Plasma concentrations of progesterone in female red deer (Cervus elaphus) during the breeding season, pregnancy and anoestrus.

Concentrations of progesterone in peripheral plasma of red deer hinds were basal (less than 1 ng/ml) during lactation/seasonal anoestrus, but increased abruptly at the onset of the breeding season. Lactating hinds (N = 19) started ovarian cycles 10 days later (P less than 0.01) and conceived 16 days later (P less than 0.001) than did 13 weaned hinds. There was no evidence, from plasma progesterone values, of silent oestrus at the start of the season. Progestagen/PMSG treatment induced early ovulations in 8 anoestrous hinds but fertility was low, only 2 conceiving and giving birth. Pregnant hinds (N = 42) had high plasma concentrations of progesterone (mean 3-5 ng/ml) which declined just before parturition.