Genetic parameter estimates of performance traits in Iranian Thoroughbred race horses using a Bayesian approach.
Authors: Taned M, Zandi M B, Salek Ardestani S, Abdoli M, Spangler M L
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Genetic Parameters in Iranian Thoroughbred Racehorses Effective breeding programmes depend on understanding how much of a racehorse's performance is determined by genetics versus environmental factors, yet this information is sparse for non-European Thoroughbred populations. Researchers analysed nearly 15,000 Iranian Thoroughbreds' pedigrees and race records (2002–2021) using Bayesian statistical methods to estimate heritability and genetic trends for race completion time, finishing rank, and average speed. Race completion time and average speed showed moderate heritability (0.25 and 0.23 respectively), suggesting meaningful genetic selection is possible, whilst finishing rank was largely environmentally determined (heritability of 0.09); concerning genetic trends emerged despite stable phenotypic performance, with completion times deteriorating by 0.15 seconds per year and average speed declining 0.02 m/s annually—patterns masked at the surface level by strong rider and race-day environmental effects. These findings suggest Iranian breeding programmes have inadvertently selected for slower horses, and breeders and trainers should reconsider selection criteria and pedigree management to reverse unfavourable genetic trends and sustain long-term competitiveness.
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Practical Takeaways
- •Breeding programs should prioritize selection against increasing race completion times and declining speeds, as moderate heritability indicates genetic improvement is achievable through selective breeding
- •Environmental factors (rider skill, race conditions) significantly influence race outcomes, so consistent management and rider training are important alongside genetic selection
- •Current phenotypic stability masks unfavorable underlying genetic trends; breeders should use genetic predictions rather than race results alone when making breeding decisions
Key Findings
- •Heritability estimates were moderate for race completion time (0.25) and average speed (0.23), but low for rank at end of competition (0.09)
- •Unfavorable genetic trends showed increased race completion time by 0.15 seconds per year and declining average speed of -0.02 m/s per year over the study period
- •Rider and race environmental effects contributed notably to variation in performance traits, masking underlying genetic changes in phenotypic trends
- •Despite stable phenotypic performance, genetic trends indicate need for revised breeding strategies to improve long-term genetic merit in Iranian Thoroughbreds