Effects Of Bovine Mastitis On Activity Of Milk Enzymes, Content Of Acute Phase Proteins And As Potential Indicator Of Cow's

Bovine mastitis is one of the most harmful diseases in dairy production.With development of dairy industry and rising attention to public health,people pay more attention to the harm of bovine mastitis.Early diagnosis of bovine mastitis has very important significance,especially subclinical mastitis.The routine indicators of diagnosis have some drawbacks.Therefore,we urgently need an alternative method.In order to seek sensitive diagnosis indicator of subclinical mastitis,and provid scientific evidences to value the effect of medication and prognosis,we carried out the following studies:Research 1.Effects of bovine mastitis on activities of milk enzymes and as potential indicator of cow's subclinical mastitisTo explore the effect of subclinical mastitis on activities of milk enzymes,such as N-acetyl-β-D-glucosaminase(NAG),lactate dehydrogenises(LDH),myeloperoxidase (MPO),alkaline phosphatase(ALP) and lactoperoxidase(LP) in milk of 220 lactating Holstein cows,somatic cells were counted(SCC) and activities of five enzymes were measured in milk.A SCC threshold of 50×10⁴ cells/mL in milk was used as the classification standard of subclinical mastitis.220 milk samples were divided into five groups(Ⅰ～Ⅴ).Groupâ… ,â…¡andâ…¢were healthy milk(SCC＜50×10⁴mL·^-1).Groupâ…£andâ…¤were subclinical mastitis milk(SCC＞50×10⁴mL^-1).Correlations between these enzymes and SCC,the sensitivity(SEN),specificity(SPE),positive predictive value(PPV),negative predictive value(NPV) and Jouden index as the indicators to diagnose subclinical mastitis were analyzed.The results showed that(1) the positive correlation between activities of five enzymes and SCC(lgSCC) in bovine milk: LDH(r=0.978,P＜0.01),MPO(r=0.965,P＜0.01),NAG(r=0.947,P＜0.05),ALP(r=0.953, P＜0.05),LP(r=0.914,P＜0.05),(2) The activity of LDH in groupâ…¤was 5.23 times to groupâ… .The amplitude variation of LDH activity in different groups was more than NAG,ALP,LP and MPO.Therefore variation of LDH activity in different SCC threshold was sensitive.(3)＞100 IU/L of LDH activity as the threshold to diagnose subclinical mastitis,its diagnosing SEN,SPE,PPV,NPV,index Jouden were 70%, 82.3%,59.0%,88.7%and 0.52 respectively.These results indicate that LDH could be used as a candidate indicator in earlier diagnosis of subclinical mastitis in cows.Research 2.Effects of bovine mastitis on contents of acute phase protein and as potential indicator of cow's subclinical mastitisThe milk samples and method of divided groups were same as research 1.Somatic cells were counted(SCC) and contents of serum amyloid A(SAA),haptoglobin(HP), C-creative protein were measured in milk.Correlations between three proteins and SCC, the sensitivity(SEN),specificity(SPE),positive predictive value(PPV),negative predictive value(NPV) and Jouden index as the indicators to diagnose subclinical mastitis were analyzed.The results showed that(1) the positive correlation between contents of there proteins and SCC(lgSCC) in bovine milk:SAA(r=0.952,P＜0.05), HP(r=0.901,P＜0.05),CRP(r=0.881,P＜0.05).(2) HP content in subclinical mastitis cows were higher than the healthy,whereas not detected HP in groupâ… .The content of LDH in groupâ…¤was 16.82 times to groupâ…¡.Variations of HP content in different groups were significantly(P＜0.05).The amplitude variation of HP content in different groups was more than SAA,CRP.Therefore variation of HP content in different SCC threshold was sensitive.(3)＞110 ng/mL of HP content as the threshold to diagnose subclinical mastitis,its SEN,SPE,PPV,NPV,Index Jouden were 72.4%,95.2%,94.7%, 76.9%and 0.70 respectively.These results indicate that HP could be used as a candidate indicator to earlier diagnosing subclinical mastitis in cows.Research 3.Establishment of experimental mastitis model by LPS via teat duct in rabbit22 healthy rabbits of parturition 6d were divide into two groups randomly,11 rabbits of one group.Two doses of lipopolysaccharide(LPS),0.15mg/KW and 0.075mg/KW, were infused into glands of rabbit.The ear venous blood and glandular tissue were collected at 2h before,and 6h,12h,24h,48h,72h,5d,7d after infusion with LPS respectively.Untreated rabbits were concerned as control groups,and the rabbits which infused with LPS were as test group.The activities of NAG,LDH,LP,ALP,MPO, superoxide dismutase(SOD),contents of HP,SAA,CRP,maleic dialdehyde(MDA), total antioxygen capacity(T-AOC) were determined at different time point,and the variations of dynaic pathology of gland tissue through making pathological section were observed.The results showed that(1) rabbits appeared with clinical symptoms of acute mastitis after infusion LPS via teat candal,indicating that experimental mastitis model was successfully established.(2) The activities of enzymes and contents of acute phase proteins in serum were correlative with inflammatory degree of gland in rabbits. Activities of MPO,NAG,LDH,LP,ALP and contents of HP,SAA,CRP significantly increased with inflammatory degree of gland(P＜0.05),contrary to content of ALB. Variations in different times and doses of groups were sentitive in activity of LDH and content of HP.(3) These results indicate that LDH and HP could be used as candidate indicators to value degree inflammation of gland.