Racing Performance of the Quarter Horse: Genetic Parameters, Trends and Correlation for Earnings, Best Time and Time Class.
Authors: Faria Ricardo, Vicente António, Silva Josineudson
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Researchers in Brazil analysed 38 years of sprint racing records (1978–2015) from 5,861 Quarter Horses to quantify the genetic basis of racing performance, examining earnings by age two, best racing time, and time classification at both 301 m and 402 m distances using Bayesian statistical methods. Heritability estimates ranged from 0.10 to 0.37 for individual traits and 0.15 to 0.41 when analysed together, indicating that whilst genetics influences racing performance, environmental factors remain substantial contributors—a finding that should encourage practitioners to recognise the limits of selective breeding alone. A notable discovery was the strong negative correlation between early earnings and best time (–0.95 to –0.96), meaning that horses earning more at two years consistently ran faster, yet this relationship weakened considerably at the genetic level (–0.29 to –0.37), suggesting that earnings capture phenotypic variation that pure speed genetics do not fully explain. Whilst the overall dataset showed positive genetic trends across all measured traits, analysis of the final decade (2006–2015) revealed either negative genetic change or stagnation, indicating that the Brazilian Quarter Horse racing population may have plateaued despite decades of selection. For breeding programme design, the authors recommend combining earnings data with direct measures of racing time and time classification to create more effective selection indices that capture both economic and performance outcomes—an integrated approach more likely to sustain genetic improvement than relying on any single performance metric.
Read the full abstract on PubMed
Practical Takeaways
- •Include earnings alongside best time and time class in Quarter Horse breeding selection programs to maximize genetic gains in sprint racing performance
- •Monitor recent genetic trends closely—recent decade shows performance plateau or decline despite historical improvements, indicating need for breeding program review
- •Racing performance traits show sufficient heritability (10-41%) to respond to selection, though non-genetic factors also substantially influence race outcomes
Key Findings
- •Heritability estimates for racing performance traits ranged from 0.10 to 0.37 (single-trait analysis) and 0.15 to 0.41 (two-trait analysis), indicating low to moderate genetic influence
- •Strong additive genetic correlations (-0.95 to -0.96) exist between earnings at 2 years and best time at both 301m and 402m distances
- •Positive genetic trends were observed across the 38-year study period (1978-2015), but the last decade (2006-2015) showed negative genetic trends (loss) or stagnation
- •Repeatability estimates of 0.31 to 0.46 suggest moderate consistency of racing performance across repeated races