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  • Horses
  • Performance

4. 11. 2026

Genes behind Performance - MSTN, PDK4, COX4I2

Selecting horses based on their performance is one of the fundamental principles of breeding, and while it’s historically mainly based on performance results and observations, today, science allows us to also take a glimpse into the genetic background. However, genetics is only one of the many puzzle pieces that’s needed to make a great performance horse – as the saying goes, breed the best to the best, and hope for the best!

Most genetic studies on this topic have been conducted on Thoroughbreds, so let’s look at some of the genes associated with their performance.

  • The MSTN (Myostatin) gene, also known as the speed gene, is probably the most established performance gene in horses. It affects skeletal muscle growth and fibre composition, and it’s used to predict optimal racing distance. Horses with the C/C genotype are considered more suitable for short distances than horses homozygous for the T allele, which are predicted to be more successful over long distances. Find out more about this gene here!

  • The PDK4 gene encodes pyruvate dehydrogenase kinase, (isozyme 4), a mitochondrial enzyme associated with energy metabolism. A 2010 study describes a connection to handicap rating – individuals with A/A or A/G genotypes were found to have a 16.2- 16.6 lb (roughly just under 7.5 kg) handicap advantage over G/G horses.

  • The COX4I2 gene encodes cytochrome c oxidase (subunit 4, isoform 2), an important enzyme for the mitochondrial electron transport chain and thus an important enzyme for energy gain. A 2010 study found a weak but significant link between this gene and racing performance, with the T allele being favourable over the C allele.

These three genes are just a glimpse of what an equine genome may potentially hide regarding performance. If you want to know everything hidden in your horse’s genome, EquineTest might be just what you are looking for! Find out more about how it works here!

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Start with a sample DNA report or order a whole genome DNA test for your horse.

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