Glucocorticoid assessment in the domestic horse: the impacts of time and climatic variables on sample integrity

Background: Assessment of faecal glucocorticoid metabolites (FGM) offers a noninvasive method of monitoring adrenal activity in domestic horses. Samples are collected on an opportunistic basis and, if they are not fresh or have been exposed to the elements before they are identified, may not accurately reflect FGM concentrations. Objectives: To explore the impact of a range of environmental conditions upon the integrity of FGM levels in equine faeces. Study design: In vitro experiment. Method: Equine faeces were exposed to six controlled environmental conditions intended to simulate a range of weather and seasonal patterns (temperate climate, high heat, high heat and rainfall, temperate climate and rainfall, high heat/temperate climate, freeze/thaw) over a period of 5 days. FGM were quantified using an enzyme-linked immunoassay. Results: Faecal samples exposed to room temperature and high heat demonstrated significant increases in FGM levels over time. No changes in FGM levels were observed in the remaining treatments. Main limitations: The study should be repeated in field conditions and with known high and low levels of FGM to further inform sampling regimes. Conclusions: Adrenal monitoring in the domestic horse should be performed with consideration of the impact of climate on the integrity of faecal samples in order to further inform sampling schedules and improve the reliability of results