The effects of dietary Baccillus subtilis supplementation, as an alternative to antibiotics, on growth performance, intestinal immunity, and epithelial barrier integrity in broiler chickens infected with Eimeria maxima

Authors: PARK, INKYUN - US Department Of Agriculture (USDA); LEE, YOUNGSUB - US Department Of Agriculture (USDA); GOO, DOYUN - US Department Of Agriculture (USDA); ZIMMERMAN, N.P - Arm & Hammer Animal And Food Production; SMITH, A.H - Arm & Hammer Animal And Food Production; REHBERGER, T. - Arm & Hammer Animal And Food Production; Lillehoj, Hyun

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2019
Publication Date: 2/1/2020
Citation: Park, I., Lee, Y., Goo, D., Zimmerman, N., Smith, A., Rehberger, T., Lillehoj, H.S. 2020. The effects of dietary Baccillus subtilis supplementation, as an alternative to antibiotics, on growth performance, intestinal immunity, and epithelial barrier integrity in broiler chickens infected with Eimeria maxima. Poultry Science. https://doi.org/10.1016/j.psj.2019.12.002.
DOI: https://doi.org/10.1016/j.psj.2019.12.002

Interpretive Summary: Good bacterial populations in the gut of growing poultry is critical for good gut health and optimum production of commercial poultry. Beneficial bacteria in the gut plays an important role in successful poultry growth and optimum performance of poultry. Many factors influence gut health, including diet composition, disease status, stress and feed change. Currently, with the increased regulation of antibiotic use in animal agriculture, there is a great need for the development of novel alternatives that could positively influence gut health by improving host immune responses and gut barrier function. In this paper, ARS scientists report recent studies that were carried out in collaboration with private industry to show that certain direct-fed microbials (DFM), often referred to as probiotics, represent a non-antibiotic nutritional approach to modulate gut function to enhance intestinal health in young chickens. The results show that dietary Bacillus subtilis-based probiotic supplementation promoted feed efficiency and gut immunity. Furthermore, the broiler chickens fed diets with various levels of B. subtilis exhibited significant improvements in body weights compared to non-supplemented controls. The intestinal epithelium is an integral component of gut mucosal immunity and serves as a physical barrier against invading pathogens and toxins. In this study, the authors also showed that the oral administration of a probiotic mixture improved intestinal barrier function and optimal gut health. Taken together, this study documented the immunomodulatory activities of B. subtilis strains in the gut. From these results, it can be concluded that supplementation of broiler diets with B. subtilis probiotics beneficially influences a diverse array of immune gut barrier functions and provide many beneficial effects for poultry health.

Technical Abstract: The objective of this study was to investigate the effects of dietary Bacillus subtilis supplementation on growth performance, jejunal lesion scores, oocyst shedding, and cytokine and tight junction protein expression in broiler chickens infected with E. maxima. A total of 196 male day-old Ross 708 broilers were given a non-experimental diet until 14 days of age. Then all chickens were randomly assigned to one of seven dietary treatments: two basal diets (CON and NC); CON + virginiamycin (AB1); CON + bacitracin methylene disalicylate (BMD; AB2); CON + B. subtilis 1781 (PB1); CON + B. subtilis 747 (PB2); or CON + B. subtilis 1781 + 747 (PB3). At day 21, all chickens except those in the CON group were orally inoculated with E. maxima oocysts. At 7 days post E. maxima infection, the body weight gains of chickens fed PB2 and PB3 increased (P = 0.032) as much as those in chickens fed AB2. The body weight gain and feed efficiency of chickens fed PB2 were significantly increased (P < 0.001), and PB2 chickens showed (P = 0.005) the lowest lesion scores after E. maxima infection. Infection with E. maxima increased (P < 0.05) cytokine mRNA expression (IL-1ß, IL-2, IL-6, and interferon-') in jejunal tissue, whereas chickens fed PB2 showed (P < 0.05) lower mRNA expression of IL-1ß in infected chicken groups. Chickens in the AB1, AB2, PB1, PB2, and PB3 groups showed (P < 0.05) greater mRNA expression of junctional adhesion molecule 2 in jejunal tissue, whereas occludin expression increased (P < 0.05) in the jejunal tissue of chickens fed AB2 or PB2. Dietary B. subtilis supplementation significantly improved the growth performance of young chickens to a level comparable to that induced by virginiamycin or BMD under normal growth conditions without E. maxima infection. After infection with E. maxima, dietary virginiamycin and BMD significantly enhanced the epithelial barrier integrity, and the dietary B. subtilis 747 showed significantly enhanced growth performance, intestinal immunity, and epithelial barrier integrity. Together our results indicated that certain strains of B. subtilis have the potential to replace antibiotic growth promotors in broiler chickens and that one of the Bacillus strains reduced the effects of E. maxima infection