Effects of stocking density and vitamin C status on vitamin E-adequate and vitamin E-deficient fingerling channel catfish
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Previous studies have reported some very different responses of channel catfish (Ictalurus punctatus) fed vitamin E-deficient diets, especially with respect to gross deficiency signs. In an attempt to elucidate the cause of these differing responses, two experiments were conducted in aquaria to determine if stocking density or vitamin C status would affect the sensitivity of catfish to vitamin E deficiency. In the first experiment, catfish were stocked at four different densities and fed vitamin E-deficient or vitamin E-supplemented diets for 19 weeks. No gross deficiency signs were observed in catfish fed the vitamin E-deficient diet at each stocking density; however, vitamin E deficiency was manifested as elevated lipid peroxidation of hepatic microsomes. Increasing stocking density significantly reduced catfish growth and feed efficiency; however, circulating cortisol levels were not affected. In the second experiment, a purified basal diet and diets supplemented with either vitamin C or vitamin E or both of these nutrients were fed to fingerling channel catfish for 20 weeks. Catfish fed diets without supplemental vitamin C had significantly reduced growth and feed efficiency regardless of vitamin E supplementation. No gross deficiency signs were observed in catfish fed the vitamin E-deficient diet with supplemental vitamin C, and combined deficiencies of vitamin E and vitamin C did not induce overt signs of vitamin E deficiency. However, vitamin E deficiency was once again confirmed by elevated microsomal lipid peroxidation. Results from this study indicate that stocking density and vitamin C status did not affect the severity of vitamin E deficiency in channel catfish, and lend further support to the hypothesis that variable responses of catfish to vitamin E deficiency are due to varying degrees of susceptibility in different strains of catfish. 1986.
