If possible, put him in a pasture/lot/trap where he doesn't have to travel as much for grazing and water for a couple of weeks. But only if you can keep him far away from the cows that need dates AND have a couple of bred cows to keep him company. That combined with Dun's Rx often works well.
Under the Animal Medicinal Drug Use Clarification Act of 1994, FDA has prohibited the use of phenylbutazone(bute) in food animals. fullerf's vet was acting outside the law by prescribing bute at all, and even back in the days when it was allowed, 6-8gm/day was far in excess of the recommended dosage.
I know - I used to use it.
"Phenylbutazone, known as "bute," is a veterinary drug only label-approved by the Food & Drug Administration for use by veterinarians in dogs and horses. It has been associated with debilitating conditions in humans and it is absolutely not permitted for use in food-producing animals. USDA/FSIS has conducted a special project to for this drug in selected bovine slaughter plants under federal inspection. An earlier pilot project by FSIS found traces less than 3% of the livestock selected for testing, sufficient cause for this special project. There is no tolerance for this drug in food-producing livestock, and they and their by-products are condemned when it is detected. Producers must not use this drug in food-producing livestock and if it is found, those producers will be subject to FDA investigation and possible prosecution."
I know, I'll get the argument - 'But, I wasn't going to send him to slaughter.'
Sure, he got better - but if he'd not returned to functional service, were you willing to just shoot & bury him and forego the salvage price you might have gotten sending to slaughter or through the salebarn for the killer-buyers?
Those of us trying to produce safe, clean beef have enough problems with the lies and mistruths PETA, HSUS and the misguided mainstream press put forward about beef without folks giving them real ammunition, like bute residues, to use against us.