I have a 15 yr old gelding that I haven't been riding lately and my farrier says he REALLY needs to lose about 150 lbs. He is having some problem with grass founder. We have thirty acres of pasture so he stays on pasture 24/7. I am going to close off the bigger pastures and let him stay in the 3 acre pasture near my house and keep him in the barn at night. Do I need to give him hay(coastal bermuda hay) or just grass. Also will he need some grain for variety. I have never had this problem with any of my other horses. I live in NC and we had a really mild winter so I didn't feed him any grain during the winter and he still is fat as a mole. Help!!