Genetic influences on reproduction of female red deer (Cervus elaphus) (2)Seasonal and genetic effects on the superovulatory response to exogenous FSH

This study evaluated the influences of seasons and genotype on the superovn latory response to a standardised oFSH regimen in red deer (Cervus elaphus scoticus) and its hybrids with either wapiti (C.e. nelsoni) or Pere David's (PD) deer (Elaphurus davidianus). Adult red deer (n = 9), F-1 hybrid wapit i x red deer (n = 6), and maternal backcross hybrid PD x red deer (i.e., 1/ 4 PD hybrid; n = 9) were kept together in the presence of a vasectomised st ag for 13 months. At 6 weekly intervals, all hinds received a standardised treatment regimen used routinely to induce a superovulatory response in red deer hinds, with 10 consecutive treatments spanning an entire year. This i nvolved synchronisation with intravaginal progesterone devices and delivery of multiple injections of oFSH (equivalent to 72 units NIH-FSH-S,). Laparo scopy to assess ovarian response was performed 6-7 days after the removal o f the devices. Both season and genotype had significant effects on ovulatio n rate (OR) and total follicular stimulation (TFS)(P < 0.05). For all the t hree genotypes, ovarian responses were highest from March to November (bree ding season) and lowest in the period from December to January, inclusive. Mean OR for red deer kinds ranged from 3.7 to 1.8 during the breeding seaso n, with no observable trend. All red deer hinds were anovulatory during Dec ember and January. A similar pattern occurred for 1/4 PD hybrids, although mean OR during the breeding seasons were twofold lower than for the red dee r. For F-1 wapiti hybrids, the first two treatments in March and April resu lted in the highest mean OR observed (15.6 and 11.7, respectively). Thereaf ter, mean values ranged between 6.3 and 4.7 for the remainder of the breedi ng season. Furthermore, mean OR of 3.0 and 0.5 were recorded in December an d January, respectively. For the red deer and F-1 wapiti hybrids, between-h ind variation in OR was not randomly distributed across the treatment dates , indicating that the individuals varied significantly in their ability to respond to oFSH, at least within a given season. In conclusion, the study has shown that relative to red deer, F-1 wapiti hy brid hinds exhibit a higher sensitivity to oFSK, whereas 1/4 PD hybrid hind s have a lower sensitivity. However, individual variation within genotype w as very marked. A seasonal effect was apparent for all genotypes, although some F-1 wapiti hybrid hinds exhibited ovulatory responses throughout the y ear. (C) 2000 Elsevier Science B.V. All rights reserved.