Egg whites (raw) have a substance in them that interferes with biotin uptake. However, egg yolks have a lot of biotin in them, far more than a dog needs, so the effect is largely negated if you feed whole raw eggs. If you cook the egg prior to feeding it destroys the substance in the egg whites that interferes. Two scrambled eggs split between three dogs isn't going to have any ill effect on the dogs whatsoever. My vet always recommends eggs to people who need to supplement their dog's food for one reason or another because they are a great source of protein. Don't get me wrong, she doesn't believe in feeding "people food" to dogs, but she does realize that a dog reaches a point in their life (typically the end) when they get to eat whatever they want because offering only dog food to a dog that won't eat and is debilitated is a great way to starve a sick animal.