Lack of association of Neospora caninum infection with late embryo losses in grazing dairy cow

QUINTERO RODRIGUEZ, L.E.; CAMPERO, L.M.; MORÉ, G.; DOMINGUEZ, G.; VENTURINI, M. C.; DE LA SOTA, R.L.; MADOZ, L.V.; GIULIODORI, M.J.

Simposio; 10th International Ruminant Reproduction Symposium (IRRS 2018); 2018

The fertility of high-producing, lactating dairy cows has decreased during the last decades. Pregnancy losses in dairy cows are an important aspect of infertility leading to poor economic performance. Late embryo losses (LEL) are assumed to be of multifactorial origin, with N. caninum infection being a potential cause. The objective of this study was to evaluate the association of N. caninum infection with LEL in grazing dairy cows. A case-control study was carried out in a commercial dairy herd (32°49 ́ S, 62°52 ́ W, Argentina) in which Holstein cows (n=92) were enrolled. Pregnancy was diagnosed by ultrasonography at 30-44 days post-insemination. Lack of heart beats, identification of membrane detachment, and disorganization or echoic floating structures including embryo remnants were used as indicators of LEL (CASE cows). Cows with positive pregnancy diagnosis on the same date of each case were considered as control (CON) and the ratio of case-control was 1. For each case animal, the conceptus was sampled (day 0) with an insemination pistol attached to a 10-mL syringe and transported at 4°C in a 1.5-ml tube. Cows were bled on days 0 and 30 for serological studies. Blood samples were refrigerated at 4°C and transported to the laboratory within 24 h, centrifuged and sera were stored at - 20°C until analysis. Sera were tested by indirect fluorescent antibody test (IFAT) for the detection of antibodies against N. caninum using a cut-off titer of 1:200 and processed to final titer. The DNA from conceptuses from seropositive cows was extracted using a commercial kit according the manufacturer's recommendations. The DNA samples were analyzed by PCR with the specific primer pair Np6+/Np21+ for N. caninum. Chi squared test was used to detect differences between groups and P