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THE PREDICTABILITY OP THE BUTTERFAT T RAN S KITT11'-GAB ILITY OP DAIRY BULLS By JAMES PREDERIGK SMITHCORS A THESIS Submitted to the School of Graduate Studies of Michigan State College of Agriculture a nd A pplied science in partial fulfillment of the requirements for the degree of DOCTOR OP PHILOSOPHY Department of Animal Husbandry 1951 TABLE OP CONTENTS INTRODUCTION 1 R EVIEW OF LITERATURE I. II. The heritability of butt; e r f a t production The prediction of t r a n s m i t t i n g III. Environmental influences production ability upon m i l k II. 6 and butterfat 11 PREDICTION OF BUTTERFAT T R A N S M I T T I N G A B I L I T Y IN THE MICHIGAN I N S T I T U T I O N H E R D S I. 4 OF BULLS Source of data 20 Methods 22 RESULTS I. Correlation of average d e L x n - d a u g n t e r p r o d u c t i o n II. Per cent chance of p r e d i c t i n g certain limits 26 p r o d u c t i o n within 27 III. Correlation coefficients oetween dam-daughter production at v a r y i n g l e v e l s o f p r o d u c t i o n 29 IV. Comparison of rankings of* t r a n s m i t t i n g a b i l i t y w i t h actual daughter a v e r a g e 30 DISCUSSI ON I. II. III. IV. Correlation analysis of production data 35 Diallel crossing 38 Environmental indices 42 Worksheets 45 SU MMA RY 47 REFERENCES *9 APPENDIX 61 VITA Tile au tho r was born Ma r c h 27, 1920 at Glassboro, New Jersey an d spent his early life in a rvral background. he received the B.S. degree from Rutgers University in 1941, ing In dairy husoandry. major The *:.S. degree was ob tained at Cornell University in 1943 w h i l e an assistant in animal breeding. The author then entered the New Y o r k State Veterina ry College and received the D.V.M. degree In 1945. One yea r of this time was spent as a m emb er of the Arm y veterinary training program* In Nov ember 1945 the author was app oi n t e d Assista nt Pro fessor of An a t o m y at Mi chi gan State College whe re he entered the Graduate School in 1945. He is the author or co- aut hor of two laboratory textbooks and of four scientific articles in the field of endocrinology. He is currently employed as Ass oc i a t e Professor of A n a t o m y at M i c h i g a n State College. INTRODUCTION On e o f tn e m o s t important problems f a c i n g tiie d a i r y m a n is tie p r e d i c t i o n o f w h i c h o f s e v e r a l p r o s p e c t i v e sires is most l i k e l y to t r a n s m i t tiie ti.igh.est l e v e l o f b u t t e r f a t produc tion* from That no a c c u r a t e m e a n s the m e a g e r p r o g r e s s pound a year, in i m p r o v e m e n t o f the p r o g r e s s improvement of p r o d u c t i o n , two d e c a d e s or longer. that has in environment. P e w o f t n e s t u d i e s m a d e u p o n the have oeen s u c c e s s f u l tinguishing between hereditary and environmental dicting S t i l l f e w e r o f the t e c h n i q u e s Dutterfat in d i s factors In in c o m m o n u s e f o r p r e p r o d u c t i o n r e c o g n i z e the ment other than correcti