Grain can be
grain - corn, oats, etc, in a "textured" feed -- or it can be pelleted feed.. I'd go with the pelleted feed, as some animals are prone to pick what they like out of textured feed. If what they like happens to be cracked corn and they eat more of that than anything else, it throws the Ca

balance of the feed off.. Corn has a Ca

ratio of about 1:4, and can
certainly lead to UC in bucks and wethers if they eat a lot of it.
As for whether mixed hay is OK for bucks and wethers...kimmy and I have disagreed on this before. She recommends straight alfalfa, which is fine, I guess....if not a bit expensive.. There's some indication that too much calcium can lead to "nutritional arthritis," but I don't have any firsthand experience with that..
Personally, though, I think mixed hay is OK provided that there's enough calcium in it to offset the high phosphorus content of the grass. Straight alfalfa is about 6-8:1, Ca

which is far more calcium than is actually necessary to offset the phosphorus.. Grass hay is often 1:1 Ca

or lower, but you still have to look at calcium and phosphorus by weight -- not just by the ratio.. Obviously, what you want is for your hay to have at least twice as many grams of calcium as it has phosphorus.
Based on my reading, most 50/50 alfalfa-grass mix hays will end up being about 2.5-3:1 Ca

, and about 16-18% protein.. As the alfalfa content decreases, the Ca

ratio gets more dangerous and the protein level falls.. And naturally, as it increases, the ratio should improve and the protein levels come up..
It seems like there was some extenuating circumstance that led to kimmy seeing cases of UC unless her wethers were on straight alfalfa hay.. If I'm not mistaken, she was creep feeding free choice grain to the wethers in question for maximum weight gains, and I think she may even have noted that the grain they were getting wasn't balanced 2:1, Ca

.. As such, she needed to add lots of calcium to the diet, and straight alfalfa hay did that for her.
Now, unless your free-feeding unbalanced grain for maximum weight gain, I would personally be of the opinion that a nice alfalfa/grass mix hay with a decent amount of alfalfa in it -- 40%, at least -- should be fine.. If you add a little bit of appropriate goat grain a day, that
should be fine too -- so long as you don't overdo it. Remember that they don't necessarily
need grain!
And, clean water at all times. That's very, very important.
