Genetics vs Genomics for Horse People

Phoebe Bright talked with UCD Associate Professor Emmeline Hill about her work in equine genomics

A version of this article was published in The Irish Field, October 6, 2017

Emmeline Hill grew up with horses.  Her father bred and kept horses in training with Jim Bolger and Paddy Mullins, while her grandmother  who bred national hunt horses and owned Dawn Run, rode point-to-points into her 60s.  But she has made her mark, not with exploits on horseback, but in and the study and practical application of equine genomics.  Her science studies at Trinity College Dublin focused on genetics which because the basis for her PhD.  In 2004 she was funded by Science Foundation Ireland to establish the world's first research programme dedicated to studying the genes for performance traits in thoroughbred horses. And the rest is history.

Genetics and Genomics

Horse breeders study genetics, how the characteristics of different mares and stallions are passed on to their foals.  We see how some stallions stamp their foals with certain traits, both desirable and undesirable, and look at previous crosses from our mare and see what traits she has passed on.  Our breeding decision will depend on many factors, including the type of horse we want to produce and the importance we put on each trait, speed, soundness, trainability, conformation etc.  Finally we make a choice and wait to see what the outcome will be.  But until now we haven’t been able to determine which genes were actually passed on, we could only look at the horse and then see how the horse turned out.

Equine genomics is the study of how a particular gene, or more commonly a group of genes influence a particular trait. But this study can't happen until the DNA for that species has been sequenced.  Once we have the sequence it's like being given a book in an unknown language, the detective work to decode the language can begin.  Emmeline had an early success when she found that the trait for speed vs. distance was linked to just one gene, which was quite remarkable considering most traits are linked to a combination of different genes and take longer to decode.

What led to the Speed Gene discovery?

In 2004, as her research programme began, Emmeline was not expecting to see the horse genome sequenced in her lifetime, but this was to happen only a few years later in 2007, thanks to a major collaborative effort, and the hunt was now on to find how traits matched to genes. In the early days, the challenge was to collect samples and accurate data about the horse's traits, in particular their speed and distance abilities as they developed in training.  With the support of some Irish trainers and breeders Emmeline was able to collect enough data to find a clear link between one particular gene and the preference for short or long races, not only that but this gene was inherited in a predictable way. She called it the “Speed Gene”. A breeder who knows the speed gene value for both their mare and proposed stallion can predict with a high degree of certainty what distance the progeny will be best suited for.

Turning Genomics into a Business

In the past the horse was a book written in a language we could not understand and we had to judge the book by it's cover.  Research in horse genomics is leading to businesses that provide genetic tests, that start to translate this book into information we can use to make breeding decisions, assess untried youngsters, inform training decisions, race choices and assess risk for different kinds of disease and injury.  The company founded by Emmeline, Equinome is now a part of  Plusvital which offers, alongside the Speed Gene Test, additional tests for likely optimum distance, dirt vs. turf and projected height.  Over 80 stallions speed gene results are published on the Plusvital site with stallion owners seeing sharing this information as adding value to their stallions by helping breeders make decisions more likely to lead to a successful racehorse.

What Makes a good or bad racehorse?

Now that Plusvital has tested over 15,000 horses, the next challenge is to work out what traits make a successful racehorse and see if they can be linked to particular genes or groups of genes.   Some of the traits currently being investigated include behavioural traits - some horses adapt well to the training yard and it's routines, others do not, physiological traits and traits that affect health and soundness.

Even if we can decode the full equine genome, this is only the starting point to producing a successful horse. Factors including training, diet, rider skills, accidents and luck will still be the deciding factors on whether a horse is successful as a racehorse, show jumper or as a treasured companion.  There are only a few genetic tests available today (see there will be more every year.  If you could reduce the risk of breeding an unsalable horse and increase the chances of breeding a successful horse, would that be worth the cost of genetic testing? Hindsight is a great thing, foresight is much better.   

See Emmeline Hill at The HorseTech Conference 2017