Association of progesterone concentration and lactation number on percentage of endometrial polymorphonuclear cells in dairy cows

The objectives of this study were to assess the association between progesterone concentration and lactation number with the percentage of endometrial polymorphonuclear cells (PMN) obtained by low volume lavage (LVL) for the diagnosis of subclinical endometritis in dairy cows. Dairy cows at 30days in milk (DIM), were clinically examined and reproductive tract were evaluated for any abnormality. Cows (n=150) with sound reproductive tract were included in this study. Endometrial cytology (LVL) and blood (tail vessels) samples were obtained at 30 DIM and at 40 DIM, and used for measuring percentage of PMN and Progesterone concentration, respectively. Two-blinded operators determined the percentage of PMN obtained by cytology. Data were analyzed with PROC FREQ, PROC CORR and PROC GLIMIX, in SAS 9.1. There was a significant negative correlation between serum progesterone concentration and percentage of PMNs (r = -0.58, P2 and peripheral progesterone concentrations >1 ng/mL were significantly associated with lower PMN percentages at 40 DIM (P = 0.0041, 0.0187, respectively). According to the current study, cows with higher serum progesterone level, had lower chance of displaying subclinical endometritis assessing with the evaluation of PMNs% in the uterus at 40 DIM. This finding can be explained by the fact that the cows with higher serum progesterone level start estrous cycle earlier, which is prerequisite step for cleaning the postpartum uterus.