Genetic influences on reproduction of female red deer (Cervus elaphus) (1) Seasonal luteal cyclicity

This study compared the onset and duration of the breeding season of female red deer (Cervus elaphus scoticus) and its hybrids with either wapiti (Cervus elaphus nelsoni) or Pere David's (PD) deer (Elaphurus davidianus). In Trial 1 (1995), adult red deer (n = 9), F1 hybrid wapiti x red deer (n = 6) and maternal backcross hybrid PD deer x red deer (i.e., 1/4 PD; n = 9) were maintained together in the presence of a vasectomised red deer stag for 12 months. They were blood-sampled daily or three times weekly so that concentration profiles of plasma progesterone could be used to identify the initiation, duration and cessation of luteal events. There was clear evidence of luteal cyclicity between April and September, with the transition into breeding associated with an apparent silent ovulation and short-lived corpus luteum (i.e., 6-12 days) in every hind. A significant genotype effect occurred in the mean time to first oestrus (P < 0.05), with wapiti hybrids and 1/4 PD hybrids being 9 and 5 days earlier than red deer. Between six and nine oestrous cycles were exhibited by each hind, with no difference in mean cycle length (19.5-19.6 days) between genotypes (P > 0.10). The overall length of the breeding season was significantly longer for wapiti hybrids (143 days) than for either red deer (130 days) and 1/4 PD hybrids (132 days, P < 0.05). In Trial 2 (1998), adult red deer (n = 5), 1/4 PD hybrids (n = 5) and F-1 PD x red deer hybrid (n = 5) hinds were maintained together from mid-February (late anoestrus) to early May, in the presence of a fertile red deer stag from 1 April. Thrice-weekly blood sampling yielded plasma progesterone profiles indicative of the onset of the breeding season. Again, there was a significant genotype effect on the mean time to first oestrus (P < 0.05), with F-1 PD hybrids and 1/4 PD hybrids being 13 and 5 days earlier than red deer. However, conception dates were influenced by the timing of stag joining, and were not significantly different between genotypes. The results indicate genetic effects on reproductive seasonality. However, seasonality observed for PD x red deer hybrids more closely approximated that of red deer than PD deer. (C) 2000 Elsevier Science B.V. All rights reserved.