I've been pasturing my Hereford cows on mostly alfalfa pastures for a couple weeks now.  I do have a mix of grasses and clover in with the alfalfa but have had no problem. We have not had a real hard frost yet although one is predicted tonight or tomorrow night.

It seems to me that the key is to limit them to a very small area per cow at first. They do get real loose but even that has lessened after they've gotten used to the alfalfa.  Folks have also told me not to put them on it the first time if they are very hungry.

This is just my recent experience, yours may differ with your herd.

You certainly want to get as much grazing done as possible before winter really sets in.

Good luck.

Jim