An epidemiological study of calcium metabolism in non-paretic postparturient Holstein cows

Data from 1021 lactations of non-paretic Holstein cows followed in 14 Québec dairy herds were used to describe calcium 'metabolism' after calving in healthy cows. Serum total calcium, phosphorus, magnesium, potassium, albumin, and glucose were measured on the first and seventh days post-calving. The distributions were described and compared between the first and seventh day postpartum. The relationships between serum calcium on the one hand and the other serum metabolites and the cow's age on the other hand were assessed using a general linear model. Serum calcium and phosphorus values were lower on the first day postpartum than a week later (2.03 +/- 0.26 vs 2.26 +/- 0.18 mmol/l, 1.78 +/- 0.48 vs 1.93 +/- 0.39 mmol/l, respectively), whereas it was the opposite for glucose, magnesium, and potassium (3.98 +/- 0.95 vs 3.12 +/- 0.60 mmol/l, 1.01 +/- 0.35 vs 0.95 +/- 0.13 mmol/l, 4.84 +/- 0.40 vs 4.69 +/- 0.38 mmol/l, respectively). Albumin values were similar (25.7 +/- 3.3 vs 25.2 +/- 3.4 g/l). On the first day postpartum, serum calcium was associated in a curvilinear fashion with age, phosphorus and albumin. It also was associated, but to a lesser extent, with glucose and magnesium, whereas it was not associated with potassium. On the seventh day postpartum, calcium was associated with age, phosphorus and with an increased importance of albumin. The results are discussed with regard to postpartum hypocalcemia, the interpretation of serum metabolite values after calving, and the use of the physiological stress at calving. We concluded that (1) postpartum hypocalcemia was an event to be expected, especially for the older cow, (2) a multivariable approach should be used to interpret biochemical profiles after calving, and (3) such profiles could be used to better assess the cow's health.