This process ends at five years of age. These may make eating grain and hay difficult for awhile. They also may be shy around the mouth when being bitted. They may be directly in the way of the bit, particularly a snaffle bit. They are painful and cause head slinging if the horse is agitated.
Some horses have a genetic defect that prevents their front incisors from matching.
A horse with extreme parrot mouth has difficulty grazing. Such horses may be good work horses, but it may be necessary to supplement their pasture diet with grain or other feed during most of their lifetime. When parrot mouth appears in a foal, the sire and dam are both carriers of this genetic fault. Using such horses as breeding stock is questionable. Since horses make their living in motion, they should have an athletic look.