Abstract
The objective of this study was to investigate the impact of a high-grain (HG) diet on the microbial fermentation, the composition of the mucosa-associated bacterial microbiota, and the gene expression of tight junction proteins in the small intestine of goats. In the present study, we randomly assigned 10 male goats to either a hay diet (n = 5) or a HG diet (56.5% grain; n = 5) and then examined changes in the bacterial community using Illumina MiSeq sequencing and the expression of tight junction proteins using qRT-PCR in the mucosa of the small intestine. The results showed that HG diet decreased the luminal pH (p = 0.005) and increased the lipopolysaccharide content (p < 0.001) in the digesta of the ileum, and it increased the concentration of total volatile fatty acids in the digesta of the jejunum (p = 0.015) and ileum (p = 0.007) compared with the hay diet. MiSeq sequencing results indicated that the HG diet increased (FDR = 0.007-0.028) the percentage of the genera Stenotrophomonas, Moraxella, Lactobacillus, and Prevotella in jejunal mucosa but decreased (FDR = 0.016) the abundance of Christensenellaceae R7 group in the ileal mucosa compared with the hay diet. Furthermore, the HG diet caused downregulation of the mRNA expression of claudin-4, occludin, and ZO-1 in jejunal and ileal mucosa (p < 0.05). Collectively, our data suggested that the HG diet induced changes in the relative abundance of some mucosa-associated bacteria, in addition to downregulation of the mRNA expression of tight junction proteins in the small intestine. These findings provide new insights into the adaptation response of the small intestine to HG feeding in ruminants.