Lack of Response of Channel Catfish (Ictalurus punctatus) to Dietary Myo-inositol

Abstract

Channel catfish (Ictalurus punctatus) fingerlings were fed for 28 wk in aquaria (28 ± 1 °C) on semipurified diets with supplemental myo-inositol (400 mg∙kg diet−1), without myo-inositol, and without myo-inositol but with succinylsulfathiazole to suppress intestinal bacteria synthesis. Omission of myo-inositol from the diet, with or without the antibiotic, did not reduce growth rate, produce overt signs of myo-inositol deficiency, or cause a decrease in tissue (muscle, liver, and brain) concentration of myo-inositol. No lipid accumulation occurred in liver or kidney when myoinositol was deleted from the diet. The only possible lipotropic effect of myo-inositol deficiency was a slightly higher (P < 0.07) amount of lipid in brain tissue. Myo-inositol synthesis by enzymes in liver and brain tissues was not affected by myo-inositol in the diet. Rates of myo-inositol synthesis were 39.8 and 67.3 μmol∙h−1∙g protein−1 for liver and brain, which are higher than synthesis rates reported in rodents (myo-inositol synthesis has not been measured in other fish). This study showed that de novo synthesis of myo-inositol by fingerling channel catfish was sufficient for normal growth and maintenance of tissue levels of myo-inositol and to prevent overt signs of myo-inositol deficiency when the vitamin was not included in the diet.