INFLUENCE OF PRENATAL PHOTOPERIOD ON POSTNATAL PLASMA-CONCENTRATIONS OF PROGESTERONE AND PROLACTIN IN FEMALE RED DEER (CERVUS-ELAPHUS) REARED IN CONSTANT EQUATORIAL PHOTOPERIOD

Prenatal photoperiod influences postnatal prolactin secretion and the timing of reproductive development in male red deer reared from birth in a constant equatorial photoperiod (12:12 light:dark). The present t rial investigated whether a similar phenomenon occurs in female red de er. Female deer whose mothers had been exposed for the last 14 weeks o f gestation to long (group L, 18:6 light:dark) or short day length (gr oup S, 6:18 light:dark) were kept from birth in constant equatorial da y length with food available ad libitum. Both groups showed similar li ve-weight gain to 90-100 weeks of age. Blood samples taken once or twi ce weekly were analyzed for progesterone and prolactin. Progesterone c oncentrations indicated that there was no difference between the group s in the timing of the first incidence of ovarian (luteal) activity, w hich occurred at a normal or late age for natural puberty (67 weeks or older). Only one individual per group exhibited normal repeated lutea l cyclicity since there was a high incidence of irregular or abnormal luteal function. Plasma prolactin concentrations at birth were higher in group L than group S (P < 0.001). Thereafter, although the mean and peak values did not differ significantly between the groups, there wa s a significant difference in the pattern of secretion; deer in group L showed significant clustering of prolactin peaks (P < 0.01) at a mea n age of 48 weeks, whereas deer in group S showed a random distributio n of peaks. Therefore, for female red deer raised in constant equatori al photoperiod, prenatal long day lengths did not advance timing of pu berty. However, the long-term pattern of prolactin secretion tended to be synchronized by long but not by short day lengths experienced pren atally.