Saddles with broken, green stick fractured, missing chuncks or compresssed trees are not safe to use at all. Salvage the leather parts (if your into repairing leather goods) sell it to a person for home decor only or to a store/restaraunt with a western motif for a few bucks. You can also use it as a practice saddle on a 55 gallon barrel "horse" for fun.
Yes you can use the fenders (salvage) if they are in good shape. They have nothing to do with a tree, I have done this a few times.
"The question is not, can they reason? nor, can they talk? but, can they suffer?" Jeremy Bentham