Associations between periparturient calcium dynamics of multiparous Holstein cows and inflammation markers during the transition period.

Recent work has established that proper classification of cows based on their periparturient status has important implications for risks of health, production, and reproduction outcomes during the postpartum period. However, the dynamics of blood calcium (Ca) status and inflammation are far less understood. The objective of this study was to determine the relationship between subclinical hypocalcemia (SCH) dynamics and periparturient circulating serum amyloid-A (SAA), haptoglobin (Hp), tumor necrosis factor-α (TNFα), interferon-γ (IFNγ), and interleukin-10 (IL-10) concentrations, DMI, and milk production during the first 9 wk of lactation. Data collected from multiparous Holstein cows (n = 96) were retrospectively classified into 1 of 4 calcemia groups based on blood concentrations of total Ca (tCa) at 1 and 5 DIM: normocalcemic (NC; [tCa] >1.95 mmol/L at 1 DIM and >2.32 mmol/L at 5 DIM, n = 53); transient SCH (tSCH; [tCa] ≤1. 95 mmol/L at 1 DIM and >2.32 mmol/L at 5 DIM, n = 15); delayed SCH (dSCH; [tCa] >1. 95 mmol/L at 1 DIM and ≤2.32 mmol/L at 5 DIM, n = 15); and persistent SCH (pSCH; [tCa] ≤1. 95 mmol at 1 DIM and ≤2.32 mmol/L at 5 DIM, n = 13). The MIXED procedure of SAS (v. 9.4, SAS Institute Inc.) was used to analyze pre- (-28 and -1 d relative to calving) and postpartum (1, 3, 5, and 7 DIM) blood mineral concentrations, SAA, Hp, cytokines, milk production, and differences between Ca groups, using repeated measures for time. Prepartum blood concentrations of IL-10 tended to be greater in tSCH cows compared with NC, dSCH, and pSCH. Postpartum concentrations of Hp, SAA, and TNFα were different by Ca group. Concentrations of SAA and Hp were highest in the pSCH group at d 3, and TNFα was highest for cows categorized as dSCH, irrespective of time. Overall, our results suggest that cows experiencing different SCH dynamics display different patterns of inflammatory markers and that elevated concentrations of proinflammatory biomarkers accompany some categories of hypocalcemia during the early lactation period.