Genetic Markers


Researchers at Equinome presented two studies last week demonstrating the association of specific genetic markers with precocity and height in Thoroughbred racehorses. These will allow owners and trainers to better identify which individuals are more likely to win at a young age and also those that are more likely to be of the desired height suitable for their requirements.

The two studies were presented to a gathering of the leading equine geneticists in the world at the 10th International Havemeyer Equine Genome Mapping Workshop, which took place last week in the Azores.


The first study showed that the specific genetic variant in the myostatin gene used in the Equinome Speed Gene Test – which predicts the optimum race distance of a Thoroughbred – is significantly associated with age of first win in flat racing Thoroughbreds. Horses with the T:T genetic type were on average seven months older than those horses with the C:C types when they won their first race. However, the later-maturing T:T-type horses subsequently went on to earn significantly higher average total lifetime earnings than C:C types.

The segment of chromosome 18 encompassing the gene encoding myostatin was identified as the genomic region with the strongest association with first race win across the entire horse genome.

Another finding of the study was that no genomic regions were shown to be significantly associated with age of first race. This indicates that many C:T and T:T type horses are commencing their racing careers prematurely and would be better suited to racing later in their two-year-old season or even as a three-year-old.


The second study validated the association of sex and a marker in the gene ECA3 with mature height in 299 Thoroughbred horses. Using this information, it was found that mature height at withers can be predicted within 2.54cm (1 inch) with a 70% success rate.

Individuals with the T:T variant in the ECA3 gene are typically at the short end of the range, those with the C:C variant in the ECA3 gene are typically at the tall end of the range and those with the C:T variant are typically of medium height. Breeders can therefore use this information to ensure they produce more horses of the desired height by testing their mares and stallions prior to breeding decisions, and purchasers can predict with a high level of confidence the future height of an individual when it is still a foal.

Click here for the details of the study on precocity.

Click here for the details of the study on height.


Byword is a C:T classification