Gross reduction in size and histologic repair of the endometrium are complete in dairy cows by 40 to 50 days after calving. For the first two weeks after calving, cows normally expel lochia, which may range in color from dark red or brown to white. If involution is delayed, discharge of lochia may continue until 30 days postpartum. The producer shouldn't consider the discharge of lochia abnormal unless the fluid is fetid, continues to be discharged for longer than 30 days or the cow develops other clinical signs. Some cows do develop uterine infections.
Many factors influence the severity and prevalence of uterine infections in cows.
They include the species and pathogenicity of the causative organism, defenses and dietary management of the affected animal, and environmental sanitation. Bacteria contaminate the uterus of all cows during parturition. Most of the organisms are merely transient residents of the reproductive tract and the involuting uterus in normal cows eliminates them. In cows that develop uterine disease, Corynebacterium pyogenes persists in the uterus and is the most significant cause of disease. In addition, gram-negative anaerobic bacteria are frequently isolated from cases of severe uterine disease.