Superovulation of farmed red deer ( Cervus elaphus) and fallow deer ( Dama dama) : Incidence of ovulation and changes in plasma hormone concentrations during the pre-ovulatory period in relation to ova recovery and fertilisation

Abstract

The effects of various gonadotrophin regimens on ovarian responses, endocrine changes and recovery/fertilisation rates of ova in red deer ( Cervus elaphus) and fallow deer ( Dama dama) were examined. Fifty mature females of each species were treated during their respective breeding seasons with intravaginal progesterone releasing (CIDR) devices for 14 days and one of five doses of ovine follicle stimulating hormone (FSH; 0, 0.25, 0.5, 0.75, 1.0 units). All animals received 200 IU pregnant mare serum gonadotrophin (PMSG) on the 11th day of device insertion and eight equal doses of FSH administered at 12 h intervals starting at administration of PMSG. After removal of CIDR devices, all females were run with fertile males of the same species (10:1 ratio) but also received intravaginal inseminations ((20–30) × 10 6 motile thawed conspecific spermatozoa per insemination) on four occasions at 12 h intervals starting 24 h after device removal. Four animals in each treatment were blood sampled every 2 days from insertion of CIDR devices until 22 days after device removal and every 2 h for 72 h after device removal. Plasma was analysed for concentrations of luteinising hormone (LH), progesterone, oestradiol-17β and androstenedione. Ova were recovered by flushing the uterus during mid-ventral laparotomy under general anaesthesia 7 days after removal of CIDR devices. The numbers of corpora lutea (CL) and unruptured follicles (over 5 mm) were recorded. Both species exhibited a curvilinear pattern of ovarian response to increasing doses of FSH. The highest numbers of CL were observed following treatment with 0.5 units of FSH. Mean (± SEM) ova recovery rates were 32.7 ± 5.1% for red deer and 30.6 ± 5.1% for fallow deer, with no significant differences between treatment groups. The mean (± SEM) fertilisation rate of ova recovered from red hinds was 50.2 ± 8.2%, and the majority of the embryos were at the morula stage. None of the ova recovered from fallow deer had cleaved. Species differences in pre-ovulatory endocrine changes were apparent, with fallow deer exhibiting more erratic profiles of plasma progesterone and greater elevations in plasma androstenedione than red deer. For both species, concentrations of plasma oestradiol were elevated for multiple ovulating females. We conclude that failure of fertilisation in fallow deer may reflect perturbation of oocyte development,, sperm transport and/or ovulation through excessive secretion of progesterone and oestradiol during the pre-ovulatory period. The unusual patterns of progesterone secretion may be due to either inappropriate follicle development leading to premature luteinisation, or adrenal progesterone as a consequence of stressful treatment regimens. There are indications of marked sensitivity to PMSG in fallow deer.