I need to get hay before the snow falls for a horse that's at our farm and I have no idea how much to get! The horse is about 20 years old and is out all the time. She comes down from the woods to be fed in the winter, but even on the coldest nights she has no interest in standing in the barn. Last year we fed her hay and sweet grain, with fresh carrots and apples as snacks, and will do the same this year BUT I have never purchased the hay before (don't look at me, I just load/unload the truck! ha ha ha) How much do I need? Thanks for any input.