Inflammatory and metabolic markers in postpartum dairy cows developing chronic reproductive tract disease: A case-control study

We investigated associations of early postpartum systemic inflammatory and metabolic markers with different manifestations of chronic reproductive tract inflammatory disease (RTID) in Holstein cows. A retrospective case-control study was conducted using data from 1,509 cows in 2 commercial dairy herds in Ontario, Canada. Herds were visited twice weekly, and cows were sampled at 2 and 6 ± 2 DIM to measure serum haptoglobin (Hp), total Ca, and nonesterified fatty acids; at 5, 8, 11, and 15 ± 2 DIM for blood BHB; and at 21 and 35 ± 3 DIM for serum Hp. Cows with a calving-related or clinical disorder before 35 ± 3 DIM were excluded, and only clinically healthy cows were evaluated (n = 355 primiparous and 548 multiparous). Purulent vaginal discharge (PVD), via Metricheck (Simcro), and endometritis (≥6% PMN in endometrial cytology), via cytobrush, were assessed at 35 ± 3 DIM. Disease status was classified as subclinical endometritis (SCE, endometritis without PVD; n = 147), PVD (PVD without endometritis; n = 64), clinical endometritis (CE, endometritis with PVD; n = 73), or healthy controls (no PVD and no endometritis; n = 619). Data were analyzed with multivariable linear regression models with disease status as fixed effects and blood markers as outcomes and logistic regression models with blood markers (continuous scale), parity, and interactions as predictors and disease status (compared with healthy) as outcomes, both including covariates and herd as a random effect. Concentrations of Ca were lower in CE than in SCE, PVD, or healthy at 2 and 6 DIM. Concentrations of Hp were greater in CE or SCE than in PVD or healthy at 2 and 6 DIM. At 6 DIM, Hp concentration was positively associated with greater odds of SCE or CE, and BHB at 15 DIM with greater odds of SCE or PVD. In primiparous cows only, Ca concentration at 2 DIM was negatively associated with the odds of CE. The present data suggest that transition period maladaptation, characterized based on different markers of systemic inflammation or metabolic imbalance, predispose cows to develop different manifestations of RTID.