Allele frequency of muscular genetic disorders in bull-catching (vaquejada) quarter horses.
Authors: Sperandio L M S, Lago G R, Albertino L G, Araújo C E T, Ferreira C, Borges A S, Oliveira-Filho J P
Journal: Journal of equine veterinary science
Summary
Quarter horses competing in vaquejada (Brazilian bull-catching) carry significant genetic burden from muscular disorders including myosin-heavy chain myopathy (MYHM), polysaccharide storage myopathy (PSSM1), and hyperkalemic periodic paralysis (HyPP), yet prevalence data for this high-performance population were previously unavailable. Researchers genotyped 129 vaquejada QH athletes from northeastern Brazil to characterise allele frequencies of these four muscular genetic conditions. MYHM emerged as the most common variant with an allele frequency of 0.04, followed by PSSM1 at 0.01 and HyPP at 0.004; notably, no horses carried the malignant hyperthermia mutation, and all positive animals were heterozygous carriers without homozygosity detected. For equine professionals working with performance QH—whether in competition preparation, rehabilitation, or breeding programmes—these findings underscore the importance of genetic screening, particularly given that carrier status could influence exercise tolerance, metabolic demands, and response to anaesthetic protocols during surgical intervention. Establishing genetic testing protocols and informed breeding decisions within the vaquejada community could substantially reduce the transmission of these pathogenic alleles in subsequent generations.
Read the full abstract on PubMed
Practical Takeaways
- •Vaquejada quarter horse breeders should implement genetic screening protocols, particularly for MYHM given its relatively high allele frequency, to prevent transmission of pathogenic alleles to offspring
- •Performance horses competing in bull-catching events showing muscle dysfunction or exertional rhabdomyolysis should be genetically tested for MYHM and PSSM1, as these conditions are present in the competitive population
- •This baseline prevalence data enables targeted breeding decisions and early identification of carriers to reduce clinical disease incidence in this Brazilian athletic horse population
Key Findings
- •MYHM showed the highest allele frequency at 0.04 ± 0.01 in vaquejada quarter horses
- •PSSM1 allele frequency was 0.01 ± 0.01, followed by HyPP at 0.004 ± 0.01
- •All identified variants were present only in heterozygous form in the 129 studied animals
- •Malignant hyperthermia variant was not detected in this population of Brazilian Northeast vaquejada horses