Does homozygosity contribute to the asymmetry of common white leg markings in the Arabian horse?

Abstract

Common white and facial markings have a multifactorial mode of inheritance in Equus caballus and result from the absence of melanocytes in the unpigmented areas. Directional asymmetry and fluctuating asymmetry apparently account for the total asymmetry of common white leg markings. Using computerized records obtained from the Arabian Horse Registry of America, Inc., and the International Arabian Horse Association, studies were carried out to determine if homozygosity increases the total asymmetry in common white leg markings by presumably promoting fluctuating asymmetry. The results were as follows: (1) Arabian horses that are symmetrical and asymmetrical for common white leg markings have similar distributions of inbreeding coefficients; (2) Arabian and half-Arabian horses have similar concordance values, in general, for specific white markings in both their forelegs and hind legs. It is concluded that homozygosity does not contribute to the total asymmetry of common white leg markings in the Arabian horse.