Effects of dried algae Schizochytrium sp., a rich source of docosahexaenoic acid, on growth, fatty acid composition, and sensory quality of channel catfish Ictalurus punctatus

A laboratory study was conducted to investigate the effect of supplementation of dried algae Schizochytrium sp., a rich source of 22:6 n-3, on growth, fatty acid composition, and sensory quality of channel catfish Ictalurus punctatus. Five isonitrogenous (28% crude protein) and isocaloric (2.78 kcal/g), all-plant diets were formulated to contain 0, 0.5, 1.0, 1.5, and 2.0% dried algae. These diets were fed once daily to satiation for 9 weeks to channel catfish with an average initial weight of 20.4 g per fish in a flow-through system. Fish fed diets containing 1.0% and 1.5% dried algae gained significantly more weight than fish fed diets containing 0% and 0.5% dried algae. Feed efficiency ratio of fish fed 0.5%-2.0% dried algae was significantly greater than that of fish fed the control diet without dried algae. No significant differences were observed in fillet protein, fat, and moisture concentrations, or overall preference and fishy taste scores among fish fed various levels of dried algae. As dietary levels of dried algae increased, 20:5 n-3, 22:6 n-3. total n-3, total n-3 long-chain polyunsaturated fatty acids (LC-PUFAs), 22:5 n-6, and total n-6 LC-PUFAs in the fillet generally increased. These results indicate that supplementation of dried algae increases weight gain of fish and feed efficiency ratio of the fish. Addition of 2% dried algae in the diet markedly improves the levels of 22:6 n-3 and total n-3 LC-PUFAs in the edible tissue of fish. Dried algae Schizochytrium sp. can play an important role to supply essential fatty acids to fish, and humans who consume the fish product enriched with n-3 LC-PUFAs. (C) 2009 Elsevier B.V. All rights reserved.