I was lecturing on Vancouver Island this week, where we did two talks on infertility in the canine species. Certainly one of my favourite topics, since this is an area on which my former team was definitely quite active. BTW, thanks again for all our participants in Victoria and Nanaimo, hope they enjoyed these talks as much as I did !
When I do this lecture, I always like to emphasize how unique the canine species is in terms of reproductive physiology. Why? Because many aspects of canine reproduction still remain a mystery. And that’s why it is an exciting field of veterinary medicine. We still have plenty of things to discover, and even if it was not on the long run, I was happy to be somehow part of this scientific adventure.
So do you know what these unique characteristics are? Well, let me give you the answer here:
– Canines exhibit what we call an early luteinisation of the ovarian follicles. What does this mean? In most mammals (cows, mares, sows, women …), after ovulation, the ovarian follicle will transform itself in a structure called “corpus luteum”. This structure will produce the hormone progesterone, and is the main source of progesterone in the body of these animals. In the bitch: totally different scenario. During the estrous cycle, the ovarian follicles will start producing progesterone. This hormone can therefore be detected in the blood BEFORE ovulation even happens. From a clinical point of view, that’s what allows us to follow progesterone to determine the day of ovulation.
– In most mammals, mature oocytes are released during ovulation. Therefore, if there are spermatozoas around, the oocytes can immediately be fertilized and lead to embryo development. However, in canines, again, we have to deal with a totally different scenario: the oocytes that are ovulated are premature and will require, before fertilization can occur, 55 to 72 hours of intra-tubal maturation. The optimal fertility window starts therefore 2-3 days post-ovulation: that explains why most of the time it will be recommended to breed the bitches 2 days post-ovulation.
As you can see, canine reproduction is unique. And these specific features can be seen as an advantage when it comes to canine breeding. Why? Because we can definitely use them to efficiently define the optimal breeding protocol in this species. But that’s another story…