Genome‐wide association mapping of heritable temperament variation in the Tennessee Walking Horse

Abstract

Temperament is a key criterion in the selection of horses for both leisure and competitive riding to ensure optimal performance and safety. The Tennessee Walking Horse (TWH) is described as a calm, docile breed and is often used as a trail, show and pleasure horse. However, among horse owners and caretakers, there are anecdotes supporting familial and disciplinal typical behaviors and personalities. To investigate the contribution of genetics to temperament, we collected a behavior questionnaire, brief training history and identifying information for 276 TWH, as well as blood or hair samples for DNA. Factor analysis was conducted on the 20-item questionnaire for the set of 216 horses that met inclusion thresholds. Factor analysis identified four temperament factors in TWH: 'anxious', 'tractable', 'agonistic' and 'gregarious'. These four factors account for 64% of the total trait variance. DNA from 113 TWHs were selected and genotyped using the Equine SNP70 bead chip for three separate genome-wide association studies (GWAs) using the factor 1-anxious, factor 2-tractable and factor 3-agonistic scores as the phenotype. Quantitative association analysis identified significant candidate loci for each factor that warrant further investigation.

Priming for welfare: gut microbiota is associated with equitation conditions and behavior in horse athletes

“…Further support for this hypothesis has been elegantly reviewed by Johnson et colleagues 65 , who reported evidences that symbionts have evolved to manipulate host behaviour for their own ends. As genetics have been insufficient to explain the physiology of horses with extreme differences in behavior 66,67 , microbiability offers a new opportunity to define novel contributory mechanisms through the gut-brain axis.…”

Imputed genomes of historical horses provide insights into modern breeding

“… 49 However, neither Baron nor Ronald carried an excess of derived alleles for variants associated with anxiety or agonistism. 48 Overall, the imputation methodology developed here and implemented for the first time in historical horses showcases how the range of characterizable phenotypes can be advantageously extended beyond what measurable from their skeletal anatomy and described in historical sources.…”

“… 47 Finally, Ronald was homozygous for derived mutations in TUFM , GSG1L , and VPS13B , which are associated with tractability and are rare in modern Thoroughbreds. 48 He was also heterozygous for an allele in HTRA1 , which has been associated with lower tractability in Thoroughbreds. 49 However, neither Baron nor Ronald carried an excess of derived alleles for variants associated with anxiety or agonistism.…”

Factor analysis of evaluated and linearly scored traits in Swedish Warmblood horses

“…Besides benefits for genetic evaluation and ranking of horses, knowledge about interrelationships between traits and reduction of trait number can also facilitate genomic analyses of linearly scored traits. Previous genome‐wide association studies used principal component analysis or factor analysis to reduce the number of linearly scored temperament or body measurements traits in Tennessee Walking horses (Staiger, Al Abri, et al, 2016; Staiger, Albright, & Brooks, 2016) or number of accelerometer gait traits in young sport horses (Ricard et al, 2020). Furthermore, genome‐wide association studies in other species such as goats and cattle could find plausible candidate region(s) or genes(s) associated with principal components or factor traits (Miles et al, 2021; Nazari‐Ghadikolaei et al, 2018).…”