Characterisation of white facial markings in Pura Raza Española horses (a worldwide population genetic study)

White markings are characteristic of many equine breeds, being quite common in the Pura Raza Español horses (PRE). These white markings are the result of a lack of melanocytes in the skin and hair. In certain horse breeds, such as the PRE, the presence and extension of white facial markings is penalised in the breed’s patron and morphological competitions, so it would be interesting to include it in their selection genetics programs to select against the presence of this special feature. The aim of this study was to calculate the prevalence of white facial markings in a representative population sample of PRE and determine its prevalence depending on the coat colour, its genetic parameters and the influence of systematic effects. The white facial markings have been classified into 5 score. A total of 42,080 PRE horses were analysed. Genetic parameters were estimated using a Bayesian procedure with the BLUPF90 software. Systematic effects included in the model were: birth period, sex, birth stud geographical area and inbreeding coefficient. The pedigree information included 93,322 horses. The prevalence was 34.2%. Systematics factors were significant in the presentation of facial white markings. Heritability in real scale ranged from 0.53 for black to 0.32 for the chestnut coat colour population, both in the linear heterogeneity model. White facial markings were more prevalent in inbred chestnut males of Spain. The additive genetic base shows that the prevalence could be managed by genetic selection.