Aging and How It Affects the Response to Exercise in the Horse
Authors: McKeever Kenneth Harrington
Journal: Equine Geriatric Medicine and Surgery
Summary
# Editorial Summary: Ageing and Exercise Response in Horses Durability in racehorses—encompassing traits like racing longevity and competitive soundness—carries significant economic value and welfare implications, yet little is known about how these characteristics respond to the physiological demands of ageing and training. McKeever's investigation examined the heritability of durability traits and whether genetic markers could predict racing participation, analysing over 4,500 Thoroughbreds to establish that the number of 2- and 3-year-old race starts carries a heritability of 0.11 (±0.02), indicating moderate genetic influence. Three candidate genes emerged from genome-wide association analysis: neurotrimin (NTM), which influences brain development and was selected during domestication; opioid-binding protein/cell adhesion molecule-like (OPCML); and prolylcarboxypeptidase (PRCP), a gene implicated in voluntary exercise motivation and body composition regulation in mammalian models—suggesting genetic variation in exercise motivation may underpin a horse's capacity to tolerate training intensity and racing stress. A predictive model incorporating relevant single nucleotide polymorphisms (SNPs) accounted for 24.7% of heritable variation, and when validated in an independent cohort of 528 horses, horses with high genetic potential showed significantly lower failure-to-race rates (16% unraced versus 27% in low-potential horses) and superior racing outcomes. For practitioners, this research indicates that genetic screening may eventually help identify which young horses possess inherent physiological resilience to training demands, potentially informing selection decisions and allowing tailored conditioning programmes to optimise durability and welfare.
Read the full abstract on PubMed
Practical Takeaways
- •Genetic testing using SNP panels may help identify young Thoroughbreds with greater likelihood of racecourse participation and performance, potentially reducing wastage of unsuitable horses
- •Candidate genes (NTM, OPCML, PRCP) linked to exercise motivation and body composition suggest some horses may have inherent biological predisposition to training demands
- •Approximately 75% of heritable variation remains unexplained by current SNP models, indicating other genetic and environmental factors significantly influence racecourse durability
Key Findings
- •Heritability of racecourse starts in 2-3 year old Thoroughbreds estimated at h² = 0.11 ± 0.02 (n=4499)
- •Genome-wide association identified NTM, OPCML, and PRCP genes as candidates associated with racecourse durability
- •Random forest model identified SNPs contributing to 24.7% of heritable variation in racecourse starts
- •Horses with high genetic potential had 16% unraced vs 27% unraced in low potential cohort, with more favourable race outcomes (n=528 validation set)