Concentrations of progesterone in peripheral plasma of red deer hinds were basal (< 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<0\m=.\01) and conceived 16 days later (P< 0\m=.\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\p=n-\5 ng/ml) which declined just before parturition.

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Lactating (N = 12) and non-lactating (N = 6) red deer hinds and one stag at pasture were given concentrates (500 g/head) containing melatonin (5 mg/head) daily at 16:00 h from 18 June to 16 October. The stag shed the antler velvet and started rutting 5 weeks ahead of untreated stags, and hinds had their first oestrus and ovulation of the breeding season in mid-September, 5 weeks in advance of control lactating (N = 9) and non-lactating (N = 5) hinds. Treated hinds were allowed to mate with the treated stag and control hinds ran in an adjacent paddock with an untreated stag. All hinds became pregnant during the study with all but 2 melatonin-fed hinds (1 lactating, 1 non-lactating) and 1 control hind (lactating) conceiving at the first oestrus. Melatonin-treated hinds lost slightly more live weight than did controls from June to November, but their suckled calves grew throughout at a rate similar to those of control hinds.

Eighteen pregnant red deer hinds were slaughtered at known stages of gestation between 72 and 224 days (term = 233 days). The udder was removed and the gravid uterus was separated into foetal, placental, empty uterus, amniotic fluid and allantoic fluid components. Equations were fitted to the weights of each component to describe the effects of stage of gestation. Hind weight at mating had no significant effect. For the foetal weight (Y, kg) the data were closely fitted by a version of the Gompertz equation,where t is time in days from conception and . ? is the sex of the foetus (male = -1, female = 1). The weights of the placenta and empty uterus were similarly fitted by versions of the Gompertz equation and mammary tissue by an exponential relationship. However, the weight of (log c ) amniotic fluid was best described by a third degree polynomial, and that of (log e ) allantoic fluid by a linear equation.Using the equations and their first differentials, respectively, estimates were made of mean weights and daily rates of gain at different stages of gestation. These indicated altogether relatively slow growth and low weight of the red deer conceptus. Udder development occurred typically late in pregnancy.

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