Dietary lipid sources influence responses of channel catfish ( Ictalurus punctatus) to challenge with the pathogen Edwardsiella ictaluri

Abstract

Two experiments were conducted to evaluate the effect of feeding various lipid sources at high and low water temperatures on responses of channel catfish to challenge (25°C) with Edwardsiella ictaluri. Semipurified diets were fed which contained 7% beef tallow, corn oil, linseed oil, menhaden oil or a 1:1:1 mixture of beef tallow, corn oil and menhaden oil. In Experiment 1, fish (14.3±0.3 g average initial weight) fed the menhaden oil and linseed oil diets for 13 weeks at 28°C had lower survival than fish fed the other diets ( P<0.05). In Experiment 2, the fish (0.7±0.01 g average initial weight) fed the menhaden oil and the linseed oil diets for 9 weeks at 28°C also had lower survival than fish fed the other diets ( P<0.05). There was no difference in survival among treatments when fish were fed at 17°C. At the higher temperature, the fish fed the menhaden oil and the mixed oil diets had equal or higher weight gains than the other dietary treatments in both experiments; there was no difference in weight gain among treatments at the lower temperature. The reduced resistance to infection by channel catfish fed menhaden oil or linseed oil at the high temperature may be caused by the competitive inhibition of arachidonic acid metabolism by n−3 fatty acids as occurs in warm-blooded animals. A combination of menhaden oil and corn oil, or sources of n−3 highly unsaturated fatty acids and linoleic acid, appear to be desirable in practical catfish feeds to optimize immunocompetence and growth.