Effect of Bacillus-based direct-fed microbials on macrophage functions and Eimeria maxima infection in broiler chickens (46.18)

The present experiment was conducted to study the effect of dietary Bacillus-based direct-fed microbials (DFMs) on macrophage functions and resistance against experimental coccidiosis in broiler chickens. Birds were fed diets containing one of eight Bacillus subtilis strains (designated Bs2084, LSSAO1, 3AP4, Bs18, 15AP4, 22CP1, Bs27, and Bs278) or one multiple-strain DFM product (AVICORR™) for 21 days, and then the chickens were uninfected or orally infected with 5000 Eimeria maxima (EM) oocysts. At day 21 (before EM challenge), strong phagocytosis ability using BSA-coated fluorescent latex beads and GFP-labeled salmonella was seen in animal given Bs18, 15AP4, Bs27, or Bs278 compared with the no DFM control group. At day 27 (6 days post infection), EM-induced reduction of body weight gain was significantly decreased by adding 15AP4 or Bs27 into broiler diets compared with no DFM/EM inoculated control. Serum Nitric oxide levels were increased in infected animals fed with Bs27 compared with the no DFM/EM inoculated control. The levels of Eimeria-specific antibody were increased in infected chickens fed with LSSAO1 compared with the no DFM/EM inoculated control. Finally, all experimental diets increased concanavalin A-induced splenocyte mitogenesis in infected broilers compared with the no DFM/EM inoculated control. In summary, dietary DFMs reduced the clinical signs of experimental avian coccidiosis and increased various parameters of immunity in broiler chickens.