| Cecum is one of the most important fermenters for ruminants. Diet, environment and individual factors all can induce excessive carbohydrates to flow to hindgut, where the excessive fermentation occurred, resulting in the production of abnormal metabolites. Here, the cecal ability of fermentation for substrate with grain in vitro was studied. In addition, we investigated the difference of ability to ferment grain between rumen and cecum. Further, we studied the effect of high grain feeding on cecal fermentation, cecal microbiota and the changes in the cecal epithelium in goats. The results were listed as following:1. The comparison of the effects of substrates with different percentages of grain on the cecal and ruminal fermentation in vitroThis study was aimed to investigate the effects of substrates with different percentages of grain on the cecal and ruminal fermentation in vitro. Four different proportions (0%:Ao,20%:A0.2,40%:A0.4 and 60%:A0.6 of grain) in substrates were used in this study. The results showed that the total gas production increased with the increasing grain in substrates (P< 0.001). Moreover, the gas produced in rumen was higher (P< 0.001) than that in cecum with the same substrate. The total VFA produced in 40% and 60% grain group of cecum feremtation system was not less than that of rumen system. The concentratin of acetate in cecum system was much less than that in rumen in Ao group (P< 0.001). The amount of propionate in cecum was less than that in rumen (P< 0.001). However, the ratio of acetate to propionate was higher in cecum than that in rumen (P< 0.001). There was no significant difference (P> 0.10) in concentration of butyrate between A0 and A0.2 groups. When the percentage of grain in substrate was 40%, more butyrate were observed in cecum group compared with rumen. The concentrations of propionate, butyrate, isobutyrate, isovalerate, valerate and total VFA in rumen and the amounts of acetate, propionate, butyrate, isobutyrate, isovalerate and total VFA increased linearly with the increasing proportion of grain in substrate. In general, the ruminal microbial fermentation was more active compared with the cecal microbiota, and high concentration of TVFA was observed when the cecal contents were used as inoculant.2. The effects of high-grain diet on cecal fermentation and the concentrations of LPS and biogenic aminesThe objective of this study was to investigate the effects of high-grain diet on cecal fermentation and the concentrations of LPS and biogenic amines in ceceum of goats.10 male goats were randomly assigned to either a hay diet (0% grain; n= 5) or HG group (65% grain; n= 5) to characterize the changes in the cecal fermentation. The test last for 7 weeks. The results indicated that HG feeding increased the concentration of VFA in cecal content of goats significantly (P< 0.001), with acetate (P< 0.001), propionate (P< 0.001) and butyrate increasing (P= 0.002) and isobutyrate (P= 0.01) and the acetate-propionate ratio (P<0.001) decreasing. The pH of cecal content of goats fed with HG feeding was much lower that of goats fed with all hay diet. There was no significant difference in the concentration of lactate between two groups. HG feeding increased the concentration of LPS in significance (9803 vs.14515, P= 0.001) and did no effect on biogenic amines. Correlation analysis revealed that the concentration of LPS was correlated with pH negatively (r=-0.81, P= 0.005). There were no correlations between biogenic amines and VFA, pH or lactate except the relationship between tyramine and propionate (r= 0.650, P= 0.042). In general, high-grain diet induces excessive carbohydrates to flow to cecum, resulting in cecal excessive fermentation.3. The effects of high-grain diet on the composition of luminal and mucosa-associated bacterial microbiota in cecum of goatsThe objective of study was to investigate the effects of high grain feeding on the composition of luminal and mucosa-associated bacterial microbiota in cecum of goats. Pyrosequencing determination revealed that 17 phyla and 22 phyla were found in cecal content and mucosa correspondingly across all samples, while the genera detected in mucosa were much more than that detected in content (340 vs.133). Phylum Firmicutes had an absolute advantage in abundance in cecal content, accounting for more than 75% of total sequences. Phylum Spirochaetes was in a little higher relative abundance, possessing more than 40% of microbial community on average in cecal mucosa. In the level of phylum,3 phyla (Actinobacteria, Spirochaetes, Chloroflexi) in cecal content (P< 0.01) and 12 phyla (Planctomycetes, Fibrobacteres, Nitrospirae, Verrucomicrobia, Armatimonadetes, Elusimicrobia, Firmicutes, Bacteroidetes, Chloroflexi, Cidobacteria, Deinococcus-Thermus, Deferribacteres) in cecal mucosa (P< 0.05) were affected by diet treatment significantly. HG feeding caused dramatic shifts in microbial populations in cecal content and mucosa being characterized by enrichment predominant genera Turicibacter and Clostridium in lumen (P< 0.05) and Turicibacter, Clostridium, Unclassified Gamma proteobacteria and Unclassified Rikenellaceae in mucusa (P< 0.05), while decreasing unclassified Ruminococcaceae in lumen (P< 0.05) and Mucispirillum in mucusa (P< 0.05) compared with hay group. In general, cecal microbiota is dramaticly affected by high-grain diet, resulting in the decrease of relative abundance for some autochthonous flora in cecal mucosa.4. The effects of high-grain diet on cecal mucosal morphology and the relative expression of inflammatory cytokines in goatsThe object of this study was to investigate the high-grain feeding on cecal mucosal morphology and the relative expression of inflammatory cytokines in goats. The results revealed that high grain feeding resulted in a damage to cecal epithelium, which was proven by paraffin slice, scanning and transmission electron microscopy visually methods. The tight junction in adjoining cells of goats fed with high-grain feeding became loose, and the top gap between two epithelial cells was larger compared with the control group. However, there was no difference in tight junction proteins mRNA expression level between two groups. High-grain feeding significantly up-regulated the gene expression of IL-1β (P< 0.001), IL-6 (P< 0.01), IL-10 (P< 0.01), IL-12 (P< 0.001) and IFN-y (P< 0.05) when compared to the control, while there was no significant difference in the relative expression levels of TNF-a and IL-2 between the control and HG group. Correlation analysis revealed that the relative expression levels of IL-6 and IL-12 were correlated with pH negatively and LPS positively. There was also some correlation between the microbiota in cecal mucosa and the relative mRNA expression level of inflammatory cytokines. Generally, high-grain feeding leads to a considerable injury to cecal mucosa, resulting in local inflammatory response in cecum. |
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