Study On The Correlation Between Serum Selenium Level And Recessive Mastitis In Dairy Cows

Se is an important nutrient element in dairy cows.It can enhance the immune system's ability to resist diseases by regulating the level of Se.Se has certain significance in protecting the immune function of mammary gland and reducing the risk of recessive mastitis in dairy cows.The purpose of this experiment is to detect the serum selenium content,somatic cell number,antioxidant capacity,immune ability and milk quality of dairy cows under the same background.Through data analysis,the correlation between selenium level and each detection index of dairy cows is found,and the relationship between selenium and recessive mastitis of dairy cows is found out,which provides experimental basis for the prevention of recessive mastitis of dairy cows through nutritional immunity.Fifty dairy cows with similar background data were randomly selected from an intensive dairy farm.Blood was collected from jugular vein and serum was separated.Selenium content was detected by ICP plasma emission spectrometer.The number of somatic cells(SCC)and milk composition were measured.According to the serum selenium level,cows whose serum selenium level was lower than 0.05 mg/L were divided into three groups: normal selenium control group 1,control group 2 and control group 3.Again,the serum of cows in each group was collected and separated.The serum GSH-Px,T-AOC,IL-2,IL-6,IgG,IgM,IFN-gamma and TNF-alpha were detected by enzyme-linked immunosorbent assay(Elisa).The correlation between serum selenium level and recessive mastitis in dairy cows was analyzed by data statistics.The results are as follows:(1)The prevalence of recessive mastitis was 42% and selenium deficiency was 38%.SCC in low selenium group was higher than that in control group(P > 0.05).However,with the increase of serum selenium level in dairy cows,the incidence of recessive mastitis in dairy cows showed a downward trend,and Pearson analysis showed that serum selenium level was negatively correlated with SCC(R=-0.28,P=0.045).(2)Serum IgM of low selenium group was lower than that of control group(P > 0.05),serum IgG was lower than that of control group 2 and 3(P > 0.05),and Pearson analysis showed that serum selenium level was not correlated with IgG and IgM.(3)Serum TNF-alpha and IFN-gamma levels in selenium-deficient dairy cows were lower than those in control group 2 and 3(P > 0.05),and serum IL-2 levels were lower than those in control group(P > 0.05).Pearson analysis showed that serum selenium level was not correlated with TNF-a,IFN-gamma and IL-2 in lactating dairy cows.Serum IL-6 in selenium deficiency group was higher than that in control group 1 and 3,and lower than that in control group 2(P > 0.05).Pearson analysis showed that serum selenium level was negatively correlated with IL-6,and IL-6decreased with the increase of selenium level in dairy cows.(4)The level of serum GSH-Px in low selenium group was lower than that in control group 2(P< 0.05),and Pearson analysis showed that there was a significant positive correlation between serum selenium level and GSH-Px.Serum T-AOC in selenium-deficient group was higher than that in control group 1 and 3(P > 0.05),and Pearson analysis showed that serum selenium level was not correlated with T-AOC.(5)With the increase of selenium level,milk yield,milk fat rate and lactose rate increased(P >0.05).(6)Establish a binary logistic model to predict the risk of recessive dairy cow mastitis by SPSS software.The model analysis showed that IL-6 and GSH-Px could better reflect the risk of recessive mastitis in dairy cows.Through ROC curve analysis and Yoden index calculation,the optimum critical value of each index is obtained.When the serum GSH-Px < 148 U/L and IL-6 >451 pg/mL,the risk of recessive mastitis in dairy cows increased.According to the results of the experiment,the following conclusions were drawn: Selenium was negatively correlated with the number of somatic cells in dairy cows.GSH-Px was positively correlated with serum selenium level,while IL-6 was negatively correlated with serum selenium level.Serum GSH-Px < 148 U/L and IL-6 > 451 pg/mL increased the risk of recessive mastitis in dairy cows.