Effect of Ambient Temperature and Dietary Amino Acids on Carcass Fat Deposition in Rats

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Abstract
Sixty-three rats of the Sprague-Dawley strain were used in each of two experiments to study the effects of ambient temperature (7, 23 and 33°) on diet utilization. In experiment 1, dietary protein levels and protein-amino acid sources were: A) 31.7%, casein; B) 15.85%, casein; and C) 31.7%, diet B plus casein-simulating crystalline amino acid mixture. The rats, average initial weight of 122 g, were confined to individual metabolism cages and fed ad libitum for 20 days, then killed for carcass analysis. Diet intake increased significantly with decrease in temperature. Gain was highest at 23°, lowest at 7°. Gain-to-feed ratio results were similar at 23 and 33°, with both significantly higher than at 7°. Carcass fat decreased significantly as temperature decreased. For experiment 2, diet C of experiment 1 served as the control and the effects of deletions of certain of the crystalline amino acids were studied. With isonitrogenous diets, omission of the crystalline essential amino acids or of only the basic amino acids increased fat deposition. Carcass fat deposition, however, responded more to ambient temperature than to amino acid imbalance.