Effects of novel feed additives on gut health and overall performance in birds challenged with 'Clostridium perfringens'

The capacity for 'Lactobacillus johnsonii' and an organic acid (OA) blend to prevent necrotic enteritis (NE) was studied. Additionally, we evaluated the influence of 'Clostridium perfringens' challenge, zinc bacitracin (ZnB), 'L. johnsonii' and OA on the intestinal microbiota. Cobb 500 birds were allocated into six groups; unchallenged (Control), challenged (Cp), zinc bacitracin (ZnB), organic acid (OA), 'L. johnsonii', and vehicle (n = 25 birds/pen, 8 pens/treatment). All birds were challenged with 'C. perfringens' except for the Control group. Only birds fed ZnB were protected from NE as indicated by maintenance of body weight, low mortality and clostridia levels, and decreased intestinal macroscopic lesion score compared to Cp-challenged controls. 'L. johnsonii'-fed birds had reduced lesion scores whilst OA-fed birds had reduced clostridia levels. Both 'L. johnsonii' and OA-fed birds had improved feed conversion ratios; however, mortality and body weights were not improved by either treatment. Microbial profiling indicated that 'C. perfringens' significantly altered the jejunal microbiota. The microbiota of ZnB-fed birds was different to all other treatments. Whilst OA and 'L. johnsonii' altered some intestinal parameters, no protection against NE was observed. The search for alternatives to antibiotics is important for the poultry industry. Knowledge of the mechanisms involved in ZnB-mediated protection may lead to the identification of compounds (or combinations) that promote a similar intestinal environment.