The Effects of <i>Poria cocos</i> Polysaccharides on Growth Performance, Immunity, and Cecal Microflora Composition of Weaned Piglets

This paper aims to identify <i>Poria cocos</i> polysaccharides (PCPs) as a potential feed additive used for swine production; thus, we explored the effects of different dietary inclusion levels of PCP on growth performance, immunity, and cecal microflora composition in weaned piglets. For this, a total of 120 28-day-old Duroc × Landrace × Yorkshire weaned piglets (8.51 ± 0.19 kg; 28 ± 1 days of age) were randomly allocated to five groups that were fed a basal diet supplemented with 0, 0.025%, 0.05%, 0.1%, and 0.2% PCP, respectively, for 42 days. The results indicated that the average daily gain (ADG) and gain/feed ratio were higher in the PCP treatment groups than in the control group, with a linear effect. The serum concentrations of IgG, IgA, IL-2, IFN-γ, the number of CD4⁺ T cells, and the CD4⁺-to-CD8⁺ T-cell ratio (CD4⁺/CD8⁺) were increased, while the levels of IL-6 and TNF-α were decreased in the PCP supplementation groups compared with those in the control group. Furthermore, the cytokine mRNA expression levels exhibited a similar trend in the spleen. PCP supplementation also reduced the abundance of <i>Escherichia coli</i> and <i>Salmonella</i> and enhanced that of <i>Lactobacilli</i> and <i>Bifidobacteria</i> in the cecum. In summary, dietary PCP inclusion exerted positive effects on the growth performance, immunity, and cecal microbiota of piglets and showed potential for use as a feed additive for improving the health of weaned piglets, with 0.1% being the optimal dosage.