But too little protein may be. Calcium and phosphorus are often over-supplemented. DOD is frequently noted when more phosphorus than calcium is fed. Young, growing foals should always get more calcium than phosphorus. Young foals often receive too much grain.
Grains are higher in phosphorus than calcium, while hays are the other way around.
This is a prescription for problems. A field study reported that breeding farms feeding higher levels of copper and zinc to growing foals had fewer DOD problems. But research hasn't proved this to be true. Keep rations for young, growing foals properly balanced. Use safe facilities while managing mares and foals to minimize injuries.