g t h e "breeding v a l u e o f an a n im a l. Lush (1940) d e f in e d h e r i t a b i l i t y i n th e "n arrow s e n s e " a s th e p r o p o r t i o n o f th e t o t a l v a r i a n c e i n a t r a i t t h a t i s a t t r i b u t e d to t h e a v e r a g e o r a d d itiv e e f f e c ts of genes. 2 _____________ 1 "i Because o n ly a d d i t i v e g e n e t i c e f f e c t s i n a p o p u l a t i o n c o n t r i b u t e to th e perm anent g a i n from s e l e c t i o n , an e s t i m a t e o f h e r i t a b i l i t y i n th e n arro w s e n s e i s more d e s i r a b l e f o r p r e d i c t i n g th e r e s u l t s from s e l e c t i o n p r o c e d u r e s (L ush, 1945)D ic k e rso n (1958) d i s c u s s e d th e a d v a n ta g e s and d i s a d v a n t a g e s o f v a rio u s e stim a te s of h e r i t a b i l i t y . He s u g g e s te d th e r e g r e s s i o n o f o f f s p r i n g on m id p a re n t (LQ-p-) i s t h e most n e a r l y u n b ia s e d e s t i m a t e o f e ffe c tiv e h e rita b ility . However, i t i s s u b j e c t to b i a s from e n v i r o n ­ m e n ta l c o r r e l a t i o n betw een p a r e n t and o f f s p r i n g and by s e l e c t i o n o f p a r e n t s i f th e r e g r e s s i o n i s n o n l i n e a r . A nother e s t i m a t e s u g g e s te d was th e d o ub led r e g r e s s i o n o f o f f ­ s p r i n g on dam (2 b Q(j ) . I t i s u s u a l l y computed w i t h i n s i r e p r o g e n ie s to a v o id e f f e t s o f any a s s o r t a t i v e m a tin g o r e n v ir o n m e n ta l c o r r e l a t i o n s (L ush, 1940). D ic k e rso n p o i n t s o u t t h a t when compared to h Qp i t o v e r e s t i m a t e s h e r i t a b i l i t y by ( . 5 o 2 + a 2 ) * ( l / o 2) where a 2i s th e m mg p m v a r i a n c e a t t r i b u t a b l e to m a te r n a l f a c t o r s , ia n c e and cr2 i s th e p h e n o ty p ic v a r ­ a 2 i s th e c o v a r ia n c e betw een th e m a te r n a l and g e n e t i c mg p o rtio n of v a r ia tio n . A s i m i l a r e s t i m a t e i s th e doubled r e g r e s s i o n o f o f f s p r i n g on s i r e ( 2 b QS) , however i t te n d s to u n d e r e s t i m a t e th e t r u e h e rita b ility . 35 T h ree a d d i t i o n a l m ethods were p r e s e n t e d by D ic k e r s o n : s i r e component ( h | g ) , 2 ) from th e dam component ( h ^ ) f u l l - s i b c o r r e la tio n ( h |+ s ) . l) f r o m th e o r 3) from th e The f i r s t method i s i d e n t i c a l w ith th e q u a d ru p le d c o r r e l a t i o n betw een p a t e r n a l h a l f - s i b s ( 4 r p p ) . The m agni­ tu d e o f t h e b i a s o f th e e s t i m a t e depends on th e g e n e - e n v ir o n m e n t in te ra c tio n . H e r i t a b i l i t y - F e e d lo t T r a it s S w ig er e t a l . c a ttle . (1963) e v a l u a t e d th e p o s tw e a n in g g a in i n b e e f They d i s c o v e r e d t h a t h e r i t a b i l i t y i n c r e a s e d a s age o f c a l f in c re a se d . U ric k e t a l . H e r i t a b i l i t y o f 5 5 0 -d ay w e ig h t was e s t i m a t e d a s .37* (1957) found s i m i l a r r e s u l t s w i t h h e r i t a b i l i t i e s o f p o s tw e a n in g g a i n v a r y i n g from .09 to .43* They c o n c lu d e d t h a t v a r y i n g amounts o f p r o g r e s s f o r r a p i d g a i n i n g a b i l i t y c o u ld be made b a se d on s e l e c t i o n a t d i f f e r i n g p o i n t s i n th e p o s tw e a n in g g a i n . C a r t e r and K in c a id (1959) e s t i m a t e d f e e d l o t d a i l y g a i n h e r i t a b i ­ l i t y by v a r i o u s m e th o d s. sib , T h e i r e s t i m a t e s w ere: . 3 8 ; r e g r e s s i o n o f p ro g e n y a v e r a g e on s i r e , r e g r e s s i o n o f o f f s p r i n g on dam, p a te rn a l h a lf . 2 1 ; and i n t r a - s i r e .40. Some o f t h e p u b l i s h e d e s t i m a t e s o f h e r i t a b i l i t y f o r f e e d l o t t r a i t s a r e p r e s e n t e d i n T a b le 6 . As can be s e e n , th e f e e d l o t t r a i t s te n d to be m o d e r a te l y to h i g h l y h e r i t a b l e i n d i c a t i n g t h a t s e l e c t i o n f o r th o s e t r a i t s s h o u ld be s u c c e s s f u l . 36 T a b le 6 . H e r i t a b i l i t y E s t i m a t e s o f F e e d l o t T r a i t s i n B eef C a t t l e . P o s tw e a n in g d a ily g a in A u th o r F in a l w e ig h t Y e arlin g w e ig h t Benyshek (1981) .52 .52 ----- B la c k w e ll e t al_. (1962) .76 .70 .10 Buchanan et_ a l . .42 ----- .30 Busch & D in k e l (1967) .55 .85 ----- C h e n e tte et_ a l . ----- ----- .14 . 88 1.00 ----- .26 .48 ----- D in k e l & Busch (1973) .55 .85 ----- Dunn et_ a l . ----- .56 ----- Knapp & C la r k (1950) .65 .8 6 ----- Knapp & Nordskog (1946a) .46 .69 ----- Koch (1978) .92 ----- .69 Koch & C la r k (1955a) .39 ----- .47 Koch & C la r k (1955b) .18 ----- .43 Koch e_t a l . ----- ----- .57 ----- ----- (1982a) (1981) C h r i s t i a n s e_t a l . D ic k e r s o n et_ a l . (1962) (1974) (1970) (1974b) L askey (1972) ( . 1 9 , .4 6 )a Newman e t a l . (1973) ----- 0 .45 S h e lb y e t a l . (1955) .60 .84 ----- S h e lb y e t a l . (1963) .48 .64 ----- .4 5 -.5 0 ----- .5 0 -.6 0 Warwick & L e g a te s (1979) The f i r s t e s t i m a t e was b a s e d on b u l l s and t h e second on h e i f e r s . 37 H e r i t a b i l i t y - C arcass T r a i t s B la c k w e ll e t a l . (1962) p r e s e n t e d e v id e n c e t h a t v a r i a b l e p r e t e s t c o n d i t i o n s c o u ld m a t e r i a l l y a f f e c t e s t i m a t e s o f g e n e t i c p a r a m e t e r s . Knapp and N ordskog (1946b) d e te r m in e d i n an e x p e rim e n t to e s t i ­ mate h e r i t a b i l i t i e s o f c a r c a s s t r a i t s th a t d re ssin g p ercen t is c o n t r o l l e d more by i n d i v i d u a l e n v ir o n m e n ta l i n f l u e n c e s th a n g e n e t i c . However, C h r i s t i a n s e t a l . (1962) found e v id e n c e to th e c o n t r a r y ( s e e T ab le 7 ) . A summary o f h e r i t a b i l i t y e s t i m a t e s f o r c a r c a s s t r a i t s i s g iv e n i n T a b le 7. These h e r i t a b i l i t i e s a l s o te n d to be r e a s o n a b l y h ig h . However, s e l e c t i o n f o r c a r c a s s t r a i t s i s n o t p o s s i b l e . T herefore, c o r r e l a t i o n s betw een f e e d l o t t r a i t s and c a r c a s s t r a i t s would be d e s i r ­ a b l e i n o r d e r to p r e d i c t th e amount o f i n d i r e c t p r o g r e s s made i n c a r c a s s t r a i t s w h ile s e l e c t i n g f o r a grow th t r a i t . P h e n o ty p ic and G e n e tic C o r r e l a t i o n s Warwick and L e g a te s (1979) d e f i n e d t h e g e n e t i c c o r r e l a t i o n a s th e c o r r e l a t i o n betw een th e a d d i t i v e b r e e d i n g v a l u e s f o r two t r a i t 3 (§1 >g2 ^ o r tw een th e sum o f a d d i t i v e e f f e c t s o f th e g en es i n f l u ­ e n c in g th e s e two t r a i t s . These c o r r e l a t i o n s r e s u l t from p r i m a r i l y p l e i o t r o p y , a s i t u a t i o n where a gene i n f l u e n c e s b o th t r a i t s . a d d i t i o n , l i n k a g e may p l a y a s m a ll t r a n s i t o r y p a r t . In However, even w ith a g e n e t i c c o r r e l a t i o n o f - 0 . 4 5 , a l a r g e p r o p o r t i o n o f th e a d d i t i v e l y g e n e t i c e f f e c t s f o r th e two t r a i t s a r e in d e p e n d e n t. When th e Table 7. Heritability Estimates of Carcass Traits in Beef Cattle. Author Benyshek (1481) B lac k w e ll e t a l . (1962) B r a c k e l s b e r g e t a l . (1971) Busch and D inkel (1967) C a r t e r and K incaid (1959) C h r i s t i a n s e t a l . (1962) C u n d iff e t a l . (1964) C u n d iff e t a l . (1971)b C u n d iff e t a l . (1971)c C u n d iff e t a l . (1971)d D inkel and Busch (1973) Dunn e t a l . (1970) Knapp and C la r k (1950) Knapp and Nordskog (1946) Koch (1978) Laskey (1972)^ S helby e t a l . (1955) Swiger e t a l . (1965) Wilson e t a l . (1976) Wilson e t a l . (1971) a C a rc a s s w t/d a y o f age. b . Age c o n s t a n t . c Weight c o n s t a n t . ^ Age and w eight c o n s t a n t . Q Average o f 1 to 5 s t u d i e s . Hot c a r c a s s w eight .48 .92 D re ssin g percent .31 .25 ---------- ---------- .96 . 39a .56 .74 ------------------.68 .46 .73 ------. 32a ------------.15 ---------------------------- R ib -eye area .40 F at th i c k n e s s .52 ---- ---- .40 .25 .43 .57 ---- ---- .76 .73 .41 .32 .32 .25 .02 .68 .69 .28 .70 .72 .38 .43 .50 .53 .51 .57 .94 ---.42 .47 ------.68 .38 .38 .50 .41 .18 C u tab ility .49 C a rc a s s grade Y ie ld g ra d e ---- ---- .73 .31 .74 ---------------- M arbling .47 ------------------- ---------- .28 .35 .35 .66 .65 .31 .33 .30 .31 -.1 5 ---------- .34 ---- ------------------.44 ---- ------- ---------.33 .09 ---.20 .78 .62 .34 .08 .33 .84 .48 .16 .32 ------- .36 ------------------.01 ------------------- 39 g e n e t i c c o r r e l a t i o n s b e tw e e n two t r a i t s a p p ro a c h 1.0 o r - 1 . 