Influence of Concentration of Dietary Energy on Protein Needs of Growing-Finishing Cattle

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Abstract
A 4 X; 4 factorial design with two replications (32 lots of five head each) was used to study the performance of crossbred steer calves fed diets containing four protein levels with each of four concentrations of dietary energy. Supplements were formulated from ground corn and a 1:9 ratio of urea (45% N) and soybean meal (50% protein) and fed in a 1:6 ratio with the rest of the diet to meet the 9, 11, 13 and 15% crude dietary protein levels. No increase (P>0.10) in average daily gain was observed by increasing the protein level for the cattle fed the high-corn silage diets. Significantly (P<0.05) greater gains were observed by increasing the protein level with high concentration of dietary energy. A significant (P<0.01) linear response in daily gain was observed by increasing the energy level. Steers that were fed all-concentrate diets consumed less air-dry feed, however, voluntary intake was not influenced by protein or the other energy levels. Gain-to-feed ratios increased in a linear manner as energy or protein increased. More concentrate in addition to the roughage was required per unit of gain when low levels of roughage were added to the diet. Significantly (P<0.01) less energy was required per kilogram of gain when higher-energy diets were fed. Dressing percent increased with increasing dietary energy (P<0.01). Predicted retail yield of the four boneless trimmed retail cuts, loin-eye area, rind thickness per kilogram of carcass weight, and cutability score improved (P<0.06) when dietary energy increased. No difference was observed in the amount of kidney, heart or pelvic fat. Copyright © 1973. American Society of Animal Science . Copyright 1973 by American Society of Animal Science

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