Risk factors associated with postpartum subclinical hypocalcemia in dairy cows

Area of Science:

• Veterinary Medicine
• Animal Science
• Dairy Production

Background:

• Subclinical hypocalcemia (SCH) is a metabolic disorder in dairy cows, impacting herd health and productivity.
• Early identification of risk factors is crucial for effective management and prevention strategies.

Purpose of the Study:

• To assess the relationship between prepartum plasma magnesium and subclinical hypocalcemia (SCH) at parturition.
• To identify cow-level risk factors associated with SCH at calving and 2 days in milk (DIM).

Main Methods:

• A cohort study involving 301 dairy cows from two New York herds.
• Blood samples analyzed for plasma macrominerals (Ca, K, Mg, P), albumin, and β-hydroxybutyrate at prepartum, calving, and 2 DIM.
• SCH defined as postpartum calcium concentrations ≤2.1 mmol/L.

Main Results:

• Prevalence of SCH at calving was 2% (first parity), 40% (second parity), and 66% (third+ parity).
• Prepartum calcium levels ≤2.4 mmol/L and third+ parity were associated with higher SCH risk at calving (RR=1.4 and 1.7).
• SCH at 2 DIM was linked to calving calcium status and lameness, with nonlame cows (Ca ≤2.1 mmol/L) and lame cows (normocalcemic) at parturition at higher risk.

Conclusions:

• A prepartum calcium threshold can identify cows at higher risk for SCH at calving.
• Risk factors for SCH vary depending on the timing of diagnosis relative to parturition.
• Prepartum magnesium levels were not sufficiently low to assess their association with SCH in this study.