Effects of Short Chain Fatty Acids (SCFAs) Modulation on Potentially Diarrhea Causing Pathogens in Yaks Through Metagenomics Sequencing

Abstract

Yaks are of great importance on the plateau; however, an emerging endemic diarrheal disease during the last few years is posing a great threat to the health of these animals. Yaks have special gut microbiotal community and short-chain fatty acids (SCFAs) which are not only the principle nutrient substrates of intestinal epithelial cells but can also regulate the epithelial barrier. Until now, metagenomics sequencing has not been reported in diarrheal yaks. A scarce information is available regarding the levels of fecal SCFAs and diarrhea in yaks. The purpose of our study was to identify the potential pathogens that cause the emerging diarrhea and also to explore the potential relationship of short-chain fatty acids in this issue. We estimated diarrhea rate in yaks after collecting the equal number of fecal samples from affected animals. Metagenomics sequencing and quantitative analysis of SCFAs were performed which revealed 15-25% and 5-10% prevalence in diarrheal yak’s calves and adults yaks respectively. Significant difference was observed in GC contents (44.69%~46.08% vs 46.12%~46.38%) under two reference groups (p<0.05). Violin box plot also showed the higher degree of dispersion in gene abundance distribution of diarrhea yaks, while genes of normal yaks were relatively gathered. We found 366163 significant differential abundance genes in diarrheal yaks, with 141305 up-regulated and 224858 down-regulated genes as compared with normal yaks via DESeq analysis. Metagenomic binning analysis indicated the higher significant of bin 33 (Bacteroidales) (p<0.05) in diarrheal animals, while bin 10 (p<0.0001), bin 30 (Clostridiales) (p<0.05), bin 51 (Lactobacillales) (p<0.05), bin 8 (Lachnospiraceae) (p<0.05) and bin 47 (Bacteria) (p<0.05) were obviously higher in normal animals. At different levels, an obviously difference in Phylum, Class, Oder, Family, Genus and Species was noticed as 4, 8, 8, 16, 17 and 30 respectively. Compared with healthy yaks, Acetic acid (p<0.01), Propionic acid (p<0.01), Butyric acid (p<0.01), Isobutyric acid, Isovaleric acid (p<0.05) and Caproic acid (p<0.01) were all observed obviously at lower rate in diarrheal yaks. In conclusion, besides the increased pathogens level of Staphylococcus aureus, Babesia ovata, Anaplasma phagocytophilum, Bacteroides fluxus, viruses, Klebsiella pneumonia, and inflammation-related bacteria; the decreased of SCFAs caused by the imbalance of intestinal microbiota may potentially leads to emergence of diarrhea in yaks.

Effects of Pathogenic Escherichia coli Infection on the Flora Composition, Function, and Content of Short-Chain Fatty Acids in Calf Feces

“…Our results showed that pathogenic E. coli induced calf diarrhea, and the contents of SCFAs in feces were significantly lower than those of healthy calves in the NG, such as acetic acid, propionic acid, butyric acid, and total acid. This is consistent with the findings of Li et al, who identified that the content of SCFAs in the feces of diarrhea-type yaks was significantly lower than that of healthy yaks [48]. Through correlation analysis of the bacteria with significant differences in the abundance and content of SCFAs, we can further demonstrate that calf diarrhea induced by pathogenic E. coli affects intestinal florae-particularly reducing SCFAs and producing bacteria abundance-thereby affecting the production of SCFAs.…”