Texas Equine Veterinary Association

• 25 • growth rate produces mature horses that will grow as big as their genetic growth rate will allow. Rapidly growing horses will reach their mature height and weight much earlier than those fed for a moderate rate of growth. Since that time much has been learned about feeding foals and management of foals. ere have been many studies made on the relationships of bone density and bone and cartilage development to nutrition and to exercise management. We know that different nutrients and their levels in the diet are important, as well as the nutrient's relationship to each other. It can be just as wrong to have an excess of a nutrient or nutrients, as it is to have a deficiency of a nutrient or nutrients. We also have learned that exercise management can have a profound influence on bone and cartilage development and the relationship to soundness later in training and racing. A major concern of horsemen is the occurrence of Developmental Orthopedic Disease in young horses. is is a group of disorders known as: 1. Epiphysitis/Physitis – inflammation of the growth plate – "Open knees" "Hour glass fetlocks"—an enlarged ridge just above or below a joint 2. Flexural deformities—May be present at birth (congenital) or acquired. "Bucked knees", "Contracted Tendons", "Club Feet". "Knuckling Over" 3. Angular limb deformities— Valgus conformation ("Knock knees") or ("Cow hocked"), or varus conformation ("Bow legged") 4. Osteochondrosis—Cartilage/ bone fragments usually involving a joint or bone cysts that may or may not communicate with a joint. 5. Cuboidal Disease—seen in knees and/or hocks in newborn foals. Bones in those affected joints are not developed and this condition is manifested with weak joints incapable of supporting the foal properly 6. "Wobblers"—Malformation of spinal vertebrae producing an alteration of gait because of spinal cord impingement. All of the above disorders have a genetic, a nutritional and a management relationship. At present we have to live with the genetic considerations; the nutrition and management factors we can do something about. Developmental Orthopedic Disease appears to have a multifactorial relationship. Contributory factors are as follow: 1. Excessive amounts of energy in the diet. It is still not clear if the excess energy is the problem or possibly that the increased energy level is not supported by all the other nutrients. is is sometimes referred to as "empty" or "hollow" calories. 2. Rapid growth rates. ere appears to be a relationship with fast growing horses. Rapid growth also creates exaggeration of conformation defects thereby increasing uneven weight bearing. 3. Compensatory growth clinically is thought to cause DOD. Angular limb deformities and contracted tendons can follow a rapid growth spurt. It is also suspected that cartilage abnormalities can result when a foal experiences a growth setback followed by a period of accelerated growth. 4. Excessive protein has been blamed for causing DOD but this has not been proven. A deficiency of protein has been shown to be a contributing factor. Bone begins as a protein matrix so a protein deficiency at these developmental stages may be a factor. 5. Mineral deficiency, particularly calcium and phosphorus, and trace mineral deficiencies of copper and possibly manganese and zinc. 6. Mineral imbalance may contribute to DOD. Excess minerals may interfere with the absorption of others by forming insoluble complexes making them unavailable. 7. Confinement of as little as 2 weeks causes a loss of bone density. Regular exercise or "bone loading" is important for developing bones to create the stress necessary for strong bones. 8. Trauma appears to have a definite role. Many times when foals have been confined then are allowed to exercise, joint surfaces may be traumatized. ere appears to be "windows of vulnerability" at which time certain bones in the developmental stage may be more susceptible to trauma. An example of that relates to foals confined early having a tendency to have fetlocks involved, whereas foals confined later seem to have a higher incidence of hock and stifle problems. 9. High blood sugar and high blood insulin levels have shown a relationship with osteochondrosis. Raising a good foal starts with the pregnant mare. Balanced nutrition in the pregnant mare is important at all stages of pregnancy. A foal's development really accelerates when she enters her last 90 days before foaling. Sixty-five (65%) percent of the growth of the unborn fetus occurs the last 90 days. e mare's energy needs (caloric intake) go up 20%, her protein needs go up 35% and her calcium and phosphorus needs go up 90%. Increased levels of potassium, magnesium, and selenium are also needed. e most common error in broodmare management is not increasing a mare's nutrition the last ninety days and having mares foal with their ribs showing (Body Score < 5; "...disorders have a genetic, a nutritional and a management relationship. At present we have to live with the genetic considerations; the nutrition and management factors we can do something about."

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