0 , l e s s and l e s s in d e p e n d e n t a d d i t i v e l y g e n e t i c e f f e c t s would be a v a i l a b l e f o r se le c tio n . H azel e t a l (1943) f i r s t d e m o n s tr a te d th e e x t e n s i o n o f v a r i a n c e component a n a l y s i s to e s t i m a t i o n o f c o r r e l a t i o n s . An e x p r e s s i o n f o r th e g e n e t i c c o r r e l a t i o n i s : r g 1 g 2 = d! l g 2 / ( eg 1 eg 2 ) w here, th e n u m e r a to r i s th e c o v a r ia n c e b e tw ee n th e a d d i t i v e b r e e d in g v a lu es fo r t r a i t s and X2 and an<^ g 2 a r e gen® tic s t a n d a r d d e v i a t i o n s o f th e two t r a i t s . P h e n o ty p ic c o r r e l a t i o n s a r e th e g r o s s c o r r e l a t i o n s t h a t i n c l u d e b o th th e e n v ir o n m e n ta l and th e g e n e t i c p o r t i o n s o f th e c o v a r ia n c e s ( L a s le y , 1972). An e x p r e s s i o n f o r co m p u tin g th e p h e n o ty p ic c o r r e l a ­ tio n is : r X1X2 X 1X 2/^X 19 X2^ w here, th e n u m e r a to r i s th e c o v a r ia n c e b e tw e e n th e p h e n o ty p ic v a l u e s f o r th e two t r a i t s and 6 ^ and a r e th e p h e n o ty p ic s t a n d a r d d e v i a ­ t i o n s o f th e two t r a i t s . Thus, we a r e i n t r o d u c e d to th e c o n c e p t o f c o r r e l a t e d s e l e c t i o n response. A c o r r e l a t e d r e s p o n s e i s one i n w hich s e l e c t i o n i s p r i m a r ­ i l y f o r one t r a i t , b u t due to a g e n e t i c c o r r e l a t i o n a change o c c u rs i n a second t r a i t (Warwick and L e g a te s , 1979). The d i r e c t re s p o n s e to s e l e c t i o n , i n p o p u l a t i o n s where a n im a ls a r e s e l e c t e d on t h e i r own p e rfo rm a n c e , can be r e p r e s e n t e d a s GD = h21i a p1 = h 1i a g1 w here, i i s th e s e l e c t i o n d i f f e r e n t i a l i n s t a n d a r d d e v i a t i o n u n i t s . 40 L i k e w is e , t h e c o r r e l a t e d r e s p o n s e can be e x p r e s s e d Gc = r 2 l - , h2 2&L iap2 = reie, h2iagl ap2 S1B From t h e above e x p r e s s i o n s , i t i s a p p a r e n t t h a t i f r ^ ^ = 1 .0 and h j h 2 th e n th e d i r e c t and c o r r e l a t e d r e s p o n s e s would be e q u a l . Warwick and L e g a te s (1979) sum m arized t h e r e l a t i o n s h i p s b etw een s e l e c ­ t e d b e e f p r o d u c t i o n c h a r a c t e r i s t i c s a nd c a r c a s s t r a i t s : 1) T h ere a r e p o s i t i v e g e n e t i c r e l a t i o n s h i p s betw een a l l m e a s u re s o f s i z e and g ro w th . T hus, s e l e c t i o n f o r w e ig h t a t any age o r f o r r a t e o f grow th a t any l i f e s t a g e would b e e x p e c t e d to h av e i n d i r e c t e f f e c t s a t o t h e r a g e s . 2) T h e re i s a h i g h p o s i t i v e g e n e t i c c o r r e l a t i o n b etw een r a t e o f p o s tw e a n in g g a i n and g a i n p e r u n i t o f f e e d consumed when t e s t s a r e f o r g a i n th r o u g h a p r e s c r i b e d w e ig h t p e r i o d su ch a s 225 to 405 kg o r f o r f i x e d p e r i o d s o f tim e . The c o r r e l a t i o n i s much s m a l l e r and may be n e a r z e ro i f f e e d i n g i s t o a c o n s t a n t d e g re e o f f a t n e s s . 3) Growth r a t e s a n d w e ig h ts a t s p e c i f i c a g es a r e n e g a t i v e l y r e l a t e d to a l l m e a s u re s o f c a r c a s s f a t n e s s when s l a u g h t e r i s a t a s t a n d a r d w e i g h t . The r e l a t i o n s h i p s a r e much lo w e r i f s la u g h te r i s a t a stan d a rd age. 4) P e r c e n t o f m a tu re w e ig h t a t t a i n e d a t any age te n d s to be n e g a t i v e l y r e l a t e d t o m a tu re w e i g h t . T h is means t h a t c a t t l e h e a v y a t m a t u r i t y te n d to m a tu re more s lo w ly . T a b le 8 g i v e s e s t i m a t e s o f p h e n o ty p ic and g e n e t i c c o r r e l a t i o n s b etw een y e a r l i n g w e ig h t a n d o t h e r b e e f p r o d u c t i o n c h a r a c t e r i s t i c s o f in te re st. A lth o u g h t h e r e a r e numerous s t u d i e s g i v i n g c o r r e l a t i o n s b e tw ee n f i n a l w e ig h t and o t h e r b e e f c h a r a c t e r i s t i c s , w hich l o o k a t y e a r l i n g w e i g h t . t h e r e a r e few C a r t e r and K in c a id (1959) o b s e r v e d a h ig h p o s i t i v e c o r r e l a t i o n b etw een g a i n from b i r t h to w eaning and f e e d lo t g ain ( .6 9 ) . Table 8 . P h e n o ty p ic (P) and G e n e tic (G) C o r r e l a t i o n s Between Y e a r lin g Weight and V ariou s Beef C a t t l e P r o d u c tio n T r a i t s . F in a l w eight Author B lack w ell e t a l . (1962) D ickerson e t a l . (1974) Koch (1978) Koch and C la rk (1955a) Weight g a in C arca ss w eight D re s s in g percent C arcass g rad e F at th ic k n e s s M arbling R ib-eye area P G .53 .48 .22 .24 >1 .54 >1 .14 .92 .11 --------- --------- --------- P G --------- .84 .96 --------- --------- --------- .29 .11 .15 -.1 6 --------- P G --------- .80 .87 .94 .96 ----- ' ----- ___ ----- .33 .86 .13 - .5 7 .35 .01 P G --------- .76 .83 --------- --------- --------- --------- --------- --------- MATERIALS AND METHODS B ase P o p u l a t i o n Henry and E d s e l F o rd d o n a te d a h e r d o f H e r e f o r d cows to M ich igan S t a t e U n i v e r s i t y i n 1966. Two h u n d re d cows w ere th e n s e l e c t e d to r e p r e ­ s e n t t h e b a s e o f a b r e e d i n g p r o j e c t a t th e Lake C i t y E x p e rim en t S t a t i o n . These cows w ere d i v i d e d i n t o age g ro u p s and random ly a s s o r t e d i n t o f o u r g ro u p s o f 50 cows e a c h . The f i r s t m a tin g s o f t h e p r o j e c t w ere made i n 1967 w i t h t h e F^ dams p r o d u c in g t h e i r f i r s t c a l v e s i n 1970. B re e d in g Program Four b r e e d i n g g ro u p s of 50 f e m a le s e a c h w ere in v o lv e d i n t h e b a se b reed in g h e rd . The b r e e d i n g g ro u p s w e re: 1 )u n s e l e c t e d c o n t r o l ; 2 ) s e l e c t i o n on y e a r l i n g w e ig h t u s i n g H e r e f o r d b u l l s ; 3 ) y e a r l i n g w e ig h t s e l e c t i o n and c r o s s b r e e d i n g u s in g Angus, C h a r o l a i s , H e r e f o r d and Simm e n ta l b u l l s ; and 4 ) s e l e c t i o n b a s e d on y e a r l i n g w e i g h t , and r o t a t i o n a l c r o s s b r e e d i n g u s in g Angus, H o l s t e i n - F r i e s i a n , H e r e f o r d and Sim mental s i r e s . The number o f s t e e r s i n t h e e x p e r im e n t i s shown i n T a b le 9. T h is s tu d y 4 f o c u s e s on t h e e f f e c t o f th e v a r i o u s b r e e d in g s t r a t e g i e s on f e e d l o t and c a r c a s s t r a i t s a f t e r a d j u s t m e n t f o r c e r t a i n n u t r i t i o n a l and management p ra c tic e s. 42 43 T a b le 9. B re e d in g group 1 2 3 4 Number o f S t e e r s W ith in Breed Group. S e le ctio n None Y e a r l i n g w e ig h t Y e a r l i n g w e ig h t Y e a r l i n g w e ig h t M ating System Random u s in g h e r e f o r d b u lls n 66 S t r a i g h t b r e d u s in g h erefo rd b u lls 64 C r o s s b r e d u s in g Angus, C h a r o l a i s , H e r e f o r d , and Sim m ental 61 C ro s s b re d u s in g Angus, H o l s t e i n F r ie s ia n , H ereford, and Sim m ental 66 44 Group 1 was an u n s e l e c t e d group o f s t r a i g h t b r e d fe m a le s u s e d a s a c o n tro l. Each fe m a le was m ated t o one o f f o u r b u l l s u n s e l e c t e d f o r y e a r l i n g w e ig h t. R ep lacem ent h e i f e r s w ere t a k e n from w i t h i n t h e l i n e and w ere r e t a i n e d a c c o r d i n g t o b i r t h d a t e . The t e n o l d e s t h e i f e r s w ere sav e d e ac h y e a r i n an a t t e m p t t o a v o id u n i n t e n t i o n a l s e l e c t i o n f o r y e a r l i n g w e ig h t. S i m i l a r l y , t h e f i r s t m ale c a l f b o rn t o e ac h s i r e w i t h i n group 1 was r e t a i n e d t o be u se d a s a s i r e t h e f o l l o w i n g y e a r . T h ese b u l l s w ere u se d a s c l e a n - u p b u l l s t h e i r f i r s t y e a r o f s e r v i c e . F o llo w in g t h e f i r s t b r e e d i n g s e a s o n , semen was c o l l e c t e d and f r o z e n from e ac h young s i r e and u se d t o i n s e m i n a t e cows t h e f o l l o w i n g y e a r . Each s p r i n g , up t o f i f t e e n h e i f e r s w ere s a v e d i n g ro u p s 2, 3 and 4 b a s e d on t h e i r a c t u a l y e a r l i n g w e i g h t . In th e f a l l , t h i s number was re d u c e d t o 10 b a s e d p r i m a r i l y on t h e p re g n a n c y t e s t and s e c o n d a r i l y on y e a r lin g w e ig h t. B u l l s i n t h e s e g ro u p s w ere s e l e c t e d from b r e e d e r s t h a t w ere s e l e c t i n g w i t h i n t h e i r h e r d s on y e a r l i n g w e ig h t. The H o l s t e i n - F r i e s i a n b u l l s w e re s e l e c t e d on t h e b a s i s o f t h e i r e s t i m a t e d g e n e tic a b i l i t y f o r y e a r lin g w e ig h t. The d a i r y s i r e s w ere o b t a i n e d from S e l e c t S i r e s w here C l i n t Meadows o f M.A.B.C. (M ic h ig an Animal B re e d in g Co-op) e s t i m a t e d t h e i r e x p e c te d b r e e d i n g v a l u e s . Management Cows Cows w ere w eighed e a c h y e a r a t w eaning and once a g a i n a t th e b e g in n in g o f p a s t u r e s e a s o n i n mid t o l a t e May. A l l cows w ere k e p t t o g e t h e r e x c e p t f o r t h e l a s t 45 days o f t h e b r e e d i n g s e a s o n w hich b egan a ro u n d t h e m id d le o f A p r i l and l a s t e d f o r 90 d a y s . The cows 45 w ere b r e d a r t i f i c i a l l y f o r t h e f i r s t 45 days o f t h e b r e e d i n g s e a s o n and t h e n a s s i g n e d by b r e e d i n g g rou p t o d e s i g n a t e d c l e a n - u p b u l l s on p a s t u r e f o r t h e f i n a l 45 d a y s . P r i o r t o c a l v i n g , e a c h cow was g iv e n an a n n u a l V ita m in A and D in je c tio n . At t h e same ti m e , t h e y w ere i n o c u l a t e d f o r l e p t o s p i r o s i s and v i b r i o s i s and wormed. I n t h e f a l l , when t h e cows w ere p re g n a n