Bred for Speed? By Shannel Cacho

Bred for Speed?


Can we breed horses for speed based off of their genetics?  In 2010, researchers from the Trinity College Dublin and the University College Dublin announced they had discovered a “speed” gene, after looking at the DNA of twelve Thoroughbred stallions. However, before I start explaining the “speed” gene, let me give you some genetics definitions to aid you in the reading of this blog.


Gene: Basic physical and functional unit of heredity. Genes are comprised of DNA. Horses have two copies of each gene; they get one from their dam and one from their sire.

Alleles: A variant (due to mutation) of a gene.

Nucleotide:  Building blocks of DNA.

Non-coding DNA: DNA sequences that do not encode for proteins.

Polymorphism: The presence of genetic variation within a population.

Single Nucleotide Polymorphism (SNP): Variation of DNA at a specific location (nucleotide)

Short Interspersed Nuclear Elements (SINE): A polymorphism that causes non-coding sequences of DNA.

Myostatin: Protein that influences muscle cell growth and differentiation.


Let’s get the rest of the technical stuff out of the way before explaining exactly how this research might benefit the thoroughbred industry.  The “speed” gene is a polymorphism in the horse’s myostatin gene. According to a study by Rooney et al 2018 “Polymorphisms in the myostatin gene (MSTN), a pronounced inhibitor of skeletal muscle growth that has been shown to almost singularly account for gene-based race distance aptitude in racehorses.” There are two polymorphisms in the horse’s myostatin gene that creates the “speed” gene. One of the polymorphisms is a SINE and the other is a SNP, the SNP is the polymorphism that the scientists believe to have the highest correlation with optimal race distance.


So if there’s a gene that is indicative of speed in horses, how do you determine what speed/distance your horse should perform best? In 2010, Equinome launched the Speed Gene Test, which has proven to be over 90% accurate, to determine a horse’s optimal race distance.


How does the test determine that you ask? In order to get this test done, one must submit a blood sample from the horse that they would like to have tested. This blood will have its DNA extracted for analysis, where the myostatin gene will be isolated to determine which alleles for that gene that horse possesses. There are two alleles, ‘C’ and ‘T’ that determine the expression of the myostatin gene. From these two alleles, you can get three different types of horses. ‘CC’ horses tend to be earlier maturing, have a larger mass, and tend to be the tallest of the three types. These physical attributes result in ‘CC’ horses being your sprinter types, who are best suited to run faster speeds at short distances (one mile or less). ‘CT’ horses are deemed to be your middle distance runners, and are the most versatile of the three. ‘TT’ is the last possible combination and these horses tend to be later maturing, but excel in longer races that require stamina. ‘TT’ horses are considered the “wild type” or most common type, followed by ‘CC’ and then ‘CT’ types.


What’s the benefit? The biggest benefit from having the knowledge of which type horse you have, is that it can save time and energy when training and also when you are trying to decide which races may fit your horse best when starting out. 


Although this test is not 100% accurate, it can provide a good starting place. For example, if your horse is ‘TT’, chances are you will understand that you should probably wait to start it until it is three years old and has had time to mature. This test simply provides trainers and owners with the knowledge of what distance their horses should run best, and they can be handled accordingly. This “speed” gene can be utilized to increase a horse’s chance of winning and better match breeding’s to desired outcomes. At the end of the day this test is simply another tool for horsemen to optimize.