I have heard that, in the right situation, a bit of sugar or molasses can really help. Only way to find out for sure is try it. If it doesn't help in a week or two, quit adding it.

Better to find out why your forage is so un-digestible. "Here" I have found that I can over-apply potash by following university or fertilizer suppliers recomendations. Makes for high yields of poorly digestible feed. Tests good, feeds poor.

One guy put it, "A silo full of popple brush don't do you no good."