Oh my goodness, I can't belive I missed this post! Do you still have this pony? Did you have the vet out yet? Please be VERY careful with grass and introducing feeds, start very slowly. If she were mine, I would be feeding a good quality grass hay only. Supplimenting with a complete feed per instructions on the bag for the weight/condition of the pony. I would not put her on grass due to risk of founder. Just because a pony is "skinny" doesn't mean they cannot plump up very fast. If you do allow her grass, limit her to a couple hours in the morning and at night. if you are using beet pulp, dont forget to soak it, it does cause choke in horses. Has she been wormed? Do you know her age? Could she be a Cushings candidate? How are her teeth? She is just darling!!!!!! If you have any questions, please do not hesitate to ask!!!!! Good luck!!!