Developmental Orthopaedic Diseases in Young Growing Horses

By Gail Sramek BApplSc Agr – Consulting Nutritionist to Mitavite


DOD or Developmental Orthopaedic Diseases is a term given to a range of conditions that occur in the growing horse. They generally encompass conditions such as physitis, oseochondrosis, angular limb and flexural deformities, and vertebral and tarsal bone malformations. The occurrence of DOD is associated with irregularities of skeletal growth that is linked with how the cartilage is converted to bone by a process known as endochrondral ossification.


The typical time for the onset of physitis and osteochondrosis is from approximately 3-20 months for osteochondrosis and 4-12 months for physitis. These are critical times where the formation of good, solid bone needs to be achieved to minimise the incidence of the disease. There are some key factors that when combined can contribute to DOD. These include:

  • Excessive growth
  • Feeding an unbalanced ration
  • Genetics - some breeds are more susceptible to bone growth disorders
  • Trauma and exercise - excessive exercise may contribute to bone disorders. Free paddock exercise in a paddock no smaller than 5 acres will allow young horses to develop muscle to support the bone and build bone density
  • Hormonal factors


Nutrition can have a large impact on the incidence of DOD particularly in the areas of energy intake and correct mineral balances.


The growth rate of a horse is related to the energy a young growing horse receives. It is important that optimal growth rates are obtained, not maximum when growing out young horses. Research on DOD has suggested that rapid growth is a major contributing factor to DOD in some horses. Feeding excess energy levels above approximately 130% of maintenance have been shown to induce skeletal abnormalities and disturb the metabolism of the growth plate cartilage, in some horses.



Feeding the correct amount of macro and micro minerals and vitamins help to build good strong bone. Minerals such as calcium, phosphorous, magnesium, copper and zinc are needed in the correct amounts and in the right ratios. In a study it was reported that oesteochondrosis was more prevalent in foals with a lower bone mineral density. Feeding too much of a mineral is just as bad as not feeding enough. Feeding excess levels of Phosphorous for instance can disrupt the calcium:phosphorous ratio influencing the strength of the bone. Excess levels of Zinc can affect the uptake of Copper as these minerals use the same transport mechanism in the small intestine.


Research on the Dietary Cation Anion Balance (DCAB) in a ration has shown how DCAB can have an impact on bone related disorders. Studies have suggested rations with a low or poor DCAB can cause an increase in urinary excretion of chloride and calcium. This can contribute to a metabolic acidosis and cause the horse to be in a negative calcium balance. If this type of ration is fed over a prolonged period demineralisation can occur and the skeletal system can become weakened.


New research on the function of Vitamin K1 has found it has an integral role in the formation of strong, dense bone. A protein in the bone called oestocalcin needs Vitamin K1 to stick the major components of bone together, Collagen and Hydroxyapatite. Without adequate levels of Vitamin K1 the oestocalcin cannot bind the major components of the bone together to build bone with good structure and density. Research by Ray Biffin and his associates have shown that there has been a reduction in the incidence of bone diseases in young growing horses supplemented with Vitamin K1. The bone density of these trial horses has improved over the period of supplementation. We would strongly suggest that any diet for a young growing horse should contain Vitamin K1 to ensure good bone density and geometry.


When formulating a ration for young growing horses correct bone growth is of primary importance. The foundations of the bone are being set in the first twelve months of the horses life which need to be correctly formed and strengthened to minimise injury and promote soundness during training and racing. When feeding horses that have been diagnosed with DOD we suggest feeding a diet that is correctly formulated and balanced. The ration detailed below is suitable for horses post surgery or for horses with positive x-rays to minimise the need for surgery.


Promita is a fully steam extruded concentrated, nutrient dense, premium breeding feed that is low in sugar and starch and fed at low rates, but will still provide the protein, vitamins and minerals young growing horses need to build good skeletal structure and lean muscle. Promita contains Bonafide to correctly form strong dense bone. Some studs like to ‘double dose’ on Bonafide by feeding an additional 10g with the Promita ration to enhance the building of strong bone. This ration is a broad guideline and you may need to make adjustments depending on the response of the horse to the ration and your assessment of the horse.


Daily Ration: 6-12 Month Weanling - Estimated Mature Weight 500kg

Mitavite Promita1.5kg
Vitamite Bonafide10g
Lucerne Chaff/HayApprox 1kg
Mixture Pasture or Oaten/Meadow HayAd lib pasture or 2.5 - 4.5kg


Understanding the signs and causes of developmental orthopaedic diseases can help stud managers to prevent and treat this disease. Incorporating a feeding regime that is tailored for these young growing horses can minimise the incidence of this disease and help to repair damaged bone and cartilage.


For further information on feeding young horses, contact us via our diet analysis service or call us on our toll free number 1800 025 487.