Assessment of systemic inflammation following oral calcium supplementation in healthy postpartum multiparous dairy cows-A randomized controlled trial.

Around parturition, dairy cows inevitably and perhaps necessarily experience some degree of systemic inflammation, but when excessive or dysregulated, it may contribute to health disorders. As immune activation decreases blood Ca, greater extracellular Ca availability may potentiate or sustain inflammation. We hypothesized that in clinically healthy multiparous cows, postpartum administration of supplemental Ca would increase serum concentrations of inflammatory markers. The objective of this randomized controlled trial was to investigate a possible effect of supplementing calcium (Ca) on postpartum systemic inflammation in dairy cows. Healthy cows (n = 101) from 2 commercial dairy farms in Ontario calving into parity 2, 3, or 4 were enrolled. Cows were blocked by parity and randomly assigned to receive an oral bolus of Ca (42 g of Ca) within 12 h after calving and a second bolus 12 h later (TRT; n = 51), or no Ca supplementation (CON; n = 49). Concentrations in serum of total Ca (tCa), haptoglobin (Hp), and albumin (ALB) were assessed at d 0 (within 12 h postpartum), 0.5 (12 h later), 1, 2, 4, 6, and 8 postpartum; ionized calcium was assessed at d 0, 0.5, 2, and 4, and lipopolysaccharide-binding protein (LBP) and serum amyloid A (SAA) were assessed at d 0, 2, and 4. Multivariable linear regression models of each outcome accounting for repeated measures included treatment, parity (2 vs. 3 or 4), farm, sampling day, baseline concentration (d 0), and interactions of treatment with farm, parity, and day. Results are presented as least squares means and 95% confidence intervals. Concentration of tCa tended to be greater at d 0.5 (TRT 2.07 mmol/L [2.03-2.12]; CON 2.01 [1.96-2.06]) but was lesser at d 2 (TRT 2.18 [2.13-2.23]; CON 2.27 [2.23-2.32]) in TRT than CON cows. Concentrations of LBP were greater in TRT (2.28 ng/mL [2.06-2.50]) than CON (1.99 [1.77-2.21]) in parity 2, but not different in older cows (TRT 2.28 ng/mL [2.06-2.50]; CON 1.99 [1.77-2.21]). Concentrations of SAA were greater in TRT than CON cows at d 2 (TRT 135 ug/mL [124-146]; CON 114 [75-106]). Treatment had no effect on ALB or Hp. In clinically healthy cows, oral Ca supplementation had a small transient effect on blood tCa and little indication of increasing inflammation based on the analytes evaluated.