Predictive value of prepartum amino acid and biochemical profiles for hypocalcemia in Holstein dairy cows.

Hypocalcemia occurs at the onset of lactation when homeostatic mechanisms are unable to maintain calcium homeostasis. In transition cows, amino acids are important components of protein metabolism. This study investigated the predictive ability of amino acid and metabolic profile parameters for hypocalcemia, their levels during the disease, and their potential roles in its pathogenesis. A total of 60 Holstein dairy cows, 10 ± 3 days before calving, were enrolled in the study and followed throughout the transition period. Of the cows included in the study, 10 remained disease free, while 16 developed hypocalcemia. The predictive power of 3-methylhistidine at a cutoff value of 8.30 µmol/L was 85%; that of aspartic acid at a cutoff value of 3.43 µmol/L was 77%; that of hydroxylysine at a cutoff value of 9.20 µmol/L was 82%; that of total bilirubin at a cutoff value of 0.018 mg/dL was 80%; that of low-density lipoprotein (LDL) at a cutoff value of 20.70 mg/dL was 88%; and that of cholesterol at a cutoff value of 84.1 mg/dL was 80%. Glycine showed 90% predictive power for changes of ≥ 35%. This study identified various amino acids and biochemical parameters that may contribute to the pathogenesis of hypocalcemia. It showed that prepartum 3-methylhistidine, aspartic acid, hydroxylysine, total bilirubin, LDL, cholesterol, and glycine may serve as predictive markers.