The Study On Intestinal Microbial Community Structure And Diversity Of Dairy Cows

China is a big consumer of milk in the world,with a large scale of dairy farming.Dairy cows could physiologically convert dietary plant substrates into milk,meat or other accessible nutrients.Intestinal microbiota in dairy cows plays a key role in the digestion and metabolism of nutrition materials.Healthy intestinal microbiota could significantly improve physical health level and energy utilization rate of dairy cows.From the aspect of the microbial ecology,the intestinal microbial community is relatively stable and balanced,and usually challenged by internal intestinal tract environment,diet and living environment,et al.In the thesis,the variation under the development of intestinal microbiota in dairy cows and the response of intestinal microbiota to the elevation and soil environmental microorganisms was studied during different growth stages and different feeding conditions,while the relationship between intestinal microbes and lactation performance was explored through the feature of intestinal probiotics.This research was mainly described in several aspects as below:1.High-throughput sequencing of 16 S r RNA gene amplicon sequencing of the target variable region(V4)was used to explore how intestinal microbiota of dairy cows in plain vary during different growth stages.By difference analysis,the community structure and diversity of intestinal microbiota during respective periods(lactation,weaning,breeding,adolescence,lactating and dry period)were compared,on the Illumina Hi Seq2500 platform(paired-end 250bp).How the probiotic genera of intestinal microbiota changes with the performance of growth and lactation was discovered.The results showed that the distribution of intestinal microbial community structure during six stages retained relatively stable at the phylum level.The intestinal microbiota gradually colonized with the growth of calves,alpha and beta diversity of intestinal microbiota apparently revealed "two-stage" pattern before and after breeding.Meanwhile,the relative abundance of Bifidobacterium under lactating stage was higher than other periods,and positively correlated with milk production.2.The intestinal microbiota of dairy cows in plateau was analyzed,during lactating and non-lactation periods,to manifest the correlation between probiotics in the intestinal microbiota and lactation performance of dairy cows.And the community structure and diversity of intestinal microbiota was compared.The variation of the probiotic genera at two stages(lactating and non-lactating)was mainly analyzed.The results represented that the intestinal microbiota of dairy cows retained stable at the phylum level,but the relative abundance of a few genera significantly decreased during lactating cows.In addition,there was no significant variation in the richness of intestinal microbiota(α diversity).Once again,based on the unweighted unifrac distance matrice,the results of principal coordinate analysis,indicated obvious cluster between lactating and non-lactating.The relative abundance of Bifidobacterium of dairy cows during lactating stage was significantly higher than that during non-lactation cows,while there was no significantly different of other probiotics.3.The study on the difference of intestinal microbiota of dairy cows were performed in the low and high elevation,aiming at exploring the ecological adaptability of intestinal microbiota to the altitude.The results achieved from this research,illustrated that their intestinal microbial community structure maintained relatively stable at the phylum.And the dominant core genera of lactating cows were also discovered.Principal coordinate analysis results presented obvious cluster respectively of the dairy cows in low and high elevation.The relative abundance of few genera were significantly different between individuals in low and high elevation,and also the relative abundance of Bifidobacterium of dairy cows in-high-elevation was lower than that in the low-elevation.4.Intestinal microbiota of cows under grazing and standardized captivity were compared to investigate the effect on the intestinal microbiota of dairy cows in plateau under different breeding ways.It has been found that,the relative abundance of part of genera was significantly different in the individuals under different breeding ways.The richness(α diversity)of intestinal microbiota was higher in dairy cows under standardized captivity,and the principal coordinate analysis presented obvious cluster of the lactation cows by different feeding methods.5.The correlation between soil microbes and intestinal microorganisms of cows in different habitats but same elevation was investigated to explore the influence of soil microbes on the intestinal microbiota of dairy cows.Our findings suggested that the community structure and diversity of soil microorganisms was significantly different under different natural environments,moreover,the soil microbial community structure was distinct from that of intestinal microbiota.It has also been found that,intestinal microbiota of lactation cows was significantly correlated with soil microbial community.However,the intestinal flora of lactation cows in different grazing areas had no significant change following with soil microorganisms.In conclusion,the intestinal microbiota is composed of core microbiota and changeable microbiota.The intestinal microbial community structure retains relatively balanced at the phylum level.The intestinal microbiota of dairy cows in plateau may revealed ecological adaptation to high-elevation.There exists correlation between intestinal microbes and soil microorganisms.Interestingly,it suggested that the relative abundance of intestinal microbiota may be related to lactation performance under standardized captivity in plateau and plain,meanwhile,there was correlation with milk production of cows.