Flippin' 12 degrees today

Too cold to do much of anything outside, so I went to the mall to spoil myself since I had a giftcard, then out to the barn to feed Hampton. He seemed well. I thought my fingers were going to freeze off, even with gloves. Hampton is a bit thin for my liking ... he's not severely underweight by any means, but I would like him to be more "round" (and juicy ... lol). I think his ribs will always show no matter what for a little while longer (he's growing so much), and you can't see his spine but he could use a little more cushion over his hips really. Anyway, he gets free choice hay (mostly oat hay and grass mix), plus he gets fed grain once a day. I simply do not have time to drive out there and feed him twice. He gets Purina Omelene 100, plus 1/2 cup Omega Horseshine. I just started the Horseshine, so I am going to see if this helps any. Any other ideas? Suggestions?