J. A. Seminara, C. R. Seely, and J. A. A. McArt
Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853
Calcium dysregulation at 4 DIM, or dyscalcemia, is common among multiparous Holstein cows and has been associated with increased risk of disease, decreased intake and production, and poor reproductive performance. Systemic inflammation early in lactation is well documented and has also been associated with suboptimal outcomes. The objective of this case-control study was to explore differences in the acute phase response, an important inflammatory process, between cows with and without dyscalcemia. We hypothesized that cows with dyscalcemia would experience more extreme inflammatory activation than eucalcemic cows. Blood was collected from multiparous Holstein cows on 2 farms in central New York, 1 to 3 d before parturition and once every 24 h postpartum through 4 DIM. Samples were analyzed at each timepoint for tCa and 3 acute phase proteins (APP): serum amyloid A (SAA), lipopolysaccharide binding protein (LBP), and haptoglobin (HP). Using 4 DIM serum samples, dyscalcemic cows (tCa < 2.2 mmol/L; n = 20) were matched with eucalcemic cows (tCa ≥ 2.2 mmol/L; n = 36) such that the final proportion of dyscalcemic cows in the study population would be comparable to the dyscalcemia prevalence on U.S. commercial herds (~35%). Patterns of APP over time were compared using linear mixed effects models including the fixed effects of calcium group, DIM, parity group (2, 3, or ≥4), farm, all relevant 2-way interactions, and the random effect of cow. Overall, the dynamics of APP showed that dyscalcemic cows experienced increased acute phase responses compared to eucalcemic cows. Dyscalcemic cows had elevated concentrations of HP, SAA and LBP starting at 2 DIM (HP & SAA: P < 0.001; LBP: P = 0.04). This work, though preliminary in nature, strongly supports the hypothesis that dyscalcemia and excessive inflammation are associated in postpartum dairy cows. While the causal structure of this relationship remains unknown, improved understanding of inflammation and dyscalcemia may provide insight into mechanisms by which some cows become maladapted to the early postpartum period.
Key words: dyscalcemia, inflammation, serum amyloid A, haptoglobin, lipopolysaccharide binding protein