Effects of dietary Lactobacillus reuteri on growth performance, nutrient retention, gut health and microbiota of the Nile tilapia (Oreochromis niloticus)

Abstract

The current study aimed to evaluate the effects of Lactobacillus reuteri as a dietary supplement on growth performance, nutrient retention, digestive enzyme activities, intestinal morphology, expression of intestinal tight junction (TJ) proteins and composition of the gut microbiota in juvenile Nile tilapia (Oreochromis niloticus). Fish (9.01 ± 0.11 g) were fed with a basal diet supplemented with 0 (control group), 109 (R9 group), 1010 (R10 group), or 1011 (R11 group) colony-forming units (CFU) of L. reuteri per kg of feed. After 8 weeks, the weight gain rate, specific growth rate and lipid retention were significantly enhanced in the R10 and R11 groups. In addition, villus height and mucin secretion were significantly increased in the groups supplemented with L. reuteri. Trypsin activity was increased in the foregut of the R10 and R11 groups and the midgut of the R11 group, while lipase activity was increased in the foregut of the R11. Additionally, the expression level of genes coding the intestinal TJ proteins Hif1α, ZO-1, and Occludin were up-regulated with increasing dietary L. reuteri supplementation. Furthermore, dietary L. reuteri supplementation improved the diversity (Shannon index, Simpson index and principal coordinate analysis), changed the composition of gut microbiota, and increased the relationships among bacterial species. These results indicate that dietary supplementation with L. reuteri at 1011 CFU/kg promotes the growth performance, nutrient retention, gut health and microbiota of O. niloticus.