A cohort study of racing performance in Japanese Thoroughbred racehorses using genome information on ECA18.

This study investigates the impact of certain genetic variations on the racing performance of Japanese Thoroughbred racehorses. Findings suggest that specific single nucleotide polymorphisms (SNPs) on the 18th equine chromosome, particularly those within or close to the gene encoding myostatin (MSTN), may influence factors like race distance and subsequently affect performance rank and lifetime earnings of these horses.

Study Approach and Participants

• The researchers conducted a cohort study with a sample of 1710 Japanese Thoroughbred racehorses. The major aim was to investigate how different genotypes at four specific SNPs on equine chromosome 18 (ECA18) influenced racing performance.
• The selected SNPs for the study were identified in a prior genome-wide association study, showing potential links to racing performance, lifetime earnings, and performance rank.

SNPs and Racing Performance

• The findings revealed significant associations between certain genotypes at the SNPs and the performance rank of the horses, both male and female. For male horses, the SNPs g.65809482T>C and g.65868604G>T had significant relationship with performance rank (P=0.005).
• Among female horses, g.65809482T>C (P=1.76E-6), g.65868604G>T (P=6.81E-6), and g.66493737C>T (P=4.42E-5) showed strong relationships with performance rank. These SNPs also influenced the lifetime earnings of the female horses (P<0.05).

Genotypes and Racing Distance

• The researchers observed significant associations between all four SNPs and the win-race distance (WRD) among all winning racehorses, and best race distance (BRD) among elite racehorses (P<0.001).
• Such results suggest that genotypes in the ECA18 region might have an influence on the optimal racing distance for Thoroughbred racehorses. Consequently, the association of these SNPs with performance rank could be linked to a bias in race distances.

Implication of Myostatin Gene

• Researchers posit that the regulation of the MSTN gene, which the identified SNPs are within and nearby, may affect racing performance in Thoroughbred racehorses.
• The SNPs g.65809482T>C, g.65868604G>T, and g.66493737C>T specifically, or their combinations, could potentially serve as genetic diagnostic markers for performance indicators like WRD and BRD in racing.