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Growth and Reproductive Performance of Bulls and Heifers Fed Purified and Natural Diets I. Performance from 14 to 189 Days of Age¹

U. S. Department of Agriculture

Abstract

Angus bull and heifer calves were offered purified diets containing either urea or isolated soy protein or a natural diet ad libitum starting at 14 days of age and were weaned onto the diets at 84 days of age. Data is presented through 189 days of age.

Performance of calves fed the natural diet and the isolated soy purified diet was very similar while performance of calves fed the urea purified diet was about 80% as good as these groups prior to weaning. After weaning, performance of calves fed the urea purified diet was about 50% as good as calves fed the isolated soy purified diet. During this same time period the performance of calves fed the isolated soy purified diet was about 75% as good as that of calves fed the natural diet. Bulls fed the purified diets made considerably greater gains than heifers fed these diets and were able to utilize the urea purified diet more efficiently than heifers after weaning. Free-gas bloat was a problem with calves fed the purified diets during the study and this undoubtedly was partially responsible for the lowered feed intake exhibited by these calves.

Water consumption and rectal temperatures were not significantly affected by diet or sex of the calves but were significantly affected by age. Age of calves at first observed rumination was similar for all treatment groups.

¹ The authors gratefully acknowledge the assistance of B. L. Phillips, L. I. Colbert and J. R. Lunsford for the care of the experimental animals and L. L. Slyter for the analysis of the ruminal gas samples.

² Animal Husbandry Research Division, ARS, Beltsville, Maryland.

³ Biometrical Services, ARS, Beltsville, Maryland.