My wolfhound swallowed a beef rib bone (whole) last night. What should I do? He's had a normal bowl movement this morning.

Cooked or raw?

If it's raw and he swallowed it fine there shouldn't be a problem, dogs can digest raw bones easily.

Cooked however is a different story...

Best case scenrio:
Feed him a few slices of bread, this will help cushion the bones and hopefully prevent perforations.

Worst case scario:
The bones may become lodged or pierce an internal organ. Watch out for signs like struggling to move bowels, excessive drooling, moaning, lethargy, bloody stools.
If you see any of these signs get him to the vet immediately.

Please consult your vet ASAP! [What was the consistency of the bowel movement?]