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Growth and Reproductive Performance of Bulls and Heifers Fed Purified and Natural Diets. IV. Semen Characteristics, Body Measurements and Fertility of Bulls (22 to 156 Weeks of Age)

U. S. Department of Agriculture,^,2 Beltsville, Maryland 20705

Abstract

Eight Angus bulls were reared on purified diets which contained either urea or isolated soy protein as the sole sources of dietary nitrogen or a natural diet in order to determine the influence of diet on semen characteristics, sexual behavior, body measurements and fertility. Bulls fed the isolated soy diets and natural diets attained puberty at 43 and 42 weeks, respectively. Urea fed bulls reached puberty at 48 weeks of age. Body weight was lower at puberty in urea and soy fed bulls. Body weight was similar for bulls fed the three diets at 82 weeks of age. Bulls fed natural diets were superior to bulls fed urea and isolated soy diets in semen volume and total sperm production over the period from SO weeks to 148 weeks of age. Fertility was not affected by feeding either the urea or isolated soy diet. Data from this study indicate that protein is not essential in the diet of beef bulls to obtain fertility.

¹ The authors gratefully acknowledge the assistance of B. L. Phillips in obtaining body measurements and for the care of experimental animals.

² Animal Science Research Division, A.R.S.