Little puppies and kittens are so cute – but getting them can sometimes be tricky. The reproductive systems of various species are really quite different. Only primates truly menstruate! Both dogs and cats have gestation periods (pregnancy times) of about 63 days and they have an elongated uterus that can accommodate litters of pups or kittens. Their heat cycles are quite different. Dogs tend to start to cycle at 5-9 months of age and have a heat cycle every 5-8 months. This cycle starts with a period of proestrus that lasts about a week. During this time females will bleed a bit, attract males, but they are not fertile and generally will not allow a male to mount. The next phase is actual estrus. This can last for 3-14 days. During this time the female will ovulate and allow a male to mount. After estrus, the female enters a dormant time called diestrus if she is not pregnant. This period is hormonal similar to pregnancy and some dogs will go through a œfalse pregnancy  – they nest, get enlarged nipples and even produce a bit of milk! Cats are seasonal – they only cycle in the beginning of the year. They are induced ovulators, meaning they ovulate only if bred. Typically cats will cycle about every 30 days for about half of the year. In most cases, dogs and cats can give birth with no assistance – in fact they seem to resent our meddling. Animals with large head, small litter or other conformational changes often require assistance or C-section for delivery.
While we have an overabundance of dogs and cats in this country, it can be quite difficult to get the purebred dogs and cats pregnant. Next week we ™ll look at reproductive diseases and troubles with pregnancies.

by Bonnie Markoff, DVM, ABVP