Comparing effects of high starch diet or high lipid diet supplemented with different levels of zinc on intestinal barrier and microbe community in largemouth bass Micropterus salmoides.

Zinc is essential for normal growth and reproduction in all animals and plays a crucial role in many biological processes. The present study aimed to compare the intervention effects of zinc on intestinal health in a high lipid diet or high starch diet. Seven iso-nitrogenous (∼520 g kg) diets were formulated containing a positive control diet (115 g kg lipid + 115 g kg starch + 20 mg kg Zn), three high starch diets (HS, 166 g kg starch) and three high lipid diets (HL, 182 g kg lipid), with 0 (HS-LZn, HL-LZn), 20 (HS-MZn, HL-MZn) and 150 (HS-HZn, HL-HZn) mg kg Zn being supplemented. High starch diet and high lipid diet promoted feed efficiency, as evidenced by the lower feed conversion ratio. Three-way factorial ANOVA analysis showed high starch diet (166 g kg) significantly decreased final body weight and weight gain compared to the normal starch level (115 g kg). Diamine oxidase in serum significantly increased in diets HS-LZn and HL-LZn. In addition, distal intestinal mucosal fold damage and inflammatory infiltration were observed in the HS-LZn, HS-HZn, HL-LZn and HL-HZn groups. Fish fed HL diets (HL-LZn, HL-MZn, HL-HZn) showed lower expressions of claudin 5 and claudin 34, and higher IgD and IgM. Diets HL-LZn and HL-MZn significantly up-regulated C4 and C7. Proinflammatory cytokines including il8, il1β and tnfα significantly up-regulated in diet HL-LZn, even higher than the HS-LZn. Intestinal microbial composition indicated the abundance of Cetobacterium in HL-LZn was significantly higher than the control and HL-MZn diets. Similarly, LEfSe showed that Cetobacterium (P = 0.039) significantly enriched in the HL-LZn group. This study clarified high energy diet induced intestinal damage, which can be alleviated by zinc.