Effects of biotin deficiency in rainbow trout (Salmo gairdneri) fed diets of different lipid and carbohydrate content

The effects of variations in diet composition on biotin deficiency symptoms were studied in rainbow trout. Fish were fed one of six diets differing in lipid type, carbohydrate and biotin content. Fish given biotin-deficient diets gained less weight, and had inferior feed conversion ratios than the appropriate controls but did not suffer from anorexia nor were any pathological signs observed either by gross or microscopic analysis. Marked reduction in liver biotin concentration and activities of pyruvate carboxylase and acetyl CoA carboxylase, characteristic of biotin deficiency, were observed. Some less marked changes also occurred in the levels of other liver components and enzymes; these changes were influenced by diet composition as well as biotin intake. Hepatic lactate levels tended to increase in biotin deficiency when diets contained starch while the activities of citrate synthase and α-ketoglutarate dehydrogenase decreased, but these changes were reversed when diets lacked starch. Consequently, some secondary effects of biotin deficiency are related to diet composition. In certain treatments, palmitic and oleic acids in muscle triglycerides of biotin-deficient trout were significantly lower than in control fish; but there was no evidence among muscle lipids of chain elongation of linolenic acid in trout given biotin-supplemented diets.