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A 56‐day feeding trial was conducted to evaluate the effects of supplemented diets with β‐glucan (BG) at four levels [0 (D1), 250 (D2), 500 (D3) and 1000 (D4) mg BG kg−1] on red sea bream, Pagrus major. The obtained results revealed a significant increase (P < 0.05) in final body weight, weight gain, specific growth rate, feed intake, body protein content, lysozyme activity and tolerance against low‐salinity stress test in all BG‐supplemented groups when compared with BG‐free group. Furthermore, D4 group resulted in a significant increase in feed efficiency ratio, protein gain, protein and lipid digestibilities, serum bactericidal activity and peroxidase content when compared with D1 group (P < 0.05). Haematocrit and plasma protein content in D3 group were significantly higher than those in D1 group (P < 0.05). Interestingly, BG supplementation decreased glutamic oxaloacetic transaminase (GOT) in D2 group and reactive oxygen metabolites in D2, D3 and D4 groups when compared with D1 group. Following low‐salinity stress test, significantly higher amounts of secreted mucus were observed in fish fed D2 and D4 diets than those from fish fed D1 diet (P < 0.05). In conclusion, the supplementation of BG improves growth, stress resistance and immune response of P. major.

A 56‐day feeding trial was done to investigate the interactive effects of astaxanthin (Ax) and vitamin E (α‐Toc) on the performance of kuruma shrimp (Marsupenaeus japonicus). A 2 × 3 factorial experiment was conducted with six experimental diets containing two levels of Ax (0 and 0.6 g/kg diet [Ax0 and Ax0.6]) and three levels of α‐Toc (0, 0.2 and 1 g/kg diet [α‐Toc0, α‐Toc0.2 and α‐Toc1]). The results indicated that growth performance was significantly (p < 0.05) increased in shrimp fed with the Ax0.6 × α‐Toc0.2 diet. Interactive effects between Ax and α‐Toc on the growth parameters were observed. Furthermore, pigmentation performance was significantly (p < 0.05) better in the Ax0.6 groups. Interaction between Ax and α‐Toc was also found in the Ax content of shrimp body parts. Interestingly, dietary α‐Toc helped to reduce the Ax consumption rate, promote the absorption and increase the deposition of Ax in the muscle. Shrimps from the Ax0.6 groups showed significantly (p < 0.05) improved hepatopancreatic digestive enzyme activities compared with those of the Ax0 groups. Although no interactive (p > 0.05) effects were found between dietary α‐Toc and Ax on total haemocyte count and tolerance against freshwater, dietary Ax and α‐Toc supplementation showed better performance on these two parameters. It was concluded that dietary Ax and α‐Toc functioned synergistically, and the shrimp fed with the diet containing 0.6 g Ax/kg diet Ax and 0.2 g α‐Toc/kg diet showed improved growth and pigmentation performance compared with the other groups in the current study.

The effect of rapeseed meal (RM) and Aspergillus oryzae fermented rapeseed meal (RM‐Koji) on red sea bream (Pagrus major) was examined. Three groups of fish (initial weight, 4.5 ± 0.02 g) were fed a basal diet (RM0) and two test diets where half of fishmeal was replaced by RM (RM50) and RM‐Koji (FRM50) for 56 days. The obtained results showed that fish fed RM0 and FRM50 exerted significantly higher growth performance, feed utilization and haemoglobin level but lower triglyceride and cholesterol than RM50 group (p < 0.05). Interestingly, except of antiprotease activity, all the immune parameters including lysozyme, respiratory burst (NBT) and bactericidal activities were significantly increased in fish fed RM0 and FRM50 diets compared to RM50 diet (p < 0.05). In addition, malondialdehyde and reactive oxygen metabolites were significantly reduced in RM0 and FRM50 groups over RM50 group (p < 0.05). The present results suggest that fermented RM induced better growth performance and immune responses than feeding red sea bream with non‐fermented RM and both RM and RM‐Koji improved the antioxidative status of fish, making RM‐Koji an interesting candidate as a functional feed for aquatic animals.