Effects of dietary starch levels on growth performance, hepatic proximate composition and non‐specific immunity of snakehead ( Channa argus )

The present study aimed to investigate the effects of dietary starch levels on growth performance, hepatic proximate composition and non-specific immunity of juvenile snakehead (Channa argus). Seven isonitrogenous and isolipidic diets, supplemented with graded levels of α-starch, 0%, 3.0%, 6.0%, 9.0%, 12.0%, 15.0% and 18.0%, were fed to triplicate groups of juvenile snakehead (initial body weight, 11.83 ± 0.02 g) for 8 weeks. Results showed that dietary starch levels had no significant effect on the growth performance of snakehead, while the survival rate was significantly elevated when the inclusion level of starch was higher than or equal to 9%. The content of hepatic crude protein and crude lipid was significantly reduced with the increase in dietary starch levels, while hepatic glycogen content was significantly elevated, which was partly related to the significantly increased hepatosomatic index and viscerosomatic index. The content of malondialdehyde and serum aspartate aminotransferase and aspartate aminotransferase activity was significantly elevated, while serum lysozyme activity was significantly decreased when dietary starch inclusion content exceeded 9%. Gene expression analysis revealed that the inclusion of starch exceeded 9% significantly promoting the expression of NF-κB P65. Meanwhile, the increase in dietary starch levels led to an increased expression of pro-inflammation factor, IL-1β and COX-2, and their expression in 15% and 18% starch inclusion groups was significantly higher than that in the 0% and 3% starch inclusion groups. In conclusion, the recommended dietary starch inclusion level is 9% based on the reasonable compromise of the above biomarker responses.