Back in Sarawak there have been a few discussions as to when should a Doe be mated? The general opinion is that to breed as soon as she is able to! There seems to be little regard as to if the Doe is too young or even fit enough to be bred.
There are some of those ( admittedly myself) who waited until a doe was at least 18 months old before breeding her. But seriously, there is no reason to wait this long. Some farmers do this because they feel the Doe’s kids will grow better if they wait to breed her, but if the Doe is well taken care of she will give kids that grow just as well.
As often as possible we try and stick to our usual ‘synchronized’ breeding program. We had twin does where one fell into a “breeding batch” in her first year and was accidentally mated but luckily her twin doe was not into heat when they were mistakenly mixed into the breeding batch. So the second doe’s heat dates did not fall into the “batch” and because of this she never got bred until the next breeding season one year later. Hence one twin was bred when she was 40kg/9months and the other twin didn’t get bred until the next breeding batch cycle, when she was 46kg/17months. Their kids weighed in with almost no difference and the recorded kid’s weight for the first Doe first kidding also showed no difference.
When they reached reached 24 months of age, the resulted kids were almost exactly the same size and grew with no obvious difference recording consistent height and weight gains. This has seen this over and over and from this experience I know you can breed at 9 months of age with no effect to the kid. But remember, you just must make sure you take good care of and properly feed your Doe’s that are earmarked for breeding.