Developmental Orthopedic Diseases and Nutrition

Long name, sounds complicated.  "Developmental Orthopedic Diseases (DODs)" sounds difficult to understand and probably doesn't apply to me.  How could it have anything to do with my horse or foal?  Fact is, in young horses, DODs are extremely common and, if not managed properly from an early age, may lead to chronic unsoundnesses in the horse as he grows.  Most importantly, many of these conditions are preventable and/or treatable with nutritional management.

What are DODs?


DODs are exactly what the name implies.  As the foal/young horse grows, abnormalities of growth cause orthopedic problems to develop.  These may show up as tendon contractures, where the knees or ankles buckle forward when the foal is standing, physitis, where inflammation and pain occur in the growth plates, or osteochondrosis (OCD), where the normal ossification of cartilage is disrupted.  All of these conditions can result in chronic lamenesses or crooked legs or both.  These are conditions that develop in young foals to yearlings and primarily during phases of rapid growth.

What Causes DODs?


Normal growth and development depends upon a delicate balance of mineral availability, vitamin cofactors, normal hormone balance, exercise and injury prevention.  The easiest method of preventing DODs is to provide proper nutrition and regular exercise.  This sounds easy, but is actually more complicated than it sounds.  There are several points to consider. 


(1)  Major minerals such as calcium and phosphorus must be present in the diet of foals and adolescent horses in a ratio of 2:1.  Imbalances in these major minerals result in abnormal growth.  While it's fairly easy to make sure that the grain fed to a horse has the right ratio of minerals (because the feed companies make them that way), hay can vary widely.  In particular, alfalfa hay can have a calcium:phosphorus ratio of anywhere from 4:1 to 8:1, making balancing the minerals in the complete diet almost impossible, unless you have the hay analyzed.


(2)  Trace minerals such as zinc and copper, as well as vitamin cofactors are key elements of enzymes that build the cartilage and convert cartilage to bone (ossification) during growth.  All of the minerals must be present within a certain range of total intake and balance, because too much of one mineral can result in deficiencies of the others.  Just a mineral block is not enough, because horses don't know when they need minerals.


(3)  Glycemic index is a term that is gradually working its way into the common vernacular.  A feed with a high glycemic index causes a spike of blood glucose and insulin in the body.  A feed with a low glycemic index is not associated with this insulin and glucose response.  The reason that this is important is that these wildly variable fluctuations in glucose and insulin contribute to the abnormal cartilage growth that results in physitis and OCD.  Therefore, low glycemic index feeds are ideal for feeding young horses.


How do I prevent DODs?


Fortunately, all this research is not just available to you and me, it is also available to the feed companies.  Therefore, most feed companies that produce horse feed, and specifically specialty feeds for growing foals and young horses provide minerals in the correct balance in their feed already.  There are only a few additional things that we need to closely watch to make sure that there are no mistakes.


(1)  Seems counterintuitive, but DON'T allow foals to eat from the mare's feed.  Mare feed is designed for high calories in order to support milk production.  The gastrointestinal tract of foals is not able to properly digest grain until at least 3 months of age.  The only thing the grain will accomplish is to produce the dreaded high glycemic response.  Foal creep feeds such as Foal Starter and Creep (Progressive Nutrition) which are milk based feeds with cooked oats or barley are designed for the intestinal tract of the foal.


(2)  Feed grain mixtures that are designed to be fed with grass hay to growing horses.  If you must feed alfalfa hay, then get it analyzed and consult the nutritionist for the feed company to have a specific grain mixture recommendation.  It is critical that the calcium:phosphorus ratio is correct for growing horses, or tendon contractures, OCDs and physitis will be inevitable.


(3)  Diet balancer mineral products are perfectly balanced in minerals for your growing horse, but the quantity may vary depending upon the age, weight and how fast the horse is growing.  Fortunately, there is almost a standard formula for these products across feed companies.  Similar products are available from most feed companies (M30, Stamm 30, Grow N Win, Purina 32); my personal favorite is Proadvantage (Progressive Nutrition).  A "unit" of balancer turns out to about a pound, or a pint volume of feed, no matter which company's product you are using.  Progressive Nutrition makes a handy chart for the horse owner to use to determine how much diet balancer you need for a growing horse in his stage of growth (http://www.prognutrition.com/pdf/GrowthChartDailyFeedPlannerLT05.pdf).

How do I treat DODs?


