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Influence of Dietary Energy, Protein and Biological Type of Steer upon Rate of Gain and Carcass Characteristics¹

U.S. Department of Agriculture, Clay Center, NB 68933

Abstract

In three experiments, effects of steer genotype, dietary energy density and protein levels were evaluated in terms of growth rate, feed efficiency and carcass characteristics. Feed intake and efficiency data were grossly different among the trials, and the difference was attributable to severe environmental stresses during the trial 2 feeding period. Crude protein levels in trial 2 (11.0 vs 12.9%) resulted in few meaningful differences in the traits measured suggesting the lower level was adequate to meet protein demands for the rates of gain attained. Dietary energy densities (2.66, 2.77 and 2.93 in trial 1 and 2.68 and 2.94 Meal ME/kg DM in trial 2) significantly influenced final live weight, carcass weight and percentages fat, protein and water in the carcasses. Trends were similar in trial 3 when diets containing 2.78, 2.89 or 2.95 Meal ME/kg were fed. Most of the increase in carcass weight due to increased energy density of the diet apparently resulted from increased carcass fat. No differences in amount of carcass protein or edible product were attributable to energy level. Breed group had significantly affected all carcass traits measured. Carcasses from large-type steers were heavier and contained greater amounts of protein and edible product than carcasses from small-type steers. Rate of gain favored the large-type steers, but feed efficiency was similar between the two types. Interactions between breed type and dietary treatment and between energy density and protein content of the diet were not significant. Protein and edible product produced per unit feed intake was greater in the larger, faster growing steers than in smaller, earlier maturing steers.

¹ U.S. Meat Animal Research Center, North Central Region, ARS.

² Present address: The Andersons, P.O. Box 116, Maumee, OH 43847.

³ Present address: Harrodsburg Road, Danville, KY 40422.