Stressed out: New insights for racehorse welfare from cutting-edge genomics research

Temperament is often referred to by winning connections as a crucial element of a racehorse’s success. Temperament reflects patterns of thought, behaviour and emotion and includes the ability to cope with the demands of training. Horses that do not easily adapt to the training environment may have extended periods out-of-training and unsuitable temperament is responsible for one in 16 thoroughbred horses discontinuing a racing career. Temperament traits therefore have animal welfare and economic implications, and may impact on handler and rider safety.

Scientists at University College Dublin and Plusvital Ltd, Ireland, have published new research in the peer-reviewed journal Animal Genetics, which describes the discovery of genes that are associated with stress and coping in the training environment. The article titled “Integrative genomics analysis highlights functionally relevant genes for equine behaviour” is the result of a four-year PhD research project that examined the stress hormone cortisol and the results of a questionnaire in 100 yearlings as they encountered key milestone events during the early training period.

Lead scientist on the project, Dr Amy Holtby said, “The most stressful event for a young racehorse is the first time it is backed by a jockey, with studies showing that it causes the greatest cortisol response in the horse. Some horses cope better than others, with lower cortisol reactions.”

A key finding of the research was that observations of the yearlings’ behaviour by highly experienced handlers did not agree with the cortisol results, indicating that cortisol identifies a distinct aspect of the stress response that is not perceivable to handlers.

Senior scientist, Professor Emmeline Hill said, “This means that some horses experience stress without acting out, and this could have detrimental long-term effects if it cannot be managed appropriately. Identifying genetic markers for the stress response could therefore have value in identifying horses most susceptible to stress.”

The scientists compared the genetic profiles of the yearlings that were best able to cope with early training to those less able to cope. Next they used genetic data from two different brain tissues that regulate the fear response and the modification of behaviour to pinpoint the genes that were most likely to impact on the ability to cope. This approach highlighted a set of genes that function (in other species) in social behaviour, suicide, stress-induced anxiety and depression, neurodevelopmental disorders, neuroinflammatory disease, fear-induced behaviours, and alcohol and cocaine addiction.

The gene that was most important in the thoroughbred stress response was NDN (necdin). This gene is associated with temperament in cattle, measured as ‘flight time’ (the time taken for an animal to reach a fixed distance following release from an enclosure). In mice the gene is associated with behaviour traits, and in humans it is associated with paranoia.

Dr Holtby said, “Everyone involved with racehorses recognises the importance of maintaining the mental well-being of their animals and balancing the training routine to keep them happy and engaged with their work. It is one of the most crucial aspects of training.”

Professor Hill said, “Genetics doesn’t have all the answers, but our research provides a sound scientific basis for genetic screening tools to support the highest welfare standards for the thoroughbred.

“The ‘nurture’ aspect of behaviour is of course a major factor, with the management of the animal impacting on its temperament. Our research has revealed genetic markers that could be used to identify animals that will benefit most from more nuanced handling. In time these makers could also be developed into tests to inform breeding decisions.”


Journal: Animal Genetics  Animal Genetics – Wiley Online Library

Special Issue: Functional Genomics and Annotation of Domestic Animals

Direct access link to scientific paper:

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