Males will breed for a long time; girls usually indicate their breeding days are over by having smaller litters, etc. Females who are used as kitten mills (generally, 2 litters in a calendar year is regarded as the absolute limit and one a year is better for them) won't breed as long - usually.

It's kindest to spay your (registered, pedigree) female by about 5 yrs, and of course, best to neuter any non-pedigree as realy as your vet will do it - 3 mths or 1.5kg

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Lesley (Tasmania)