Dietary effect of different levels of fermented canola on growth, feed utilization, body composition, and digestive enzymes activity of Nile tilapia (Oreochromis niloticus) fingerlings

The present study was carried out to investigate the effect of different dietary levels of fermented canola meal by the Bacillus isolated from Caspian Sea sediments on growth and nutritional indices, proximate body composition, and digestive enzymes activity of Nile tilapia fingerlings. A total of 225 fry fish with an average weight of 1.90±0.05 g were fed with five different experimental diets including treatment 1: a diet without fermented canola, treatment 2: a diet containing 12.5% ​fermented canola, treatment 3: a diet containing 25% fermented canola, treatment 4: a diet containing 37.5% fermented canola, and treatment 5: a diet containing 50% fermented canola for 8 weeks. Results revealed that the growth and nutrition indices did not significantly differ among various experimental groups (p>0.05). Proximate analyses of the body composition showed that the protein contents of treatments 2, 3, and 4, the lipid and moisture contents of treatments 3, 4, and 5, and also the ash contents of treatments 4 and 5 were increased compared to the control group (p<0.05). Also, the results of digestive enzymes activity showed that the alkaline protease activity of treatments 3 and 4, lipase activity of treatments 2 and 3 and also the alpha amylase activity of treatment 3 were increased in comparison with the control group (p<0.05). In general, it was concluded that incorporating 50% of fermented canola did not affect growth performance and nutritional indices in Nile tilapia fingerlings.