Influence of subclinical hypocalcemia on plasma biochemical parameters, liver histologic changes, and common postpartum diseases in dairy cows
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We hypothesized that cows with subclinical hypocalcemia at calving would have greater elevations in liver associated biochemical parameters and non-esterified fatty acid (NEFA) concentrations compared to normocalcemic cows. One hundred multiparous Holstein cows were assigned to one of two groups 1) normocalcemic (n=49; ionized calcium [iCa] ! 1.0 mmol/L) or 2) hypocalcemic (n=51; [iCa] [less than 1.0 mmol/L) based on whole blood [iCa] on the day of calving. Blood samples were collected from all cows for measurement of [iCa], NEFA concentrations, and plasma chemistry profiles at days -14, 0 (calving), 3, 7, 14, 21, and 35. On day 0, hypocalcemic cows had lower [iCa] than normocalcemic cows (P [less than] 0.001) and lower total plasma Ca (P [less than] 0.001). Hypocalcemic cows had lower plasma phosphorus concentrations on days 0 (P = 0.002), 7 (P = 0.05), 14 (P = 0.03), and 21 (P = 0.04). Hypocalcemic cows had higher NEFA concentrations on days 0 (P = 0.01) and 21 (P = 0.02). Hypocalcemic cows also tended to have higher NEFA concentrations on day 14 (P = 0.12). Hypocalcemic cows had more lipid in the hepatocytes on day 35 (P = 0.0008). No differences were detected between groups for total or direct bilirubin concentration, gamma glutamyl transferase or aspartate aminotransferase activity (P [greater than] 0.05). These data provide evidence of an association between calcium status at calving, fat mobilization, and liver lipid infiltration.