Desempenho reprodutivo de vacas leiteiras naturalmente infectadas por Neospora caninum

Abstract

The demand for better reproductive performance of the dairy cows is necessary to minimize economic losses direct by improvably herd fertility or indirect by milk production. Abortion is one of the reasons that reflect negatively on the reproductive performance of a herd. Neospora caninum infection is recognized as an important cause of abortion in dairy cattle worldwide. Reproductive losses in the dairy industry due to neosporosis abortions include professional assistance, reduced milk production and culling. Abortion beyond the loss of pregnancy and the period that the female is unproductive in the herd may lead to retained placenta and uterine infections. Considering the importance of N. caninum infection in dairy cattle, this study evaluated the influence on reproductive parameters of seropositive and seronegative dairy cows. The study was performed on six herds with a total of 839 cows and 395 heifers. The percentage of seropositive cows was 20.4% (171/839) and 18.2% (72/395) in heifers. Abort occurred on 30.4% in seropositive and 3.2% in seronegative dams. Sixteen fetuses obtained from seropositive cows, seven showed a positive RT nested PCR reaction. The main infectious cause of abortion in N. caninum seronegative cows was Leptospira sp. Occurrence of retained placenta and uterine infections was higher in cows that had aborted. The reproductive performance was lower in aborted cows as a higher number of inseminations were needed to obtain conception and a greater interval between abortion and the next conception in cows that had abort and had uterine infection. The data showed evidence that the higher the percentage of seropositive cows in the herds, the greater the negative impact on reproductive rates.