Investigation of intestinal health of broiler chickens after Salmonella Typhimurium and coccidiosis vaccination

Salmonella enterica and coccidia, i. e. Eimeria spp., are intestinal pathogens in broiler production. Salmonella has a high zoonotic potential, and coccidia are responsible for large economic losses in the broiler industry. Live vaccines can reduce shedding of Salmonella and minimize the impact of coccidia infections in chickens. The aim of this pilot experiment was to investigate the interaction of both vaccines on the intestinal health of broiler chickens in a 2 x 2 experimental design with the factors vaccination against Salmonella Typhimurium (ST) on day 14 and vaccination against coccidiosis on day 1. On day 28, all groups were challenged with a ST marker strain. Re-isolation of ST from liver and ceca on day 42 indicated a higher susceptibility for systemic infection with ST in birds vaccinated against coccidiosis compared to birds that were not vaccinated against coccidiosis. On day 42 cecal IgA against ST were decreased in the group vaccinated against ST and coccidia compared to all other groups. IgG antibodies in the cecal content were significantly decreased in the group vaccinated against coccidiosis compared to the group vaccinated against ST. There was no difference in systemic IgG. The analysis of the cecal microbiota revealed a significant difference in the beta-diversity on days 28 and 42 between the groups vaccinated against coccidiosis compared with the groups not vaccinated against coccidiosis. Functional pathway profiling showed an increased activity in pathways associated with carbohydrate and arachidonic acid metabolism in the group vaccinated against ST compared to the other groups. Gene expression of claudin 1, claudin 4, E-cadherin, beta-catenin and zonula occludens 2 in the cecal wall differed between groups on days 28 and/or 42. These findings indicate a significant influence of ST and coccidiosis vaccines and their interaction on the intestinal health of broiler chickens, but further investigations are needed to clarify the implications for the health and performance of broiler chickens.