Subclinical Mastitis Detected during the Last Gestation Period Can Increase the Risk of Stillbirth in Dairy Calves

We hypothesized that subclinical mastitis detected during the last gestation period can increase the risk of stillbirth in dairy calves. The aim was to investigate the relation of subclinical mastitis detected during the last gestation period and its pathogens with the stillbirth of calves. Cows from the 210th day of pregnancy were selected for the study. They were divided into two groups: the first group-subclinical mastitis was confirmed on the farm by the California mastitis test (CMT); the second group of cows-mastitis was not confirmed by the CMT test. Groups of cows were compared according to the results of their calving-the number of stillborn calves. A stillborn calf was defined as a calf that dies at birth or within the first 24 h after calving, following a gestation period of 260 days. Our results suggest that decreasing the incidence of subclinical mastitis during the last gestation period (from the 210th day of pregnancy) can decrease the risk of stillbirth in dairy calves. Further, it is important to identify the pathogen because the highest risk of stillbirth was found in cows with mastitis caused by , , , pathogenic Staphylococci and other Streptococci. Cows at the first calving had a 1.38-1.65-times higher risk of having stillborn calves than cows of parity ≥ 2. From a practical point, veterinarians and farmers can consider the effect of subclinical mastitis during late gestation on the risk of stillbirth and it could help for strategies of optimizing reproductive performance in dairy cows.