Antibiotics, Growth, Food Utilization and the Use of Chromic Oxide in Studies with Rabbits

Abstract

When terramycin or aureomycin was fed at levels ordinarily recommended for other species of animals, no growth improvement was shown for young rabbits fed a pelleted natural ration. Terramycin did not improve growth when the diet contained 0.5% sulfathalidine. This antibiotic also was ineffective in improving the growth of rabbits which received a semi-purified ration containing either 25% casein or 24.7% soy protein, plus 0.5% methionine. Purified rations consisting either of 10% casein plus niacin or 20% casein without niacin were observed to be inadequate for the growth of rabbits. Nevertheless, terramycin did not improve these rations. The chromic oxide method was found to be applicable in digestion trials with rabbits. However, a preliminary feeding of 5 days appeared necessary. Rabbits appear to improve the utilization of protein and dry matter by consumption of their own excreta. The cecum apparently functions in the digestion of crude fiber and the synthesis of vitamin B₁₂ while both the cecum and large intestine seem to absorb appreciable amounts of other nutrients. The rabbits required 2.7 ± 0.7 or 3.7 ± 0.7 gm of dry feed to produce one gram of live body weight from weaning to 6 or 12 weeks of age respectively.