The cat should not be too young
Even if starting to call is a sign that it is possible for a cat to get pregnant, it is not the best to start so soon. In a german breeding club there is a rule that the maiden queen has to be at least 10 month old, or 9 if a veterinarian has given their ok. http://www.evbl.net/zuchtrichtlinien.htm
I found a homepage of a breeder who says the following (https://thecatswhiskers.wordpress.com/2008/04/05/when-should-you-breed-your-cat/):
- If your queen is a maiden queen (i.e. never been bred before), then the rule of thumb seems to be wait until she is a year old, or has called at least 3 times. However, some breeds of cats come into call earlier than 12 months. For e.g. the Orientals have been known to go on heat at 4 months old!
In the end, you have to play it by ear – a calling cat can lose condition if she calls repeatedly – and take the advice of the breeder who sold you your queen. She owns the mother cat to your cat, and in most instances what applies to the mother cat applies to the daughter too.
On a comment he/she is answering a question about the 3-times-rule:
This three times rule is not set in stone. I think it applies more to young maiden queens who start calling before the age of 1. And again, restricting the first mating to over 1 year old depends.
When I first started, I waited until my queen was a year old – I was told by her breeder that this was to ensure she was mature enough. If the queen is too young, then there could be issues with the birth etc. because she’s not physically ready to have kittens.
So finally I would say:
If you want to be sure that your cat is old enough: Wait until she is 1 year old. Or ask your vet.
The cat should not be too old
When cats get older, they have more problem with getting pregnant or, if they are maiden, there can be health complications. To avoid problems, a general rule is that cats which are 4 to 6 years old should not be bred or only if a veterinarian is watching and gave the ok.