| Mongolian cattle,originated in the Mongolian Plateau,is the indispensable milk and meat source for local herdsmen.Mongolian cattle in Xilingol region of Inner Mongolia have the largest number and large meat yield.The grassland in Inner Mongolia is wide from east to west,with diversified natural ecological conditions and a typical continental climate.Its year-round grazing,without covered fold or composite feed,average temperature in winter at-30℃,and average temperature in summer about 35℃.Under such extensive and primitive feeding and management conditions,Mongolian cattle can still live normally,reproduce offspring and have good genetic stability.In this study,highthroughput sequencing was used to investigate the composition and potential functions of intestinal microorganisms in different regions,seasons,gastrointestinal sites and breeds of grazing Mongolian cattle.The excellent characteristics of grazing Mongolian cattle was analyzed from the perspective of microbiology,so as to provide scientific basis for the protection of Mongolian cattle resources.This study mainly includes 4 experiments,and the research contents and results of each experiment are as follows:Experiment Ⅰ.Comparative analysis of the composition and structure of intestinal microorganisms of grazing Mongolian cattle in different regionsIn this experiment,animals were selected from Sunid Left Banner of Xilingol League,Inner Mongolia Autonomous Region(XM,n=20);Xin Barag Left Banner,Hulunbeier(HM,n=20),Alxa Left Banner,Alxa League(AM,n=20),the fecal samples from a total of 60 healthy and disease-free Mongolian cattle,at the age of 3～4,with similar body weight were collected.It is year-round grazing,consumed herbage,without composite feed.The composition and structure of intestinal microorganisms were analyzed by 16S rRNA sequencing.The results showed that:the diversity index of the intestinal microbial community(Shannon index)of HM and XM groups was significantly higher than that of AM group,but there was no significant difference between the two groups;richness estimates(Chao1 and ACE index)were significantly different,with HM group having the highest value,followed by XM group and AM group having the lowest value;at the phylum level,Firmicutes and Bacteroidetes were the dominant phyla,with significant differences among different groups.The abundance of Firmicutes and Verrucobacteria in AM group was significantly higher than that in other groups;at the family level,Ruminococcaceae was the dominant family in the three groups,the abundance of Ruminococcaceae and Lachnospiraceae in AM group was higher than that in other groups;at the genus level,Ruminococcaceae_UCG-005 was the dominant genus,and the relative abundance of Akermansia and Christensenellaceae_R-7_group in AM group was higher than that in other groups;PCoA results showed that the intestinal microbial communities of grazing Mongolian cattle in different regions were significantly different.The samples of HM and XM groups were clustered together,while the samples of AM group were clustered separately.In conclusion,under natural grazing conditions,the composition and structure of intestinal microorganisms of Mongolian cattle in different regions are significantly different,and the bacteria related to disease resistance in AM group are the most abundant,which is speculated to be related to the strong disease resistance of Mongolian cattle.Experiment Ⅱ.Comparative analysis of the composition and structure of intestinal microorganisms of grazing Mongolian cattle in different seasonsIn this experiment,the stool samples from healthy and disease-free Mongolian cattle,at the age of 3～4,with similar body weight were collected from a family ranch in Sunid Left Banner of Xilingol League,Inner Mongolia Autonomous Region in the spring(n=20),summer(n=20),autumn(n=20)and winter(n=20)respectively.It is year-round natural grazing,free choice feeding and water,without composite feed in winter.The difference in the composition and structure of intestinal microorganisms were analyzed by 16S rRNA amplicon sequencing.The results showed that:the observed species index of grazing Mongolian cattle samples in autumn was significantly higher than that in summer and winter(P<0.05);in spring,Shannon index was significantly higher than that in summer and winter(P<0.0001);at the phylum level,for Mongolian cattle samples in summer and winter,the abundance of Firmicutes decreased,while the abundance of Bacteroidetes increased.In winter,the abundance of Verrucomicrobia and Euryarchaeota was significantly higher than that in other seasons;at the genus level,the relative abundance of Rikenellaceae_RC9_gut_group,Akkermansia and Romboustia in the intestine of grazing Mongolian cattle was significantly higher in winter than in other seasons;The results of PCoA showed that the Mongolian cattle samples in spring and autumn were partially overlapping and clustered together,while the samples in summer and winter were clustered separately,and the microbiota structure was different.