As oxen get larger, the weight on the heel can be substantial and will lead to undue pressure on the pasterns. This weight on the heel and pastern puts too much stress on the tendons of the lower limb and causes the heel horn to crack, often leading to infection and premature culling in big oxen.
Hoof problems are the number one reason for culling among heavy oxen.
When selecting calves to train as oxen, the main conformational defects to watch out for pertain to the legs. The main defect relating to the conformation of the front legs is toeing out. Calves should have all four hooves pointing straight forward, not toed out. The higher the better. A hairline that is near the ground on a calf usually indicates that the animal is weak in the pasterns and will be prone to sickle hocks.