Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2008
Publication Date: 1/1/2009
Citation: Li, M.H., Robinson, E.H., Tucker, C.S., Manning, B.B., Khoo, L. 2009. 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. Aquaculture. 292:232-236. Interpretive Summary: There is strong scientific evidence that n-3 fatty acids, especially n-3 long-chain polyunsaturated fatty acids (LC-PUFAs), play important roles in the modulation and prevention of human diseases, particularly coronary heart. The n-3 LC-PUFAs are also essential in brain and eye development in infants. It is well established that Western diets are rich in n-6 and deficient in n-3 fatty acids. Enrichment of n-3 fatty acids, especially n-3 LC-PUFAs in food sources would increase their intake and improve human health. Results from the present study indicate that supplementation of 1 .5% dried algae increases weight gain of channel catfish and a level of 0.5% dried algae and above improves FER. Levels of dried algae up to 2% did not impact the flavor quality of edible tissue. Feeding 2% dried algae markedly increased n-3 LC-PUFA levels in the edible tissue without adverse effects on flavor quality of catfish product. With global fishmeal and oil production remaining at roughly the same levels or declining, dried algae from Schizochytrium sp. and other algal species rich in n-3 LC-PUFAs can play an important role to supply EFAs to farmed animals and humans because these algae are a sustainable source of EFAs. At current prices it is not economical to use the dried algae in feeds for catfish food fish. However, with the advancement of technology in large-scale algal culture, it may be economically feasible to use dried algal products, such as Schizochytrium sp., in the diet to enhance LCPUFAs of fish products in the near future.
Technical Abstract: 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% .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.n-3 LC-PUFAs in the edible tissue of fish.