Effect of feeding various dietary levels of fermented canola meal withBacillus sp. from the Caspian Sea sediments on growth, liver antioxidative and metabolic enzymes activity of Nile tilapia (Oreochromis niloticus) fingerlings

Producing cost-effective aquafeed and using very available feed ingredients play an important role in sustainable aquaculture development. Such an undeniable necessity has resulted in special attention to local feed ingredients and application of biotechnological solutions to improve the ingredients. The present study was carried out to investigate the effect of various dietary contents of fermented canola meal with Bacillus sp. from sediments of the Caspian Sea on growth, liver antioxidative and metabolic enzymes activity of Nile tilapia fingerlings. 225 fish with an average weight of 1.9±0.05 g were fed five different experimnetal diets including, treatment 1 (control group): diet without fermented canola meal, treatment 2, diet containing 12.5% ​fermented canola meal, treatment 3, diet containing 25% fermented canola meal, treatment 4, diet containing 37.5% fermented canola meal and treatment 5, diet containing 50% fermented canola meal, for 8 weeks. Results revealed that the growth indices did not significantly differ among various experimental groups (p>0.05). Liver antioxidative enzymes activity showed that activity of SOD in treatment 4, and activity of GPX in treatments 3 and 4 increased compared to the control group (p<0.05). Although, activity of CAT did not significantly differ among various experimental groups (p>0.05), significant difference was observed between treatments 3 and 4 in this regard (p<0.05). Also, liver metabolic enzymes activity showed that AST activity of treatments 2, 3 and 4, and ALT activity of treatments 2, 3, 4 and 5 increased in comparison to control group (p<0.05). In general, it was concluded that incorporating 50% of fermented canola meal did not affect growth indices of Nile tilapia fingerlings.