Plasma catecholamine concentrations in lambs and calves during the perinatal period

Concentrations of the plasma catecholamines (CA), adrenaline, noradrenaline and dopamine, were measured using a specific and sensitive radioenzymatic assay in 7 ewes and their single lambs chronically catheterized in utero between days 127 and 145 of gestation and during the first week of postnatal life. These concentrations were also measured during the first month after birth in 18 Holstein x Friesian calves, of which 9 were born spontaneously at term (278 days) and 9 by caesarean section on day 260 of gestation. Plasma CA concentrations in ewes showed no significant variations during the sampling period. Plasma adrenaline, noradrenaline and dopamine concentrations in lambs at birth rose significantly to 1 800 +/- 520, 3 782 +/- 781 and 575 +/- 90 pg/ml, respectively. These values remained higher than those measured in ewes until 2, 24 and 48 h after birth, respectively. On days 5 and 10 after delivery, plasma dopamine and noradrenaline concentrations were higher in calves delivered by caesarean section than in those born spontaneously at term, while plasma adrenaline concentration was never different between the two groups. These results indicate that the surge in plasma CA concentration normally occurring at birth might be delayed post partum in animals delivered before term. This might partly explain why these animals were less resistant to stress during the first days of postnatal life.