Aww so he should be more comfortable. Has he had any access to female feed or summat too high in goodies which has caused waterbelly/urinary calculi. Is he bloated, full of fluid. We ve had it here, if it is that when the mr went and fed ewe nuts to some rams, they went off food, we're depressed. I drenched them with lemon juice and water and add a little juice to water too. They improved speedily. The juice alters the pH and so helps break down the crystals and flush them out. I understand that this may not be what he's got,but I wouldn't rule it out. Or perhaps he had a knock, or he's deficient in Sc, b12.that would cause thriftiness.
I'd pick him some browse too, unless the vet said not to x