The contribution of myostatin (MSTN) and additional modifying genetic loci to race distance aptitude in Thoroughbred horses racing in different geographic regions.
Authors: Hill E W, McGivney B A, Rooney M F, Katz L M, Parnell A, MacHugh D E
Journal: Equine veterinary journal
Summary
# Editorial Summary: Genetic Determinants of Race Distance Aptitude in Thoroughbreds Myostatin (MSTN) accounts for the majority of heritable variation in Thoroughbred race distance aptitude, but a multinational study of over 3,000 horses—including 835 elite performers—confirms that additional genetic loci also contribute meaningfully to this trait. Researchers genotyped 48,896 single-nucleotide polymorphisms across animals from Europe, the Middle East, Australasia, North America and South Africa, estimating heritability of best race distance at between 0.40 and 0.51 depending on career success level. The MSTN locus dominated the genome-wide association signal (with lead SNP BIEC2-438999 showing P = 2.33 × 10⁻⁴², most dramatically in elite horses), yet a genomic prediction model incorporating all SNP variation could stratify horses into distinct short- and long-distance cohorts with greater nuance than MSTN genotype alone. Whilst owner and trainer placement decisions introduce confounding factors that the study could not control, these findings suggest that genomic prediction tools could help align individual horses' inherited distance potential with race selection, potentially reducing unsuitable race entries and improving both performance outcomes and equine welfare.
Read the full abstract on PubMed
Practical Takeaways
- •Genetic testing for MSTN variants can reliably predict whether individual Thoroughbreds are genetically suited for sprinting or distance racing, enabling more appropriate race placement
- •Racing professionals can use genomic prediction models to match horses to race distances aligned with their inherited genetic potential, potentially improving performance and welfare outcomes
- •While MSTN is the dominant genetic factor, other genetic loci contribute to distance aptitude; comprehensive genomic panels will provide more nuanced predictions than single-gene testing alone
Key Findings
- •Heritability of best race distance is high (h² = 0.51 for elite horses, 0.42 for nonelite, 0.40 for all winning horses)
- •MSTN gene accounts for most genetic variation in race distance aptitude, with SNP BIEC2-438999 showing strongest association (P = 2.33 × 10⁻⁴² for best race distance in elite horses)
- •Genomic prediction algorithm successfully partitioned horses into short and long distance cohorts based on MSTN genotype plus additional minor contributing loci
- •Additional modifying genes with minor contributions to best race distance were identified beyond MSTN