Neonatal changes in the plasma levels of cortisol, cortisone and aldosterone in the calf.

Plasma levels of cortisol, cortisone and aldosterone were measured during the first 20 days of life in 10 healthy calves. Cortisolemia, high at birth, decreased from birth to day 15. Changes in plasma cortisone were similar to those of cortisol. The value of the cortisol/cortisone plasma ratio increased from birth to day 8 and remained steady until day 20. A positive correlation was found between plasma levels of cortisol and cortisone, during the 6- to 20-day period; no correlation was observed before that. These results raise the question of whether, as is assumed in the human, maternal cortisol would cross the placenta with conversion to cortisone in the bovine. Plasma aldosterone increased from day 1 to day 3, and decreased steadily until day 20 when its level was very low. Negative correlation found between the values of aldosterone and sodium led us to think that natremia regulation by this hormone could be functional in the neonatal calf.