
The younger the goat the greater the success in transitioning them from a life of leisure to a life of having to rustle up their own grub. And a pampered goat isn't going to get out there unless they don't have an alternative. Also the younger the goat the more likely they will develop the rumen necessary to process that forage into tasty and healthier milk.
So take a moment to read up on this at the Goat Dairy Library.