Influence of Dietary Aureomycin and Carbohydrate on Growth, Intestinal Microflora and Vitamin B12 Synthesis of the Rat

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Abstract
Weanling rats fed a purified diet deficient in vitamin B12 grew faster with dextrin as the sole dietary carbohydrate than with sucrose. The incorporation of aureomycin (100 p.p.m.) in these rations stimulated growth, even when the rations were fortified with vitamin B12 (25 µg/kg). The feeding of aureomycin rapidly induced changes in the intestinal microflora which were influenced to a marked degree by the type of dietary carbohydrate (sucrose or dextrin). The bacteria affected were, primarily, Proteus spp., Lactobacillus spp., Clostridium perfringens, enterococci, coliforms and aureomycin-resistant types. The concentration of “free” vitamin B12 was significantly greater in the intestines of the rats reared on aureomycin-containing diets than in those of animals fed the control ration. Furthermore, a high correlation, most marked in those rats fed rations devoid of B12, was noted between the growth response and the intestinal concentration of “free” B12. The concentration of B12 in the kidney or liver was increased by fortification of the diet with B12 but not by supplementation with aureomycin.