Dynamics of bacteriologic and cytologic changes in the uterus of postpartum dairy cows.

The objectives of this study were to characterize clinical, intrauterine, bacteriologic and cytologic changes during the first month after parturition in healthy dairy cows and in cows with subclinical endometritis (SE) or clinical endometritis (CE). Furthermore, risk factors related to clinical bacteriologic and cytologic findings were determined. A total of 170 calvings were enrolled, and intrauterine samples were collected on Days 0, 3, 9, 15, 21, and 28 postpartum using the cytobrush technique. The presence of Escherichia coli and Trueperella pyogenes was determined by Fourier transform infrared spectroscopy. The cows were categorized according to their uterine health status (UHS) on Day 21 as healthy (clear or absent vaginal discharge and <5% polymorphonuclear cells [PMN] in the cytologic sample), SE (clear or absent vaginal discharge and ≥5% PMN), or CE (vaginal mucus containing any signs of pus). The prevalence of SE and CE on Day 21 was 27.9% and 58.4%, respectively. Generally, samples from cows with SE and CE showed a greater bacterial growth density (BGD) than those from healthy cows. The BGD tended to be affected by the interaction of time by UHS (P = 0.057). Differences between healthy, SE, and CE cows were found from Day 3 to the last sampling day. Furthermore, the percentage of PMN differed between healthy, SE, and CE cows and was affected by time in a cubic way (decrease/increase/decrease). Overall, E coli was found in 25.4% of the samples, and T pyogenes was identified in 30.2% of the samples. The risk for CE was increased by BGD and the presence of T pyogenes. Conversely, the presence of E coli had no effect on the risk of CE or the risk of SE. The risk for an infection with T pyogenes was greater in the first-parity cows and in cows with assisted calving. In conclusion, changes in BGD and proportion of PMN varied with the UHS (healthy, SE, and CE), which was affected by the presence of T pyogenes but not E coli.