If you go to the FAQs at the top of the index you will find a ton of information that you are looking for http://www.backyardherds.com/forum/viewtopic.php?id=767
I think the answer is 3lbs per head.
I get all my info from the FAQs and fiasco farmshttps://fiascofarm.com/goats/feeding.htm
our ND's have forage, grass and hay 24 hrs day... we only need to feed 1 - 1 1/2 cups of high quality feed to each daily. (we don't use sweet feed)
we mostly use this just to help keep a good balance and nec vit/minerals in check.
Goats lactating also get alfalfa hay and alfalfa pellets.
A lot of times I just venture over to the FAQs page and read up of some different things. It's all very interesting and I find it helpful. For instance, I had read about feeding a bottle to a baby who was originally nursing several weeks ago (even though I didn't have a bottle baby). Well then I bought one and went to buy some items I'd be needing for her and all the information I had read just came back to me! I was so glad I had read that information even though I didn't need it at that time.