Risk factors associated with gastric disease prevalence in extensively kept horses in Iceland evaluated four times in a calendar year

Background It is unknown whether the high prevalence of Equine Squamous (ESGD) and Equine Glandular (EGGD) Gastric Disease in extensively grazed Icelandic horses in the autumn/winter is seasonally driven. Objectives To determine the prevalence of, and risk factors for, gastroscopically significant ESGD (ESGD SIGN :score of ≥2/4); gastroscopically severe ESGD (ESGD SEV :score of ≥3/4) and gastroscopically significant EGGD (EGGD SIGN :score of ≥1/2) in extensively pasture‐managed Icelandic horses at four timepoints. Study Design Prospective longitudinal cohort. Methods Gastroscopy was undertaken in 80 Icelandic horses (3–26 years) from four farms in three different Icelandic regions on four different occasions in one calendar year (May: n = 80, August: n = 70, November: n = 66, and following February: n = 63). Various morphometric, clinical, behavioural, and management factors were evaluated as potential risk factors through multivariable logistic regression. Results Prevalences of 48%–72% (ESGD SIGN ) and 33%–45% (EGGD SIGN ) were recorded across the year. Seven risk factors were associated with ESGD SIGN : including reduction in grass availability but no additional forage provided (OR 10.55 [95% confidence interval 1.78–62.71] vs. low grass with forage provided); and Region (South: OR 10.11 [2.82–36.28] vs. North); body‐condition score (BCS ≥7/9 odds ratio 4.44 [1.43–13.75] vs. BCS 6/9). Four risk factors were associated with EGGD SIGN , including presence of ESGD SIGN (OR 3.38 [1.73–6.61]), age (OR 2.93 [1.23–6.97] for horses >14 years compared to those 3–4 years old), dental score >0/2 (OR 2.30 [1.08–4.88]). Main Limitations Loss of horses over study period; specific pasture nutrient content is unknown. Conclusions Confirmation of consistently moderate EGGD prevalences in extensively managed horses not being intensively exercised, and moderate/high prevalences of ESGD in horses not being fed high starch/sugar‐rich diets. New potential risk factors were identified. Unknown social factors, associated with increasing herd size, might influence the prevalence of ESGD under such conditions, whilst age and dental abnormalities might be important for EGGD.