Influence of Bacillus subtilis on immune-response of broiler chickens

The number of the solitary lymphoid follicles occurring in the connective tissue layer of the mucous membrane increased in chickens fed with B. subtilis supplementation. According to the microbiological examination the dietary inclusion of Bacillus subtilis was significantly reflected in the chicken caecal samples. The birds from the groups fed Bacillus subtilis consequently showed stronger response to vaccine of Newcastle disease. Introduction Probiotics have been administered to poultry to enhance production performance and immune responses. In addition that the probiotic supplementation has been shown to improve production parameters body weight, FCR, mortality – (Jin et al., 1996; Mohan et al., 1996; Huang et al., 2004) and can protect the fowls against pathogens by colonization in the gastrointestinal tract (Jin et al., 1996; La Ragione et al., 2001) the probiotics have positive effect on humoral and cellular immune responses (Yunis et al., 2000; Koenen et al., 2004, Huang et al., 2004) too. In group of probiotic microorganisms, members of the genus Bacillus occupy a unique position since they are delivered as spores. Because B. subtilis is not a member of the normal intestinal microflora and is a strict aerobe, it is not able to grow or metabolise vigorously in the gut. As a result of continuous feeding to poultry, however, larger numbers of this microorganism can exist and become active in the gut and thus influence the microbial milieu of the intestine. Bacillus subtilis spores have been shown to enhance the response of human peripherial blood lymphocytes to mitogens like phytohaemagglutinin and concanavalin A (Spreafico et al., 1980). Over a wide range of concentrations, B. subtilis spores are capable of inducing an increased expression of antigens MLP3, MLR4 and HLA-DR in cultures of peripherial mononuclear cells. At high concentration of B. subtilis spores the effect is both quantitatively and qualitatively similar to that induced by the mitogens phytohaemagglutinin and concanavalin A (Fais et al., 1987). The gut-associated lymphoid tissue (GALT) has evolved with specialized cytological features that reflect its role as the first line of defence at mucosal surfaces. The GALT in chickens includes the bursa of Fabricius, the cecal tonsils, Peyer’s patches, and lymphocyte aggregates within the epithelium and in the lamina propria of the wall of the gastrointestinal tract (Lillehoj, 1993). Bacillus subtilis spores in broiler chicken feeds may exert their beneficial effects among others by activation of intestinal function (Samanaya and Yamauchi, 2002), to create a more favourable environment for beneficial anaerobic species by enhanced immune responses (Fiorini et al., 1985), Material and Methods Animals and housing: Five hundred and sixty day-old Ross 308 broiler chicks were randomly assigned to two treatment groups. There were 35 chicks (17 chicks/m2) per replicate and eight replicates per treatment. Birds were housed in floor pens. Diet: For the experiment, antibioticand coccidiostat-free one-phase basal diet ( 12.63 MJ/kg BE, 20.0 % crude protein, 4.0 % crude fiber,1.15 % Lysine, 0.46 % Met, 0.44 % Cystine) was used from day old to 42 days of age. Control groups were fed with basal diet containing only the carrier whey powder in a dose of 500g/t feed. The treated groups received basal diet