That is going to depend on a few things. Straight alfalfa is better for lactating does because it has more protein and TDN than grass or grass/alfalfa mix. If your does are open or short bred, then straight alfalfa can cause them to get too fat - especially if you grain them. For heavy bred does, there is evidence to suggest that the calcium content in alfalfa can cause a doe to quit producing calcium then, when she kids and has to mobilize calcium from her body, she can go into milk fever. Most alfalfa hay contains more protein and TDN then open or short bred does need, so the excess is eliminated through urine and manure. There goes your hard earned money. If you get a better quality of alfalfa than your girls are used to, it can also cause bloat. I also find that straight alfalfa is too 'hot' a lot of the time, and leads to excessive fighting, getting into trouble, etc. If your winters are cold, a grass/alfalfa mix will help keep them warmer than straight alfalfa because grass is harder to digest and digestion is what creates heat. As a general rule of thumb, I would not buy 1st cutting alfalfa if I could help it because it tends to be more stemmy and goats do not like stemmy hay, therefore they waste it. I hope this helps.