Abstract
Salmonella enterica ser. Enteritidis (S. Enteritidis) is widely found in chickens and eggs, and it can potentially induce human illness. The investigation in this study centers on the impacts of long-term dietary supplementation with coated sodium butyrate (CSB) on intestinal well-being and the colonization of cecum Salmonella in laying hens infected with S. Enteritidis. We segregated a total of 120 Lohmann laying hens aged 51 weeks into four treatment categories: 0 (CON), 300 (CSB1), 500 (CSB2), and 800 (CSB3) mg/kg of CSB, supplemented with CSB from the first day of the experiment. A 24-week observation process was carried out for each laying hen. The S. Enteritidis was orally administered to all chickens on the morning of the first and third days of week 22 of the trial. After the S. Enteritidis challenge, egg production decreased the most in the CON group. Compared to the CON group, the three doses of CSB significantly improved egg production after the S. Enteritidis challenge (P(ANOVA) < 0.05). S. Enteritidis challenge increased plasma DAO activity, but CSB supplementation reduced plasma DAO activity (P(line)(ar) < 0.05). The S. Enteritidis challenge disrupted intestinal villi morphology; compared to the CON group, the three dosages of CSB resulted in an increase in villus height (VH) and the ratio of villus height to crypt depth (V/C) in the duodenum, jejunum, and ileum of infected laying hens (P(line)(ar) < 0.05), with a significant increase in jejunal villus height (P(ANOVA) < 0.05). A decrease in ileal crypt depth was also observed (P(line)(ar) < 0.05). CSB2 and CSB3 markedly increased the content of butyric acid in the cecum (P(ANOVA) < 0.05). Additionally, in contrast to those in the CON group, the propionic acid content in the CSB supplementation group increased (P(line)(ar) < 0.05). Compared with those in the CON group, mRNA relative expression of the IL-6 and IL-1β in jejunum (P(line)(ar) < 0.05) and mRNA relative expression of the IL-1β in ileum (P(ANOVA) < 0.05) were significantly lower, and mRNA relative expression of the IL-10 in ileum (P(line)(ar) < 0.05) were significantly higher in the CSB group. In addition, in contrast to the CON group, the CSB supplementation group significantly upregulated mRNA relative expression of the ZO-1 and CLDN1 (P(ANOVA) < 0.05). Additionally, CSB supplementation reduced the number of Salmonella and increased the number of Lactobacilli in the cecum (P(line)(ar) < 0.05) and tended to increase the total bacteria count (P(line)(ar) = 0.069) and reduce the E. coli count (P(line)(ar) = 0.081). In conclusion, long-term dietary supplementation with coated sodium butyrate can alleviate intestinal injury and the colonization of cecum Salmonella in laying hens infected with S. Enteritidis.