Evaluation of Alfalfa-Corn Cob Associative Action. I. Interactions between Alfalfa Hay and Ruminal Escape Protein on Growth of Lambs and Steers

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Abstract
Three trials evaluated associative action of alfalfa in ammonia (NH3)-treated corn residue diets and(or) potential ruminal degradable protein × escape protein interactions. In trial 1, 128 crossbred steers (250 kg) were fed 0 or 3% NH3-treated residue diets replaced by 0, 15, 30 or 100% of alfalfa hay. Basal diets were formulated to contain adequate metabolizable and crude protein but were nearly devoid of ruminal degradable protein. Ammonia treatment increased (P<.02) dry matter (DM) intake of residues. Pooled across residue treatment, intake increased linearly (P<.01) with increased level of alfalfa. A residue treatment × level of alfalfa interaction (P<.02) for daily gain resulted because the response to level of alfalfa was linear (P<.01) for nontreated residues and quadratic (P<.01) for NH3-treated residues. Similar responses (P<.07) were found for efficiency of gain, indicating that addition of 15 or 30% alfalfa promoted greater associative action for combinations involving NH3-treated vs nontreated residues. In an in vitro trial (trial 2) with the same corn cob and alfalfa diets used in trial 1, NH3 treatment increased (P<.01) in vitro DM disappearance and rate of cell wall digestion of corn cobs. Alfalfa had no effect on rate of nontreated cob cell wall digestion, but increased (P<.01) the rate for NH3-treated cobs. In trial 3, 36 crossbred wethers (25 kg) were fed NH3-treated corn cob diets containing 0 or 30% alfalfa with supplemental protein being either 100% nonprotein N or 50% nonprotein N and 50% high ruminal escape protein. Alfalfa increased (P<.01) intake, daily gain and efficiency of gain for NH3-treated cob diets. Supplementation of 50% of the crude protein requirement as slowly degraded protein increased (P<.01) daily gain. Alfalfa and supplemental N source interacted (P<.01) on efficiency of gain. In the three trials, alfalfa contributed ruminal escape protein, degradable protein and(or) other nutrients to improve utilization of NH3-treated cob diets. Copyright © 1986. American Society of Animal Science . Copyright 1986 by American Society of Animal Science

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