Characterization of greying, melanoma, and vitiligo quantitative inheritance in Old Kladruber horses

The paper deals with the greying process, melanoma, and vitiligo depigmentation occurrence in Old Kladruber horses (OKH). The study includes 376 animals of both sexes at the age of 1-25 years. The evaluation was performed repeatedly during 4 consecutive years. The greying status was measured spectrophotometrically on four body parts using L*a*b* colour system. Melanoma and vitiligo were detected visually and by palpation in all the animals and classified using 5 (3) grade scale. The GLM procedure of SAS package was used to examine the influence of the effects of line, age, sex, stud, and year of evaluation. The GLM analysis confirmed a significant impact of age on greying. Parameter L* showed progressive increase until 10 years of age when all horses reached final grey level. Subsequent analyses suggested the influence of sex, i.e. a notably higher level of greying in mares. The incidence of melanoma was confirmed. Melanoma in OKH most frequently occurs on the bottom of the tail or at the anal and perineal area. Probably only benign forms of melanoma have been detected. The global occurrence of melanoma in OKH (ca. 13%) is substantially lower than in Lipizzan and Camargue horses. Overall incidence of melanoma in horses at the age of 15 and older reached 68%. Genetic parameters were estimated for melanoma grade, grey level, and vitiligo. Greying is strictly influenced by age (h2 = 0.52 ± 0.07). Prevalence of melanoma progresses with age (h2 = 0.07 ± 0.04). Vitiligos of both facial and anal parts are influenced by the effects studied (h2 = 0.20 ± 0.05 and 0.34 ± 0.06 for vitiligo A and vitiligo F, respectively).