Crypto-tobiano horses in Hucul breed

Abstract

The aim of the study was to verify the hypothesis that the crypto-tobiano horses which do not exhibit the full tobiano white-spotting pattern nonetheless transmit the dominant To gene to the progeny. The study was conducted on the Hucul population. Seven horses with white patches on their limbs, and with or without a small patch on the head, neck or trunk, were selected. At least one of the parents of the horses had to be tobiano or crypto-tobiano. Occasionally such horses produced a tobiano foal from a crossing with a solid-coloured horse. The white patches of the horses used in our study were divided into categories. To identify the To gene, DNA was tested in the Animal Genetics Laboratory (UK). The ratio of non-tobiano, crypto-tobiano, and tobiano foals born from 36 matings of the studied horses was analyzed. The study substantiates the occurrence of crypto-tobiano horses in the Hucul breed. Horses that have patches on their limbs as well as a small white or intermingled patch on the head, neck or trunk, are crypto-tobianos, although crypto-tobianos may have no white on the head, neck, and trunk. The crypto-tobiano pattern occurs in horses which have a tobiano parent or grandparent. The results suggest that the activity of an inhibitor gene suppresses the To allele penetrance in the crypto-tobiano horses. As in the case of many white-spotting patterns, the presence of the To gene in a horse's genotype should be documented by DNA testing or test matings.

Keywords

• coat-colour phenotype
• marking
• to gene
• white-spotting pattern