基于母女对设计的三河牛隐性乳房炎诊断阈值及影响因素分析OA

[Objective]Bovine mastitis is a common multifactorial disease that adversely affects production performance,cow health,and milk hygiene safety.This study aimed to elucidate the influencing factors of lactation performance and subclinical mastitis traits in Sanhe cattle,and determine the diagnostic threshold of somatic cell count(SCC)for subclinical mastitis,thereby providing a scientific basis for genetic improvement of Sanhe cattle populations in Inner Mongolia.[Method]A total of 30 Sanhe cattle(15 dam-daughter pairs)were included in this study.Dairy herd improvement(DHI)testing and California mastitis test(CMT)were conducted every 5 days for four consecutive times.Based on 115 DHI records and 442 CMT records,the population characteristics and background patterns of lactation performance traits and CMT scores were analyzed.Subsequently,a linear mixed model(LMM)and an ordinal multinomial logistic regression model(OMLRM)were applied to investigate the influencing factors of lactation performance and subclinical mastitis traits in Sanhe cattle.Finally,Youden's index(J)was used to determine the optimal decision threshold for identifying high-risk subclinical mastitis cases.[Result]Sanhe cattle were characterized by high lactose percentage,high protein percentage,and low somatic cell score(SCS),indicating generally favorable lactation performance.Parity,year-season(Ys),and group had significant effects on certain lactation performance traits(P<0.05).SCS effect had an extremely significant influence on subclinical mastitis traits(P<0.01),and stage significantly affected some lactation performance traits as well as subclinical mastitis traits(P<0.05).Moreover,when SCC exceeded 120 000/mL,Youden's index showed a marked downward trend.Therefore,120 000/mL was recommended as SCC diagnostic threshold for subclinical mastitis in Sanhe cattle.[Conclusion]Using 120 000/mL as SCC diagnostic threshold for subclinical mastitis in Sanhe cattle,in combination with CMT,could effectively improve the accuracy and standardization of subclinical mastitis detection in Sanhe cattle populations in Inner Mongolia.