| Mastitis is one of the most serious diseases affecting the dairy industry,which not only brings huge economic losses to the livestock industry,but also causes a huge threat to human health.Especially,subclinical mastitis(SCM)lacks obvious clinical symptoms and is usually ignored.However,it often causes huge economic losses due to its significant increase of somatic cell number(SCC)and serious impact on milk yield and milk quality.The occurrence of mastitis is influenced by a variety of factors.In production practice,it has been found that the increased incidence of mastitis,especially SCM,is closely associated with ketosis in dairy cows during the early stages of lactation.Ketosis is the most common metabolic disease in postpartum peripartum cows and is characterized by hypoglycemia,high non-esterified fatty acids(NEFA),high blood ketones,and a severe negative energy balance.The energy of ruminants is mainly obtained through the fermentation of feed by rumen microorganisms to produce volatile fatty acids(VFA)such as acetic acid,propionic acid and butyric acid.50-60% of the glucose required in the body is produced by propionic acid through gluconeogenesis.Carbohydrates ingested by ruminants are converted in the rumen into acetic and butyric acids capable of ketogenesis and into propionic acid capable of sugar production.Postpartum stress,lactation stress,and abrupt dietary shifts in periparturient cows often lead to disturbances in the rumen flora,resulting in changes in nutrient metabolism and immune function.It was found that rumen flora disorders were closely related to the occurrence of ketosis and mastitis.Accordingly,we hypothesize that rumen microbiota disturbance may be the root cause of the increased incidence of ketosis and mastitis in periparturient dairy cows.During the periparturient period,rumen microbiota disturbance occurs in cows due to various factors,and the body's ability to produce sugar is reduced and the ability to produce ketones is increased,resulting in elevated blood ketones.Hyperketonemia leads to decreased immunity and increased susceptibility to disease.On the other hand,with elevated postpartum lactation,a large number of ketone bodies enter the mammary tissue,affecting normal nutrient metabolism and immune mechanisms in the mammary gland,leading to mastitis or increased susceptibility to mastitis.To test this theoretical hypothesis,the following experiments were carried out:Investigation and correlation analysis on ketosis and mastitis in the peripartum period in a dairy farm.From January 2020 to December 2020,a total of 842 cows were selected from a large-scale dairy farm in Shandong Province and the incidence of ketosis and mastitis in dairy cows at 1-6 weeks after parturition were counted.The incidence of clinical ketosis(CK),subclinical ketosis(SCK),clinical mastitis(CM)and SCM in different months,parity,and weeks postpartum were analyzed separately,and correlations were performed based on the incidence of both diseases.The results showed that the overall incidence of ketosis in cows on the farm was 10.57%,with 6.77% of SCK and 3.80% of CK.The incidence of ketosis in cows at different months and parity was not significantly different.The incidence of ketosis in the second postpartum week was significantly higher than that in the third,fourth,fifth and sixth weeks,but not significantly different from that in the first week.The overall incidence of mastitis in dairy cows was 26.13%,of which the incidence of CM was 9.62% and the incidence of SCM was 16.51%,and the highest incidence of mastitis was observed in August and September.The difference of incidence for mastitis in cows of different parity was not significant.The incidence of CM in the6 th postpartum week did not differ significantly from the 3rd,4th and 5th postpartum weeks,but was significantly higher than the 1st and 2nd postpartum weeks.Both SCK and CK resulted in a significantly higher incidence of mastitis in dairy cows,and there was no significant difference in the incidence of mastitis caused by them.From the above experiment,it was tentatively determined that there was a correlation between ketosis and the occurrence of mastitis in postpartum peripartum cows.Changes in physiological functions of subclinical ketosis cows and effects on subclinical mastitis.The effects of SCK on the organism and the onset of SCM were observed by detecting various physiological indicators of the organism and various components of blood,milk and rumen fluid.The results showed that the blood levels of ?