Heritability and repeatability of insect bite hypersensitivity in Dutch Shetland breeding mares.

The study focuses on determining the heritability and repeatability of Insect Bite Hypersensitivity (IBH) in the Dutch Shetland pony population. It concluded that IBH, which is an allergic reaction to certain insect bites, is indeed a heritable trait and can potentially be minimized in the population through selective breeding.

Research Overview

The research uses observations from thousands of Dutch Shetland mares to calculate the heritability and repeatability of Insect Bite Hypersensitivity (IBH).

• Insect Bite Hypersensitivity (IBH) is a seasonal, reoccurring allergic reaction in horses to the bites of certain species of Culicoides insects. It’s a worldwide phenomenon and has significant implications for horse healthcare.
• The study utilized 7,924 IBH scores collected from 6,073 Shetland mares during foal inspections in 2003, 2005, and 2006. These mares were scored for clinical symptoms of IBH from June until February by 16 different inspectors.
• The distribution of observations varied, with 74.4% of mares having a single observation, 20.7% having two, and 4.9% having three. This allowed the researchers to compare IBH instances over different years.

Key Findings

The research draws several significant conclusions around the heritability and repeatability of Insect Bite Hypersensitivity (IBH):

• The overall average IBH prevalence was found to be 8.8%. This refers to the percentage of the studied Dutch Shetland mares that showed clinical symptoms of IBH.
• The heritability of IBH was determined to be 0.08 on the observed binary scale (presence or absence of IBH), and 0.24 on the underlying continuous scale (considering varying degrees of reaction). Heritability measures the extent to which offspring resemble their parents in terms of the trait being studied—in this case, susceptibility to IBH.
• The repeatability of IBH was calculated to be 0.30. Repeatability is the measure of consistency in a trait in an individual animal across different times or situations. A higher repeatability suggests that accurate selection for breeding can effectively reduce the prevalence of IBH in the population.
• The researchers conclude that, based on clinical symptoms, IBH is indeed a heritable trait amongst the Dutch Shetland pony population. This means that the prevalence of IBH could potentially be reduced through selective breeding.