Effects of Different Dietary Zinc (Zn) Sources on Growth Performance, Zn Metabolism, and Intestinal Health of Grass Carp

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-1) diets were formulated containing a positive control diet (115 g kg-1 lipid + 115 g kg-1 starch + 20 mg kg-1 Zn), three high starch diets (HS, 166 g kg-1 starch) and three high lipid diets (HL, 182 g kg-1 lipid), with 0 (HS-LZn, HL-LZn), 20 (HS-MZn, HL-MZn) and 150 (HS-HZn, HL-HZn) mg kg-1 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-1) significantly decreased final body weight and weight gain compared to the normal starch level (115 g kg-1). 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.

Selenium- and/or Zinc-Enriched Egg Diet Improves Oxidative Damage and Regulates Gut Microbiota in D-Gal-Induced Aging Mice

Eggs, with their high nutritional value, are great carriers for enriching nutrients. In this study, selenium- and/or zinc-enriched eggs (SZE) were obtained and their effects on ameliorating oxidative stress injury, alleviating cognitive impairment, and maintaining intestinal flora balance in a D-gal-induced aging mice model were investigated. As determined by the Y-maze test, SZE restored the learning and memory abilities and increased the Ach level and AChE activity of aging mice (p < 0.05). Meanwhile, supplementation of low-dose SZE increased antioxidant levels and decreased inflammation levels (p < 0.05). High-dose SZE increased anti-inflammatory levels but were less effective than low dose. Additionally, SZE maintained the intestinal flora balance and significantly increased the ratio of Firmicutes and Bacteroidota. Blautia, as a probiotic, was negatively correlated with pro-inflammatory factors and positively correlated with antioxidant levels (p < 0.05). These results suggest that SZE might improve organ damage and cognitive function by attenuating oxidative stress and inflammatory response and maintaining healthy gut flora.