Intestinal microbiota diversity and expression of pattern recognition receptors in newly weaned piglets

• Gastrointestinal microbial diversity was investigated in newly weaned piglets.
• The expression of intestinal pattern recognition receptors (PRRs) was analyzed.
• Weaning decreased microbial diversity in the ileum and on d 4 post-weaning.
• Weaning affected the expression of intestinal PRRs on d 1 and d 4 post-weaning.
• The expression of special PRRs was triggered to recognize distinctive microbiota.

This study evaluated the gastrointestinal microbial diversity and the expression of pattern recognition receptors (PRRs) of the small intestine during the first week post-weaning in newly weaned piglets. Sixteen piglets were sacrificed on days 0, 1, 4, and 7 post-weaning. Luminal contents from the stomach, ileum, and colon were collected to determine the microbiota diversity; intestinal mucosa from the ileum was collected to assess mRNA expression of PRRs, including toll-like receptors (TLRs) and NOD-like receptors (NLRs); sections of ileum were examined immunohistochemically to assess the immunoglobulin-secreting cells. The results showed that the number of denaturing gradient gel electrophoresis (DGGE) bands from the ileum and colon contents were significantly reduced in the d 4 post-weaning group. Biodiversity indexes (Shannon–Wiener index, richness index, and evenness index) were significantly decreased in the ileum of weaning groups. These indexes decreased in the colon of the d 4 post-weaning group. No significant differences were obtained in the stomach. With the exception of TLR5, the mRNA expressions of TLR2, TLR4, and TLR7 increased post-weaning. The mRNA expressions of NOD1 and NOD2 were significantly affected in the d 4 post-weaning group, and there were no significant differences in the d 1 or d 7 post-weaning groups. Analysis of the immunoglobulin-secreting (IgA, IgG, and IgM) cells showed that the ratio of each immunoglobulin was significantly higher on d 7 than d 0. The results revealed that microbial diversity was lower in the ileum and on d 4 post-weaning. Weaning significantly affected the expression of intestinal PRRs mainly on d 1 and d 4 post-weaning. The expression of specific PRRs was triggered by weaning to recognize distinctive microbiota and promote the development and maturation of the intestinal mucosal immunity.