To determine the mechanisms by which Weizmannia coagulans SANK70258 (WC) supplementation improved growth performance and coccidial symptoms, we assessed the gene expressions and the microbiota compositions in the small intestinal tissues and digestas of coccidium-infected broilers previously given WC or lasalocid-A sodium (AM). WC supplementation significantly upregulated the gene expressions related to intestinal immunity and barrier functions, such as IL17A, IL17F, IL10, cathelicidin-2 and pIgR. Body weights, and Claudin-1 and IL10 expressions were positively correlated (r = 0.41, p < 0.05 and r = 0.37, p = 0.06, respectively), whereas lesion scores of the small intestine and IL17A expression were negatively correlated (r = −0.33, p = 0.09). The microbiota analysis detected that genus Alistipes was more abundant in WC-supplemented broilers than in control, and positively correlated with body weights and Claudin-1 expression (r = 0.61, p < 0.05 and r = 0.51, p < 0.05, respectively). Intriguingly, genus Enterococcus was most abundant in WC-supplemented broilers and positively correlated with IL17A expression (r = 0.49, p < 0.05). Interestingly, Escherichia-Shigella was significantly more abundant in the small intestinal digestas of AM-administered broilers than in those of control. To summarize, WC supplementation modulated and immunostimulated the microbiotas of broilers, specifically genera Alistipes and Enterococcus, which led to the improvement of weight gain and coccidial symptoms, without disrupting the intestinal microbiota compositions, as AM did.
