Stoat artificial reproductive technologies

Artificial reproductive technologies in stoats (Mustela erminea) are currently being developed in New Zealand to control and manipulate stoat reproduction in captivity. In this study, methods were established for liquid (short-term) and frozen (long-term) storage of stoat sperm. Frozen-thawed sperm were shown to be biologically competent in vitro, based on the maintenance of sperm motility and acrosome integrity after culture. A non-surgical artificial insemination technique is in development to confirm that frozen-thawed stoat sperm are capable of fertilising eggs in vivo, but its success is reliant on developing methods of inducing ovulation in females. Ovulated eggs and embryos were only recovered after mating oestrous females. Treatment of anoestrous females with pregnant mare serum gonadotrophin (PMSG) did not reliably stimulate ovarian follicle development and failed to induce ovulation. Treatment of oestrous females with PMSG did not improve the reliability and yield of eggs and embryos recovered after natural mating, or their capacity to develop in vitro compared with untreated controls. For the first time, in vitro culture and the development of in vivo derived one- to four-cell embryos to the blastocyst stage was achieved in stoats, with up to 8% of these hatching. This culture system did not support the viability of diapausing blastocysts in vitro, suggesting that alternative substrates, nutrients and/or co-culture with uterine cell layers may be required. The findings from this study will enhance our ability to breed stoats in captivity and will help establish robust protocols for efficient testing and prioritisation of reproduction-based targets for stoat fertility control.