Enhanced mucosal immunity against Eimeria acervulina in broilers fed a Lactobacillus-based probiotic

The effect of feeding a Lactobacillus-based probiotic on intestinal intraepithelial lymphocyte (IEL) subpopulations and subsequent protection against coccidiosis was investigated in broiler chickens. Day-old male broilers were fed standard rations without control (CONT) or with a commercial probiotic (PROB) Primalac. Differences in IEL subpopulations were assessed by flow cytometry at 21 d postprobiotic treatment. At 25 d of age, a group of randomly selected birds from each diet was inoculated orally with 10,000 (per bird) sporulated oocysts of Eimeria acervulina and kept on the same diets. Fecal material, sera, and intestinal washes were collected 10 d postchallenge with E. acervulina. Birds on the PROB diet had more IEL expressing the surface markers CD3, CD4, CD8, and alphabetaTCR than those of the CONT diet. The probiotic-fed chickens produced less oocysts (P < 0.0001) compared to the untreated, control group (368 x 10(6) in CONT vs. 89 x 10(6) in PROB). The interferon-gamma levels in both serum and intestinal secretions were not significantly different between the two groups. However, CONT group showed higher antibody levels against a recombinant coccidial antigen in the intestinal secretions than the PROB group. No significant difference was found in serum antibody levels against the same antigen. These results dearly indicate that the probiotic bacteria impacted the local immune response as characterized by altered IEL subpopulations and increased the birds' resistance to E. acervulina as reflected by reduced oocyst shedding.