c y ch e c k e d , t h e y w ere t r e a t e d f o r l i c e and g ru b s a n d , when a p p r o p r i a t e , te ste d fo r b ru c e llo s is . R ep lacem ent H e i f e r s The r e p la c e m e n t h e i f e r s w ere g ro u p e d and f e d t o g e t h e r a t w e a n in g . They w ere f e d c o rn s i l a g e and enough g r a i n t o f a c i l i t a t e r e p r o d u c t i v e e ffic ie n c y . A l l h e i f e r s w ere g iv e n b o o s t e r im m u n iz a tio n s a g a i n s t i n f e c t i o u s b o v in e r h i n o t r a c h e i t i s (IB R ), b o v in e v i r u s d i a r r h e a (BVD) and p a r a i n ­ f l u e n z a (P I^ ) p r i o r t o t h e b r e e d i n g s e a s o n . F o llo w in g t f e f i r s t 45 d ays o f t h e b r e e d i n g s e a s o n d u r i n g w hich th e y w ere a l l b r e d by a r t i f i c i a l i n s e m i n a t i o n ( A - I ) , t h e h e i f e r s w ere g ro u p ed w i t h t h e cows and t u r n e d i n t o p a s t u r e w i t h c l e a n - u p b u l l s c o r r e s p o n d i n g to t h e i r r e s p e c t i v e b r e e d i n g g r o u p s . C alv es S h o r t l y a f t e r b i r t h , e a c h c a l f was t a t t o o e d , e a r - t a g g e d , w eighed and g iv e n v i t a m i n s h o t s o f A, D and s e l e n i u m - t e c o p h e r o l . A l l m ale c a l v e s w ere c a s t r a t e d w i t h t h e e x c e p t i o n o f th e f o u r c a l v e s m a i n t a i n e d a s s i r e s i n group 1. I n a d d i t i o n , a l l h o rn e d c a l v e s w ere d e h o rn e d . P r i o r to p a s t u r e s e a s o n , t h e c a l v e s w ere v a c c i n a t e d a g a i n s t b l a c k l e g 46 and m a lig n a n t edema. At w e a n in g , t h e c a l v e s w ere w eig hed and g iv e n im m u n iz a tio n s h o t s f o r IBR, BVD and At t h i s t i m e , t h e s t e e r c a l v e s w ere moved to t h e B eef C a t t l e R e s e a r c h C e n te r (BCRC) o f M ich ig an S t a t e U n i v e r s i t y i n E a s t L a n s in g , a p p r o x im a te ly 150 m i l e s away. S te e rs Upon a r r i v a l a t E a s t L a n s in g , t h e s t e e r s w ere w eighed and s o r t e d i n t o e i g h t p e n s , two pens c o r r e s p o n d i n g t o e ac h b r e e d i n g g ro u p . W eights w ere r e c o r d e d a p p r o x im a te ly e v e r y 28 d ay s w h ile t h e s t e e r s w e re on te st. W hile t h e s t e e r s w ere a t t h e B eef C a t t l e R e s e a r c h C e n t e r , t h e y w ere in v o lv e d i n numerous n u t r i t i o n a l and management t r i a l s . i n v o lv e d d i f f e r e n c e s i n r a t i o n a n d / o r ho rm o n a l i m p l a n t s . T h is T h erefo re, a t r e a t m e n t f a c t o r was i n c l u d e d i n t h e m odel t o remove any e f f e c t due to management o r t r e a t m e n t . T r e a tm e n ts w ere ran d o m ized i n e a c h b r e e d i n g group t o i n s u r e a b a la n c e d d e s i g n . From 1978 t o 1980 t h e s t e e r s w ere s l a u g h t e r e d when a com m itte e o f ju d g e s e s t i m a t e d t h a t 80% o f t h e s t e e r s would r e a c h U .S.D .A . c h o ic e g rade. I n 1981, th e c a t t l e w ere s l a u g h t e r e d when t h e y w ere d e te r m in e d t o r e a c h c h o ic e g r a d e , w hich r e s u l t e d i n t h r e e d i s t i n c t s l a u g h t e r g ro u p s . A l l c a t t l e w ere ta k e n to a c o m m ercial p a c k in g p l a n t w here th e y w ere s l a u g h t e r e d . Hot c a r c a s s w e i g h t s w ere o b t a i n e d and t h e c a r c a s s e s w ere c h i l l e d f o r 24 h o u r s . A governm ent g r a d e r y i e l d g r a d e d a t a , w h i l e M ich ig an S t a t e c o l l e c t e d q u a l i t y and p erso n n el a s s is te d in o b ta in in g l o i n eye a r e a and e x t e r n a l f a t m e a s u re s ( 1 2 th r i b ) . Numbers o f s t e e r s 47 by s i r e b r e e d group and by y e a r a r e p r e s e n t e d i n T a b le 10. The p r im a r y t r a i t s o f i n t e r e s t w ere f e e d l o t d a i l y g a i n ( l b ) , c a r c a s s w e ig h t ( l b ) , a d j u s t e d y e a r l i n g w e ig h t ( l b ) , m a r b l i n g , q u a l i t y g r a d e , i n t e r n a l f a t (KPH), 2 f a t t h i c k n e s s ( i n ) , y i e l d g ra d e and l o i n eye a r e a (cm ) . S t a t i s t i c a l A n aly sis A t o t a l o f 267 r e c o r d s on Lake C i t y s t e e r s w ere c o l l e c t e d from 1978 t o 1981. However, due t o t h e s m a l l number o f c a l v e s p ro d u c e d by Angus, C h a r o l a i s and H o l s t e i n s i r e s , t h e s t e e r s s i r e d by t h e s e b r e e d s w ere dro p p ed from t h e a n a l y s i s . A p r e l i m i n a r y a n a l y s i s was c o n d u c te d t o d e te r m in e v a r i a b l e s o f im p o r ta n c e i n e s t i m a t i o n and t e s t i n g p r o c e d u r e s f o r t h e d e p e n d e n t v a r ­ ia b le s of in te r e s t . The f o l l o w i n g p r e l i m i n a r y model was exam ined: Y ..,. = y + a . + 6 . + (a(3) . . + x , . N, + y . + S . . + E. . ljk lm n i j ij (i)k 1 ( l) m i jk lm n t w h e re, ^ ijk lm n i s th e n th o b s e rv a tio n of th e p a r t i c u l a r t r a i t of i n t e r e s t ; th e n in e t r a i t s of i n t e r e s t a re f e e d lo t d a ily g a in ( l b ) , c a r c a s s w e ig h t ( l b ) , a d j u s t e d y e a r l i n g w e ig h t ( l b ) , m a rb lin g , q u a lity g rad e, i n t e r n a l f a t (K P H ^gfat th i c k ­ n e s s ( i n ) , y i e l d g r a d e and l o i n eye a r e a (cm ) ; y i s a c o n s t a n t common t o a l l o b s e r v a t i o n s ; a. 1 i s t h e f i x e d e f f e c t o f t h e i t h y e a r , w i t h i = l , 2 , 3 , 4 w hich r e p r e s e n t s t h e f o u r y e a r s 1978, 1979, 1980 and 1981, re sp e c tiv e ly . 8. ^ i s t h e f i x e d e f f e c t o f t h e j t h b r e e d g ro u p , j = l , 2 , 3 , 4 w hich r e p r e s e n t s t h e f o u r b r e e d i n g g ro u p s a s p r e v i o u s l y d e s c r i b e d ; 48 T a b le 10. Number o f S t e e r s by Y ear and S i r e B reed Group. Y ear S i r e Breed 1978 Angus C h aro lais H o lstein Sim m ental H e re f o rd 45 1979 Angus C h a ro la is H o lstein Sim m ental H ereford 0 0 0 ^ 9 \,, 35 1980 Angus C h a ro la is H o lstein Sim m ental H ereford 1981 Angus C h aro lais H o lstein Sim m ental H ereford Number 3 0 0 0 1 0 ??>62 34' 3 0 1 “30' >55 49 (a 3 ).. i s t h e f i x e d i n t e r a c t i o n e f f e c t o f t h e i t h y e a r and j t h breed g ro u p ; i s th e fix e d e f f e c t o f th e k th tre a tm e n t n e ste d w ith in y e a r, k -1 ,2 ,3 ,4 ; U;iC i s t h e f i x e d e f f e c t o f th e 1 th b re e d o f s i r e , w ith 1=1,2 1 c o r r e s p o n d s to H e r e f o r d and 2 to Sim m ental; S ,.. where i s t h e random e f f e c t o f t h e mth s i r e n e s t e d w i t h i n th e 1 th breed of s i r e , m = l,2 ...7 ; m E . , i s t h e random r e s i d u a l e f f e c t a s s o c i a t e d w ith t h e n t h o b s e r v a t i o n , n -l,2 ...2 6 7 . Season was n o t in c lu d e d i n t h e e q u a t i o n s i n c e a l l c a l v e s were b o rn i n th e fa ll. The e q u a t i o n can be r e w r i t t e n i n m a t r i x form: y = gb + Zji + e w h e re , y i s t h e o b s e r v a t i o n v e c t o r o f l e n g t h o f 267 when c o n s i d e r i n g f e e d l o t t r a i t s and 257 when c a r c a s s t r a i t s a r e u n d e r c o n s i d e r a t i o n ; X i s a 267 X 43 m a t r i x c o r r e s p o n d i n g to b . I t c o n t a i n s O 's and l ' s c o r r e s p o n d i n g to an o b s e r v a t i o n ’ s p r e s e n c e o r a b se n c e i n e ac h c l a s s . The column c o r r e s p o n d i n g t o y c o n t a i n s a l l l ' s ; b i s an unknown v e c t o r o f l e n g t h 43 c o n t a i n i n g t h e c o n s t a n t s o f t h e f i x e d e f f e c t s , i . e . 4 y e a r s , 4 b r e e d i n g g ro u p s , 16 t r e a t m e n t w i t h i n y e a r row s, 16 y e a r by b r e e d in g group row s, 2 b re e d o f s i r e s and one row f o r y; Z i s a 267(257) X 49 i n c i d e n c e m a t r i x c o n t a i n i n g l ' s and O 's c o r r e s p o n d i n g t o t h e p r e s e n c e o r a b se n c e o f o b s e r v a t i o n s w i t h i n each s i r e ; u i s an unknown v e c t o r o f l e n g t h 49 c o n t a i n i n g t h e random e f f e c t s fo r s ir e s ; e ~ i s an unknown v e c t o r o f random r e s i d u a l e f f e c t s o f l e n g t h 267 o r 257; A ssum ptions f o r t h e model w ere: 1) E(y)=Xb and 2) V a r(s ) =<3=1^0*; fin a l a n a ly sis; Var(y)=V=ZGZ' + R t h i s a s s u m p tio n w i l l be r e l a x e d i n t h e t h i s im p l i e s in d e p e n d e n t sam p lin g o f 50 s i r e s w i t h mean 0 and v a r i a n c e a 2 ; s 3) The s i r e s a r e n o r m a lly d i s t r i b u t e d ; 4) V a r(e )= R = l 2 gyCJ2 w hich f u r t h e r i m p l i e s t h e e r r o r s a r e i n d e p e n d e n t l y tra w n from t h e same p o p u l a t i o n w i t h mean 0 and v a r i a n c e a 2 ; e 5) I t i s f u r t h e r assumed t h a t t h e r e s i d u a l s a r e n o rm a lly d istrib u te d ; 6) C o v (u ,e )= 0 ; 7) A l l i n t e r a c t i o n s o t h e r t h a n y e a r by b r e e d i n g group a r e triv ia l. _____ 1 The v a r i a n c e - c o v a r i a n c e m a t r i x f o r t h e random f a c t o r s i s : u -267 — Z icr2 s 0 (72 sy m m etric I -2 6 7 s_ e The mixed model e q u a t i o n s a r e : X'X X'Z b Z'X Z'Z s X 'y I'I w hich a r e e q u i v a l e n t t o t h e n orm al e q u a t i o n o f G e n e r a l i z e d L e a s t S q u a re s f o r t h e f i x e d e f f e c t s (Mao, 1 9 8 1 ). A l l f i x e d e f f e c t s w ere t e s t e d u s in g t h e u s u a l F - r a t i o . The f u l l model a n a l y s i s i n d i c a t e d t h e y e a r by b r e e d i n g group i n t e r a c t i o n was n o t i m p o r t a n t (P > .01) f o r any o f t h e n i n e t r a i t s . T h e r e f o r e , t h i s f a c t o r was drop ped from t h e model and t h e r e m a in d e r o f t h e a n a l y s e s w ere p e rfo rm e d u s in g t h e g iv e n model w i t h t h e i n t e r a c ­ t i o n te rm removed. B a r t l e t t ' s T e s t o f Homogeneity C lo se i n s p e c t i o n o f t h e d a t a r a i s e d th e q u e s t i o n c o n c e r n in g t h e 51 e q u a l i t y o f v a r i a n c e s b e tw ee n b r e e d s o f s i r e . B a r t l e t t 's t e s t of h om ogeneity a s d e s c r i b e d by G i l l (1978) was u s e d t o t e s t t h e h y p o t h e s i s , a i =C72* The t e s t s t a t i s t i c i s c a l c u l a t e d a s f o l l o w s : t t t t q = { ( Z v , ) l n ( Z s s . / Z v .) - Z ( v . l n s . ) } / g i= l i= l 1 i= l1 i= l 1 1 w h e re , ^ = t h e d e g r e e s o f freed o m f o r t h e i t h b r e e d s s ^ = t h e sum o f s q u a r e s f o r t h e i t h b r e e d s . = th e s ta n d a rd d e v ia tio n o f th e i t h breed l t = t h e number o f b r e e d s g = {1 + t (Z(l/v.) i=l 1 t - (1/Zv.)