| Mastitis is one of the most common diseases of dairy cows,and it is also the most serious disease that causes dairy industry loss.Dairy cow mastitis includes clinical mastitis and subclinical mastitis.Somatic cell count(SCC)is one of the better indicators to evaluate the occurrence of subclinical mastitis in dairy cows.It is generally believed that the occurrence of subclinical mastitis in dairy cows when the number of Somatic cells in milk is more than 500,000/mL.Because of the skewed distribution of SCC,it is usually converted into somatic cell score(SCS)for analysis.The somatic cell score of dairy cows is obtained by the calculation formula SCS=log2(SCC/100 000)+3.Many factors affect SCC and SCS in milk,including farm management,parities,lactation stages,measurement seasons,calving seasons,etc.This study first conducted a questionnaire survey on 12 dairy farms in Jiangsu Province,and collected the dairy herd improvement(DHI)data of 1.01 million since 2010.Multi-factor ANOVA model was used to analyze the effects of 18 factors on milk SCC and SCS,such as farm size,feeding mode,cow mattress material,milking machine type,parities,farm ages,measuring seasons,calving season and so on.On this basis,the Logistic regression model of subclinical mastitis in dairy cows was established and verified with new DHI data,in order to provide scientific basis for reducing the occurrence of subclinical mastitis in dairy cows in Jiangsu province.The main results are as follows:Results 1:The milk SCC and SCS were extremely significantly affected by 18 factors,such as farm size,feeding mode,cow mattress material,milking machine type,parities,farm ages,measuring seasons,calving season and so on(P<0.01).Among them,farm size is 5001-10000 cows,scattered bar feeding,fermentation cattle bed,the farm age and milking machine use age were 3-4 years,adopt imported rotary milking machine,wipe the breast with a towel,subclinical mastitis tests were performed twice a month,do clinical mastitis drug sensitivity test and use forklift,parity 1,autumn and winter calving,previous SCS 0 is low,SCC and SCS in milk are relatively small.Farm size is 1001-2000 cows,tie-down breeding,saw dust pad material,pipe milking machine,domestic milking machine,the milking machine should be used for 1-2 years,the wiping material is disposable paper towel,and the replacement of milk lining is the same as the original factory,there is no laboratory in the cattle farm,the detection frequency of recessive mastitis is once a month,no clinical mastitis drug sensitivity test,artificial automatic suction truck,the farm age is more than 10 years,parity 5 and above,autumn measurement,spring calving,the 13th lactation month,the progenitor cells were divided into 9 points,and the milk SCC and SCS were relatively large.Results 2:Incidence of subclinical mastitis in dairy cows were extremely significantly affected by 18 factors,such as farm size,feeding mode,cow mattress material,milking machine type,parities,farm ages,measuring seasons,calving season and so on(P<0.01).Among them,cows with farm size is 1000-2000 cows,tie-down breeding,saw dust pad material,pipe milking machine,domestic milking machine,the milking machine should be used for 1-2 years,the wiping material is disposable paper towel,and the replacement of milk lining is the same as the original factory,there is no laboratory in the cattle farm,the detection frequency of recessive mastitis is once a month,no clinical mastitis drug sensitivity test,no clinical susceptibility test for mastitis,artificial automatic suction truck,the farm age is more than 10 years,parity 5 and above,autumn measurement,spring calving,the end of lactation,the progenitor cells were divided into 9 points had a higher incidence than the other levels.The OR value of each factor at different levels was basically consistent with the actual prevalence rate of subclinical mastitis.Based on 18 influencing factors,the Logistic model for risk assessment of subclinical mastitis in dairy cows was established as follows:Logit(P)=-6.848-0.201× X1+0.411 × X2-0.016 × X3-0.032 ×X4+1.042 × X5-0.125 ×X6-0.269 × X7-0.277 × X8+1.265 ×X9+0.55× X10+0.211×X11+0.369 × X12+0.293 ×X13+0.047× X14+0.03 × X15-0.045×X16+0.101×X17+0.451×X18.The model was used to verify the new DHI data,and the prediction accuracy reached 87.51%.Conclusion:The 18 influencing factors,such as different farms,farm size and feeding methods,all had extremely significant effects on SCC,SCS and the incidence of subclinical mastitis.Based on 18 influencing factors,a Logistic model for risk assessment of subclinical mastitis in dairy cows in Jiangsu was established.The prediction accuracy was 87.51%,which could be used to predict the incidence risk of subclinical mastitis in actual Holstein cows. |
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