Influence of SCC Change Patterns in Milk on the Incidence of Subclinical Mastitis in Dairy Farms in Jiangsu Province from 2010 to 2020
Subclinical mastitis(SCM)in dairy cows is an asymptomatic type of mastitis,usually mani-fested by the increased somatic cell count(SCC),decreased milk fat content and lactose content.This re-search explored the factors affecting the incidence of SCM in dairy farms in Jiangsu under the influence of SCC change patterns,853 936 records of dairy herd improvement(DHI)records were collected from 2010 to 2020 in 14 dairy farms in Jiangsu.Based on the division of 4 SCC change patterns(continuously healthy,newly infected,cured and persistently infected),the Chi-square test was used to explore the effects of dif-ferent farm sizes,parities,calving seasons,calving intervals and 305-days milk production on SCC change pattern.The results showed that the percentages of the four patterns in the records were:83.52％(contin-uously healthy)＞6.02％(newly infected)＞5.89％(persistently infected)＞4.57％(cured).There were extremely significant differences in the distribution of SCC patterns between different levels of each factor(P＜0.01).Among them,cattle in small and medium-sized farms and with high parity,spring cal-ving,calving interval greater than 441 d and 305 d milk yield of 13 001～15 000 kg had a higher SCC in the next lactation month,which increased the risk of SCM in dairy cows.Cattle in farms with a size of more than 5 000 cattle,of parity 1,autumn calving,and with a milk yield of 9 001～11 000 kg in 305 days were continuously healthy in high proportion.The results indicate that farm size,parity,calving season,calving interval,and 305-day milk production have extremely significant effects on the SCC change patterns in Holstein cows,which provides reference for the prevention of SCM in Jiangsu large-scale farms.
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