}/3(t-l)} i=l T h is s t a t i s t i c i s th e n compared to t h e t a b l e v a l u e o f y 2 „ . . a ,t-l A ll t e s t s w ere p e rfo rm e d a t a = .2 t o i n s u r e t h e d e t e c t i o n o f h e t e r o g e n e i t y . When r e s u l t s i n d i c a t e d h e te r o g e n e o u s v a r i a n c e s t h e s u b s e q u e n t a n a l y s e s w ere p e rfo rm e d w i t h i n b r e e d . V a ria n c e Component E s t i m a t i o n U n t i l r e c e n t y e a r s v a r i a n c e com ponents have b e e n e s t i m a t e d u s i n g t h e t r a d i t i o n a l ANOVA method o f e q u a t i n g t h e c a l c u l a t e d mean s q u a r e s to t h e i r e x p e c ta tio n s . I n 1953, H e n d erso n d e v i s e d t h r e e m ethods o f e s t i m a t i n g v a r i a n c e com ponents from u n b a la n c e d d a t a . Each method was s p e c i f i c t o a p a r t i c u l a r k in d o f model and e a c h u t i l i z e d ANOVA t e c h n i q u e s b u t d id n o t r e q u i r e an u n d e r l y i n g d i s t r i b u t i o n . The n o rm al e q u a t i o n s w ere in v o k e d , t r e a t i n g e v e r y e f f e c t a s i f i t w ere f i x e d . I n 1967, H a r t l e y and Rao p r e s e n t e d t h e method o f maximum lik e lih o o d (M L ) 52 assum in g a m u l t i v a r i a t e n o rm a l d i s t r i b u t i o n . The ML method p o s s e s s e s c e r t a i n p r o p e r t i e s w hich makes i t more a d v a n ta g e o u s th a n H e n d erso n m ethods 1, 2 and 3 . T hese e s t i m a t e s a r e alw ays n o n - n e g a t i v e and a r e a s s y m p t o t i c a l l y n orm al and e f f i c i e n t b e in g f u n c t i o n s o f t h e m in im a l su ffic ie n t s ta tis tic s . However, t h e ML e s t i m a t e s a r e b i a s e d due t o s im u lta n e o u s e s t i m a t i o n o f t h e f i x e d f a c t o r s w h ich make them u n d e s i r a b l e f o r a n im a l b r e e d i n g r e s e a r c h . The r e s t r i c t e d maximum l i k e l i h o o d (REML) p r o c e d u r e was o b t a i n e d by m axim izin g t h e random p o r t i o n o f t h e l i k e l i h o o d w hich i s i n v a r i a n t to t h e f i x e d e f f e c t s i n t h e m o del. P a t t e r s o n and Thompson (1971) g e n e r ­ a l i z e d t h e REML method o f e s t i m a t i n g v a r i a n c e c o m p on ents, w h ic h h a s become w id e ly u s e d i n d a i r y r e s e a r c h . Some o f t h e more d e s i r a b l e p r o p e r t i e s o f REML a r e : l ) n o n - n e g a t i v i t v i s g u a r a n t e e d w i t h i n t h e p a r a m e te r s p a c e , 2) REML t e c h n i a u e s l e n d th e m s e lv e s to i t e r a t i v e p r o c e d u r e s due t o t h e v a r i o u s p a r a m e te r d e p en ­ d e n c i e s and 3 ) i n a d d i t i o n , REML i s e a s i e r t o im plem ent i n te rm s o f c o m p u ta tio n . However, b e c a u s e o f t h e i t e r a t i v e p r o c e d u r e , no m a th e ­ m a t i c a l m ethods a r e a v a i l a b l e f o r d e t e r m i n a t i o n o f t h e b i a s e d n e s s p ro p e rty o f th e e s tim a to r s . I n a d d i t i o n , t h e i t e r a t i o n p r o c e s s can a l s o be a b i g d i s a d v a n t a g e due t o t h e l a r g e number o f i t e r a t i o n s r e q u i r e d . Due t o t h e method o f c h o o s in g s i r e s f o r g ro up one some g e n e t i c r e l a t i o n s h i p s e x i s t e d among t h e s i r e s o f t h a t b r e e d ( H e r e f o r d ) . T here­ f o r e , a r e l a t i o n s h i p m a t r i x was i n c o r p o r a t e d i n t o t h e mixed model eq u a­ tio n s f o r th e H ereford a n a l y s i s . T a b le 11. These r e l a t i o n s h i p s a r e shown i n T a b le 11. R e l a t i o n s h i p M a trix (A *) f o r H e re fo rd S i r e s i n Group 1 123 130 131 123 1 130 0 1.125 131 0 0 1 132 0 0.078 0 133 0 0 0 134 0 0.078 0 135 500 0 0 136 0 0 137 0 139 132 133 134 135 136 137 139 140 141 143 144 145 1 0 0 .2 50 SYMMETRIC 1 0 1 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0..0625 0 0 0 0 0 0 1 140 125 0 0 0 0 0 0 .0625 0 0 0 1 141 0 0 0 0 0 0 0 0 0 0 0 1 143 125 0 0 0 0 0 0 .0625 0 0 0 0 .2 5 0 0 1 144 0 0.500 0 0 .5 0 0 0 0.125 0 0 0 0 0 0 0 1 145 0 0 0 .500 0 0 0 0 0 0 0.03125 0 0 0 0 1 146 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 146 54 Mixed Model E q u a tio n I n g e n e r a l i t i e s , t h e mixed model e q u a t i o n s (MME) w i t h t random fa c to rs are • | z 2+g 12" -1 22 Z'ZR Z2+G 5 ' 5 _1x u. -1 5 [ 5 _1Z u -> ~2 ? 2 ? _1X I ZJR IT £>) \ 1 Zl +G 11 » 1 1 ! ZJR IT 1 I 4J N! H X'R_1Z, X 'R ^ X j X'R_1Z1 • - 1 Z +Glt: . ~ l Z +G2 t ~t ~t ~ - • SYMMETRIC 'h ~t u„ ? 3 _1x ~t ~ -11 -12 * * • S it ?22 ‘ * ’ 10 Var(u)=G= 1 1—* 11 w h e re , V ar(e)= R and ~GU ~2t sy m m etric G12 . . . GXt G2 2 . * * ? 2t sym m etric GCt i , For t h i s p a r t i c u l a r a p p l i c a t i o n , t h e a s s u m p tio n was made t h a t R*I cr^. F or t h e Sim m ental a n a l y s i s , t h e a d d i t i o n a l a s s u m p tio n was made t h a t ~_T ^~2 . (j=I. - -t s The s i m p l e s t mixed model e q u a t i o n th e n becomes x ' z 0/ a 2 . . . X'Z. / a 2 z ^z2/ a 2 . . . ZjZc/ a 2 z 2Z2 / a 2+ i / a 2 . . . Z2Zt / a 2 SYMMETRIC ' XI' I 1 1 1 x 'z ,/a 2 HzJZ^/aV i£ 2 U -1 u-2 • z'jz^l a 2+ i £ — c ~ _u t X 'y/a2 Zjy/a2 Z^y/ cr2 • • Zt y / a 2 55 M u l t i p l y i n g b o t h s i d e s o f th e e q u a t i o n by a 2 , t h e e q u a t i o n becomes x 'x 1 x 'z . V&2 * • • z;zt ~2~2+ ~k 2 * ~2~t • • V z *1 l[z • • -V 4 z • SYMMETRIC Z i Z ~ t+I~k t where k^= ~b ‘ -< M • !1 Z .'Z.+Ik ~1~I ~ 1 I 1 1 1 . . x 'z t x 'z 2 . However, when t h e a n a l y s i s was d u p l i c a t e d f o r t h e H e r e f o r d s i r e s a c o m p l i c a t i o n a r o s e due t o t h e i r r e l a t i o n s h i p s . T h ese r e l a t i o n s h i p s w ere a c c o u n te d f o r by s u b s t i t u t i n g t h e Ik ^ i n t h e MME by A ^ k ^ , where t h e o f f - d i a g o n a l e le m e n ts i n A a r e a d d i t i v e g e n e t i c r e l a t i o n s h i p c o e f f i c i e n t s betw een i n d i v i d u a l s and d i a g o n a l s a r e one p l u s t h e i n b r e e d i n g c o e f f i c i e n t o f th e i n d i v i d u a l . x~ ' x~ iI x~ ' z~1. 1 11 Ii Z~1~1 j Z . + A~ k .1 ! i i x~ ’ z-2„ The MME t h e n becomes . . X ’Z t b‘ . . Z j Z t + A 11: k t Hi . . Z i Z + A~2 t k t Uo -A ~ X 'y " 1 Z ; z 0 + A k 2, . ~1~2 ~ z~2~2 : z . + A~22k „2. z;y I™ c A ct ** I Z ’Z + A t t k iN SYMMETRIC I t h a s been shown t h a t b i a s e s due to s e l e c t i o n o f s i r e s can be e l i m i ­ n a t e d by i n c l u s i o n o f t h e r e l a t i o n s h i p m a t r i x . I t a l s o a i d s i n compar­ i s o n o f b u l l s w hich c o u ld o t h e r w i s e n o t be compared due to d i s c o n n e c ­ t e d n e s s (Mao, 1981). S o l u t i o n s t o t h e MME a r e g e n e r a t e d by m u l t i p l y i n g t h e r i g h t hand s i d e o f t h e e q u a t i o n by t h e g e n e r a l i z e d i n v e r s e o f t h e c o e f f i c i e n t m a trix . L et C r e p r e s e n t t h e i n v e r s e o f t h e c o e f f i c i e n t m a t r i x . 