Effect of Available Energy Level of Fattening Rations on Utilization of Nitrogen and Digestibility by Steers

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Abstract
Three digestion and nitrogen balance trials were conducted with six Angus yearling steers to study metabolism of nitrogen and digestibility by steers fed fattening rations containing three available energy concentrations. The three rations contained approximately 12.5% crude protein. The available energy concentration was varied by changing the proportions of shelled corn and corn cobs. Equal amounts of the rations were fed. The determined digestible energy levels were 2763, 2842 and 2995 kcal. per kg. of dry matter for the low, medium and high energy rations, respectively. This represented a significant (P<.01) linear effect. Metabolizable energy and TDN values followed similar patterns. Increasing the available energy concentration had no significant effect on nitrogen retention, expressed as grams per day or as percent of intake. Biological value was highest for the medium energy level, and the quadratic ffect was significant. The apparent digestibiilty of crude protein and ether extract was not influenced significantly by available energy concentration. Digestibility of dry matter, organic matter, energy and NFE increased (P<.01) and digestibility of crude fiber decreased (P<.01) with each increase in available energy concentration. Copyright © 1965. American Society of Animal Science . Copyright 1965 by American Society of Animal Science