Endurance Exercise Ability in the Horse: A Trait with Complex Polygenic Determinism.

Area of Science:

• Equine genetics and genomics
• Animal physiology and performance

Background:

• Endurance horses exhibit exceptional performance, relying on intense aerobic metabolism, efficient thermoregulation, and pain tolerance.
• Genetic factors are known to influence endurance performance and related physiological traits in Arabian horses, suggesting a heritable basis for adaptation to extreme exercise.

Purpose of the Study:

• To conduct a genome-wide association study (GWAS) to identify single nucleotide polymorphisms (SNPs) associated with endurance racing performance in Arabian horses.
• To investigate genetic underpinnings of traits including total race distance, average race speed, and finishing status (qualified, eliminated, retired).

Main Methods:

• A genome-wide association study (GWAS) was performed on 597 Arabian horses.
• Three mixed models incorporating fixed allele/genotype effects and random polygenic effects were utilized.
• Statistical significance was assessed using quantile-quantile plots and regression coefficients for log10(p-values).

Main Results:

• The GWAS identified five significant quantitative trait loci (QTL) comprising 6 SNPs on chromosomes 1, 6, 7, 16, and 29.
• Significant SNPs had corrected p-values ranging from 1.7 × 10^-6 to 1.8 × 10^-5.
• Two coding genes, SORCS3 (chromosome 1) and SLC39A12 (chromosome 29), potentially involved in neuronal tissues, were identified within QTL. A novel equine long non-coding RNA (KCNQ1OT1 ortholog) associated with cardiac rhythm regulation was also validated on chromosome 6.

Conclusions:

• Equine performance in endurance races is a complex polygenic trait influenced by multiple genetic loci.
• At least 5 QTL, including two coding genes with neuronal roles and three loci with regulatory functions (e.g., heart rate regulation), contribute to endurance performance.
• The findings provide insights into the genetic architecture of equine endurance and potential targets for selective breeding.