Quantitative genetic aspects of coat color in horses.

This study seeks to determine and understand the genetic factors that contribute to the different coat colors in horses. The research involved quantitatively measuring horse coat colors using established international procedures, and then using statistical methods to evaluate the heritability and repeatability of these color traits within and across different breeds and color classes.

Methodology

• The research took into consideration four coat color classes namely; gray, chestnut, bay, and black. These phenotypes were quantitatively measured in line with standardized international procedures defined by the Commission Internationale de l’Eclairage, abbreviated as L*, a*, and b*, in which L* denotes lightness, a* represents color saturation from red to green, and b* signifies color saturation from yellow to blue. The total color saturation, derived from a* and b*, was labeled as Chroma.
• An area assortment of the horse, including the neck, shoulder, and belly, from 294 horses across Lipizzan, Nonius, Arabian Pure Bred, Shagya Arabian, and Gidran breeds contributed to these measurements.
• Using the Restricted Maximum Likelihood (REML) method, the researchers derived estimates of heritabilities, both within individual breeds and color classes, and across different ones, and repeatabilities. They conducted this analysis through univariate animal models distinctly specified for gray and nongray horses.

Results

• For the gray horse category, within-breed heritabilities for L* were estimated between 0.45 to 0.49, whereas for a*, b*, and Chroma, these figures ranged between 0.09 to 0.52. These values suggest a moderate polygenic effect on these traits.
• For horses in the nongray category, heritabilities across different color classes were high, between 0.70 to 0.85. However, within-color class heritabilities were negligible, with the only significant values observed for L* measured on the neck and belly, at 0.21 and 0.34, respectively.
• The study also describes the relationship between L* and the total melanin content of the horse’s coat hair, discovering a strong negative linear relationship for both gray and nongray horses (significance level P < 0.01).

Conclusion

• The spectrometric measures derived in this study and these results demonstrate a possible approach for estimating the polygenic component that contributes to the inheritance of coat color in horses. This information contributes valuable data to ongoing research into coat color genetics, improving breeders’ understanding of color inheritance and bringing additional precision to horse breeding strategies.