Relationships between endometritis and metabolic state during the transition period in pasture-grazed dairy cows.

The primary objective of this study was to identify relationships between endometritis and metabolic state during the calving transition and early lactation periods. A subset of mixed age and breed dairy cows (n=78) from a seasonal, pasture-grazed herd of 389 cows was examined. The selected cows were grouped as having endometritis at d 42 postpartum or being unaffected by endometritis. Endometritis was defined as >6% (upper quartile) of uterine nucleated cells being polymorphonuclear cells (H-PMN; n=38); unaffected by endometritis was defined as ≤1% of nucleated cells being polymorphonuclear (L-PMN; n=40). Milk yield was determined at each milking, and milk composition (fat and protein) was determined at 2-wk intervals. Blood samples collected on d -14, 0 (d of calving), 4, 7, 14, 28, and 42 were analyzed for indicators of energy status (nonesterified fatty acids, glucose, and urea), liver function (albumin, globulin, glutamate dehydrogenase, and aspartate aminotransferase), inflammation (haptoglobin), and mineral status (Ca and Mg). Samples collected weekly from d 21 to 63 or 70 were analyzed for progesterone content. The postpartum anovulatory interval was defined to end on the first day postpartum that plasma progesterone concentration was ≥1 ng/mL. A greater percentage of H-PMN cows failed to ovulate before d 63 or 70 (34%) compared with L-PMN cows (10%), although the proportions of cows ovulating within either polymorphonuclear group was similar through d 56 postpartum. Plasma concentrations of albumin and the albumin:globulin ratio were consistently lower in H-PMN cows. Plasma Mg was lower, whereas glutamate dehydrogenase and aspartate aminotransferase were higher, in H-PMN cows during early lactation compared with L-PMN cows. Circulating metabolites indicative of energy status (nonesterified fatty acids, glucose, and urea) were not different between polymorphonuclear groups. Among 3- to 5-yr-old cows, daily milk yield for the first 42 d after calving was lower for H-PMN cows than for L-PMN cows. Among cows >5 yr old, protein percentage was lower in H-PMN cows compared with L-PMN cows. In summary, endometritis at 42 d postpartum in the herd studied was associated with an increased likelihood of remaining anovulatory. These cows had lower albumin concentrations throughout the calving transition period, perhaps indicating impaired liver function, with lower plasma Mg and evidence of hepatocellular damage in early lactation. Similar profiles of nonesterified fatty acids and glucose indicated that energy status was not a risk factor for endometritis.