Abstract
Functional longevity is essential for the well-being of horses and the satisfaction of riders. Conventional selection using longevity breeding values calculated from competition results is not efficient because it takes too long to obtain reliable information. Therefore, the objective was to identify early criteria for selection. We assessed two types of early criteria: gait traits of young horses and QTLs. Thus, our aim was to estimate the genetic correlation between gait traits and longevity and to perform a genome-wide association study (GWAS) for longevity. Measurements of gaits by accelerometry were recorded on 1,477 show jumping horses that were 4 to 5 years old. Gait analysis provided 9 principal components describing trot, canter, and walk. Longevity estimated breeding values (EBVs) for stallions were calculated using a survival analysis of more than 900,000 years of performances by 179,448 show jumping horses born from 1981 onwards. Longevity was measured as the number of years spent in competition. Model included region and month of birth, age at first competition, year, and performance level. Longevity EBVs were deregressed to obtain weighted pseudo-performances for 1,968 stallions. Genomic data were available for 3,658 jumping horses. Seventy-eight percent of the horses measured for gaits and twenty-five percent of those measured for longevity were genotyped. A GWAS of longevity revealed no significant QTLs. Genetic parameters between each of the 9 principal components of the gait variables and longevity were evaluated with a bi-trait animal linear mixed model using single-step GBLUP analysis with the relationship matrix constructed from genomic data and genealogy (24,448 ancestors over four generations). The heritability of the gait traits varied from 0.11 to 0.44. The third principal component for trot (high lateral activity) and the first principal component for canter (high dorsoventral activity and low stride frequency) were moderately genetically correlated with higher longevity: rg = 0.38 (0.15) and 0.28 (0.13), respectively. Our study revealed that functional longevity is a polygenic trait with no major genes. We found new correlations between longevity and gait traits. Before using gait characteristics in a selection plan, these correlations need to be understood better at the biomechanical level.
Highlights
Jumping is one of the most popular equestrian sports in Europe and the main breeding objective of riding horse breeds (Koenen et al, 2004)
The aim of this study was to use a description of gaits based on accelerometric data and competition results to estimate the genetic correlation between functional longevity and gait characteristics
We found no genetic correlation between the height at withers and functional longevity
Summary
Jumping is one of the most popular equestrian sports in Europe and the main breeding objective of riding horse breeds (Koenen et al, 2004). Recent advances in wearable technologies readily allow locomotor performances to be objectively measured in the field using kinematic or accelerometric analysis (see Egan et al, 2019 for a review) Another way to identify early criteria for the selection of horses with a better longevity is through the use of genomic information because it can be available at birth. This is an option when there are QTLs. the availability of detailed genomic data can improve the efficiency of genetic analysis, with a more accurate relationship matrix between relatives
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