Investigating The Influence Of Dairy Cow Gut Microbiota On Mastitis Through Microbiome Analysis And Fecal Microbiota Transplantation Techniques

Mastitis is one of the most common diseases in dairy farming.Mastitis not only causes health problems in dairy cows,but also reduces milk production and quality,which brings great economic losses to dairy industry.At present,there have been many studies on the relationship between intestinal flora and host health.Microbial infection is one of the main causes of mastitis in dairy cows,and mastitis can cause changes in intestinal flora of dairy cows.In this study,the changes of immune function of cows with mastitis and the effect of mastitis on intestinal microbiota were explored through cow test and mouse test,and the effect of intestinal microbiota changes on mammary gland health was explored by fecal microbiota transplantation in germ-free mice.Part one: Effects of different mammary gland health status on performance and gut microbiota of dairy cowsIn the dairy experiment,18 healthy lactating Holstein cows were selected and divided into healthy group(H group),subclinical group(SM group)and clinical group(CM group)according to somatic cell count.The results showed that with the deepening of the severity of mastitis,the production performance of dairy cows decreased significantly,and the somatic cell count increased significantly.Analysis of the effects of different mammary health conditions on intestinal microbiota of dairy cows showed that there were 1425 shared OTUs(operational taxa representing microbial communities)in the healthy,subclinical and clinical mastitis groups,with 32,73 and 63 unique OTUs,respectively.At the phylum level,Firmicutes and Bacteroidetes were dominant groups.At the generic level,the relative abundance of UCG-005 in healthy group was significantly higher than that in the other two groups(P < 0.05).The relative abundance of Rikenellaceae＿RC9＿gut＿group,UCG-010,Alistipes and Clostridia＿vadin BB60＿group in subclinical mastitis group was significantly higher than that in the other two groups(P < 0.05).The relative abundance of Mogibacterium and Eubacterium＿hallii＿group in clinical mastitis group was significantly higher than that of the other two groups(P < 0.05).Part two: The effects of fecal microbiota transplantation on physiological and biochemical indexes and intestinal microbiota in germ-free miceIn order to further explore the effects of intestinal microbiome on mastitis health,24 ICR mice(11 to 13 weeks old,weight 35 to 45 g)with lactation for 5 to 7 days were selected and randomly divided into three groups: CON group(gavage of normal saline),HS group(transplantation of healthy cow coprobiotic bacteria)and CM group(transplantation of mastitis cow coprobiotic bacteria).Before fecal transplants,all mice were given a broadspectrum antibiotic in their drinking water(for 3 days)to remove their gut microbes.The fecal transplants lasted for 7 days.The main test results are as follows:Fecal bacteria transplantation was performed on mice.24 lactating mice were selected and divided into CON group,HS group and CM group.Before transplantation,the mice were given broad-spectrum antibiotics to remove the gut’s own microbes.The results showed that after transplantation,the HS and CM groups had breast and intestinal injuries,blurred liver structure,increased liver cell permeability and hemorrhage.After fecal bacteria transplantation,the level of inflammatory factors in CM group increased significantly.Intestinal flora analysis showed that the Alpha diversity index of intestinal flora in mice decreased significantly after transplantation of mastitis dairy cow flora.At the species level,the relative abundances of Clostridium＿sensu＿stricto＿1,Anaeroplasma,Mogibacterium and other genera increased significantly in the CM group after transplantation,while the relative abundances of Bacteroides and Lactobacillus decreased significantly.In conclusion,mastitis can affect the body immunity of dairy cows,reduce the lactation performance of dairy cows,and disorder the intestinal microbiota of dairy cows.Transplantation of the intestinal microbiota of cows with mastitis into germ-free mice can cause different degrees of inflammatory damage to the intestinal tract,mammary gland,liver and other organs,damage the barrier function of the body,and eventually lead to the symptoms of mastitis in mice,indicating that intestinal microorganisms play an important mediating role in promoting the process of mastitis.