Realimentation of Cull Range Cows. I. Effect of Final Body Condition and Dietary Energy Level on Rate, Efficiency and Composition of Gains

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Abstract
Three trials were conducted with 35 individually-fed cull range cows to determine their level of performance during realimentation. A total of 12 additional cows were slaughtered prior to the feeding trials in order to determine initial carcass composition. All cows were thin initially; mean carcass lipids for two initial slaughter groups were 6 and 31%, respectively. In each trial final body condition (evaluated by the ratio of weight to height or by visual appraisal) was the criterion for slaughter. Composition of carcass gains was estimated using the comparative slaughter technique. In trial 1, cows fed an 80% concentrate diet were slaughtered at one of three final body conditions. Mean carcass lipids for the slaughter groups were 21, 25 and 35%, respectively (P<.05). Rate and efficiency of gain tended (P>.05) to decrease (from 2.28 to 1.90 kg/day and 5.00 to 6.16 kg feed/kg gain) and percentage of lipid in the gain increased (from 52 to 63%, P<.05) as final body condition increased. In trials 2 and 3, cows were fed to a constant condition (approximately 25% carcass lipid) on diets containing 80% or 40% concentrates (trial 2) and 40% or 22% concentrates (trial 3). In each comparison higher rates and efficiencies of gain were achieved on the higher concentrate diet, although performance of all groups was acceptable. Composition of gains was not influenced by dietary concentrate level. In all trials lipid was the largest component of the carcass gain, ranging from 43 to 63%. Averaged across all three trials, carcass gain contained 51% lipid, 14% protein and 35% moisture. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.