Genetic conditions often affect both the health and the physical condition of the foal or horse. Most genetic conditions appear to be inherited from one or both parents. Genetic defects include any abnormality that is due to a change in the DNA that affects development, such as a new mutation occurring in the embryo's DNA that causes a problem, but is not inherited from either parent.
With scientists working to reveal equine genomic information and how to use molecular tools to prevent and/or heal inherited or DNA-based diseases, a number of breakthroughs can be expected during the next few years.
Among the disease mutations that affect foals, three of the most common include Junctional Epidermolysis Bullosa (JEB) Overo Lethal White Syndrome (OLWS) and Myotonia.
Junctional Epidermolysis Bullosa is a condition found in American Saddlebreds and other light breeds of horses. It results in a letha skin condition in affected foals. Both parents of the foal must have the mutation for it to affect a foal. The mutation was discovdred at the University of Kentucky Animal Genetic Testing Lab with support from the American Saddlebred Horse Association. Another form of JEB affects the Belgian Horse.
Overo Lethal White Syndrome gets its name from the affected foals which are all white or nearly all white at birth and have improperly formed rectal tissue that either results in death or requires euthanasia when they are a few days old. When two carriers of the mutation are bred, there is a 25 percent chance of a foal inheriting the mutation. Although most common in Paint, pinto, and Quarter horses, the mutation has been found in Tennessee Walking Horses, also.
Myotonia is an inherited neuromuscular disorder that has been identified in New Forest pones which is caused by an autosomal recessive mutation. Carriers of the mutation appear normal, but when two carriers are mated, a 25 percent chance exists that an affected foal will be produced.
Foals affected with Myotonia have abnormal muscle activity and spend much of their time lying down. They also exhibit gaint abnormalities.
Fortunately for horse owners, many equine teaching hospitals and centers offer testing services to disease mutation testing of animals that are to be bred. Among them are Cornell University, UC Davis, University of Florida and the Gluck Equine Center at the University of Kentucky.