Genetic parameters of insect bite hypersensitivity in Dutch Friesian broodmares.

This research sought to understand the effects of maternal and genetic factors on Insect Bite Hypersensitivity (IBH) in Dutch Friesian broodmares. The study found that IBH, an allergic skin disease caused by certain insect bites, is influenced by both these factors but the role of the maternal environment was less significant than genetic and other permanent environmental factors.

Background and Purpose of the Study

• The researchers aimed to study the maternal influence and genetic tendencies for IBH, a common seasonal allergic skin disease in horses. This disease is provoked by bites from specific types of Culicoides insects.
• Understanding the heritability and repeatability of IBH in Dutch Friesian horses was a primary objective. The team wanted to delve deeper into the occurrence and transmission patterns of IBH in this horse breed.

Methodology

• The researchers carried out the study on a large sample of 3,453 Dutch Friesian broodmares, observing clinical symptoms of IBH visually.
• Twelve inspectors scored the observations at organized foal inspections in specific years.
• IBH was analyzed as a binary trait, indicating the presence or absence of the disease in the horses. The researchers used a Bayesian approach for statistical modeling.

Findings

• An 18.2% prevalence of IBH was found among the Dutch Friesian broodmare population.
• The heritability of IBH was calculated, indicating how much of the disease’s occurrence can be attributed to genetic factors. Heritability on the liability scale was 0.16, while on the observed scale, it was 0.07.
• The repeatability, or the consistency of the disease’s presence in the population, was very high at 0.89. This indicates that if a horse had IBH once, it’s highly likely it would have it again.
• The maternal effect, showing the impact of the mother’s health and genetic makeup on the development of IBH in her offspring, was significant at 0.17, but less influential than other factors. An animal model without the maternal effect was a better fit for the data, reinforcing this conclusion.

Conclusion

• The researchers concluded that genetic and permanent environmental factors are key in understanding the occurrence and recurrence of IBH in Dutch Friesian horses.
• Though the dam’s impact on the offspring’s development of IBH, through both genetic influence and their rearing environment, is significant, the role of the environment is more substantial.