I scored most of a bale of mixed Timothy from a friend who panicked at the intermittent thistle content. My mare eats fresh thistle and loves Himalayan blackberries. She is capable of eating around unpalatable weeds in hay. I see nothing online to suggest thistles will be a problem. The other person who took. Some of this hay reports her horse is eating thistles in perefence to alfalfa. I can pick some of them out too.
This is not the year to waste hay or spurn anything edible.
Anything I should be worrying about?