Effect of dietary eicosapentaenoic acid (20:5n-3) on growth performance, fatty acid profile and lipid metabolism in coho salmon (Oncorhynchus kisutch) alevins

Abstract

A 12-week feeding trial was conducted to investigate the effects of dietary eicosapentaenoic acid (EPA, 20:5n-3) on the growth performance, fatty acid profile and lipid metabolism in coho salmon (Oncorhynchus kisutch) alevins. Six diets (47% crude protein and 13.5% crude lipid) were formulated to contain graded levels of EPA (0.04%, 0.47%, 0.94%, 1.40%, 1.85% and 2.27%). Nine hundred alevins (0.395 ± 0.02 g) were randomly assigned to 18 white plastic tanks (50 fish in each tank, 0.8 × 0.6 × 0.6 m, and 240-L/tank). Fish were reared in a freshwater flow-through rearing system and fed to apparent satiation 4 times daily. Feed conversion ratio (FCR) in the 1.40% and 1.85% EPA groups was significantly lower than that in the 0.04% EPA group (P < .05). The lowest whole-body lipid content was observed in the 1.85% EPA group, which was significantly lower than those in the 0.04% and 0.47% EPA groups (P < .05). The whole-body EPA, docosahexaenoic acid (DHA, 22:6n-3) and ∑n-3-polyunsaturated fatty acids (∑n-3-PUFAs) contents significantly increased with increasing dietary EPA levels (P < .05). The liver lipoprotein lipase (LPL) and hepatic lipase (HL) reached the lowest value in group of 1.85% EPA, and then no significant differences were observed with increasing dietary EPA levels (P < .05). The liver malate dehydrogenase (MDH) significantly decreased with increasing dietary EPA levels (P < .05), and the lowest value was found in 1.40% EPA group. At the EPA content of 1.85% group, the liver fatty acid synthase (FAS) was significantly lower than those of other groups (P < .05). Fish fed the diet with 1.40% EPA displayed higher specific growth rate (SGR) than that fed the EPA unsupplemented diet. This study revealed that adequate dietary EPA significantly promoted growth performance and lipid metabolism, and based on quadratic regression analysis of SGR indicated that the optimal dietary EPA requirement was 1.41% for coho salmon alevins.