Genetic evaluation of performance traits in Brazilian Quarter Horse.

This study undertakes a genetic evaluation of performance traits in Brazilian Quarter Horses, garnering data from Brazilian race tracks and using advanced statistical models to determine heritability, repeatability, and genetic correlations for race time and speed.

Research Objectives

This research aimed to understand the genetic underpinnings determining the racing performance of Quarter Horses in Brazil. The primary goals were to:

• Estimate the genetic parameters impacting performance using data gathered from 1994 to 2003.
• Understand the heritability and repeatability of racing time and speed index.

Data Collection

Data for the study was provided by the Sorocaba Jockey Club and was collected from three Brazilian race tracks over a decade-long period. The dataset included:

• A total of 11,875 observations of race time.
• A total of 7,775 observations of the speed index (SI).

Research Methodology

The researchers utilized the MTGSAM program to estimate variance components. Their model included a combination of numerous factors, such as:

• Random additive genetic effect: Accounting for inherited traits that impact athletic performance.
• Random permanent environmental effect: These are environmental influences that have a permanent effect on a horse’s performance.
• The fixed effects of sex, age, and race: These are specific attributes tied to each horse that do not change over time.

Results

The results of this study showed:

• Hheritabilities for race time and the SI ranged between 0.26 to 0.41 and 0.14 to 0.19, respectively.
• Repeatabilities varied from 0.36 to 0.68 for time and 0.27 to 0.42 for speed index.
• The genetic correlations ranged from 0.90 to 0.97 for time and 0.67 to 0.73 for speed index.

These findings suggest a substantial genetic influence on racing performance, with a high degree of heritability and repeatability for both time and speed index. It is indicative that these genetic factors significantly contribute to racing performance in Quarter Horses.