On the hay issue . . .
Three lactating does, six young kids, two wethers and three weaner does will eat one small square bale of lucerne a day. In comparison, a large lactating cow with 3 month calf at foot will eat the same sized bale in a day. Sorry, thats about all I can tell you going by the animals I am feeding at the moment.
A big square bale lasts between 5 and 7 days with our big group, which has approximately 80 goats. Cant compare this to the cattle, sorry, because we are feeding out rounds to the cattle.
Hope this helps, and btw, around 6 goats to 1 cow sounds about right (for my area anyway). Like any stocking rate, its all feed dependant, and depends on how much pasture is available and how much supplementary feeding you are willing to do. And with goats, if there is a high amount of browse on the land, you can stock them at higher rates than if it was just pasture.