-hydroxybutyric acid(BHBA)and NEFA in SCK cows were significantly higher,blood glucose was significantly lower,alkaline phosphatase was significantly lower,blood urea nitrogen was significantly higher,and the levels of inflammatory factors TNF-? and IL-1? in blood were not significantly different from those in healthy cows.All SCK cows showed a significant decrease in milk production,a significant change in milk composition,a significant increase in milk fat,milk protein,urea nitrogen and milk fat to milk protein ratio,a significant decrease in lactose,a significant increase in BHBA,a significant increase in SCC,and overall SCK cows suffered from SCM.The total volatile fatty acid(TVFA)and its main components,acetic acid,propionic acid and butyric acid,were significantly decreased in the rumen of SCK cows,and the ratio of acetic acid to propionic acid was significantly increased,and the proportion of butyric acid in TVFA was significantly increased.The above results indicated that SCK cows were complicated by SCM and that hyperketonemia was mainly associated with decreased rumen fermentation efficiency and altered fermentation type.Changes of microbiota in rumen and milk during subclinical ketosis.Rumen and milk microbiome were identified by 16 S r RNA gene sequencing and analyzed by Alpha diversity,weighted principal coordinate analysis(PCo A),T-test,LEf Se analysis,and spearman correlation analysis.The results showed that the rumen bacteria structure of SCK cows changed significantly compared to healthy cows.Rumen microorganism structure and relative abundance were closely related to blood BHBA,milk SCC and major components in milk.A decrease in the relative abundance of Prevotella in the rumen and an increase in the relative abundance of chryseobacterium,Christensenellaceae?R-7?group and Rikenellaceae?RC9?gut?group were closely associated with the occurrence of SCK.There was no significant change in the abundance and diversity of the milk microbiome in SCK cows,and an increase in the relative abundance of Prevotella and a decrease in the relative abundance of Succiniclasticum and Corynebacterium in milk were closely associated with the occurrence of SCK and SCM.These results suggested that rumen microbiota disorders were closely related to the occurrence of SCK.Regulation on microbiota in rumen and milk by propylene glycol.Propylene glycol(PG)administration was used to treat cows with SCK to observe the therapeutic effect on SCK and SCM.Again,16 S r RNA gene sequencing was used to identify rumen and milk microbiome to observe the effect of PG on microbiota in rumen and milk.The results showed that PG significantly reduced blood BHBA and NEFA and increased blood glucose in SCK cows,with a cure rate of 26.92% for SCK.PG significantly changed milk composition and reduced BHBA and SCC in milk,with a cure rate of 53.85% for SCM.PG significantly increased the production of acetic acid,propionic acid and TVFA in the rumen of SCK cows,and reduced the ratio of acetic acid to propionic acid ratio.PG administration resulted in an increase in the relative abundance of Succiniclasticum in the rumen and a decrease in the relative abundance of Christensenellaceae?R-7?group and Succinivibrionaceae?UCG-001.PG had little effect on the milk microbiome,but the relative abundance of ruminococcus was decreased.The above results suggestd that effective treatment on SCK was beneficial for the recovery of SCM and indirectly demonstrated that SCK could induce SCM.PG treatment was mainly used to treat ketosis by directly providing glucose precursors to ruminants,but also had some regulatory effects on some bacteria associated with SCK development.In summary,we have confirmed that cows suffer from ketosis leading to an increased incidence of mastitis during perinatal period.The mechanism by which SCK leads to the development of SCM is related to a decrease in rumen fermentation efficiency and a change in the type of fermentation due to rumen microbiota disorders,and direct treatment on SCK contributes to the recovery of SCM.The results of this experiment provide a new theoretical guidance and experimental basis for clinical control of mastitis and ketosis in dairy cows.It also suggests that peripartum prevention and control for ketosis can effectively decrease SCC,improve milk quality and reduce the incidence of mastitis in cows.And the prevention or regulation on rumen microbiota disturbance in periparturient dairy cows may be fundamental to the control of ketosis and mastitis,and even other periparturient diseases. |
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