Biotin Supplementation of Practical Diets for Channel Catfish

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Abstract
A purified diet and two practical-type diets were each evaluated with supplemental biotin (1 mg/kg), without supplemental biotin, and with a biotin antagonist (freeze-dried egg white) for channel catfish (Ictalurus punctatus) over a 17-week feeding period. Omission of supplemental biotin from the casein-dextrin purified diet, with or without egg white, resulted in anorexia, reduced growth rate, lighter skin, hypersensitivity and reduced liver pyruvate carboxylase activity by this fish. Omission of supplemental biotin from either practical diet, one containing basically soybean meal and corn and another containing basically soybean meal, corn and menhaden fishmeal, caused none of these deficiency signs. The ratio of biotin to indigestible dry matter in feces was lower than that in the diet for all fish, indicating little or no synthesis of biotin by the intestinal microflora in channel catfish. Levels of total biotin, measured microbiologically, in the all-plant and in the plant-fishmeal diets were 0.37 and 0.33 mg/kg, respectively. These results indicate that practical diets for channel catfish made from the commonly used ingredients, soybean meal, corn and menhaden fishmeal, do not need supplemental biotin.