Effects of astaxanthin on growth performance, intestinal integrity, and microbiota in Salmonella Enteritidis-infected chickens

This study investigated the effects of astaxanthin (AST) supplementation in drinking water on the growth performance, intestinal barrier function, and cecal microbiota of broilers challenged with Salmonella Enteritidis. During the 20-day experiment, two hundred and forty 1-day-old male Arbor Acres birds were randomly assigned into a 2 × 2 factorial design with four groups: a non-challenged control (CON), an S. Enteritidis-challenged group (SA), a group receiving AST treatment (AST), and an S. Enteritidis-challenged group receiving AST treatment (SA+AST). Each treatment comprised six replicate groups, and challenged groups were inoculated with S. Enteritidis from day 2 to day 4. The results indicated that S. Enteritidis infection significantly reduced the average daily feed intake (ADFI) in broilers and adversely affected average daily gain (ADG) and feed conversion ratio (FCR) by day 20. AST supplementation significantly improved FCR. While S. Enteritidis infection did not significantly affect ileal mucosa antioxidation, it significantly decreased villus height and the villus height-to-crypt depth ratio (VCR), and significantly downregulated mRNA expression of ZO-1 and Occludin. However, AST supplementation significantly enhanced antioxidant capacity (T-AOC), increased villus height and VCR in the ileum, and notably upregulated ZO-1 and MUC2 expression levels, particularly mitigating the adverse effects of S. Enteritidis infection on ileal crypt depth. Furthermore, S. Enteritidis infection significantly affected both the α- and β-diversity of cecal microbiota. Infection with S. Enteritidis was associated with changes at the phylum level, including significant increases in Alistipes, unclassified_f__Lachnospiraceae, and bacteria of the Clostridia UCG-014 grouping, alongside notable decreases in Bacteroides, Akkermansia, Blautia, and Butyricicoccus. AST supplementation significantly decreased the abundance of norank_f__Ruminococcaceae and increased the abundance of Lachnoclostridium and unclassified_f__Lachnospiraceae in the challenged group. In conclusion, AST supplementation in drinking water could improve growth performance and intestinal health in broilers challenged with S. Enteritidis.