Um, not sure actually. I have been meaning to ask someone about this. I've seen products on the websites below, and it seems that the willow toys on both are unpeeled and untreated. Given that piggers can have fresh apple branches it would make sense if willow didn't have to be dried either, but I wouldn't feed them any until you have a more definite answer. It would be very handy if they can have fresh willow branches, I'd love to know if anyone has a definite answer.
Bunnymail - Treats and toys for your furries and you! Willow Bunny Toys by The Willow Warren at West Wales Willows