Dietary supplementation of yeast polysaccharides enhance lamb growth performance by improving immune and intestinal barrier function and the abundance of cecal microbiota

Weaning stress can affect the growth performance and intestinal health of lambs. Yeast polysaccharides are green and safe feed additives that have been shown to improve growth performance and intestinal health in other animals. The aim of this study was to explore the effects of dietary yeast polysaccharides on the growth performance and intestinal health of weaned lambs. Twenty-four healthy lambs were randomly divided into four groups and fed different doses of yeast polysaccharides (Y) with a basal diet: 0 g/day (control, C), 0.5 g/day (low dose, LY), 1 g/day (medium dose, MY), and 2 g/day (high dose, HY). Results showed that the MY group had a significantly higher average daily gain and a lower feed-to-gain ratio than the control group. Yeast polysaccharide supplementation significantly increased the immunoglobin G (IgG), immunoglobin A (IgA), and β-defensin contents in serum, as well as the secretory immunoglobulin A (SIgA) content in the intestinal mucosa. It also enhanced intestinal villus development, increased the villus height-to-crypt depth ratio, and upregulated the mRNA and protein expression of Claudin1, Occludin, and ZO1. Cecal microbiota analysis revealed an increased relative abundance of Firmicutes, Ruminococcus, Clostridium, Butyrivibrio and Adlercreutzia, along with elevated volatile fatty acid levels. Taken together, these findings suggest that yeast polysaccharides improve growth performance, immune function and intestinal healthy in weaned lambs. Under the conditions of this experiment, 0.5-1 g/d is the optimal dose for production.