Dairy cows experience a temporary disturbance in mineral homeostasis around parturition. Approximately 5% of periparturient dairy cows develop parturient paresis as a result of calcium (Ca) loss in milk, and hypomagnesemia is a predisposing factor for parturient paresis [1]. Moreover, hypophosphatemia cannot be prevented in parturient cows by depleting milk production
via a mastectomy [2].
The rise in plasma cortisol concentrations before parturition is caused by the fetus and is recognized as a signal for the initiation of parturition.
However, paretic cows exhibit significantly higher concentrations of cortisol on the day of calving [2,3], suggesting that cortisol secreted from the maternal
adrenal gland may be relevant to the course of hypocalcemia.
Additionally, it has been suggested that decreased blood inorganic phosphate (Pi) concentrations in mastectomized parturient cows are caused by cortisol [2].