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

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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.