Analysis Of Physiological And Biochemical Indexes And Microbial Composition Of Rumen Liquid Of Cattle,dzo And Yak Under Grazing Conditions

Ruminants have a powerful forestomach digestive system that converts low-quality fiber feed into meat and milk that humans need,which is inseparable from the role of rumen microbes.Animals living in the alpine plateau live on grazing all year round.From autumn to spring,they can only feed on the yellow grass,so we speculate that the rumen microorganisms have stronger fiber digestion ability.In this experiment,three grazing ruminants,such as cattle,dzo and yak,were selected in the vicinity,and the rumen metabolism and the composition of rumen microorganisms were preliminarily explored in order to provide basic information for the development of rumen microorganisms in the plateau.1.Analysis of rumen fluid physicochemical properties and blood biochemical indexes of yellow cattle,yak and yak under grazing conditionsIn this experiment,10 cows,dzo and yak,which were grazing throughout the year,were selected in the vicinity,and their rumen fluid and blood were collected.The results showed that rumen pH,NH3-N showed no differences between the hosts.There was no significant difference in the total volatile fatty acid and the molar proportion of individual VFA between yak and dzo,except acetic and butyric（P>0.05）.The total VFA concentration was significantly higher in cattle compared to dzo（P<0.05）.The same result was also found for acetate（P<0.05）.The ratios of propionic in dzo and yak was significantly higher than that of cattle,and the opposite results were shown in the ratio of valeric and acetic-propionic ratio（P<0.05）.And the propotion of butyric acid in cattle and dzo was significantly lower than that of yak（P<0.01）.The activity of carboxymethylcellulose in rumen of yak was significantly higher than that of yellow cattle（P<0.05）,and the activity of avicelase was significantly higher than that of yellow cattle and dzo（P<0.01）,acetylesterase and xylanase were not significantly different between the three groups（P>0.05）.The blood index showed that the glutamate aminotransferase（ALT）in venous blood of yak was significantly higher than cattle（P<0.05）,and the difference was not significant with dzo（P>0.05）.The remaining blood indicators-blood glucose,total protein,urea nitrogen,total cholesterol,triglycerides,blood ammonia were not significantly different（P>0.05）.Based on the above results,the rumen fermentation mode of yak is better than that of yellow cattle and dzo.We speculate that yak has better adaptability in the environment of low altitude and low forage quality in alpine plateau.2.Analysis of rumen microflora of yellow cattle,dzo and yak under grazing conditionsAccording to the rumen fluid bacterial flora results,cattle rumen liquid bacterial community diversity index-ACE index was significantly lower than that of dzo and yak（P<0.05）,and the community uniformity index Simpsoneven was significantly higher than the other two groups（P<0.05）.From the PCoA results,the genetic distance of bacterial between cattle and dzo was closer（ANOSIMCattle-Dzo（R=0.2994,P=0.001））.And the rumen bacterial community structure in yaks was distinct from those in cattle and dzo（ANOSIMDzo-Yak（R=0.4378,P=0.001）,ANOSIMCattle-Yak（R=0.5526,P=0.001））.In the phylum level Bacteroides,Firmicutes,Fibrobacteres,Cyanobacteria,Proteobacteria,and Verrucomicrobia were the dominant bacteria,and their relative abundances were higher than 1%.The relative abundance of Proteobacteria in yak rumen fluid was extremely significantly higher compared to cattle and dzo（P<0.01）,and the Elusimicrobia were extremely significantly higher than that of cattle（P<0.01）,significantly higher than dzo（P<0.05）.The relative abundance of Synergistetes in yak rumen was significantly higher than that of the cattle（P<0.05）,and showed no difference with dzo（P>0.05）.At the genus level,the relative abundance of Prevotella₁,Rikenellaceae_RC9_gut_group in each group were greater than 10%,along with the genus Fibrobacter,Ruminococcaceae_UCG-011,Prevotellaceae_UCG-003,Christensenellaceae_R-7_group,Prevotellaceae_UCG-001,Succiniclasticum,Ruminococcaceae_NK4A214_group,Ruminococcaceae_UCG-010,and Ruminococcus₁ were predominant genus.According to LEfSe analysis,the genus significantly elevated in the cattle mainly appeared in the family Ruminococcaceae（Firmicutes）,Lachnospiraceae（Firmicutes）and order Bacteroidales（Bacteroidetes）.The genus