The contribution of myostatin (MSTN) and additional modifying genetic loci to race distance aptitude in Thoroughbred horses racing in different geographic regions.

The study delves into the genetic factors, particularly the myostatin gene (MSTN) and other modifying loci, that govern the race distance aptitude in Thoroughbred horses from different parts of the globe. Using genomic tests and predictive models, the researchers identified that the MSTN gene majorly contributes to a horse’s best race distance, but mentioned other genes that have minor contributions, suggesting a better use of genetic prediction models to enhance race placements.

Objective and Methodology of the Research

• The central goal of the research was to examine the contribution of the myostatin gene (MSTN) and other modifying genetic loci to determining the best race distances for Thoroughbred horses. The researchers hypothesised that, apart from MSTN, there could be other genetic locations that contribute to the optimum race distance for these horses.
• The study involved a sample of 3006 Thoroughbred horses from diverse geographic regions, including Europe/Middle-East, Australia/New Zealand, North America, and South Africa. Out of these, 835 were ‘elite’ horses which were above 3 years old and had racing records.
• To carry out the research, the team conducted genome-wide association (GWA) tests and developed a genomic prediction algorithm. The goal was to compile a comprehensive catalogue of additive genetic variations affecting the best race distance for these horses.
• Around 48,896 single-nucleotide polymorphisms (SNP) genotypes, derived from high-density SNP genotyping arrays, were generated. The team subsequently carried out heritability estimates, GWA tests, and devised genomic prediction models for different phenotypes, including average race distance and best race distance for elite, nonelite and all winning horses.

Results of the Study

• Findings revealed high heritability estimates for different phenotypes, with most variation attributable to the MSTN gene. MSTN locus SNPs had the most potent association with the trait.
• The genomic prediction algorithm facilitated the inclusion of variation from all SNPs in a model that divided horses into short and long cohorts based on the assignment of MSTN genotype.
• The research also succeeded in identifying additional genes that present minor contributions to the best race distance for Thoroughbred horses.

Conclusions Derived from the Study

• The study reaffirmed the significance of MSTN as the most crucial genetic contributor to the best race distance in Thoroughbred horses. However, it also acknowledged the roles of other modifying genetic loci.
• Though non-genetic variables like the influence of owner/trainer decisions on race placements could not be controlled, the research advocated for the use of genetic prediction models for more accurate positioning of horses in races. This indicates a shift towards data-driven practices that take into account the horses’ inherited genetic potential for distance aptitude.