Elevated plasma cortisol during induced and spontaneous hypocalcemia in ruminants.

The relationship of cortisol in blood plasma with plasma calcium and phosphorus was studied from 3 days before to 2.5 days after calving in 12 dairy cows (third or more parity). Cows were in three groups: 1) paretic (displayed hypocalcemic and lateral recumbency), 2) nonparetic (plasma calcium at least 8.0 mg/100 ml), and 3) borderline (plasma calcium less than 8.0 mg/100 ml). Cortisol concentrations from 0 to 1.5 days postpartum reflected the state of calcium stress of the groups, paretic more than borderline and borderline more than nonparetic. Phosphorus was lower from 0 to 1 day postpartum in paretic cows. Calcium and phosphorus were negatively correlated (within cow) with cortisol (-.53, -.37). In experiments with goats, cortisol was released in response to hypocalcemia and displayed no activity in initiating an onset of hypocalcemia when given exogenously. Also, the observation that cortisol-treated goats responded less severely with calcium depression and recovered faster from induced hypocalcemia by ethylene glycol-bis (beta-amino-ethyl ester) N,N'-tetraacetic acid infusions suggests cortisol may aid the animal in recovering from hypocalcemia.