Interactive Effects of Season of Year and Dietary Fat Supplementation, Lysine Source and Lysine Level on the Performance of Swine

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Abstract
Two experiments, each involving three winter and three summer feeding trials, were conducted to determine the interactive effects of season of the year and diet composition on the performance from 21.9 to 92.9 kg of pigs housed in concrete-floored pens in an open-front building. The average weekly maximum air temperatures generally ranged from 24 to 35 C in the summer trials and from −2 to 14 C in the winter trials. The dietary treatments in Exp. 1 consisted of a .95% lysine, corn-soybean meal diet containing 0 or 5% added fat. In Exp. 2 the dietary treatments were a high protein, .95% lysine diet; a low protein, .65% lysine diet, and a low protein plus .30% crystalline lysine diet. In both experiments, the dietary lysine level was redueed by .15% when the average weight of the pigs in a pen reached 58 kilograms. Pigs fed in the summer consumed less (P<.01) feed, gained more slowly (P<.05) but were more efficient (P<.01) than tliose fed in the winter. The inclusion of dietary fat tended to increase metabolizable energy intake and improved (P<.01) the growth rate and efficiency of energy utilization in pigs fed in the summer but not in those fed in the winter. Compared with the high lysine diets, the low protein, low lysine diet depressed (P<.01) the rate and efficiency of gain of pigs. The magnitude of the depression was similar in both the winter and summer environments, even though the pigs fed the low protein diet in the winter exhibited a higher daily lysine intake and growth rate than did the pigs fed the same diet in the summer. Pigs fed the low protein, lysine-supplemented diet gained as fast and efficiently as pigs fed the high protein, high lysine diet in both the cold and the warm seasonal environments. Copyright © 1981. American Society of Animal Science . Copyright 1981 by American Society of Animal Science.

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