Abstract
ObjectiveAccording to oral traditions of horse caretakers and trainers, the differences in the position and number of facial hair whorls may be associated with temperamental traits. Elucidating genetic background of facial hair whorls and its relationship to temperamental traits may promote more efficient breeding and maintenance of racehorses. In this study, we estimated heritabilities of the position and number of facial hair whorls in Japanese Thoroughbred horses.ResultsThe number of facial hair whorls varied from one to four and heritability estimate in 4024 Thoroughbred horses was low (h2= 0.160). The positions of facial hair whorls were categorized into high, medium, and low, based on their locations. This trait was estimated to have high heritability (h2= 0.643) in 3782 Thoroughbred horses. These results indicated that a larger proportion of the variation in the studied population was due to genetic factors for facial hair whorls position. Because a similar result was also observed in another horse breed, Polish Konik horses, high heritability of facial hair whorl position may be characteristic of multiple horse breeds. We expect that these results will stimulate future studies to elucidate the relationship among temperamental traits and facial hair whorls in all horse breeds.
Highlights
Horses have about 2-cm-long hairs on their body, and hair whorls exist on various body parts
Heritability estimates By eliminating horses in small paternal half-sib families and horses with the same phenotypes as in their paternal half-sib families, 4024 horses that had one (3280 horses) or two (744 horses) whorls and their 10,765 ancestors were used for estimating heritability of facial whorl number
In this study, high heritability (h2= 0.643) of facial hair whorl position was demonstrated in Thoroughbred horses
Summary
55.77% horses had one whorl at the high position, 22.93%—at the medium position, and 2.37%—at the low position. Heritability estimates By eliminating horses in small paternal half-sib families and horses with the same phenotypes as in their paternal half-sib families, 4024 horses that had one (3280 horses) or two (744 horses) whorls and their 10,765 ancestors were used for estimating heritability of facial whorl number. We calculated heritability estimate of whorl number to be 0.160 (Table 2). By eliminating horses in small paternal half-sib families and horses with the same phenotypes as in their paternal half-sib families, 3782 horses with one whorl in the high (2556 horses), medium (1111 horses), and low (115 horses) position, and their 10,592 ancestors were used for estimating heritability of facial whorl position. Heritability estimate of whorl position was 0.643 (Table 2). The posterior probabilities of the heritability of the whorl number and position showed that those heritability estimates clearly differed from zero and generally distributed normally (Additional file 1: Figure S1), indicating that these are heritable traits
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