Effect of Bacillus spp. probiotic supplementation on performance, immune response and gut health of broilers challenged with Salmonella Enteritidis

Inclusion of antibiotics in poultry diet as a growth promoters (AGPs) can reduce the prevalence of enteric pathogen such as Salmonella spp. With the emergence and dissemination of antibiotic resistance Salmonella, increasing consumer demand on use of antibiotics as a feed additive in U.S. Therefore, search for alternative strategies to replace antibiotics as a feed additive has gained interest in animal agriculture. In addition, continuing circulation of multiple serovars of Salmonella in poultry flocks, along with increasing reports of human Salmonellosis, warrants the necessity of developing control methods to decrease Salmonella load in poultry production. Bacillus subtilis and Bacillus licheniformis are potential probiotics and are currently used as a probiotic in poultry production. The overall objective in this proposal is to determine the effects of B. subtilis and B. licheniformis probiotic supplementation on performance, cecal Salmonella load, immune response, and gut morphology in broilers challenged with Salmonella enterica serovar Enteritidis.  
 
A total of 360 one-day-old broiler chicks were randomly distributed to four experimental groups a 2 X 2 factorial set up of treatments; Control, Control + Challenge, Probiotics (10 mg of B. Subtilis strain HU58/kg of feed; HU58TM plus 100 mg of B. licheniformis SC307; PreproTM/kg of feed; Microbiome LABS, Saint Augustine, FL), and Probiotics + Challenge. Each treatment was replicated in 6 pens (n=6) with 15 chicks per pen. At 21 d of age, all birds in Challenge groups were inoculated orally with 250 µl of 1 X 109 CFU S. Enteritidis.
 
At 21 d post-Salmonella challenge, chickens challenged with Salmonella had the 11% lower (P < 0.05) BW gain compared to the control non- challenge groups. Chickens that were supplemented with probiotics in the Salmonella challenged groups had only 5.1% reduction in BW compared to the control group. At 5, 12, and 21 d post-Salmonella infection, chickens challenged with Salmonella had 1.99, 1.93 and 1.71 log Salmonella CFU/g of cecal contents while chickens supplemented with probiotics and challenged with Salmonella had 0.73, 1.59, and 1.32 log lower Salmonella CFU/g of cecal contents respectively. Chickens supplemented with probiotics and challenged with Salmonella had higher (P < 0.05) anti-Salmonella IgA compared to the control birds with Salmonella infection. At 21d post-Salmonella infection, chickens supplemented with probiotics and challenged with Salmonella had comparable villi height compared to the control non-challenge group, while control birds infected with Salmonella had the shortest villi height (P < 0.05). Increased villi height and crypt depth can improve nutrient digestibility and absorption and may explain the improved production performances in probiotic supplemented birds. It can be concluded that B. subtilis and B. licheniformis probiotic can be a tool to decrease Salmonella loads in the broiler intestine and B. subtilis and B. licheniformis supplementation can be expected to decrease broiler carcass contamination with Salmonella.

Keywords: Bacillus spp. probiotic, supplementation, Salmonella challenge, immune response, broiler chickens.

Abstract presented at the 3rd International Symposium on Alternatives to Antibiotics 2019.