A mutation in the gene STX17 causes the greying phenotype in horses. Horses with this mutation are born coloured but gradually lose their hair pigmentation (not skin pigmentation) until they are grey or white at an age of about 6–8 years. The mode of inheritance is autosomal dominant. Heterozygous horses will be grey-white and, in most cases, never be completely white. Some horses show some speckling or a “flea bitten” pattern. Horses that are homozygous for the mutation will be completely white at an early age. Horses with the grey mutation show a high incidence of dermal melanomas (70–80% of Grey horses older than 15 years have melanomas) and reduced longevity. Homozygous carriers of the grey gene as well as horses born with a black coat seam to have a higher risk to develop melanomas compared to horses born with a brown coat.
The DNA test is performed out of EDTA blood or or 20-30 hair roots from mane or tail. Test kits can be ordered free of charge. (order-form). If hair is sent in, possibly the genetic material is not sufficient to run the test. In this case it would be best to send in an EDTA blood sample.
Please send in your sample together with the lab order genetic. Results will be transmitted optionally via post, fax or email. After completion of the test you will receive a separate invoice. Payment can be made via credit card or bank transfer. Breeding club discounts apply if a copy of the membership card is sent together with the respective samples. Due to administrative reasons the invoiced price can not be altered subsequently.