56 I n t h i s c a s e , o n ly one random f a c t o r ( s i r e s ) was i n c l u d e d i n t h e m odel. T h e r e f o r e , C can be r e p r e s e n t e d a s "x'x z'x x'z Z'Z+A_1k 5 x 'x ~X'S ~s'x 5s's_ Then, t h e REML e s t i m a t o r s a r e : 3* = ( y ' y " b ’ X’ y - u ' Z ' y ) / { n - r ( X ) } where r(X) i s t h e r a n k o f th e f i x e d p o r t i o n o f t h e i n c i d e n c e m a t r i x and qg i s t h e number o f s i r e s . I n t h e Sim m ental a n a l y s i s , w here t h e s i r e s w ere u n r e l a t e d , t h e e s t i m a t o r f o r th e s i r e component was dl ’ {SsSs + aIt r ( Ss'S)}/q s The p r o c e d u r e was t h e n i t e r a t e d by e s t i m a t i n g new v a r i a n c e and c o v a r i a n c e s o l u t i o n s from e a c h new s e t o f e s t i m a t e d co m p on en ts. The i t e r a t i o n can be p e rfo rm e d due to t h e d ep en d en ce o f 6 and u on k ; t h e d e p en dence o f u , S and k ; and t h e dep en d en ce o f k on CT* and a * . T h e r e f o r e , th e i t e r a t i o n s s h o u ld c o n t i n u e u n t i l t h e r e a r e no lo n g e r any c h an g e s i n any o f t h e s e e s t i m a t e s . To s p e e d up t h e c o n v e r g e n c e , a b o o s t i n g f a c t o r was i n c l u d e d i n e a c h i t e r a t i o n , a s s u g g e s te d by Mao (1 9 8 2 ). The d i f f e r e n c e b etw een two s u c c e s s i v e i t e r a t i o n s was m u l t i p l i e d by a f a c t o r whose m a g n itu d e was a r b i t r a r y d e p e n d in g on t h e c h a r a c t e r i s t i c s o f t h e v a r i a b l e u n d e r co n sid e ra tio n . To b e g i n t h e i t e r a t i v e p r o c e s s , an a p r i o r i v a l u e o f k had t o be in tro d u c e d . T h is v a l u e was o b t a i n e d by u s in g p r e v i o u s e s t i m a t e s o f 57 h e r i t a b i l i t y and t h e fo r m u la from t h e p a t e r n a l h a l f - s i b c o r r e l a t i o n : h 2 = 4 / (1+k) The _a p r i o r i v a l u e s u sed i n t h i s a n a l y s i s a r e p r e s e n t e d i n T a b le 12. H e r i t a b i l i t i e s and G e n o ty p ic and P h e n o ty p ic C o r r e l a t i o n s The h e r i t a b i l i t y e s t i m a t e s w ere c a l c u l a t e d u s i n g t h e p a t e r n a l h a l f - s i b c o r r e l a t i o n method w i t h t h e REML e s t i m a t e s o f a 2 and a 2 . s e The fo rm u la f o r t h i s e s t i m a t i o n i s : h 2 = 4S 2 / ( a 2 + a 2) s s e D ic k e r s o n (1969) o b s e r v e d t h a t b i a s e s o c c u r i n t h i s e s t i m a t e w henever 1) t h e c o v a r i a n c e betw een g e n e t i c and e n v ir o n m e n ta l e f f e c t s i s n o t e q u a l to z e r o , 2) t h e m a t e r n a l e f f e c t i s g r e a t e r t h a n z e r o o r 3) t h e c o v a r i a n c e b etw een m a t e r n a l and g e n e t i c e f f e c t s i s n o t z e r o . Kempthorne (1966) p r e s e n t e d a fo rm u la f o r c a l c u l a t i n g t h e a p p r o x im a te stan d a rd e r r o r of a h e r i t a b i l i t y e s tim a te : 3?h = <4/S*){v(S’ >>1/2 p s w h e re , t h e v a r i a n c e component e s t i m a t e s o b t a i n e d i n t h e f i n a l i t e r a t i o n /S. o f th e REML p r o c e d u r e w ere u sed f o r a s /N- and a p A. A = a+o . s e Kempthorne (1969) p r e s e n t e d t h e m ethods f o r e s t i m a t i n g th e v a r i a n c e s o f t h e r e s p e c t i v e com ponents. T h e se e q u a t i o n s a r e p r e s e n t e d below: V(S2) = ( 4 / q e ){((M Ss ) 2/ q g) + ( a V q e )} V(S2) = ( 2 ^ ) / q e w h ere, MS s i s t h e mean s q u a r e o f t h e s i r e e f f e c t . The e q u a t i o n s a r e e x a c t o n ly when a 2 i s known. Due t o th e f a c t t h a t s e l e c t i o n was t o be made b a se d on y e a r l i n g 58 T a b le 12. A p r i o r i V a lu es o f H e r i t a b i l i t i e s and k V a lu es Used i n t h e REML A n a l y s i s T ra it h2 k Y e a r l i n g W eight .378 9 .5 8 A verage D a i l y G ain .580 5 .9 0 L o in Eye A rea .460 7 .7 0 F a t T h ic k n e s s .494 7 .1 0 M a rb lin g .310 1 1 .9 0 C a r c a s s Grade .444 8 .0 1 Y i e l d Grade .185 2 0 .6 2 F i n a l W eight .730 4 .4 8 I n t e r n a l F a t (KPH) .210 18.05 59 w e i g h t , and t h e t r a i t s o f i n t e r e s t w ere f e e d l o t and c a r c a s s t r a i t s , it was i m p e r a t i v e t h e p h e n o ty p ic and g e n e t i c c o r r e l a t i o n s f o r t h e t r a i t s w ith y e a r l i n g w e ig h t to b e i n v e s t i g a t e d . G e n e tic P r o g r e s s th r o u g h S e l e c t i o n and C r o s s b r e e d in g H e re f o rd Due t o t h e d i s c o n n e c t e d n e s s e x h i b i t e d b etw een g ro u p s 1 and 2, d i r e c t s t a t i s t i c a l c o m p a riso n s w ere n o t p o s s i b l e . However, t h e l e a s t s q u a r e s means f o r e a c h group w e r e p l o t t e d and means w ere d i s c u s s e d . Sim m ental The e f f e c t s o f b r e e d i n g g ro u p s 3 and 4 w ere com pared u s i n g e s t i m a b l e f u n c t i o n s a s d e s c r i b e d by Mao (1 9 8 2 ). In a d d itio n , th e l e a s t sq uares means f o r e ac h group were p l o t t e d and d i f f e r e n c e s w ere n o t e d . H e r e f o r d v s Sim m ental B ecause o f t h e d i s t i n c t s i r e s u s e d w i t h i n e a c h b r e e d ( d i s c o n n e c t e d d a t a ) , no s t a t i s t i c a l t e s t s w ere p e rfo rm ed t o d e t e r m i n e d i f f e r e n c e s b etw een t h e two s i r e b r e e d s . However, t h e means w ere a g a i n p l o t t e d and o b v io u s d i f f e r e n c e s w ere o b s e r v e d . RESULTS AND DISCUSSION P h e n o ty p ic C o r r e l a t i o n s H e re fo rd E s t i m a t e s o f p h e n o ty p ic c o r r e l a t i o n s o f two f e e d l o t t r a i t s and s i x c a r c a s s t r a i t s w i t h y e a r l i n g w e ig h t a r e p r e s e n t e d i n T a b le 13. A ll e i g h t o f t h e o b s e r v e d t r a i t s i n t h e H e r e f o r d b r e e d w ere m o d e r a te l y to h ig h ly p o s i t i v e l y c o r r e l a t e d w ith y e a r lin g w eig h t, th e s e l e c t i o n v a r i a b l e , w i t h t h e e x c e p t i o n o f m a r b lin g and c a r c a s s g r a d e . However, t h i s would be e x p e c te d due to t h e method o f d e te r m in in g tim e o f s l a u g h t e r . The s m a ll p o s i t i v e c o r r e l a t i o n s t h a t a r e e x h i b i t e d by t h e two v a r i a b l e s may i n d i c a t e some s t r o n g e r r e l a t i o n s h i p b etw een y e a r l i n g w e ig h t and th o s e v a r i a b l e s when tim e o f s l a u g h t e r i s a t a c o n s t a n t tim e r a t h e r th a n a c o n sta n t l i v e grade. T hese e s t i m a t e s a r e somewhat h i g h e r th a n p r e v i o u s l y r e p o r t e d c o r r e ­ la tio n s. S i m i l a r c o r r e l a t i o n s w ere r e p o r t e d f o r m a rb lin g by D ic k e r s o n e t a l (1978) and Koch (1 9 7 8 ) . I n t h i s s t u d y , a v e r a g e d a i l y g a i n had a s t r o n g e r r e l a t i o n s h i p to y e a r l i n g w e ig h t th a n B la c k w e ll found i n 1962. However, D ic k e rs o n e t a l (1974) and Koch (1978) r e p o r t e d c o m p arab le c o r r e l a t i o n s ( . 8 4 and .8 0 , r e s p e c t i v e l y ) . A l l c o r r e l a t i o n s w ere d e te r m in e d to be d i f f e r e n t from z e r o , i n d i c a t i n g t h a t on th e a v e r a g e h e a v i e r H e r e f o r d c a t t l e a t 365 days w ere f a t t e r and had more m u s c lin g a t s l a u g h t e r t h a n H e re f o rd c a t t l e t h a t w ere l i g h t e r a t a y e a r o f a g e . 60 61 T a b le 13. P h e n o ty p ic C o r r e l a t i o n s o f F e e d l o t and C a r c a s s T r a i t s w i t h Y e a r l i n g W eight by B reed o f S i r e B reed o f S i r e M arb lin g .19 Y ie ld Grade .52 A verage D a ily Gain .89 L o in Eye A rea .50 I n t e r n a l F a t (KPH) .49 C a r c a s s Grade .17 F a t T h ic k n e s s .99 F i n a l Weight .88 ■ k P <-. 05 * ** ** ** ** * ** ** Sim m ental -.0 2 i o i— * H e re f o rd ** .53 ** .31 i o LO T ra it .03 -.0 5 .77 A* 62 S in m e n ta ls C o n t r a d i c t o r y r e s u l t s w ere found when t h e same e i g h t t r a i t s w ere i n v e s t i g a t e d i n t h e Sim m ental b r e e d . c a l v e s a r e p r e s e n t e d i n T a b le 13. The c o r r e l a t i o n s f o r S im m e n t a l - s i r e d The o n ly p h e n o ty p ic c o r r e l a t i o n s w hich d i f f e r e d from z e r o (P <.05) w ere l o i n ey e a r e a , f i n a l w e ig h t and average d a ily g a in . The r e p o r t e d s t a t i s t i c f o r l o i n eye a r e a a g r e e s w i t h t h e r e p o r t e d c o r r e l a t i o n by Koch (1 9 7 8 ). However, th e c o r r e l a t i o n found betw een f i n a l w e ig h t and y e a r l i n g w e ig h t was s t r o n g e r th a n t h e one r e p o r t e d by B la c k w e ll e t a l (1 9 6 2 ) . The c o e f f i c i e n t f o r a v e r a g e d a i l y g a i n was n o t as l a r g e a s o t h e r s r e p o r t e d i n t h e l i t e r a t u r e . The d i f f e r e n c e s found i n t h e S im m entals and H e r e f o r d s can be e x p l a i n e d by t h e d i f f e r i n g c h a r a c t e r i s t i c s o f t h e two b r e e d s . Sim m entals can b e c h a r a c t e r i z e d a s a medium t o t a l l b r e e d o f c a t t l e w i t h m o d e ra te to heavy m u s c lin g , w h e rea s t h e H e r e f o r d s a r e s m a l l e r fram ed w i t h l i g h t e r m u s c le . The h e a v i e r m u s c le d , t a l l e r fram ed b r e e d s , i n g e n e r a l , grow f a s t e r and p u t on l e s s f a t d u r in g t h e same p e r i o d a s t h e i r s m a l l e r , l i g h t e r m u scled c o n te m p o r a r ie s . C o n s e q u e n tly , a n e g a t i v e c o r r e l a t i o n would be e x p e c te d f o r a grow th t r a i t w ith a f a t - r e l a t e d t r a i t in th e la r g e r C o n tin e n ta l b re e d . B u t, i n c o n t r a s t , t h e s m a l l e r H e re f o rd would be e x p e c te d t o r e a c h m a t u r i t y s o o n e r and th e n b e g in p u t t i n g on f a t w hich would be r e v e a l e d i n t h e p o s i t i v e c o r r e la tio n s seen in th e H ereford breed. 