I've discussed how to prevent DODs, but how are they treated?  Some of the conditions are more easily treated than others.  Many physitis cases and tendon contractures respond to nutritional therapy.  These conditions are associated with rapid growth, likely because the mineral intake is imbalanced, and bone growth requires a different set of minerals than tendon or cartilage growth.  If the minerals can be properly balanced and any deficiencies corrected, synchronous growth of all the structures can be restored.

In order to restore mineral balance, I will typically feed these young horses 1/2 to 1 pound more diet balancer than the recommended quantity for their stage of growth.  If they are on alfalfa hay, it has to be discontinued and replaced with grass hay.  In suckling foals, mineral supplementation can be achieved by administering a paste or drench mineral supplement, such as Rejuvenaide (Progressive Nutrition) or Foal Aide (Buckeye Nutrition).  Again, for foals that already have a DOD showing up, I administer 15 - 25% more than the label recommendation.  Fortunately, in suckling foals, contractures will respond within just a few days to this mineral supplementation.  Physitis may take longer to respond, because the bony enlargement associated with physitis doesn't go down; it just stops getting bigger, and the foal grows into them.

If trauma or concussion is contributing to the DOD, such as can be the case with physitis, some exercise restriction is recommended.  Generally, the young horse should be restricted to a small paddock with one other buddy, so that excessive concussion from "running with the herd" is avoided.

What about non-nutritional treatments?

Physitis:  Many people advocate the use of poultice to help remove heat from inflammation of the growth plate.  This may help, but the majority of the heat and abnormal cartilage is deep within the growth plate and unaffected by the poultice.  Topical anti-inflammatory treatment with Surpass may also help, but again will only affect the superficial parts of the growth plate.  If the young horse is actually stiff or lame with the physitis, systemic anti-inflammatory medication is warranted, preferably Equioxx for 2-3 weeks.  Other anti-inflammatory drugs such as bute can predispose to stomach ulcers, so should be used with Gastrogard.

If the physitis is actually causing asymmetry of growth such that the legs are becoming crooked, then some other intervention is required.  Non-invasive therapies include trimming the feet lower on the side of the physitis to encourage growth on that side.  Shock wave therapy of the affected side may decrease the pain associated with the inflammation, increase blood flow and decrease inflammation, thereby stimulating growth of the affected side of the physis, and ultimately straightening the leg.  Some people are also advocating internal or external blistering of the affected side of the growth plate, also to increase the blood flow.

If the angular limb deformity ("crookedness") is severe, then surgery, where a screw is placed across the growth plate on the less affected side is indicated.  A screw is used to slow growth on the faster growing side of the physis and then allow the more affected side to catch up.  When the leg is straight, the screw is removed.

Contracture:  Caught early, nutritional treatment should correct most cases of contracture.  If allowed to progress, then complex splinting procedures, or even surgery, where tendons and ligaments are cut may be necessary.

OCDs:  OCDs can be prevented, but not treated with nutritional therapy.  Most researchers agree that the very beginning of OCD occurs in utero, so adequate mineral balance in the pregnant mare, and particularly in third trimester is critical.  The early signs of OCD in the young horse usually becomes evident from 8 - 12 months of age.  Treatments in this age group range from adminstration of Adequan (polysulfated glycosaminoglycans) or Legend (hyaluronic acid) to feeding calcium containing supplements.  As previously discussed, imbalanced high calcium or high phosphorus diets can cause OCDs, so additional supplementation should probably be avoided.  Shock wave therapy to stimulate blood flow to cartilage may be useful.  Platelet Rich Plasma (PRP) has also been advocated because of the growth factors that may be present in the PRP.  Equine Growth Hormone also stimulates the presence of local growth factors in cartilage that may return normal function to the cartilage.  Finally, surgery to inject corticosteroids into the lesion or remove the abnormal cartilage may be necessary.

Conclusion:


If your equine interests include foals or young horses, then developmental orthopedic diseases should be at the top of your list of concerns.  The most important factor that you can control is the nutrition.  Do not allow your foal to eat from the mare's feed tub, and provide a creep feed designed for the foal's digestive tract.  Make sure that your young horse has good quality grass hay and feed a diet balancer that is designed to be used with grass hay.  Avoid high glycemic index grains, like sweet feed until at least 2 years of age.  Allow foals to run in groups and spend at least 8 hours a days in free turnout for exercise.  Follow these simple steps to lay the foundation for a healthy and sound partnership for life.