Genomic loci associated with performance limiting equine overriding spinous processes (kissing spines)

Commonly known as "Kissing Spines" (KS), the pathological mechanisms underlying impingement and overriding of spinous processes (ORSPs) in horses are poorly understood. Thoroughbreds, Warmbloods, and stock-type breeds, including Paint Horses and Quarter Horses are at increased risk for developing clinical signs of KS. A total of 155 stock-type and Warmblood horses presented at collaborating veterinary clinics and hospitals were examined using a strict clinical and radiographical phenotyping scheme to grade each horse from 0 for unaffected controls to 4 for severe KS. Following genotyping with the Illumina Equine SNP70 array (Illumina, Inc.) a Genome Wide Association Study (GWAS) using 61,229 filtered individual Single Nucleotide Polymorphisms (SNPs) was performed to the KS grade phenotype. Two significantly associated SNPs (BIEC2-668062 and BIEC2-668013) on chromosome 25 defined a ~1.4 Gb candidate region containing approximately 17 coding genes (EquCab3) and 195 ENSEMBL annotated variants. Investigation of the best associated SNP (BIEC2-668062) on chr25 demonstrates a significant correlation with an increase in one KS grade, on average, per A allele in this population. A significant effect of breed group, age, height or sex was not observed in this population. These preliminary results demonstrate the potential for KS diagnosis and preventative measures for WB/ST individuals supported by increased genetic risk for more severe KS grade. We propose further research including other affected breeds and evaluating causative variants, as well as the effect of BIEC2-668062 in these populations.

Comparison of American Quarter Horses Competing in Western Pleasure, Hunter under Saddle, and Reining Using Linear Traits

Simple Summary

This study analyzed differences between successful American Quarter Horses competing in different disciplines by using linear traits. The goal was to detect whether American Quarter Horses successful in specific disciplines significantly differed in exterior traits. Traits were measured analogically and photometrically. Differences in lengths, angles, ratios, and circumferences were detected. Further studies are needed to better examine the specialized traits and the effect of genomic variance.

Abstract

To investigate differences in American Quarter Horses conformation suggesting specialization and subpopulations within the breed, a total of 45 horses were studied. These horses were classified according to their specific sport discipline: Western Pleasure (WPL, n = 15), Hunter under Saddle (HUS, n = 15), and Reining (RN, n = 15). Fifteen linear traits (comprising lengths, angles, and circumferences) were measured analogically and photometrically. Afterwards, 9 ratios and differences were calculated, so that a total of 24 traits were examined. The results showed significant differences between horses depending on their sport discipline. HUS horses were significant taller and were characterized by higher values in (nearly) all length traits; they were followed by WPL and RN horses. RN horses displayed the lowest values in length traits but the largest difference between height at withers and height at croup. Nine parameters were analyzed through correlations to the height at withers; all differences were significant, with high to moderate correlation coefficients. The detected differences between the groups support recent studies on the conformation and genotype of subpopulations within a breed and reveal new findings in relation to the selected disciplines. Image analysis worked well and provided reliable data; therefore, this method can be used to examine horses in a time-efficient manner, reducing the stress caused to the animal. Further studies are required to gain more information and to associate the features of AQH anatomic structures with successful performance.