White muscle disease is also called nutritional myodegeneration. It happens in foals of mares grazed on selenium or vitamin E deficient pasture. It causes skeletal and cardiac problems. Selenium helps to prevent muscle damage. It can be seen in cardiac muscle, this is often acute and happens quickly. The foal is often weak and may die due to heart failure and suffer respiratory stress. When it is seen in skeletal muscle it is more chronic, it causes the foal to be weak and it may have problems suckling. This type can be reversed, as long as it is not too severe. Selenium is a component of glutathione peroxidise which is an antioxidant and prevents muscle damage, which is why there are problems when it is not there. Muscle fibres are fragmented, mineralisation happens and there is inflammation of the surrounding fat. Selenium can also be toxic.
Developmental Orthopaedic Disorders (DODs) ecompass many different disorders such as physitis, subchondral bone cysts, angular limb deformities, wobble syndrome. Osteochondrosis dissecans (OCD) is when there is abnormal cartilage formation. There are many theories to the cause of these such as genetic, trauma, nutritional, or all of these. If it was nutrition then it could be due to high carbohydrate which is associated with insulin secretion. Low exercise, excess or deficiencies of proteins may also have an effect along with copper deficiency in the uterus and in growing youngsters and Ca:P inbalance. To treat or manage this you should restrict exercise to minimise damage, reduce carbohydrate intake, copper supplements, intra-articular steroids and arthoscopic surgery, this can be used to remove the damaged fragments of bone, and it is debrided.
Exertional Rhabdomolysis has a number of clinical signs- stiffness, changes in gait, pain in gluteals, hard swollen muscles, sweating, recumbancy, increased respiratory rate and myoglobinurea.This could be due to electrolyte deficiency or selenium or vit E deficiency or a hormonal disturbance. There is muscle fibre damage from increased enzyme activity and the leakage of enzymes and myoglobin into peripheral circulation. It is treated by giving pain relief and muscle relaxants, the Na+ and K+ blood concentrations should be monitored. Selenium and Vit E should be supplemented. They may also be given fluid therapy. The diet should be managed by reducing the starch/ sugar carbohydrate in the diet. You can give them electrolytes. Ensure the vitamins and minerals are correctly balanced. And avoid lush fast growing pasture.
These disorders show the importance of correct feeding in the equine!