How much of the old hay do you have? If it was under cover, it may be worth having it tested to see what it's nutritional content is. Sometimes year old hay, or even older hay is still fine, as long as it isn't moldy.

Old hay also works great as mulch or livestock bedding. We have a friend who moved into a farm down the road from us, and the barn was full of hay that was between 4 and 5 years old. I had the hay tested, and it wasn't too bad, but it had lost quite a bit of it's nutritional value. I bought it from him for 50 cents/bale (small squares, of course) and used it for bedding for my goats and sheep. It wasn't moldy, so if they ate some of it, that was fine, but I didn't use it primarily for feed. I have a friend who bought a farm and one of the barns was filled with VERY old hay. She had it tested, and it was still quite good, so she mixed it with fresh hay and fed it to her goats and sheep. They all did fine with it.