Probiotic Bacillus amyloliquefaciens H57 ameliorates subclinical necrotic enteritis in broiler chicks by maintaining intestinal mucosal integrity and improving feed efficiency

Previous broiler feed trials conducted with Bacillus amyloliquefaciens strain H57 (H57) indicated variable bird performance. In this study, a subclinical necrotic enteritis (NE) challenge model was induced in broiler chicks. The challenge consisted of a high dose of Eimeria spp. vaccine in the drinking water on day 9, and Clostridium perfringens (Cp) culture mixed in the feed on days 14 and 15. The aim was to evaluate the effects of probiotic H57 in improving intestinal health and preventing NE in chicks. Day-old Ross 308, male broilers (288) were weighed and randomly assigned to six treatment groups (six replicate cages/treatment and eight birds/cage). The treatment groups were: Group 1(Control group) birds were fed the basal wheat-soybean diet without H57 treatment or NE infection; Group 2, (Eimeria group) birds were treated with Eimeria-alone; Group 3 (Cp group) birds were treated with Cp-alone; Group 4 (NE group) birds received both Eimeria and Cp; Group 5 (NE-H57 group) birds received NE infection and H57 supplementation; and Group 6 (H57 group) birds only received H57 supplementation. The basal diet of chicks in Groups 5 and 6 was supplemented with H57 at a density of 2 x 108 spores/g feed from day-old. On day 21, there were no significant treatment effects on body weight and feed intake between control and H57 birds. However, on day 21, the feed conversion ratio (FCR) of birds challenged with NE and supplemented with H57 (NE-H57), was significantly improved when compared to NE birds (1.28 vs. 1.36; P < 0.001). Birds challenged with NE had a higher occurrence of pasty vent, than birds infected with either Eimeria-alone, Cp-alone or NE-H57 (41% vs. 27% vs. 29% vs. 19%; P < 0.001). Intestinal lesion scores of NE birds were also higher than in Eimeria-alone, Cp-alone, and NE-H57 birds (5.67 vs. 2.56 vs. 2.78 vs. 2.10; P < 0.001). Pasty vent and lesion scores were correlated (Pearson’s r = 0.56; P < 0.001). Microscopic evaluation of ileal mucosa showed mucosal damage and necrosis in NE birds. In contrast, villi from NE-H57 birds were normal in appearance, with no damage or infiltration with Eimeria or Cp. It was concluded that H57 is effective in birds subjected to an infectious challenge. Birds challenged with NE and fed H57 maintained epithelial barrier integrity and had improved feed efficiency