63 G e n e tic C o r r e l a t i o n s H erefords A l l g e n e t i c c o r r e l a t i o n s b etw een f e e d l o t and c a r c a s s t r a i t s w ith y e a r l i n g w e ig h t i n t h e H e r e f o r d b r e e d w ere d i f f e r e n t from 0 o t h e r th a n in te rn a l fa t. However, t h e g e n e t i c c o r r e l a t i o n s r e v e a l e d some i n t e r e s t i n g r e l a t i o n s h i p s t h a t w ere n o t s e e n when o b s e r v i n g th e p h e n o ty p ic c o r r e ­ la tio n s . T hese c o r r e l a t i o n s a r e shown i n T a b le 14. M arb lin g s c o r e e x h i b i t e d a s t r o n g n e g a t i v e c o r r e l a t i o n g e n e t i c a l l y w ith y e a r l i n g w e i g h t . T h is a g r e e s w i t h Koch (1978) who r e p o r t e d a g e n etic re la tio n s h ip of - .5 7 . T h is would i n d i c a t e t h a t s e l e c t i o n f o r y e a r l i n g w e ig h t w i l l s i m u l t a n e o u s l y d e c r e a s e t h e amount o f i n t r a m u s c u l a r f a t , w hich i n t u r n would l i k e l y d e c r e a s e c a r c a s s g r a d e . The o b s e r v e d n e g a t i v e g e n e t i c c o r r e l a t i o n b etw een c a r c a s s g ra d e and y e a r l i n g w e ig h t su p p o rts t h i s h y p o th e sis. The l a r g e n e g a t i v e g e n e t i c c o r r e l a t i o n found b e tw ee n f i n a l w e ig h t and y e a r l i n g w e ig h t i s c o n t r a d i c t o r y t o r e p o r t e d l i t e r a t u r e et a l, 1962) and b i o l o g i c a l " s e n s e " . ( B la c k w e ll B i o l o g i c a l l y , we know t h a t f i n a l w e ig h t s h o u ld e x p l a i n a l a r g e p o r t i o n o f t h e t o t a l v a r i a t i o n s e e n i n y e a r l i n g w e ig h t a n d , t h e r e f o r e , s h o u ld e x h i b i t a p o s i t i v e , i f n o t s t r o n g p o s itiv e , g e n etic c o r re la tio n . Sim m entals The r e s u l t s i n T a b le 14 i n d i c a t e f a t t h i c k n e s s , y i e l d g ra d e and a v e r a g e d a i l y g a i n a r e a l l g e n e t i c a l l y c o r r e l a t e d t o y e a r l i n g w e ig h t. The c o e f f i c i e n t s i n d i c a t e t h a t s e l e c t i o n f o r h e a v i e r y e a r l i n g w e ig h t sim u lta n eo u sly s e l e c t s a g a in s t th e f a t - r e l a t e d c h a r a c t e r i s t i c s , i . e . T a b le 14. G e n e tic C o r r e l a t i o n s o f F e e d l o t and C a r c a s s T r a i t s w i t h Y e a r l i n g W eight by B reed o f S i r e B reed o f S i r e T ra it M a rb lin g H ereford -.8 6 Y ie ld Grade .67 A verage D a i l y G ain .58 L o in Eye A rea .72 I n t e r n a l F a t (KPH) -.3 2 C a r c a s s Grade -.4 8 F a t T h ic k n e s s .92 F i n a l W eight , -.7 1 ** ** ** ** Sim m ental -.2 8 -.6 2 .49 .10 -.3 8 ** ** ** .00 -.8 9 -.0 4 65 f a t t h i c k n e s s , m a r b lin g and i n t e r n a l f a t , i n t h e Sim m ental b r e e d . T h e re was a n e g a t i v e c o r r e l a t i o n b e tw ee n y i e l d g ra d e and y e a r l i n g w e ig h t. T h i s , t o o , would be e x p e c te d s i n c e t h e s i n g l e , m ost i m p o r t a n t f a c t o r a f f e c t i n g y i e l d g ra d e i s f a t . A g re e a b le r e s u l t s w ere found i n t h e Sim m ental and H e r e f o r d g e n e t i c c o r r e l a t i o n s f o r most c h a r a c t e r i s t i c s . D isc re p a n c ie s o ccu rred in th e r e l a t i o n s h i p b etw een y e a r l i n g w e ig h t and y i e l d g ra d e and y e a r l i n g w e ig h t and f a t t h i c k n e s s . T hese d i f f e r e n c e s a g a i n can be e x p l a i n e d by th e in h e re n t d if f e r e n c e s in th e b re e d s. H e rita b ilitie s H ereford T a b le 15 p r e s e n t s t h e s i r e and e r r o r v a r i a n c e components e s t i m a t e d from 144 H e r e f o r d s t e e r s u s i n g t h e r e s t r i c t e d maximum l i k e l i h o o d (REML) method o f a n a l y s i s . E v e ry e s t i m a t e r e q u i r e d a t l e a s t t h i r t y " e q u i v a l e n t " ro u n d s o f i t e r a t i o n and some a s many a s 2000. H e r i t a b i l i t i e s and a p p ro x im a te s t a n d a r d e r r o r s w ere c a l c u l a t e d u s i n g t h e s e e s t i m a t e s and a r e shown i n t h e same t a b l e . The h e r i t a b i l i t i e s o b s e r v e d from t h e s e d a t a a r e g e n e r a l l y s m a l l e r t h a n t h o s e r e p o r t e d i n p re v io u s l i t e r a t u r e . However, a l l t h e e s t i m a t e s had h ig h s t a n d a r d e r r o r s , a r e f l e c t i o n on t h e s m a l l sam ple s i z e u sed to o b t a i n t h e e s t i m a t e s . The h e r i t a b i l i t y o f f a t t h i c k n e s s a g r e e d c l o s e l y w i t h r e s u l t s r e ­ p o r t e d by L a s l e y (1972) and S helby e t a l (1 9 5 5 ). The h e r i t a b i l i t y o f y e a r l i n g w e ig h t i s c o n s i d e r a b l y below e s t i m a t e s r e p o r t e d i n t h e l i t e r a t u r e , however i t s s t a n d a r d e r r o r i s t h r e e tim e s the p o in t e s tim a te . T h ese r e s u l t s would i n d i c a t e t h a t s e l e c t i o n on Table 15. Sire and Error Variance Components and Heritablities for Feedlot and Carcass Traits in the Hereford Breed T ra it o2 s a2 e h2 M arbling 1.48+ 0.09 6.04± 0.3 6 .7 9± .4 0 Y ie ld Grade 0.02± 0.01 0.46± 0 .1 0 . 19±.83 Average D a ily Gain 0.001 0 .0 0 0.04± 0.0 3 .02+1.59 L o in Eye Area 0.00± 0.0 2 1.10± 0 .1 5 .0 1 1 .6 8 I n t e r n a l F a t (KPH) 0.00± 0 .0 0 0 . 15± 0 .0 6 .04+1.12 C a rc a s s Grade 0.10+ 0 .0 3 1.82± 0 .2 0 .2 2 1 .5 9 F a t T h ic k n e ss 0.0 01 0 .0 0 0.03± 0.02 .36 11.62 4 3 9 .2 9 ± 7 3 .12 4858.21110.17 .3 3 1 .0 3 26 .0 3± 61 .41 4081.571 9.3 5 .0 31 .0 9 F i n a l Weight Y e a r l in g Weight 67 y e a r l i n g w e ig h t would be f u t i l e . . However, Warwick and L e g a te s (1 9 7 9 ) , Koch (1978) and Newman e t a l (1973) r e p o r t e d e s t i m a t e s w hich ra n g e d from .45 t o .6 9 . Sim m ental The REML e s t i m a t e s f o r s i r e and e r r o r v a r i a n c e s i n t h e Sim m ental b re e d a r e r e p o r t e d i n T a b le 16. from th e Lake C i t y h e r d . The e s t i m a t e s w ere b a s e d on 123 r e c o r d s The c o n v e rg e n c e to o k anyw here from 25 to 200 i t e r a t i o n s , c o n s i d e r a b l y l e s s th a n th o s e r e q u i r e d f w ith in th e H ereford b re e d . th e e s tim a te s A b o o s t i n g f a c t o r o f 5 was u sed to sp eed c o n v e rg e n c e . The r e s u l t i n g h e r i t a b i l i t y e s t i m a t e s a r e shown i n T a b le 16. Once a g a i n , t h e s t a n d a r d e r r o r s t e n d to b e l a r g e f o r m ost o f t h e t r a i t s . In a d d i t i o n , t h e r e w ere two e s t i m a t e s w hich f e l l o u t s i d e t h e p a r a m e te r space of h e r i t a b i l i t y , i.e . 0 t o 1. However, t h e i r s t a n d a r d e r r o r s i n d i c a t e t h a t t h e p rob lem c o u ld be i n s a m p lin g and n o t t h e method o f e stim atio n . The r e p o r t e d h e r i t a b l i t y f o r y e a r l i n g w e ig h t would i n d i c a t e t h a t i t would be a d e s i r a b l e v a r i a b l e f o r s e l e c t i o n , and t h e g e n e t i c c o r r e ­ l a t i o n i n d i c a t e s t h a t when s e l e c t i n g f o r t h i s v a r i a b l e , p r o g r e s s s h o u ld be o b s e r v e d i n f e e d l o t a v e r a g e d a i l y g a i n w i t h a d d i t i o n a l p r o g r e s s o b s e r v e d i n l o i n eye a r e a . r The h e r i t a b i l i t y e s t i m a t e o f .62 f o r y e a r l i n g w e ig h t c o n c u r s w ith e s t i a m t e s made by Koch (1978) and Warwick and L e g a te s (1 9 7 9 ) . r e p o r t e d e s t i m a t e s w ere lo w e r , r a n g in g from .10 to .4 7 . O th e r However, a l l e s t i m a t e s s u g g e s t t h a t y e a r l i n g w e ig h t would be a r e s p o n s i v e t r a i t on w hich t o s e l e c t . Table 16. Sire and Error Variance Components and Heritabilitites for Feedlot and Carcass Traits in the Simmental Breed T ra it d2 s 62 e h2 M arbling 2 .1 5± 0.08 4 .3 9 + 0 .3 0 1.321.41 Y ie ld Grade 0 .0 5 1 0 .0 6 0 .3 8 1 0 .0 9 .4 9 1 .8 5 Average D a ily Gain 0 .0 0 + 0 .0 0 0 .0 5 1 0 .0 3 .3011.37 Loin Eye Area 0 .1 6 1 0 .0 2 1.49+0.17 .3 8 1 .6 0 I n t e r n a l F a t (KPH) 0 .1 1 1 0 .0 0 0.22 + 0 .0 7 1 .3 8 1 .8 7 C arca ss Grade 0 .4 5 1 0 .0 2 1 .1 31 0.1 5 1 .1 4 1 .5 8 F a t T h ic k n e ss 0 .0 0 1 0 .0 0 0 .0 2+ 0.0 2 F i n a l Weight 204.19+81.42 6102.40+10.73 .1 3 1 .0 8 Y e a r lin g Weight 825 .8 21 61 .0 0 45 03 .3 0 1 9 .2 2 .6 2 1 .0 8 .2 01 1.7 3 69 The o b s e r v e d h e r i t a b i l i t y f o r f i n a l w e ig h t i s n o t i c e a b l y s m a l l e r th a n t h o s e r e p o r t e d i n t h e l i t e r a t u r e ( s e e T a b le 1 6 ). Newman e t a l (1973) o b t a i n e d a h e r i t a b i l i t y o f 0 w hich i s i n d is a g r e e m e n t w i t h t h i s and o t h e r i n v e s t i g a t i o n s . The h e r i t a b i l i t y f o r a v e r a g e d a i l y g a i n i s i n a g re em e n t w i t h D ic k e r s o n e t a l (1974) and Koch and C l a r k (1 9 5 5 a ) , b u t te n d s t o be lo w e r th a n o t h e r r e p o r t e d h e r i t a b i l i t i e s f o r t h i s t r a i t . I n t e r n a l f a t (KPH), m a r b lin g and c a r c a s s g r a d e had h e r i t a b i l i t i e s o f g r e a t e r th a n o n e. S e v e r a l e x p l a n a t i o n s e x i s t f o r t h i s outcom e. As i n d i c a t e d i n p r e v i o u s d i s c u s s i o n , t h e sam ple s i z e would be e x p e c te d to cause u n fa v o ra b le r e s u l t s f o r e s tim a tio n o f p a ra m e te rs. However, m a r b lin g and c a r c a s s g r a d e a r e b o t h d i s c r e t e v a r i a b l e s , and t h e p r o ­ p e r t i e s f o r REML w i t h d i s c r e t e d a t a a r e n o t f u l l y e x p l o r e d . G ia n o la (1979) o b s e r v e d t h a t c o n s i d e r a b l e am ounts o f n o n a d d i t i v e v a r i a n c e a r e p r e s e n t when t h e d i s t r i b u t i o n o f r e s p o n s e s by c a t e g o r y i s v e r y uneven in c a te g o ric a l d a ta . He i n d i c a t e s t h a t when t h i s o c c u r s , th e l i k e l i ­ hood o f e p i s t a t i c b i a s e s i n h e r i t