The genetics behind the athletic performance of Thoroughbred racehorses has been a popular area of research in the past few years. A large-scale study was carried out recently in Japan, the results of which corroborate those of previous studies: Identifying specific "performance genes" on equine chromosome 18 could identify the ideal distance for a Thoroughbred to race. Some industry veterinarians, however, suggest that this information should still be evaluated and used with caution.

Researchers on four separate studies have previously identified a region of DNA on chromosome 18 (which the researchers referred to as ECA18) that they believe could be associated with racing performance. One of the research teams found a specific mutation in the myostatin gene (MSTN) located on ECA18. Researchers also previously evaluated the myostatin mutation and determined that it contributes to muscle hypertrophy (enlargement) and might be useful in predicting whether a horse is better suited for short-, mid-, or long-distance races.

To further assess the ECA18 genes’ influence on athletic performance, Teruaki Tozaki, PhD, from the Laboratory of Racing Chemistry’s Department of Molecular Genetics in Tochigi, Japan, recently analyzed genetic material from blood samples collected from Thoroughbred racehorses registered with the Japan Racing Association and born between 1993 to 2000 in Japan.

Tozaki’s team identified four specific genetic mutations (single variations in the DNA) called single nucleotide polymorphisms (SNPs) on ECA18 within or near the MSTN gene using standard polymerase chain reaction (PCR) and genetic sequencing techniques. Then they compared genetic sequences of these SNPs in 1,710 horses with performance records including most successful race distance, win-race distance (i.e., the average distance of races won), performance rank, and lifetime earnings