16SV34. GUO-16S-S5

Background: Salmonella infection in broilers is a main foodborne illness that substantially threatens food security. Alfalfa polysaccharide (APS) has anti-inflammatory and antibacterial capacities; however, the effects of APS on intestinal health and the microbiota in Salmonella-challenged broilers remain unclear. Results: APS supplementation (500 mg/kg diet) improved the growth performance of broilers in the pair-fed group, but this benefit disappeared when Salmonella was introduced. However, regardless of whether Salmonella challenge occurred, APS supplementation enhanced the immune status and gut development of the broilers, as determined by alterations in intestinal morphology, tight junction proteins, and mucosal diamine oxidase activity. Cecal microbiome analysis revealed that the abundance of the dominant phylum Firmicutes decreased, while that of Bacteroidetes increased, as the chickens aged post Salmonella infection and that Salmonella infection delayed alterations in the microbiota. Proteobacteria, Actinobacteria, Ruminococcaceae, Lachnospiraceae, and Burkholderiaceae had higher abundance in the Salmonella-infected groups than in the uninfected groups, but dietary APS supplementation enhanced the abundance of Bacteroidetes, Barnesiella, Alistipes, Parabacteroides, Butyricimonas, and Prevotellaceae. The abundance of functional genes of the gut microbiota related to nutrient metabolism varied with the increased ages of broilers post Salmonella-infection. Copresence analysis of gut microbes revealed that Bacteroides and Odoribacter were the core microbes positively related to body weight (BW) across all treatments, and both APS dietary supplementation and Salmonella infection increased the numbers of core microbes related to BW. Conclusions: Dietary APS supplementation improved intestinal barrier functions and immunity in broilers by modulating the morphology of the gut lining and the composition and structure of the intestinal microbiota regardless of whether Salmonella infection was present. Salmonella infection increased the abundance of facultative anaerobic bacteria or potential pathogens in the gut microbiota, whereas inclusion of APS in broiler feed augmented beneficial bacterial proliferation. An age-dependent variation in the abundance of taxa and functional genes of the gut microbiota was observed after Salmonella-infection. The core bacteria directly related to growth performance can be utilized as primary target microbes for dietary manipulation to improve growth performance and food safety in the poultry industry.