Ⅲ:Study of the structure and function of microbiological compositions in different gastrointestinal parts of grazing Mongolian cattleIn this experiment,20 healthy and disease-free grazing Mongolian cattle,at the age of 3～4,with similar body weight were collected from a family ranch in Sunid Left Banner of Xilingol League,Inner Mongolia Autonomous Region as experimental animals for slaughter experiment,and cecal contents and rumen fluid samples were collected.The difference in the composition and structure of intestinal microorganisms were analyzed by 16S rRNA amplicon sequencing,and potential functions of intestinal microorganisms were analyzed by metagenomics sequencing.The results showed that:the diversity and abundance index of the rumen microorganisms of grazing Mongolian cattle were higher than those of cecum;at the phylum level,Firmicutes and Bacteroidetes were the dominant phyla in the rumen and cecum;the abundance of Prevotellaceae,Christensenellaceae and Fibrobacteraceae in the rumen was significantly higher than that in the cecum(P<0.05);PCoA results showed that the community structure was different;The microbial community structure of rumen and cecum was different.Metagenomic sequencing results showed that carbohydrate metabolism and aminoo acid metabolism were the most abundant functional.In addition,annotation of CAZy database showed that glycosidic hydrolase(GHs)genes had the largest number,followed by glycosyltransferases(GTs),and auxiliary oxidorereductases(AAs)had the smallest number.AMong GH genes,GH2,GH3 and GH78 family genes are more common.This study provides scientific basis for further mining rumen microbial resources of Mongolian cattle.Ⅳ.Sequencing analysis of the composition,structure and serum metabolomics of intestinal microorganisms of grazing Mongolian cattle with different varietiesIn this experiment,the healthy and disease-free grazing Mongolian cattle(n=25)and Simmental cattle(n=25),at the age of 3 or 4,were collected from a family ranch in Sunid Left Banner of Xilingol League,Inner Mongolia Autonomous Region as experimental animals for the collection of stool and blood samples.The difference in the composition and structure of intestinal microorganisms were analyzed by 16S rRNA amplicon sequencing,potential functions of intestinal microorganisms were analyzed by metagenomics sequencing,and the differential metabolites was analyzed with serum metabolomics.The results showed that:the relative abundance of Firmicutes,Bacteroidetes,Euryarchaeota,Rikenellaceae,Lachnospiraceae,Prevotellaceae,Christensenellaceae,and Peptostreptococcus in intestinal tract of Mongolian cattle was significantly higher than that of Simmental cattle(P<0.05);PCoA results showed that there was no overlap between microorganisms in the Mongolian cattle and Simmental cattle,and the community structure was different;The number of intestinal microorganism genes in Mongolian cattle was higher than that in Simmental cattle;according to annotation results of CAZy database,the corresponding genes of six major functional carbohydrate hydrolases were found in intestinal microorganisms of Mongolian cattle and Simmental cattle;There were significant differences in 238 serum metabolites between Mongolian cattle and Simmental cattle.In positive mode,the metabolites mainly related to disease resistance were differences in the blood of Mongolian cattle,such as anti-cancer,anti-tumor,hypolipidemia,hypoglycemia related metabolites,we suspect that this is related to the strong disease resistance of Mongolian cattle,which should be further verified for multi-omics analysis and exploration.At the same time,Mongolian cattle have different metabolites in secondary bile acid biosynthesis,bile secretion,primary bile acid biosynthesis,arachidonic acid metabolism and porphyrin and chlorophyll metabolism were significantly enriched.In conclusion,the results of this study confirmed the excellent characteristics of Mongolian cattle from the perspective of intestinal microbiology,such as strong adaptability,strong disease resistance and coarse feeding resistance. |
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