Lavender Foal Syndrome (LFS), also known as Coat Color Dilution Lethal, is a fatal autosomal (chromosonal, not related to sex) recessive condition of Arabian horses. LFS is found primarily in horses with Egyptian bloodlines but has also been reported in other Arabian breeding groups. The genetic defect results from a mutation in a gene that causes neurological dysfunction in newborn foals.
The Veterinary Genetics Laboratory at UC Davis offers a DNA test for lavendar foal syndrome to assist veterinarians to make the correct diagnosis and owners to identify affected and carrier horses. The test uses DNA obtained from hair root samples thus avoiding blood sample collection. Breeders can use results from the test as a tool for selection of mating pairs to avoid producing affected foals.
Thought to be a recessive gene, the syndrome will only affect foals if passed on from both parents, resulting in the foal carrying two affected genes. It is possible therefore for a horse to be a carrier and not be affected, but to pass this gene on to future progeny.
If breeding a mare and a stallion that both carry one normal gene and one affected gene, the likelihood of a foal resulting in carrying two affected genes is 1 in 4. The likelihood of carrying no affected genes is also 1 in 4 while there is a 1 in 2 chance of the foal being a carrier of one gene like its dam and sire.
For those breeding mares or stallions that have produced affected foals before, the need for future breeding should be considered and weighed against the risk of producing an affected foal. Cross breeding may assist in producing a non affected foal, however it should be considered that a lot of other breeds have Arabian bloodlines in them.
Signs of LFS are characterized by seizures, severe hyperextension of limbs, neck and back (opisthotonos), stiff paddling leg movements, involuntary eye movement and inability to stand or sit upright. LFS foals are typically born with a telltale dilute coat color described as lavender, pale pink or silver. This coloring has lead to the name of the disease.
Because birthing of LFS foals is often difficult, the signs can be misinterpreted as resulting from oxygen deprivation during delivery or from a spinal cord injury. LFS foals may have a strong suckle reflex and may be bottle fed but the disease is untreatable and will not improve.
Foals will die or have to be euthanized shortly after birth.
If you have an Arabian mare or a stallion that you wish to breed and you do not know the history of the horse, it may prove wise to discuss with your veterinarian the possibility of lavendar foal syndrome and other genetic diseases of Arabians and have your animals tested before breeding takes place.