Optimum dietary DHA and EPA levels in juvenile rock bream, Oplegnathus fasciatus

Abstract

Experiment 1.

Optimum dietary DHA level in juvenile rock bream, Oplegnathus fasciatus.

A feeding trial was conducted to evaluate the optimum dietary level of docosahexaenoic acid (DHA,22:6n-3) based on growth and non-specific immune responses in juvenile rock bream, Oplegnathus fasciatus. A basal DHA diet was used as a control, and six other diets were prepared by supplementing 0.00, 0.40, 0.80, 1.20, 1.60, 2.00 or 4.00% DHA. The actual DHA concentrations of the diets were 0.10, 0.48, 0.89, 1.31, 1.76, 2.12 and 4.14% (DHA0.10, DHA0.48, DHA0.89, DHA1.31, DHA1.76, DHA2.12 and DHA4.14) diets, respectively. Triplicate groups of fish (initial body weight, 1.05 ± 0.1 g) were fed one of 7 experimental diets at a rate of 4% body weight for 8 weeks. At the end of the feeding trial, final weight, weight gain, specific growth rate and feed efficiency of fish fed DHA1.31, DHA1.76, DHA2.12 and DHA4.14 diets were significantly higher than those of fish fed DHA0.10, DHA0.48 and DHA0.89 diet (P<0.05). The broken-line analysis of weight gain indicates that the optimum dietary DHA level could be 1.27%. Superoxide dismutase activity (SOD) of fish fed DHA1.31 and DHA1.76 diets were significantly higher than those of fish fed the DHA0.10, DHA0.48 and DHA0.89 diets. However, there were no significant differences in SOD among fish fed DHA1.31, DHA1.76, DHA2.12 and DHA4.14 diets. Fish fed DHA1.76, DHA2.12 and DHA4.14 diets showed significantly higher lysozyme activity than did fish fed the DHA0.10, DHA0.48 and DHA0.89 diets. However, there were no significant differences in lysozyme activity among fish fed DHA1.31, DHA1.76, DHA2.12 and DHA4.14 diets. Therefore, the optimum dietary DHA level could be greater than 1.27% but less than 1.31% in juvenile rock bream diet.

Experiment 2.

Optimum dietary EPA level in juvenile rock bream, Oplegnathus fasciatus.

A feeding trial was conducted to evaluate the optimum dietary level of eicosapentaenoic acid (EPA,20:5n-3) based on growth and non-specific immune responses in juvenile rock bream, Oplegnathus fasciatus. A basal EPA diet was used as a control, and six other diets were prepared by supplementing 0.00, 0.40, 0.80, 1.20, 1.60, 2.00 or 4.00% EPA. The actual EPA concentrations of the diets were 0.05, 0.43, 0.85, 1.30, 1.68, 2.10 and 4.12% (EPA0.05, EPA0.43, EPA0.85, EPA1.30, EPA1.68, EPA2.10 and EPA4.12) diets, respectively. Triplicate groups of fish (initial body weight, 1.06 ± 0.1 g) were fed one of 7 experimental diets at a rate of 4% body weight for 8 weeks. At the end of the feeding trial, final weight, weight gain, specific growth rate and feed efficiency of fish fed EPA1.68, EPA2.10 and EPA4.12 diets were significantly higher than those of fish fed EPA0.05, EPA0.43, EPA0.85 and EPA1.30 diets (P<0.05). The broken-line analysis of weight gain indicated that the optimum dietary EPA level could be 1.26% diet. Superoxide dismutase activity (SOD) of fish fed EPA1.68, EPA2.10 and EPA4.12 diets were significantly higher than those of fish fed EPA0.05, EPA0.43, EPA0.85 and EPA1.30 diets. However, there were no significant differences in SOD among fish fed EPA1.68, EPA2.10 and EPA4.12 diets. Fish fed EPA2.10 and EPA4.12 diets showed significantly higher lysozyme activity than did fish fed EPA0.05, EPA0.43, EPA0.85, EPA1.30 and EPA1.68 diets. However, there were no significant differences in lysozyme activity among fish fed EPA2.10 and EPA4.12 diets. Therefore, the optimum dietary EPA level could be greater than 1.26% but less than 1.68% in juvenile rock bream diet.