Reproduction and Productivity in Dairy Cattle after Abortions Both Related and Unrelated to Coxiella burnetii

SIMPLE SUMMARY: The bacterium C. burnetii, causing Q fever in humans and animals, is widespread worldwide, but the true extent of C. burnetii spread is not always known. Q fever in ruminants is mainly associated with abortions and reproductive disorders. However, there is a lack of research on what happens to animals after abortion and whether reproduction and productivity in animals with C. burnetii-related abortions differs from those with abortions that are unrelated to C. burnetii. In our study, we compared data on abortions, outcome of the animals after abortions both related and unrelated to Coxiella burnetii, and the reproduction and productivity data for animals which had aborted to the herd average parameters. We found that C. burnetii-related abortions are more often observed in older cows, but there were no significant differences between groups for the other compared indicators. We found that abortions, both related and unrelated to C. burnetii are economically unprofitable due to a high culling rate and due to the reproductive problems caused by abortions resulting in the absence of new pregnancies. When comparing the productivity data of animals that had aborted to the herd average, we found it to be lower if the animal had started a new lactation after an abortion. ABSTRACT: C. burnetii is a widespread pathogen, causing abortions and reproductive disorders in ruminants. The study aimed to evaluate animal reproductive capacity and productivity after abortion, related and unrelated to C. burnetii. We compared data about the abortion time, the outcome of the animals after an abortion, further reproduction, and productivity for C. burnetii-positive (n = 148) and C. burnetii-negative (n = 149) aborted dairy cows and heifers. C. burnetii-positive animals had a positive serological response or presence of C. burnetii DNA at the time of abortion. C. burnetii-positive animals had a significantly higher number of lactations at the time of abortion. However, in the other indicators, we observed no significant differences between the groups. Comparing indicators of all the aborted animals, we found that if animals started a new lactation after abortion, they had a significantly lower milk yield, lower fat, protein, and somatic cell counts (SCCs) in milk during the standard lactation for both primiparous and multiparous cows compared to herd averages in each group. Lower SCCs can be due to animals with a high SCC being culled earlier. We found an economic disadvantage to aborting, not only because of the loss of offspring, but also because of the high culling rate and lower productivity in both primiparous and multiparous cows.