a b i l i t y e s t i m a t e s becomes a g r e a t e r p o ssib ility . A d d i t i o n a l l y , G ia n o la (1979) a s s e r t s t h e a s s u m p tio n o f in d e p e n d e n c e b etw een t h e random v a r i a b l e s , u , and t h e e r r o r , e , i n t h e o b s e r v e d s c a l e s i s n o t t e n a b l e and s i n c e t h e g e n e t i c v a r i a n c e d e p en d s on t h e m ain i n c i d e n c e , i t would be n e c e s s a r y t o u s e a d i f f e r e n t v a r i a n c e c o v a r i a n c e m a t r i x f o r e a c h s u b p o p u l a t i o n d e f i n e d i n t h e m odel. The h e r i t a b i l i t y e s t i m a t e f o r y i e l d g r a d e i s l a r g e r th a n t h o s e r e p o r t e d i n th e l i t e r a t u r e . Knapp and N ordskog (1946) e s t i m a t e d t h i s h e r i t a b i l i t y a t .0 1 . The e s t i m a t e s f o r l o i n eye a r e a and f a t t h i c k n e s s a r e a l i t t l e s m a lle r th an e s tim a te s in th e l i t e r a t u r e . Once a g a i n , t h e s t a n d a r d 70 e rro rs are q u ite la rg e . Sample S iz e Due to t h e l a r g e d i s c r e p a n c i e s o b s e r v e d i n t h e d a t a , P i r c h n e r ' s (1969) method o f d e t e r m i n i n g number o f o b s e r v a t i o n s n e ed e d f o r m in im al sam p lin g v a r i a n c e was u s e d to d e te r m in e a d e s i r a b l e sam ple s i z e . e s t i m a t e s a r e p r e s e n t e d i n T a b le 17. These As can be s e e n , t h e t o t a l number o f a n im a ls n e ed ed i s l a r g e l y d e p e n d e n t on t h e a v e r a g e number w i t h i n a fa m ily . The o n ly two v a r i a b l e s i n w hich t h e s e minimums a r e o b t a i n e d i n t h i s s tu d y a r e f i n a l w e ig h t and a v e r a g e d a i l y g a i n i n t h e Sim m ental b r e e d . From o b s e r v a t i o n o f t h e d a t a , y i e l d g r a d e and i n t e r n a l f a t s h o u ld be t h e most i n a c c u r a t e o f t h e h e r i t a b i l i t y e s t i m a t e s . R esp o n se t o S e l e c t i o n Due t o t h e d i s c o n n e c t e d n e s s o f t h e u n s e l e c t e d and s e l e c t e d H e r e f o r d d a t a , no s t a t i s t i c a l t e s t s w ere p e rfo rm e d . and t r e n d s w ere o b s e r v e d . t e d and s e l e c t e d H e r e f o r d s . However, means w ere p l o t t e d F i g u r e s 1 to 9 p r e s e n t t h e means o f t h e u n s e l e c ­ T hese w ere t h e e s t i m a t e d means from t h e MME s o l u t i o n s . In F ig u re 8 i t can be ob served t h a t s e l e c t i o n f o r g r e a t e r y e a r lin g w e ig h ts w i t h i n group two h a s c o n s i s t e n t l y p ro d u c e d c a l v e s w i t h h i g h e r means t h a n t h o s e p ro d u c e d by t h e u n s e l e c t e d H e r e f o r d s o v e r t h e f o u r y e a rs o f t h i s stu d y . B oth g ro u p s i n c r e a s e d i n y e a r l i n g w e ig h t d u r in g th e f i r s t th r e e y e a r s , b u t th ey b o th d e crea se d in th e f o u r th y e a r , T h is o b s e r v a t i o n c o u ld p r o b a b ly be a t t r i b u t e d t o n u t r i t i o n a l a n d / o r management d i f f e r e n c e s from y e a r to y e a r . 1981. 71 T a b le 17. E s tim a te d Sample S i z e Needed f o r M inim al Sam pling V a r ia n c e o f H e r i t a b i l i t y T ra it h 2a tb n c Sim m ental H erefo rd M arb lin g .31 .08 13.0 221 416 Y i e l d Grade .185 .05 2 1 .7 369 6 9 4 .4 A v erage D a ily G ain .54 • 13 7 .4 125.8 2 3 6 .8 L o in Eye A rea .46 .11 8 .7 147.9 2 7 8 .4 I n t e r n a l F a t (KPH) .28 .07 14 .3 2 4 2.8 4 5 7 .6 C a r c a s s Grade .44 .11 9 .0 153 288 F a t T h ic k n e s s .49 .12 8 .1 137.7 2 5 9 .2 F i n a l W eight .73 .18 5 .5 93 .5 Y e a r l i n g W eight .38 .09 1 0.6 180 176 3 3 9 .2 h e r i t a b i l i t y e s t i m a t e s from l i t e r a t u r e b I n t r a c l a s s C o r r e l a t i o n , t= h ^ / 4 CNumber o f sam p les w i t h i n a f a m i l y , n = l / t ^ T o t a l number o f s t e e r s r e q u i r e d , T*nN w here N i s th e number o f f a m i l i e s 72 Figure 1. Means of Marbling Scores of Unselected and Selected Herefords, 1978-1981 Figure 1. UNSELECTED HEREFORDS SELECTED HEREFORDS MARBLING SCORE 12.5 12.0 11.5 11.0 10.5 10.0 9 .5 9 .0 6 .5 8. 0 1978 - 1 ■ 1980 1979 YEAR 1981 74 Figure 2. Means of Yield Grades of Unselected and Selected Herefords, 1978-1981 Figure 2. UNSELECTED HEREFORDS SELECTED HEREFORDS YIELD GRHDE 3.6 3 .0 1978 1979 19B0 YEAR 1981 76 Figure 3. Means of Average Daily Gain of Unselected and Selected Herefords, 1978-1981 Figure 3. UNSELECTED HEREFORDS SELECTED HEREFORDS RVERRGE DRILY GRIN (LB) 3 .0 2.8 2. 6 2 .4 2.2 - 2.0 l.B 1.6 .1 1.4 1978 1990 1979 YEflR 1981 78 F i g u r e 4. Means o f L o in Eye A reas o f U n s e le c te d and S e l e c t e d H e r e f o r d s , 1978-1981 4 Figure 4. UNSELECTED HEREFORDS SELECTED HEREFORDS LOIN EYE RRER (IN^) 12.6 12.4 12.2 -"■ J VO 12.0 1978 1979 1960 YERR 1981 80 Figure 5. Means of Internal Fat of Unselected and Selected Herefords, 1978-1981 Figure 5. UNSELECTED HEREFORDS SELECTED HEREFORDS INTERNAL FAT (•{) 3 .2 3 .0 2.8 2.6 2. 2 2. 0 1978 1979 1980 YEAR 1981 82 Figure 6. Means of Carcass Grades of Unselected and Selected Herefords, 1978-1981 Figure 6. UNSELECTED HEREFORDS SELECTED HEREFORDS CRRCfiSS GRflDE 12.5 1 2. 0 11.5 1 1. 0 10.5 10.0 1978 1979 1980 YEHR 1981 84 Figure 7. Means of Fat Thickness of Unselected and Selected Herefords, 1979-1981 Figure 7. UNSELECTED HEREFORDS SELECTED HEREFORDS FHT THICKNESS (IN) .60 .50 .45 1970 1979 1980 YEHR 1981 86 Figure 8. Means of Final Weight of Unselected and Selected Herefords, 1978-1981 Figure 8. UNSELECTED HEREFORDS SELECTED HEREFORDS FINRL HEIGHT (LB) 1250 1200 1150 oo 1100 1050 1000 950 900 197B 1979 1980 YEHR 1981 88 Figure 9. Adjusted Yearling Weight Means of Unselected and Selected Herefords, 1978-1981 Figure 9 . UNSELECTED HEREFORDS SELECTED HEREFORDS YEARLING HEIGHT (LB) 950 300 800 750 700 .. I. . 1980 650 1978 1979 YEAR 1981 90 By o b s e r v i n g t h e re m a in in g f i g u r e s , i t can be s e e n t h a t t h e s e l e c t e d H e r e f o r d s w ere c o n s i s t e n t l y h e a v i e r a t s l a u g h t e r and g a in e d f a s t e r i n the fe e d lo t. O b s e r v a t i o n o f t h e o t h e r t r a i t s r e v e a l s c o n s i s t e n t l y more m u scle and v a r y i n g d i f f e r e n c e s i n f a t i n d i c a t o r s . I t a p p e a r s t h a t t h e two g ro u p s re s p o n d e d d i f f e r e n t l y to v a r y i n g management re g im e s . However, t h i s i n t e r a c t i o n was n o t s i g n i f i c a n t (P >.05) i n t h e p r e l i m i n a r y a n a l y s i s i n d i c a t i n g t h e d i s c r e p a n c i e s m ust be due to sam p lin g w i t h i n t h e y e a r s . D a ir y C ro s s Dam vs B eef C ro ss Dam A l l s t e e r s in c l u d e d i n t h i s a n a l y s i s from g ro u p s t h r e e and f o u r w ere s i r e d by Sim m ental b u l l s . However, t h e cows i n group 3 w ere c r o s s e s o f Angus, H e r e f o r d , Sim m ental and C h a r o l a i s b r e e d s , w h i l e t h o s e i n group 4 w ere Angus, H e r e f o r d , Sim m ental and H o l s t e i n - F r i e s i a n c r o s s e s . T h e re ­ f o r e , t h e e f f e c t c o n s t r a s t i n g th e two b r e e d s would be com paring th e s t e e r s from a d a i r y c r o s s dam w i t h t h e s t e e r s from a C h a r o l a i s c r o s s dam. T a b le 18 p r e s e n t s t h e c o n t r a s t e f f e c t f o r e ach t r a i t . The r e s u l t s i n d i c a t e t h a t t h e d a i r y c r o s s s t e e r s o u t-w e ig h e d t h e group 3 s t e e r s a t 365 days o f ag e and a g a i n a t f i n a l w e i g h t . g a in e d f a s t e r w h ile i n t h e f e e d l o t . However, t h e group 3 s t e e r s I n a d d i t i o n , th e s t e e r s from d a i r y c r o s s e d dams w ere more d e s i r a b l e i n t h e i r m a r b lin g w hich r e s u l t e d i n a h ig h e r c a rc a s s g rad e. 91 T a b le 18. C o n t r a s t E f f e c t s o f F e e d l o t and C a r c a s s T r a i t s Between Group 3 and Group 4 T ra it F i n a l W eight A verage D a ily G ain Y e a r l i n g Weight In te rn a l Fat E ffect -3 5 .4 .0606 - 6 0 .5 2 .0048 Y i e l d Grade - .0 6 9 4 L o in Eye Are - .1 0 3 0 M arb lin g - .4 3 8 0 F a t T h ic k n e s s .0020 C a r c a s s Grade - .3 1 2 9 * P < .05 ** P<.01 N ote: D eg rees o f freed om f o r c a r c a s s t r a i t s i s 98; d e g r e e s o f freedom f o r f e e d l o t t r a i t s i s 106 * 92 C ro ssb reed in g E f f e c ts C om parisons w ere d e s i r e d c o n t r a s t i n g t h e p e rfo rm a n c e o f t h e c r o s s ­ b red c a t t l e w ith th e s e le c te d H ereford s t e e r s . However, t h i s p a r t i c u l a r e f f e c t was n o t e s t i m a b l e due to t h e d i s c o n n e c t e d d a t a . F i g u r e s 10 t o 18 i l l u s t r a t e t h e t r e n d s o f t h e t h r e e g ro u p s from 1978 t o 1981. However, t h e o b s e r v e d d i f f e r e n c e s can b e a t t r i b u t e d t o b r e e d o f s i r e a s w e l l a s d i f ­ fe re n c e s in the c ro ssb re d s t a t u s o f th e s t e e r s . The c r o s s b r e d s t e e r s w ere more d e s i r a b l e i n g ro w th t r a i t s and amount o f m u s c lin g . I n a d d i t i o n , th e y e x h i b i t e d l e s s 1 2 th r i b f a t w i t h group 4 a v e r a g i n g c o n s i d e r a b l y l e s s f a t i n 1981 t h a n e i t h e r o f t h e o t h e r g r o u p s . C arcass g r a d e s d id n o t a p p e a r t o b e much d i f f e r e n t i n c r o s s b r e d s th a n in th e s tr a ig h tb r e d H erefo rd s. However, g ro u p s 3 and 4 w e re more d e s i r ­ a b l e i n y i e l d g r a d e , w h ic h would b e a r e f l e c t i o n o f t h e i r o v e r a l l l e a n n e s s i n co m p ariso n t o t h e H e r e f o r d s . C o n t r a s t e f f e c t s com paring t h e s t e e r s i n group 2 t o t h e c r o s s b r e d H e r f o r d - s i r e d s t e e r s i n g ro u p s 3 and 4 a r e p r e s e n t e d i n T a b le 19. The s i g n i f i c a n c e o f t h e c o n t r a s t was i n v e s t i g a t e d u t i l i z i n g B o n f e r o n n i 's t s ta tistic . The group 4 s t e e r s o u t - p e r f o r m e d t h e s e l e c t e d s t r a i g h t b r e d H e r e f o r d s i n a l l gro w th t r a i t s , and y e a r l i n g w e ig h t. i.e . f i n a l w e ig h t, averag e d a i l y g a in I n a d d i t i o n , th e y w e re l e a n e r o v e r t h e 1 2 th r i b and e x h i b i t e d more m u scle a s i n d i c a t e d by t h e i r a v e r a g e l o i n eye a r e a . Group 3 and y e a r l i n g s t e e r s d i f f e r e d from t h e s e l e c t e d H e r e f o r d s i n f i n a l w e ig h t w e ig h t (P<.05 and P < .0 1 , re sp e c tiv e ly ). These r e s u l t s i n d i c a t e f a v o r a b l e f e e d l o t p e rfo rm a n c e o f t h e c r o s s b r e d s t e e r when t h e c r o s s b r e d dam c o n t a i n s some d a i r y g e n e s . 