Optimal dietary isoleucine requirement of juvenile red swamp crayfish (Procambarus clarkii): Consideration from growth performance and intestinal health

This study was conducted to assess the effects of dietary isoleucine level on growth performance and intestinal health of juvenile red swamp crayfish (Procambarus clarkii) . Isoleucine levels in each group were 0.7 %, 1.20 %, 1.70 %, 2.20 %, 2.70 %, and 3.20 %, respectively. The results showed that the 1.20 % isoleucine group significantly increased the weight gain rate, protein efficiency rate and decreased the feed efficient rate. The intestinal amylase and trypsinase activities of the 1.20 % group were significantly higher than those of the other groups. The activities of intestinal antioxidant enzymes reached the highest value in the 1.20 % group, and the content of malondialdehyde in the 1.20 % group was significantly lower than that in other groups except 1.70 % and 3.20 %. The expression levels of antioxidant-related genes ( gst , gpx , nrf2 ) and immune-related genes ( toll , tgf-β , and claudin ) reached the highest value at 1.20 %. 1.20 % group the immune-related myd88 gene was significantly higher than that of the other groups except 1.70 %. The immune-related zo-1 gene in the 1.20 % group was significantly higher than that of the other groups except 2.20 %. The antioxidant-related keap1 gene, immune-related tnf-α and il-1β genes in the 1.20 % group were significantly lower than those of other groups. The Firmicutes abundance in the 1.20 % group was significantly increased, and the Proteobacteria abundance is the opposite. Based on the growth performance and intestinal antioxidant indexes, linear regression model analysis showed that the optimal dietary isoleucine requirements of juvenile crayfish were 1.13 %-1.22 % and 1.01 %-1.38 % of dry matter. The results of this study indicate that the appropriate proportion of isoleucine in the diet can improve the growth performance, enhance the intestinal antioxidant and immune capacity, and improve the intestinal microflora balance of juvenile red swamp crayfish. • 1.20 % isoleucine level for juvenile red swamp crayfish can promote growth performance. • 1.20 % isoleucine level can improve intestinal antioxidant capacity. • 1.20 % isoleucine level can enhance intestinal immunity. • 1.20 % isoleucine level can improve intestinal microflora.