Genetic profiling of thoroughbred racehorses by microsatellite marker analysis

The thoroughbred (TB) horse breed has exceptional physiological traits and is well-known in horse racing. It has been bred for endurance, strength, and speed for 300 years. Recently, there have been many studies on the molecular characteristics or mechanisms associated with elite athletic performance of the TB breed, and sequence variants in exercise-related genes have also been reported. Here, using 12 microsatellite markers, we assessed genetic diversity and relationships among two groups of TB racehorses (registered by the Seoul Race Park of the Korea Racing Authority) that showed the 48 highest and lowest scores in races. When comparing allelic variation between the highest- and lowest-scoring TB horse groups, a total of 53 different alleles were detected by genotyping with 6′FAM-labelled primers. The genetic variation between the two groups was similar [mean number of alleles (N _A ) = 4.00 and 4.08; allelic richness (A _R ) = 3.95 and 4.01; observed heterozygosity (H _O ) = 0.53 and 0.56, respectively]. However, among the 53 alleles that we assessed, four alleles were detected only in the highest-scoring and five alleles only in the lowest-scoring racing horse group. The group-specific unique alleles indicate that the microsatellite markers could distinguish horses that showed high or low scores in a race. This study demonstrates the feasibility of microsatellite analyses for selection of superior racehorses and suggests further study to understand the relationship between molecular features and phenotype (racing performance).