Modulation of intestinal morphology and immunity in nile tilapia (Oreochromis niloticus) by Lactobacillus rhamnosus GG

The use of lactic acid bacteria from human origins as a potential probiotic supplementation in aquaculture feed is now widely accepted. Here, we examined some of the properties and mechanisms of the action of Lactobacillus rhamnosus GG, originating from humans, on growth performance, gut mucosal immunity and humoral and cellular immune response in tilapia (Oreochromis niloticus). The results suggested that supplementation of L. rhamnosus gave an advantage in promoting the intestinal structure and the mucosal immunity of tilapia. Probiotic fish had a greater villous height in all parts of the intestines and, significantly, in the proximal and middle part. The population of intraepithelial lymphocytes was significantly higher in the probiotic group than in the control group in all parts of the intestines. The population of acidophilic granulocyte in the probiotic group was significantly higher at the proximal and distal parts when compared with the control group. The higher serum complement activity as well as the enhanced phagocytosis and killing ability of the head kidney leukocytes in the probiotic supplemented fish corresponded with the higher level of TNF alpha and IL-1 gene expression, suggesting that the induction of IL-1 and TNF alpha cytokines by L. rhamnosus served as an important regulator of gut associated immune systems.