Despite common belief, it is not recommended to feed any kind of spare bones to dogs. Rib bones can upset a dog's stomach or even become lodged in a dog's throat.
Rib bones in particular can be hazardous to dogs because they are thinner than leg bones, which means they can easily splinter into shard-like pieces that can get stuck in a dog's digestive tract. These bones can also end up exiting the body in an equally splintered way, either through vomit or in the dog's stool. It is much safer to share a little meat with your dog than it is to give them a spare bone.