RESUMO
Nile catfish [Clarias Lazera] were fed diets containing different lipid sources for 12 weeks to examine their modulatory effect on performance and macrophage activity at 25 and 32C. The diets contained 7% lipid from either fish oil [highly unsaturated fatty acid, supply n-3], linseed oil [polyunsaturated fatty acid, supply n-3] corn oil [polyunsaturated fatty acid, supply n-6], beef tallow [saturated fatty acids] or an equal mixture of the 4 lipid sources. Fish fed on beef tallow and fish oil achieved the best growth and feed efficiency. Final body length, body condition and fillets analysis were not affected by lipid sources. Fatty acids composition of pronephros were closely correlated to the fatty acid composition of the dietary lipids fed to Nile catfish. At both temperature trials macrophage ability to engulf Pseudomonas was positively correlated with the level of n-3 fatty acids in the diet from either animal or plant origin [fish oil and linseed oil, respectively]. Overall results were suggested that the use of a mixture of beef tallow and linseed oil in the diet of Nile catfish achieved beneficial growth and maximal immune response, however, further research is warranted in this area to determine the proper proportion