Effect of Diet Protein Level on Weight Gains of Early Weaned Beef Calves

Abstract

Forty-eight Angus and Polled Hereford calves were weaned at an average of 48 days of age. Calves were group-fed in dry lot four diets ad libitum which contained 14.5, 18.9, 23.7 and 28.5% crude protein (diets 1, 2, 3 and 4, respectively) with each diet having approximately 14% crude fiber on a dry matter basis. After a 12-day preliminary period, calves were fed for three periods of 6, 6 and 5 weeks. Differences in daily gain due to diet were significant (P<.05) only for Angus. Period effects on daily gain were significant (P<.05) for Angus and P. Hereford males. Angus males gained significantly (P<.01) faster than P. Hereford males and P. Hereford males gained significantly (P<.01) faster than P. Hereford females. Breed-sex × diet interaction did not (P>.05) affect daily gains. Age of calf at weaning was associated with increases in daily gains of .0083 kg (P<05) for Angus and .0099 kg (P<.01) for P. Hereford males per day increase in age. Results of apparent digestibility indicated an increase (P<.05) in the digestibility of crude protein for each increase in crude protein content of the diets. Nitrogen retention of diet 1 was significantly (P<.05) lower than the other diets with the other three diets not differing significantly although the trend showed an increase in nitrogen retention with increases in protein content of the diets. Comparison of daily gain response from the various diets was made with those expected from N.R.C. protein requirements.