It's already working!! A week ago we put the round bale in his shelter. He's spent the past week with his face buried in it and only comes up for air and a poop. When he sees me coming, he always picks his head up with a hay beard. He is one happy boy. Last week the weight tape read 1140. Today, one week later, it's 1170. I have pics from day 1 & day 8. They don't show a huge difference, but there's definitely more meat between his ribs and on his butt. There's not as much waste as I'd thought there would be, so that's good. We've cut his grain back to 4 lbs a day, (formerly twice as much). And if he keeps gaining at this pace, we'll be cutting back again.
That's good to hear that the protein content with grass hay is as high at 18%. That's the big thing I was worried about. I ride 6 days a week, so I need to know he has the nutrients available to put and keep muscle on. I will still keep a vitamin supplement in his diet to catch anything he might be missing, but for now I am SOOOO thrilled.
I'll post pics and weights weekly. The top 2 are week 1 and the bottom 2 are today. Thanks for everyone's help on this issue.