Effect of vaccination against Leptospira interrogans serovar hardjo on milk production and fertility in dairy cattle.

摘要

In 3 dairy herds with evidence of active L. interrogans serovar hardjo infection, half the 183 cows were vaccinated s.c. with 2 doses, 4 weeks apart, of killed hardjo vaccine and the remaining animals served as controls. Booster vaccinations were given to vaccinated cows still present one year later. The farmers were unaware which cows were vaccinated during the trial. A comparison of the records for the vaccinated and non-vaccinated cows (200 and 215 records, respectively) showed that the 305 daymilk yield was not affected by vaccination since the affects of hardjo on milk yield appear to be transitory, but the herd fertility status was improved in vaccinated animals as a result of higher first service and overall conception rates and lower culling rates in these animals. It is suggested that vaccination may control the low fertility associated with hardjo infection by the elimination of uterine infection but larger studies are required to confirm this.