DOD can occur any time between birth and about 1.5 years of age. Foals that are genetically predisposed to fast growth may be at risk, especially if their diets are imbalanced or they are overfed. DOD is usually the result of a combination of risk factors–and improper nutrition is one of those factors.
Gary Baxter, VMD, MS, Professor of Surgery at Colorado State University, says DOD is a catch 22 problem, regarding genetics of rapid growth versus what you are feeding. “Horses that are not genetically programmed for fast growth could probably be fed the same diet (that might precipitate DOD in other horses) and not have any problems, whereas other horses that are genetically inclined to grow rapidly at certain stages of their development will be more likely to end up with a problem,” says Baxter.
“Young horses have growth spurts at different stages of their lives, just like people. Some will grow very quickly when they are young and others wait a little longer before they start that growth spurt, and there are probably also some breed differences. In general, we are concerned about hot rations contributing to development of physitis and other DOD problems. By hot I mean high energy, rather than high protein, in most cases,” he says.
“Grain supplies energy and protein along with the minerals and vitamins that a horse needs, to grow. But there must be a balance. The calcium-phosphorus ratio is important, and an imbalance in this ratio has always been viewed as potentially contributing to skeletal problems. Thus it is important to know the mineral content of forages, but a lot of people that only have a few horses don’t go to the expense of forage testing when figuring out a ration. Breeders on big farms are more likely to utilize forage testing and balancing the forage with the grain, to figure out the protein level and minerals, calcium and phosphorus,” says Baxter.
“In general, when we see a young horse with DOD problems, we try to figure some of this out, but by the time I see them (as a surgeon), the situation is usually fairly well along. With physitis, however, if you can decrease the energy in the ration you can decrease the inflammation in the growth plates,” he says. You have a little more time, and warning, in this situation, than with OCD–where the damage is already done by the time you notice the horse has a problem.
Heather Smith Thomas has raised and trained horses for 50 years and has been writing about them nearly that long, selling more than 9000 stories and articles and publishing 20 books. She and her husband raise beef cattle and horses on their ranch near Salmon, Idaho.