Dietary supplementation with <i>Rehmannia glutinosa</i> catalpol improves broiler performance by regulating intestinal immune microenvironment

Plant extracts have been widely considered as a feed additive. Rehmannia glutinosa catalpol can promote the growth performance of the host, improve the immune response, and strengthen the intestinal barrier function of the host. The broilers were fed with Rehmannia glutinosa catalpol (0.01%), and the composition of caecum microbiota in broilers was explored by 16S rRNA gene sequencing. Finally, the changes of intestinal mucosa morphology and immune function were analysed by tissue staining and RT-qPCR. The proportion of thick-walled bacteria in the treatment group was higher than that in the control group. At the genus level, the relative abundance of Faecalibacterium, Paraacteroides and Barnesiella increased after the addition of Rehmannia glutinosa catalpol. The function prediction results of PICRUSt2 showed that the microbiota mainly participated in the biosynthesis and degradation/utilization/association pathway. The results of tissue staining and RT-qPCR showed that the caecum tissue morphology and immune barrier function of broilers were significantly improved after the addition of catalpol. The results of this study show that Rehmannia glutinosa catalpol in the diet may be beneficial to the intestinal health of broilers, which may be achieved by regulating the intestinal microbiota and enhancing the immune function of broilers.