Periparturient changes in osteoimmunological markers and their association with hypocalcemia in dairy cows.

BACKGROUND

The transition period in dairy cows is associated with major metabolic adaptations, including increased calcium demand and altered bone metabolism. Osteoimmunological markers may reflect these changes and contribute to the prediction of periparturient hypocalcemia.

HYPOTHESIS/

OBJECTIVES

Evaluate osteoimmunological markers during the periparturient period and their association with parity and hypocalcemia in dairy cows.

ANIMALS: Sixty-six Fleckvieh, Holstein-Friesian, and New Zealand Friesian dairy cows and heifers from a research herd.

METHODS

Blood samples were collected at -21, -14, -7, and -0 days before calving, at calving, and at +0, +1, +3, +7, and + 14 days postpartum. Serum concentrations of total calcium, alkaline phosphatase (AP), C-terminal cross-linked telopeptide of type I collagen (CTX-I), osteocalcin (OC), receptor activator of nuclear factor κB (RANK), receptor activator of nuclear factor κB ligand (RANKL), and osteoprotegerin (OPG) were measured. Cows were classified according to postpartum serum calcium concentrations as normocalcemic, subclinical hypocalcemic, or low-calcium. Receiver operating characteristic (ROC) analysis was used to evaluate predictive performance.

RESULTS

The CTX-I concentrations were higher in primiparous and normocalcemic cows compared with low-calcium cows. Activity of AP was increased in normocalcemic cows during early lactation. OC, RANKL, and OPG showed no consistent association with calcium status. Concentration of CTX-I demonstrated high predictive value for hypocalcemia before calving (AUC, 0.75-0.90), whereas AP showed moderate and RANK limited predictive value.

CONCLUSIONS AND CLINICAL

IMPORTANCE

Markers of bone resorption, particularly CTX-I, were associated with calcium homeostasis during the transition period and may help identify cows at risk for periparturient hypocalcemia before clinical manifestations.