Encapsulated butyric acid and bacillus subtilis as antibiotic substitutes to mitigate heat stress and promote gut health and perfomance in broilers

Abstract

The removal of in-feed antibiotics has created increased focus on the potential alternatives to replace antibiotic growth promotors. With rise in global warming and the inability of birds to efficiently dissipate heat, the need to find ways to reduce the incidence and risk associated with heat stress is important by modulating the gut to reduce the negative impacts caused by heat stress. Probiotics and encapsulated butyric acid have shown promise as alternatives to antibiotics as well as potential mitigators of the effect of heat stress on the gut health and performance in broilers. The study aimed to determine the response of broiler chickens supplemented with encapsulated butyric acid and B. subtilis combined and alone against zinc bacitracin with the intention of improving overall gut health, the microbiome composition and growth performance and to mitigate the effect of heat stress in male broilers. One thousand nine hundred and twenty (1920) day-old male Ross 308 chicks were distributed amongst two environmentally controlled houses which were either at heat stress conditions or thermoneutral conditions. Both houses were run simultaneously and consisted of six dietary treatments with eight replications per treatment and twenty broilers per pen. The dietary treatments were as follows: basal diet; basal diet with zinc bacitracin; basal diet with encapsulated butyric acid (EBA); basal diet with zinc bacitracin and encapsulated butyric acid; basal diet with a B. subtilis-based probiotic; and basal diet with B. subtilis and encapsulated butyric acid. Production parameters were observed on a weekly basis. On day 21 and 35, two birds per pen were euthanised and samples of the small intestine and digesta were collected for histomorphological and microbiome analysis, respectively. Overall gut health was also scored. Dietary inclusion of B. subtilis in combination with EBA revealed no significant improvement in growth performance although results were comparable to the antibiotic treatment. Thermotolerance of the birds were improved by the inclusion of a combination of B. subtilis and EBA. Protection of the gut integrity, villi-crypt structure and intestinal microbiota environment also ameliorated the adverse effect of heat stress on gut health, resulting in growth performance being comparable to AGP.