[Di]

She must first give birth to lactate. How old is she? The "rule of thumb" is, when they reach 70-80lbs, breed them, gestation is 150 days +/-. Then she will produce colostrum for several weeks. She can then be milked (of course you will have kids to feed, so, they can be bottle or dam fed).

Here is a good website for newbies www.fiascofarm.com.