Effects of starter feeding on caecal mucosal bacterial composition and expression of genes involved in immune and tight junctions in pre-weaned twin lambs

Abstract

The objective of this study was to explore the effects of starter feeding on caecal mucosal bacterial composition and the expression of genes involved in immune and tight junctions in pre-weaned lambs. Six pairs of new-born twin lambs were selected. From 10 days of age, one lamb of each pair received ewe's milk only (M group, n = 6), while the other one was fed ewe's milk plus starter feed (M + S group, n = 6). At 56 days of age, the lambs were sacrificed, and then cecum digesta was collected to measure pH values and concentrations of volatile fatty acid (VFA), and caecal mucosa were collected to determine the changes in bacterial communities and the mRNA expression of cytokines, toll-like receptors (TLRs) and tight junction proteins. The results showed the body weight and average daily gain were not significantly different between both groups. Starter feeding significantly (P < 0.05) increased the concentrations of propionate and butyrate; the proportions of acetate, propionate and butyrate to total concentrations of VFA; and decreased the ratio of acetate to propionate in caecal contents. Principal coordinate analysis showed that samples from the M + S group could be distinguished from those from the M group; starter feeding also increased the diversity of caecal mucosal bacteria. At the genus level, starter feeding significantly (FDR < 0.05) increased the relative abundance of Alistipes, Parabacteroides, Parasutterella and Butyricimonas, and caused a decreasing trend (FDR < 0.10) in the relative abundance of Campylobacter and Helicobacter. The real-time PCR results showed that starter feeding significantly (FDR < 0.05) decreased the relative mRNA expression level of IL-12, TNF-α and TLR4 and increased the relative mRNA expression level of claudin-4. These results indicate that starter feeding altered caecal mucosal bacterial communities and decreased the expression of inflammatory factors, which may be beneficial in alleviating the weaning stress of lambs.