Effects of Dietary Terramycin and Methionine Supplements on Fat and Protein Gains in Weanling Rats

Abstract

Four groups of 10 weanling, male, albino rats each were fed the following diets ad libitum for 45 days: group 1, the basal diet (approximately 19.9% protein, 0.30% methionine, and 0.12% cystine); group 2, the basal diet + terramycin; group 3, the basal diet + 0.4% methionine; and group 4, the basal diet + terramycin + 0.4% methionine. No statistically significant effect of methionine supplementation alone of the basal diet was observed. Terramycin supplementation alone of the basal diet: (a) increased carcass dry matter significantly (12.7%, p < 0.02), increased significantly the efficiency of dry matter utilization for carcass dry matter deposition (10.0%, p < 0.05), and increased dry matter intake almost significantly (3.8%, p > 0.1); (b) increased carcass N deposition non-significantly (1.6%, p > 0.5) and decreased the efficiency of N utilization almost significantly (5.2%, p ≅ 0.064); (c) increased carcass ether extract significantly (36.1%, p < 0.01) and increased significantly the efficiency of dry matter utilization for ether extract deposition (36.2%, p < 0.01). Therefore, one may conclude that terramycin alone increased carcass dry matter gains, mainly by enhancing fat deposition. The terramycin-methionine interaction: (a) increased carcass N deposition non-significantly (4.5%, p > 0.2) and increased the efficiency of N utilization significantly (10.7%, p < 0.01); (b) significantly decreased carcass ether extract deposition (30.8%, p < 0.05) and significantly decreased the efficiency of utilization of dry matter for carcass ether extract deposition (30.6%, p < 0.05). Thus one may infer that the terramycin-methionine interaction enhanced the efficiency of utilization of dietary N and depressed fat gains. Speculations as to the mode of action of antibiotics have been advanced.