HERDA-associated variant in bull-catching (vaquejada) Brazilian Northeastern bull-catching Quarter Horses.

Overview

• This study examines the frequency of a genetic variant associated with Hereditary Equine Regional Dermal Asthenia (HERDA), a serious skin disease, in Brazilian Northeastern bull-catching Quarter Horses (QH).
• The research aims to inform breeding practices to reduce the occurrence of HERDA and its associated economic and animal welfare impacts.

Background

• Bull-catching (vaquejada): A popular equestrian sport in Brazil involving Quarter Horses, representing about 13% of sport horses in the country.
• HERDA (Hereditary Equine Regional Dermal Asthenia): A genetic skin disorder causing fragile skin, wounds, and lesions, which significantly affects the welfare and performance of horses.
• Significance of Genetic Screening: Genetic testing has become a critical tool to prevent the spread of inherited diseases like HERDA within horse populations.
• Regulatory Requirement: The Brazilian Quarter Horse Breeders Association requires screening for HERDA as part of the Six Panel DNA tests for horse registration.
• Prior to this study, the HERDA-related genetic variant had not been evaluated specifically in bull-catching Quarter Horses from Northeastern Brazil.

Objective

• To determine the frequency of the HERDA-associated genetic variant (allele frequency) in the bull-catching Quarter Horse population of Northeastern Brazil.

Methods

• Sample: 141 bull-catching Quarter Horses from Northeastern Brazil were tested.
• Testing Technique: The presence of the HERDA-associated variant was assessed using Sanger sequencing, a precise DNA sequencing method.

Results

• Eight horses were identified as heterozygous carriers of the HERDA variant, meaning they possess one copy of the mutated gene but do not exhibit the disease.
• The allele frequency of the HERDA variant was calculated at 0.028 (2.8%).
• This frequency was found to be the third highest among all Brazilian Quarter Horse disciplines evaluated for HERDA.
• Assuming random mating in the population, statistical models predict approximately one affected foal (homozygous for the variant) would be born per 1,000 births.
• Additionally, approximately 58 horses are expected to be carriers based on the allele frequency and sample size.

Conclusions

• Because breeding practices are often nonrandom (horses are selectively bred), the actual number of affected foals or carriers may be higher than predicted by random mating assumptions.
• The study reinforces the importance of mandatory genetic testing for HERDA to:
• Inform breeding decisions to avoid producing affected foals.
• Reduce economic losses related to veterinary care and loss of performance.
• Minimize animal suffering caused by the disease.
• Overall, this research provides valuable population data that support the implementation of better management and breeding control strategies within the bull-catching Quarter Horse community in Northeastern Brazil.