One of my criteria is that they no longer look like a baby. Usually this is around the 8 month mark. But there are other factors like how big they are and if they are healthy. So far I haven't bred a girl before a year old.
Generally with all goats, you are better waiting till they are 18 months old before joining. That way the doe is better able to grow out to be a normal size and handle the rigours of pregnancy, kidding the kid-rearing better.
If you choose to breed a pre yearling doe, you need to have extra good feed in front of them all the time. They will be eating to grow themselves as well as grow a baby.
Here we have had mixed success with breeding coming yearlings. It just seems to be a little tough on em AND its difficult for them to compete with older does if penned together. So we have decided against it for next year. Of course around the first of the year when the coming yearlings are nice big and in great shape we will say "We shoulda breed some of them"
I like to wait until they are at least a year. I've bred them earlier with no difficulties but I think it's a lot easier for them once they've finished growing themselves. I usually like them above 45 pounds for Nigerians if they are under a year.
Ive been wounder this myself. My Mini Lamancha doe will be 1 in December she is already taller then my nigerian buck so i was thinking it would be ok to breed her a little early. I was thinking about Breeding her in late september or October for February to March kids. But did not know the rules on minis.
I've got two april doelings, one feb doeling, and one doe from last year. Only one is a mini. They are all pretty close in size at this point, and maturing nicely. My girl from feb does not even look like she is one of this years. But I'm really thinking about waiting on the younger two... I've got a few months to make up my mind tho.
If I do breed any of the doelings it would be to my little mini alpine buck (75% Nigerian)