ETA: I also forgot to mention that I'm thinking it could be stiffness because when the video was taken he'd been moving around a bit already and may have loosened up. He was also walking faster than he normally does in the video because I was so far ahead of him (didn't want to be in the shot - bad hair day haha). When he's out in the pasture he almost drags his toes and doesn't step under himself. Could it just be laziness or lack of conditioning? Or playing too much? Or maybe the diet change? The ration balancer doesn't have as many calories as Safechoice did (although he is on beet pulp now too), but he's always been kind of lazy\laid back, even before the diet change.
Thanks for your help!