The first step should be to provide gestating mares with adequate calcium and phosphorus while avoiding excess energy and protein.
Rations with an excessive energy content (excess starch-rich cereals) should also be avoided so as to prevent excessive weight gain which would overburden the bones and tendons.
Excess protein interferes with calcium retention, and random calcium supplements hinder the assimilation of phosphorus, zinc, copper and iodine.
Copper deficiency together with excess calcium and zinc encourage osteochondrosis particularly among rapidly growing foals.
Balanced rations destined for gestating mares and foals alone provide an optimum means of preventing this disease.
The importance of providing regular exercise for foals by encouraging rearing out at pasture until fully grown should be taken into consideration.
Ask your veterinary surgeon for advice.