Endotoxin concentrations within the breathing zone of horses are higher in stables than on pasture.

This research shows that the level of endotoxins, which can cause inflammatory airway disease, is significantly higher in horse stables compared to pastures, indicating that stabling horses may be exposing them to greater health risks.

Research Context and Goals

• Common among stabled horses is an inflammatory airway disease, which has been seen in about 17.3% of pleasure horses in Michigan. It is believed that this condition could be related to exposure to endotoxins, common in stable dust and known to provoke neutrophilic airway inflammation.
• Climatic conditions such as ambient temperature and relative humidity have traditionally been considered to have influence on endotoxin concentrations in pastures.
• The primary objective of the study was to ascertain whether endotoxin levels are indeed higher in a horse’s breathing space inside stables compared to pastures, and if these endotoxin levels in pastures were directly linked to various climatological conditions.

Research Methodology

• The research used six horses as subjects to measure endotoxin exposure. These horses alternated between living in stables and pastures.
• A Limulus amebocyte lysate assay, a test traditionally used to gauge endotoxin levels, was used for the study.
• Climatological data, which might have influence over endotoxin concentration, were sourced from the US National Climatic Data Center.

Research Findings

• The research found there to be a considerable difference in endotoxin exposure between horse stables and pastures. In specific, horses in stables were exposed to endotoxin levels approximately eight times higher than when they were in pastures.
• Interestingly, on pastures, endotoxin levels exhibited a wide range of levels despite stable climatological conditions.
• It was therefore concluded that horses in stables are definitely exposed to higher levels of endotoxins, contributing to a higher health risk.
• The study also indicates that local concentrations of endotoxins may play a bigger role in determining individual horses’ endotoxin exposure than climatic conditions.