Effects of Neospora caninum on reproductive parameters in dairy cows from a closed herd in Brazil.

Dairy production and cattle reproductive parameters exhibit a strong relationship, which can be disrupted by infectious agents, such as Neospora caninum, that affect the reproductive tract of these animals. Neosporosis is a major cause of abortion in cattle worldwide and is responsible for substantial economic losses. We evaluated the impact of N. caninum infection on the reproductive parameters of 434 Holstein dairy cows from a herd in Brazil that had been closed for 4 years through the assessment of serological testing and reproductive parameters. Dairy cows older than 24 months and that required at least 2.2 inseminations to become pregnant had a higher frequency of seropositive results. Analysis of the medians of positive and negative cows revealed that seropositive cows tended to require more insemination efforts to achieve pregnancy and showed a 2-month increase in age at first calving. According to the reproductive parameters, the correlation coefficient was higher in seronegative animals, while no such correlation was detected in seropositive cows. Thus, we concluded that N. caninum negatively affects the reproductive parameters of dairy cows kept in a closed herd.