Genetic (co)variance components across age for Show Jumping performance as an estimation of phenotypic plasticity ability in Spanish horses.

The research aims at understanding the phenotypic plasticity (or the ability of an organism to change its phenotype in response to changes in the environment) of Spanish show jumping horses as they age.

Objective of the Research

• The primary objective of this research was to study the phenotypic plasticity of Spanish show jumping horses. The researchers examined how these horses’ performance in show jumping varied with age, indicating changes in their genetic potential. The study analyzes data from over 11,000 participations of about 1,085 horses within the age groups 4-, 5-, and 6-years old.

Methodology

• The researchers used two main strategies: repeatability animal models (RAM) and multiple trait animal models (MTAM). The RAM assumed that covariance components (measures of how much two random variables move in tandem) for horses are equal across all age groups. On the other hand, the MTAM treated the results of each horse at each age group as unique yet correlated traits.
• The study also considered several fixed effects, including the horse’s age, sex, starting order in the competition, and training level. They also analyzed random effects such as the animal’s individual behavior, the competition environment, and the rider.
• In total, six models were compared to evaluate different aspects of horse performance. Notably, the rider-horse interaction was added as a random effect, and a varied residual variance, which quantifies prediction errors, was taken into consideration only for MTAM.

Findings

• The research found an age-genotype interaction, indicating that horses’ performance changes with age due to environmental effects.
• This finding suggests that there are different trajectories of performance for show jumping horses as they age. Some horses might have a gradual response, slowly building up their skills over time. Others might show a precocious response, reaching their peak performance early and then gradually losing their genetic potential as they age.
• As such, understanding the phenotypic plasticity of horses could aid in their selection for different roles within equestrian sports depending on their adaptive responses to their environment.