Akhtar S, Riemann H P, Thurmond M C, Franti C E
Department of Epidemiology and Preventive Medicine, School of Veterinary Medicine, University of California, Davis 95616.
Vet Res Commun. 1993;17(3):183-91. doi: 10.1007/BF01839163.
The association between serological evidence of exposure to Campylobacter fetus and milk production performance was studied in 178 lactating cows from three California Dairy Herd Improvement Association herds using a cross-sectional study design in December 1986. ELISAs were used to determine the antibody titres against Campylobacter fetus, Haemophilus somnus and Leptospira hardjo, which were classified as either negative or positive. The status of a cow as negative or positive against C. fetus and H. somnus represents the serological evidence of natural exposure to the corresponding bacteria. However, the status against L. hardjo was assumed to be the level of vaccinal titre against this organism since all the cows studied had been vaccinated against this agent. The data on demographic and productivity variables relating to the current lactation of the cows were obtained from Dairy Herd Improvement Association individual cow records for December 1986. Four measures of milk production efficiency for the current lactation were used. The status against L. hardjo and other covariates suggested by previous studies were included in modelling the relationships of interest. Stepwise multiple linear regression was used to study the adjusted relationship of C. fetus with each measure of milk production efficiency. Multivariate analyses revealed that the adjusted relationships of C. fetus with the test-day's milk production, the extended 305-day milk production and the relative value of milk production were not significant (p > 0.1). However, after adjusting for possible covariates, C. fetus-positive cows had an average of 7.43% lower mature equivalent milk production than C. fetus-negative cows (p = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)
1986年12月，采用横断面研究设计，对来自加利福尼亚奶牛改良协会三个牛群的178头泌乳奶牛进行了研究，以探讨胎儿弯曲杆菌暴露的血清学证据与产奶性能之间的关联。采用酶联免疫吸附测定法（ELISA）来测定针对胎儿弯曲杆菌、睡眠嗜血杆菌和哈氏钩端螺旋体的抗体滴度，抗体滴度分为阴性或阳性。奶牛针对胎儿弯曲杆菌和睡眠嗜血杆菌呈阴性或阳性的状态代表了自然暴露于相应细菌的血清学证据。然而，由于所有研究的奶牛都已接种针对哈氏钩端螺旋体的疫苗，因此针对该菌的状态被假定为疫苗接种滴度水平。与奶牛当前泌乳期相关的人口统计学和生产力变量数据来自1986年12月奶牛改良协会的个体奶牛记录。采用了当前泌乳期的四项产奶效率指标。针对哈氏钩端螺旋体的状态以及先前研究提出的其他协变量被纳入感兴趣关系的建模中。采用逐步多元线性回归来研究胎儿弯曲杆菌与每项产奶效率指标之间的校正关系。多变量分析显示，胎儿弯曲杆菌与测定日产奶量、305天延长产奶量以及产奶相对值之间的校正关系不显著（p>0.1）。然而，在对可能的协变量进行校正后，胎儿弯曲杆菌阳性的奶牛平均成熟当量产奶量比胎儿弯曲杆菌阴性的奶牛低7.43%（p = 0.02）。（摘要截断于250字）
