Cat and dog reproduction (in a nutshell!)

The sun’s out (well it is as I’m writing this) and our thoughts are starting to turn towards this year’s crop of puppies and kittens- one of the best bits of the job! I thought it might be good to answer some of the common questions about breeding 🙂


Cats are easy- leave them to it and you’ll have plenty of kittens. Seriously, PLENTY of kittens! We usually see queens’ (female) fertility drop over winter, but then pick up again in the spring. They will come into heat every 3-4 weeks, and if mated will ovulate (no mating=no ovulation – different to humans and dogs). Typically they will go through puberty at 6 weeks old, so we recommend neutering between 12 weeks old and 5 months old; the earlier the better.

Female cat showing signs of being receptive during season

Tom cats are VERY persistent- if you have an unspayed cat in the house then (unless you are neurotic about keeping them isolated when fertile) they will eventually get pregnant, and kittens can be tricky to re home. Unless you have a very strong reason not to, every female cat should be neutered at an early age.


Bit more tricky- dogs have a very different cycle to other animals, including humans. Whilst most animals will cycle and ovulate every 3-4 weeks, the majority of bitches only have 2 cycles per year. Whilst development of the egg and ovulation is very similar to other animal, once ovulation occurs every bitch’s hormones will act as though they are pregnant- whether they are pregnant or not! In other animals, failure to get pregnant will result in hormonal changes which resets the cycle causing another egg to develop. In the bitch, hormones will ensure that the uterus stays full of blood vessels and further eggs are prevented from developing for approx. 63 days- the typical pregnancy length for canines. She will feel pregnant, and at around the time pups would have been born she will produce milk. This will last for 10-20 days before settling. The cycle then pauses for 3 months before restarting- thus the bitch will have 2 periods of being in heat (seasons) per year.

The reason for this is evolutionary; in the pack typically only the Alpha female will breed and produce pups. As soon as the pups are born she will disappear off hunting again leaving the nursing to “aunties” who very handily will be producing milk – despite not having had pups. In addition, hormonal changes in these aunties will ensure they are feeling maternal.

The upshot for our pet dogs is that if they are unspeyed then twice a year they may produce milk, hoard toys and generally have behavioural changes we call “false pregnancy”. These changes are normal, but if are exceptionally distressing can be medically treated. In addition, it makes timing of neutering tricky. We want to avoid times when organs are particularly active, so we need to avoid when in season AND for the 63 days afterwards AND for the period of lactation afterwards. We therefore would usually only recommend neutering in the 3 months leading up to a season.

We can neuter from around 5 months (there’s no need to allow to have a season unless as a pup she has a urinary tract infection), and we see some great benefits:

  • significant reduction in the incidence of mammary cancer if performed before the second season
  • removal of the risk of pyometra (or infection in the womb)
  • removal of bleeding on the carpets twice a year
  • stopping other male dogs camping outside the house, and being unable to attend classes or competitions twice a year
  • speyed bitches on average live for 2 years longer!

There are some disadvantages that need to be weighed against surgical speying:

  • operative risk- very low but not to be ignored
  • coat changes- some bitches can develop a “hairy” coat
  • weight gain- can be offset by simply reducing calories by 25%

There is no evidence to suggest speying increases the risk of incontinence in later life EXCEPT for pups which have had a UTI and are speyed before their first season

Male dogs don’t get the same health benefits from castration, and there is now an implant (Suprelorin) that will chemically castrate them for 12-24 months. We recommend castration from 6 months for smaller dogs, or 12 months for larger dogs