Superovulation in red deer (Cervus elaphus) and Pere David's deer (Elaphurus davidianus), and fertilization rates following artificial insemination with Pere David's deer semen

Two comparative studies were undertaken using adult, female red and Pere 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 Pere 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(CIDR) for 14 days, with 200 iu pregnant mares' serum gonadotrophin (PMSG) administered 72 h before the device was withdrawn and eight injections of ovine FSH given at 12 h intervals starting at the time of PMSG administration.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 (Pere David's deer 24.00 ± 2.32 h; red deer 24.60 ± 2.23 h). The duration of oestrus was greater in Pere 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 Pere 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 Pere 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 Pere 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 Pere David's deer and 10.80 ± 3.78 (range 4-23) in red deer. In Expt 2, six Pere 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 x 10⁶ frozen-thawed Pere David's deer spermatozoa. Embryos were recovered by laparotomy 5, 6 and 7 days after insemination. A total of six embryos (three Pere David's deer x red deer and three Pere David's deer x Pere 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.