Effects of dietary lipid on the hematology of channel catfish, Ictalurus punctatus

Juvenile channel catfish were fed diets containing either soybean oil, menhaden oil, beef tallow, or a combination of these three lipid sources. After 90 days, total erythrocyte, leucocyte, and thrombocyte counts, hematocrit, mean corpuscular volume, plasma recalcification time, erythrocyte osmotic fragility, total serum iron, and iron-binding capacity were measured. Total erythrocyte counts, leucocyte counts, and mean corpuscular volume were not significantly different (P < 0.05) among dietary groups. However, fish fed the menhaden oil diet had significantly lower (P < 0.05) hematocrits, higher thrombocyte counts, and higher serum iron concentrations. They also had the highest concentration of n − 3 fatty acids in the pronephros tissue and their erythrocytes were the least susceptible to osmotic lysis. Catfish fed the beef tallow diet had the lowest level of n − 3 fatty acids in pronephros tissue and their erythrocytes were the most susceptible to osmotic lysis. Results suggest that dietary lipids affect several hematological factors of cultured channel catfish.