93 Figure 10. Means of Marbling Scores of Groups 2, 3 and 4, 1978-1981 Figure 10. GROUP 3 CROSSBREDS SELECTED HEREFORDS GROUP 4 CROSSBREDS HRRBLING SCORE 13 12 11 \o 10 9 8 7 6 1978 1979 1980 YERR 1981 95 Figure 11. Means of Yield Grades of Groups 2, 3 and 4, 1978-1981 Figure 11. SELECTED HEREFORDS GROUP 3 CROSSBREDS GROUP 4 CROSSBREDS YIELD GRRDE 4 .0 3.8 3 .0 2. B 2.0 1978 1979 1980 YERR 1981 97 Figure 12. Means of Average Daily Gains of Groups 2, 3 and 4, 1978-1981 Figure 12. SELECTED HEREFORDS GROUP 3 CROSSBREDS GROUP 4 CROSSBREDS RVERRGE DRILY GRIN (LB) 3. 2 3.0 2.B 2.6 2. 4 2. 2 2.0 1976 1979 1980 YERR 1981 99 Figure 13. Means of Loin Eye Areas of Groups 2, 3 and A, 1978-1981 Figure 13. SELECTED HEREFORDS GROUP 3 CROSSBREDS GROUP 4 CROSSBREDS 2 LOIN EYE RREfl (IN ) 15.5 15.0 14.5 14.0 13.5 13.0 12.5 12 . 0 1978 1980 1979 YEHR 1981 101 F i g u r e 14. Means o f I n t e r n a l F a t of Groups 2 , 3 and 4 , 1978-1981 t Figure 14. GROUP 3 CROSSBREDS SELECTED HEREFORDS GROUP 4 CROSSBREDS INTERNAL FRT ('/.) 2.B .4 .2 .0 .8 1978 1979 1980 YEHR 1981 103 Figure 15. Means of Carcass Grades of Groups 2, 3 and 4, 1978-1981 Figure 15. SELECTED HEREFORDS GROUP 3 CROSSBREDS GROUP 4 CROSSBREDS CARCASS GRADE 12.5 1 2. 0 10.5 10.0 9.0 1978 1979 1980 YEAR 1981 105 Figure 16. Means of Fat Thickness of Groups 2, 3 and 4, 1978-1981 Figure 16. SELECTED HEREFORDS GROUP 3 CROSSBREDS GROUP 4 CROSSBREDS FHT THICKNESS (IN) 70 65 .60 40 30 1978 1979 1980 YEAR 1981 107 Figure 17. Means of Final Weight of Groups 2, 3 and 4, 1978-1981 Figure 17. SELECTED HEREFORDS GROUP 3 CROSSBREDS GROUP 4 CROSSBREDS FINAL WEIGHT (LB) 1450 1400 1350 108 1300 1250 1200 1150 1100 1978 1979 1980 YEAR 1981 109 Figure 18. Adjusted Yearling Weight Means of Groups 2, 3 and 4, 1978-1981 Figure 18. SELECTED HEREFORDS GROUP 3 CROSSBREDS GROUP 4 CROSSBREDS YEflRLING HEIGHT (LB) 1200 1150 1100 N. 1050 N. 1000 950 900 800 1978 979 I960 YEAR 1981 Ill T a b le 19- C o n t r a s t E f f e c t s o f F e e d l o t and C a r c a s s T r a i t s i n C r o s s b r e d S t e e r s T ra it F i n a l W eight Group 2 v s Group 3 -8 0 .0 * Group 2 v s Group 4 -1 7 3 .5 ** C a r c a s s Grade .249 .851 F a t T h ic k n e s s .03139 .21428* .1959 .6351 M a rb lin g - .1 6 0 5 .5897 I n t e r n a l F a t (KPH) - .0 9 8 9 - .2 6 9 6 L o in Eye A rea -.3 8 5 - 1 .4 4 8 * A verage D a i l y Gain - .0 9 0 8 - .2 9 2 1 Y i e l d Grade Y e a r l i n g W eight * P<.05 - 1 2 9 .0 9 ** -2 1 9 .4 k ** SUMMARY AND CONCLUSIONS Commercial b e e f c a t t l e p r o d u c e r s c u r r e n t l y a t t e m p t t o b r e e d c a t t l e i n a m anner t h a t w i l l i n s u r e t h e f a s t e s t grow ing c a t t l e on a s an e f f i ­ c ie n t a d i e t as p o s s ib le . I n a d d i t i o n , th e y e x p e c t t h e s e f a s t grow ing c a l v e s t o h a v e c a r c a s s e s w i t h t h e g r e a t e s amount o f e d i b l e b e e f p e r u n i t o f w e ig h t. For s e v e r a l y e a r s p r o d u c e r s h av e be en u s i n g c r o s s b r e e d i n g and s e le c tio n as to o ls to a ch ie v e t h e i r f i n a l g o a ls . I n o r d e r f o r them to u t i l i z e t h e s e t o o l s a s e f f e c t i v e l y a s p o s s i b l e , i t i s d e s i r a b l e f o r them t o know t h e h e r i t a b i l t i e s and c o r r e l a t i o n s o f t h e t r a i t s th e y a r e a c t i v e l y s e l e c t i n g f o r and t h e r e l a t e d t r a i t s t h a t th e y hop e t o i n f l u e n c e . I n a d d i t i o n , b e c a u s e o f t h e trem end ou s n eed t o b r e e d t h e b e s t s i r e b r e e d t o t h e b e s t dam b r e e d , i t i s n e c e s s a r y f o r them t o know how a p a r t i c u l a r c r o s s com pares t o a w e l l - e s t a b l i s h e d p u r e b r e d . The p u r p o s e s o f t h i s s t u d y w e re: 1) t o d e te r m in e t h e e f f e c t o f s e l e c t i o n f o r y e a r l i n g w e i g h t , 2) to compare t h e p e rfo rm a n c e o f c r o s s b r e d s t e e r s t o t h e p e rfo rm a n c e o f s t r a i g h t b r e d H e r e f o r d s t e e r s , 3) t o e s t i m a t e h e r i t a b i l i t i e s and c o r r e l a t i o n s o f s e l e c t e d f e e d l o t and c a r c a s s t r a i t s i n b e e f c a t t l e s e l e c t e d f o r y e a r l i n g w e ig h t and 4) to compare e s t i m a t e s o f h e r i t a b i l i t y o b t a i n e d u s i n g REML t e c h n i q u e s to p r e v i o u s l y r e p o r t e d e s t i ­ m a te s . Two h u n d re d s i x t y - s e v e n r e c o r d s on Lake C i t y s t e e r s w ere c o l l e c t e d from 1978 t o 1981. The f i n a l a n a l y s i s i n d i c a t e d t h a t t h e H e r e f o r d s s e l e c t e d on y e a r l i n g w e ig h t g a in e d more i n t h e f e e d l o t and w ere c o n s i d e r a b l y 112 113 h e a v i e r a t s l a u g h t e r th a n t h e i r u n s e l e c t e d c o u n t e r p a r t s . In a d d itio n , t h e s e l e c t e d H e r e f o r d s had c o n s i s t e n t l y more m u s c lin g t h a n t h e u n s e l e c t e d H erefords. When d a i r y c r o s s e d s t e e r s w ere compared t o b e e f s t e e r s , t h e s t e e r s from t h e d a i r y c r o s s dams o u tw e ig h ed t h e b e e f s t e e r s a t 365 d a y s o f age and a g a i n a t f i n a l w e i g h t . I n a d d i t i o n , t h e d a i r y c r o s s s t e e r s w ere more d e s i r a b l e i n t h e i r m a r b l i n g . However, t h e b e e f s t e e r s c o n s i s t e n t l y g a in e d f a s t e r w h i l e i n t h e f e e d l o t . When t h e c r o s s b r e d s t e e r s w ere compared t o t h e H e r e f o r d s t h e c r o s s ­ b r e d s w e re more d e s i r a b l e i n g ro w th t r a i t s and t o t a l amount o f m u s c l in g . The two c r o s s b r e d g ro u p s a l s o e x h i b i t e d l e s s 1 2 th r i b f a t t h a n t h e s t r a i g h t b r e d s t e e r s a n d , c o n s e q u e n t l y , p ro d u c e d more d e s i r a b l e y i e l d g rades. No d i f f e r e n c e s w ere o b s e r v e d i n c a r c a s s g r a d e s b e tw e e n t h e two g roups. P h e n o ty p ic c o r r e l a t i o n s o f t h e e i g h t o b s e r v e d t r a i t s w i t h y e a r l i n g w e ig h t w ere s i m i l a r t o p r e v i o u s l y r e p o r t e d c o r r e l a t i o n s . D iffere n c es i n c o r r e l a t i o n s w ere o b s e r v e d b e tw ee n t h e S i m m e n t a l - s i r e d s t e e r s and t h e H e r e f o r d - s i r e d s t e e r s as c o u ld be e x p e c te d due t o t h e d i s t i n c t b re e d d iffe re n c e s. U n e x p la in a b le n e g a t i v e g e n e t i c c o r r e l a t i o n s w ere o b s e r v e d b etw een f i n a l w e ig h t and y e a r l i n g w e i g h t . The o n ly a p p a r e n t e x p l a n a t i o n f o r su ch a " n o n - b i o l o g i c a l " r e s u l t i s t h e s m a ll sam ple s i z e u sed f o r e s t i m a t i o n . H e r i t a b i l i t y e s t i m a t e s w e re , i n g e n e r a l , d i f f e r e n t from p r e v i o u s l y re p o rte d h e r i t a b i l i t i e s . However, many o f t h e s e d i f f e r e n c e s c o u ld be e x p l a i n e d by t h e d i s t i n c t p o p u l a t i o n o f c a t t l e a t t h e Lake C i t y E x p e r i ­ ment S t a t i o n . I n a d d i t i o n , a s m a l l sam ple s i z e c o n t r i b u t e d t o a few o f t h e e s t i m a t e s b e i n g o u t s i d e o f t h e p a r a m e te r s p a c e . 114 I n c o n c l u s i o n , i t a p p e a r s t h a t s e l e c t i o n f o r y e a r l i n g w e ig h t com­ b in e d w i t h c r o s s b r e e d i n g w i l l p ro d u c e c a t t l e t h a t g a i n f a s t e r i n t h e f e e d l o t and p ro d u c e more d e s i r a b l e c a r c a s s e s w i t h more e d i b l e m eat p e r u n i t o f c a r c a s s w e ig h t. t LITERATURE CITED LITERATURE CITED Adams, N. J., W. N. Garrett and J. T. Elings. 1973. Performance and carcass characteristics of crosses fran inported breeds. J. Anim. Sci. 37:623. Adams, N. J., G. C. Smith and Z. L. Carpenter. 1977. Carcass and palatability characteristics of Herefords and crossbred steers. J. Anim. Sci. 45:438. Alenda, R., T. G. Martin, J. F. Lasley and M. R. Ellersieck. 1980a. 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