Categorization of endometritis and its association with ovarian follicular growth and ovulation, reproductive performance, dry matter intake, and milk yield in dairy cattle

Abstract

The objectives were to evaluate the effect of different categories of endometritis on follicular growth and ovulation, reproductive performance, dry matter intake (DMI), and milk yield (MY) in dairy cows. Lactating Holstein cows (n = 126) were examined for endometritis on 25 ± 1 day postpartum (DPP) using vaginoscopy, transrectal ultrasonography, and endometrial cytology to determine the presence and type of vaginal discharge, uterine fluid, and proportion of polymorphonuclear (PMN) cells, respectively. Cows that had mucopurulent vaginal discharge and/or presence of uterine fluid, no mucopurulent vaginal discharge or uterine fluid but 8% or more PMN, and mucopurulent vaginal discharge and/or uterine fluid and 8% or more of PMN were defined as having clinical (CLIN; n = 45), cytological (CYTO; n = 15), and clinical and cytological (CLINCYTO; n = 30) endometritis, respectively. Cows that had none of the above pathological conditions were classified as unaffected (UNAF; n = 36). The diameter of the largest follicle at first examination, intervals from calving to first dominant (diameter = 10 mm) follicle, preovulatory size (diameter = 16 mm) follicle, ovulation, presence of follicular cyst, and proportion of ovular cows at 35 and 65 DPP were recorded as the measures of follicular growth and ovulation. None of the ovarian follicular parameters analyzed was affected by categories of endometritis. The first service conception rate tended (P = 0.06) to differ among categories of endometritis; cows that had CLIN and CLINCYTO endometritis were four times less likely to conceive to the first insemination compared to UNAF cows. Cows that had CLIN (hazard ratio: 0.52) and CLINCYTO (hazard ratio: 0.40) endometritis had decreased likelihood of pregnancy at 150 DPP compared to UNAF cows. Similarly, cows diagnosed as having CLINCYTO endometritis had decreased likelihood (hazard ratio: 0.48) of pregnancy at 250 DPP compared to UNAF cows. The DMI and MY up to 5 weeks postpartum were not affected by categories of endometritis. In summary, categories of endometritis as determined at 25 DPP did not affect follicular growth and ovulation, DMI, or MY. However, the combined (CLINCYTO endometritis) category had a negative impact on first service conception rate and subsequent services.