Two comparative studies were undertaken using adult, female red and Père David's deer to examine the ovulatory response of these animals to a superovulation regimen and fertilization rates following inter- and intraspecific laparoscopic insemination. In Expt 1 six Père David's deer and 12 red deer hinds were treated during the breeding season with an intravaginal progesterone-impregnated controlled internal drug release device (CIDR) for 14 days, with 200 iu pregnant mares' serum gonadotrophin (PMSG) administered 72 h before the device was withdrawn and eight injections of ovine FSH given at 12 h intervals starting at the time of PMSG administration. Oestrous behaviour began one day after CIDR device withdrawal (Père David's deer: 24.00 ± 2.32 h; red deer: 24.60 ± 2.23 h). The duration of oestrus was greater in Père David's deer than in red deer (17.50 ± 1.43 h and 8.25 ± 3.25 h, respectively, P<0.001). The peak LH surge of Père David's deer was 68.65 ± 4.74 ng ml⁻¹ occurring 29.00 ± 2.41 h after removal of the CIDR devices. In comparison, the peak LH surge in red deer was 17.09 ± 3.64 ng ml⁻¹ (P<0.001), occurring 24.00 ± 0.00 h after CIDR device withdrawal. Pre-surge concentrations of LH were also greater (P<0.001) in Père David's deer (1.37 ± 0.11 ng ml⁻¹) than in red deer hinds (0.41 ± 0.02 ng ml⁻¹). Oestradiol concentrations increased steadily during FSH treatment in both species and reached a maximum of 15.60 ± 2.22 pg ml⁻¹ at 21.00 ± 6.20 h after CIDR device withdrawal in Père David's deer and 26.14 ± 6.20 pg ml⁻¹ at 20.40 ± 7.30 h before CIDR device removal in red deer. The mean number of ovulations recorded was 3.83 ± 1.22 (range 1–8) in Père David's deer and 10.80 ± 3.78 (range 4–23) in red deer. In Expt 2, six Père David's deer and six red deer were superovulated with an identical regimen to that described for Expt 1. All hinds were inseminated in utero 36 h after CIDR device withdrawal with 25 × 10⁶ frozen–thawed Père David's deer spermatozoa. Embryos were recovered by laparotomy 5, 6 and 7 days after insemination. A total of six embryos (three Père David's deer × red deer and three Père David's deer × Père David's deer) were collected. One pregnancy was confirmed following the transfer of all embryos to synchronized red deer recipients. This pregnancy was terminated naturally between days 70 and 78. This is the first report of an interspecific transfer of hybrid embryos in a cervid and of the comparative superovulation response in two related species. The results indicate that treatment with PMSG and ovine FSH can be used in embryo transfer programmes for these species. However, in this study there were low inter-specific fertilization rates and transferred hybrid embryos failed to develop to term.

Ovarian follicle development in response to FSH infusion was investigated in Scottish Blackface ewes with high and low body condition scores in which endogenous gonadotrophin secretion and follicle development to ≥ 2.5 mm diameter was suppressed using subcutaneous implants containing a GnRH agonist. In two experiments conducted during the normal breeding season, groups of 20 (Expt 1) and 15 (Expt 2) ewes were fed to achieve body condition scores ≥2·75 (high; H) or ≤1·75 (low; L). In both experiments GnRH agonist implants were inserted four weeks before FSH was infused for 72 h at 7 μg h⁻¹ to group H animals or at 5 μg h⁻¹ to group L animals; the infusion rates were designed to ensure similar circulating FSH concentrations in animals of both groups. In Expt 2, additional subcutaneous implants containing oestradiol were inserted 21 days after insertion of GnRH agonist implants and 7 days before the FSH infusion began. In both experiments, FSH infusion was associated with an increase in circulatory concentrations of LH (P < 0.01) and FSH (P < 0·001), but there was no difference with body condition in mean circulating gonadotrophin concentrations, the numbers of ovarian follicles ≥ 2.5 mm diameter, the proportion of these follicles that were oestrogenic or the mean rate of oestradiol secretion in vitro. It is concluded that differences in body condition of ewes do not affect the responsiveness of the ovary to FSH, in the presence or absence of oestradiol, as measured by the number, size and steroidogenic capacity of ovarian follicles present following FSH infusion.