Embryo biotechnologies in dogs

There is very little data available on the specificities of oocyte and embryo biology in bitches. The main difference with other mammals is the time of meiosis resumption: it does not occur before ovulation, but in the oviduct 48 to 60 hours later. The factors responsible for this delay are not known, which may explain why current in vitro maturation rates are so low (10 to 30%). Oocyte harvesting is also a major limiting factor, as there is no effective protocol for the induction of cycles and superovulation. In vitro fertilisation rates are equally low (10%), with a high rate of polyspermia. No puppy has yet been born from an embryo produced in vitro. As for embryos produced in vivo, their collection is difficult due to anatomical reasons and to the fact that superovulation cannot be induced. Embryo transfer to donor bitches is also hindered by difficulties to synchronise ovulations between donor and recipient bitches. Only 6 such trials have been reported in the literature, resulting in the birth of 45 puppies. In vitro cultures are very rarely used, and only four puppies were born from somatic cell cloning with only few hours of in vitro culture. Canine reproductive biotechnologies have thus largely fallen behind, due to a lack of fundamental research to improve our understanding of its specific physiological mechanisms. This deficit is all the more damaging that dogs are increasingly used as relevant biomedical models.