Mahmoud Nafisi Bahabadi

The current study evaluated the interactive impacts of water temperature and feeding rate on digestive enzymes, intestine histology, growth and stress-related genes, and cultivable intestinal microbiota of Asian seabass (Lates calcarifer). For this purpose, 180 fish (85.0±3.0 g) were reared at three different temperatures (20, 27, and 33 °C) and two feeding rates (apparent satiation and 2.5% of biomass) with three replications for 6 weeks. The results revealed no significant differences among different treatments regarding the activity of digestive enzymes (P˃0.05) of fish reared under different temperatures and feeding rates. The length, width, and thickness of intestinal villi were unaffected by different temperatures and feeding rates (P˃0.05). In addition, no variations were found in the total aerobic bacterial count of fish gut from different experimental groups (P˃0.05). At the molecular level, IGF-I and HSP70 coding genes were found to be highly expressed in experimental treatments (P<0.05). To conclude, present results showed that temperatures between 27 to 33 °C are more optimal for Asian seabass, and the different temperatures and feeding rates do not affect digestive enzymes, intestine histology, and gut microbiota after 6 weeks. Further molecular research is needed to unravel the complex impact and mechanisms of feeding rate and different rearing temperature on fish physiology.