Multifactorial inheritance of common white markings in the Arabian horse.

The research article discusses the influence of several factors on the appearance of common white markings on the face and legs of Arabian horses, suggesting these markings follow a multifactorial mode of inheritance. The factors studied include the horse’s sex and genotypes (specifically those relating to bay and chestnut coats).

Research Methodology

• The study expands previous research that focused on white facial markings in Arabian horses by including an examination of the legs.
• The research involved data from the Arabian Horse Registry of America, Inc., focusing on specific sire families—composed of the sire, his foals, and the dams of the foals.
• Each horse’s leg was scored from 0 to 5, based on the extent of white markings present. The sum of these scores provided a total leg score for each horse.
• Similarly, each horse’s face was divided into five areas, with a score from 0 to 5 assigned based on the number of areas with white markings.

Findings

• A key finding of this research corresponds to the positive correlation observed between white facial scores and white leg scores. This suggests that the same genetic mechanism influences both types of white markings.
• Analyses of the relationships between parent horses (sires and dams) and their foals align with the hypothesis that common white leg markings follow multifactorial inheritance—much like the facial markings suggested by previous research.
• Despite the main finding indicating additive gene action (polygenes) affecting the prevalence and extent of common white markings, the study also found that male horses are slightly more marked than females, and chestnut horses more so than bay horses.

This research broadens the understanding of the genetic factors influencing the appearance of white markings in horses, yet also indicating non-genetic factors such as sex contribute to the extent of these markings.