Association analyses of forehead hair whorls, behaviour, and chromosome regions in Standardbred Trotters

Abstract: Introduction: In horse breeding, athletic skills have been in focus and certain behaviour types have been found to be important for competition. Behaviour is heritable but is also affected by the environment. Just like humans, animals have their own personality and behaviour-traits. The hair whorls in the equine forehead and their potential meaning have been discussed by people practising horsemanship. They are believed to tell us things about the horse’s behaviour and personality. The hair whorls are thought to take form when the skin on the foetus expands during growth in the uterus. At a certain timepoint during development, the hair follicles get set in their angle that gives the hair its direction to grow. But exactly how the hair whorls get their specific appearance and what position they get is unclear. Since both brain and skin cells originate from the ectoderm, there are theories that the brain can be mirrored by the overlying skin. The aim of this study was to investigate if there is an association between facial hair whorls and behaviour as well as finding regions of interest for the hair whorl types in the horses’ DNA. Material and method: The behaviour data to be analysed in this study had already been collected through a survey in another project about genetics and behaviour. The behaviour traits analysed were nervosity, excitability, fearfulness, concentration, learning, memory, cooperation, will to win, stubbornness, self-control, recovery, appetite and stereotypic behaviour. In that survey the trainer gave the horses scores between 1-7 depending on how often they saw the behaviour during competition. Hair samples from the horses’ tails had also been collected. This study analysed the association between the thirteen different behaviour traits from the survey and nineteen different hair whorl types in 175 Standardbred trotters. Their DNA were extracted, and their genome low pass sequenced and analysed. Their genomic information was run in a computer program that compared the individuals in the different hair whorl groups. The hair whorls were inspected live or from a photo, a protocol was filled out and a photo was taken on the horses’ forehead. The horses were then divided into groups as low (1 and 1-2) and high (7 and 6-7) scores from the survey, and hair whorl groups that were classified as contraries. Statistical association analyses were then performed between individuals that had extreme scores (1 against 7 and 1-2 against 6-7) in the behaviour traits according to the survey, and the differing hair whorl groups. The association were analysed using two by two contingency tables. The results of this study can indicate the following; if a facial hair whorl is located to the right (to the left from a frontal view), the chance is bigger that it becomes nervous during competition in comparison to a horse with a facial hair whorl to the left (p-value: 0,025). If a horse has more than one facial hair whorl, it more often took longer for it to learn the task of competing (p-value: 0,03). Comparing the horses that had a facial hair whorl looking like a feather, there was a greater chance of the trotter to be focused and concentrated during competition if the feather went in a vertical direction, compared to if it had a horizontal or diagonal direction (p-value: 0,05). If the feather was vertical, they also had a higher chance of having good appetite after competition (p-value: 0,03). On five chromosome regions, but one especially, there was found a highly significant difference between horses with one hair whorl and horses with two hair whorls in the forehead. For future investigations in this subject, these results can serve as an interesting basis about associations between facial hair whorls, behaviour, and genetics of Standardbred trotters.