that is significantly elevated in the dzo is mainly attributed to the family Lachnospiraceae（Firmicutes）and orderBacteroidales（Bacteroidetes）.The genus enriched in yak rumen fluid were the most widely distributed,involving Firmicutes,Proteobacteria,Spirochaetae,Elusimicrobia,Tenericutes and Planctomycetes.As for rumen fungi,the diversity（Chao1,ACE）and richness（Shannon,Simpson）were extremely significant higher in yak and dzo than cattle（P<0.01）.The community uniformity index（Simpsoneven）was significantly higher in cattle compared to dzo（P<0.05）and was extremely significantly higher compared to yak（P<0.01）.From the results of PCoA,the genetic distance of rumen fluid fungi in yak and dzo were closer(ANOSIM_Dzo-Yak（R=0.2663,P=0.004）.And the rumen fungi community structure in cattle was distinct from those in yak and dzo(ANOSIM_Cattle-Dzo（R=0.8822,P=0.001）,ANOSIM_Cattle-Yak（R=0.9122,P=0.001）).At phylum level,Ascomycota,Neocallimastigomycota,and Basidiomycota are the dominant bacteria,and the sum of the three is over 99%.The relative abundance of Basidiomycota in cattle was significantly higher than that of the yak（P<0.05）,and extremely significantly higher than that of the yak（P<0.01）.At the genus level,the composition of fungi in the rumen fluid of the three animals is quite different.Cryptococcus,Caecomyces,Preussia were the predominant genus.According to LEfSe analysis,Cryptococcus,Caecomyces,Microascus,Penicillium,Acremonium were significantly elevated in the cattle.Scedosporium,Mycosphaerella,unclassified_f<sub>Lasiosphaeriaceae,unclassified_f<sub>Chaetomiaceae,unclassified_f<sub>Phaeosphaeriaceae were significantly elevated in the dzo.Preussia,Didymella,Phoma were significantly elevated in the yak.According to the rumen fluid protozoa flora results,there was no significant difference in the diversity and richness among three groups（P>0.05）.From the results of PCoA,the genetic distance of rumen fluid fungi in cattle and dzo were closer(ANOSIM_Cattle-Dzo（R=0.1596,P=0.055）).And the rumen protozoa community structure in yak was distinct from those in cattle and dzo(ANOSIM_Dzo-Yak（R=0.5624,P=0.001）,ANOSIM_Cattle-Yak（R=0.8179,P=0.001）).Three families,Ophryoscolecidae,Blepharocorythidae,and Cycloposthiidae were detected in Ciliophora.Only one genus（Charonina）,one species（Charonina_ventriculi）wasdetectedundertheBlepharocorythidae,and Charonina_ventriculi relative abundance in the cattle was significantly higher than that of the yak（P<0.01）.The Diplodinium relative abundance of yak rumen liquid was extremely significantly higher than that of yellow cattle（P<0.01）,and was significantly higher than that of dzo（P<0.05）.And the relative abundance of Ostracodinium of the yak was extremely significantly lower than the other two groups（P<0.01）The relative abundance of the Eodinium in the cattle was significantly higher than that of the dzo（P<0.05）,and was extremely significantly higher than that of the yak（P<0.01）.The Epidinium relative abundance of cattle was significantly lower than the dzo（P<0.05）,and was significantly lower than that of the yak（P<0.01）.According to the rumen fluid archaea flora results,the diversity（Sob）was significant higher in cattle than yak（P<0.05）.From the results of PCoA,the yak and dzo groups did not cluster differently(ANOSIM_Dzo-Yak（R=0.-0.321,P=0.585）).And the rumen archaea community structure in cattle was distinct from those in cattle and dzo(ANOSIM_Cattle-Yak（R=0.2354,P=0.004）,ANOSIM_Cattle-Dzo（R=0.2305,P=0.015）).On class level,the relative abundance of Methanobacteria in rumen fluid of cattle was significantly lower than that of dzo and yak（P<0.01）,and the Thermoplasmata was significantly higher than the other two groups（P<0.01）.At the genus level,the relative abundance of the Methanobrevibacter,norank_f<sub>Methanobacteriaceae,Methanosphaera were higher in the yak and dzo than the cattle,while the relative abundance of norank_f<sub>Thermoplasmatales_Incertae_Sedis,Candidatus_Methanomethylophilus were significantly higher in cattle（P<0.01）.In summary,the yak rumen liquid had the lowest acetic-propionic ratio,and the highest carboxymethylcellulose activity.Rumen microbial composition of cattle and yak samples were quite different.The bacteria,fungi,archaea and protozoa flora of dzo was mostly between cattle and yak.As a dominant species in the alpine plateau,yak has better adaptability than cattle and dzo,and the rumen microbial composition has also undergone adaptive changes.