It is unlikely you will see an adult dog with a full cleft palate since it will usually need to be treated for them to survive. One of the reasons for this is that a puppy with a cleft palate cannot close their mouth over properly. Since air escapes through the gap in the cleft, the puppy cannot create suction to feed from their mother's teats. By compromising their diet, the cleft palate causes dehydration and stunted growth.