Inheritance of hereditary equine regional dermal asthenia in Quarter Horses.

The research article investigates the inheritance and heritability of a genetic skin disease, hereditary equine regional dermal asthenia (HERDA), in Quarter Horses. The study reveals that HERDA is passed down through generations in Quarter Horses and the mode of inheritance is most likely autosomal recessive.

Objective and Methods

• The purpose of the study is to understand the heritability and inheritance pattern of HERDA in Quarter Horses—a common skin disorder prone to this breed.
• The researchers evaluated pedigree data from 1,295 horses that have Quarter Horse bloodlines, out of which 58 horses were affected by HERDA.
• Horses were sorted into categories: affected, unaffected, or undetermined. The final category included horses where the data was insufficient.
• Beyond understanding the mode of inheritance through pedigree data analysis, heritability was also estimated through the use of Bayesian statistical methods.

Findings and Results

• The heritability (ability of a trait to be passed from one generation to the next) of HERDA was estimated at around 0.38. This means that 38% of the observed variation or differences in the disease can be explained by genetic variations.
• Results showed no sex bias; both male and female horses had an equal chance of getting affected.
• Analysis of the pedigrees pointed to a single Mendelian autosomal recessive mode of inheritance. This means a horse needs to inherit the HERDA gene from both parents to exhibit the disease symptoms.

Conclusions and Implications

• HERDA in Quarter Horses comes as an inherited disease; thus, an affected horse is naturally more likely to produce similarly affected offspring.
• Given the autosomal recessive nature of this disease, breeders need to exercise caution during breeding. If a horse has been either confirmed with HERDA or it has produced affected offspring, it is highly probable that its offspring might carry the disease if mated with another carrier.
• Moreover, breeders are recommended to avoid inbreeding as it can heighten the risk of producing affected horses in the future.