Protease Complex Reduces Potentially Pathogenic Microbial Populations in the Ileum While Optimizing Performance of Broiler Chickens

A 42-day trial was conducted to assess the effects of a dietary protease on growth performance and ileum population of selected bacteria in broiler chickens fed standard diets and diets deficient in crude protein and digestible amino acids (CP/AA, ~5%) or apparent metabolizable energy (AME, 50 kcal/kg) or both. Reducing CP/AA and AME negatively affected average daily weight gain (ADG, P < 0.05) and feed conversion ratio (FCR, P < 0.05). Dietary protease improved BW at 42-d (P = 0.021, linear effect) of birds fed both standard and nutrient deficient diets but improved FCR (P = 0.0002) was only observed when supplemented to the standard diet. Serum protein concentration was not affected by the level of CP/AA and AME but decreased linearly with the level of protease (P = 0.02). Numbers of Escherichia coli¸ Salmonella spp. and Clostridium perfringens increased (P = 0.0001) with the decrease of dietary CP/AA and AME. In contrast, the numbers of studied bacteria linearly decreased (P = 0.0001) with dietary protease level. Dietary protease was found to decrease the numbers of Clostridium perfringens (P = 0.0001) when supplemented to either low CP/AA or low AME diets. It can be concluded that protease supplementation sustained the harvesting biomass in the experimental birds fed lower nutrient density diets and decreased the numbers of resident bacteria in the hind gut, some of which might be potential pathogens. Hence, the study documented not only the nutrient sparing effects but also the extra-proteinaceous effect in terms of gut health of dietary protease in broiler chickens.