Risk Factors for Equine Gastric Ulcer Syndrome Incidence in Adult Icelandic Riding Horses

SIMPLE SUMMARY: Previously, it was shown that Icelandic horses had a relatively high prevalence of gastric ulcers, in both regions of the stomach, which was found by performing gastroscopy on horses within two weeks of coming into training for the first time from the pasture. There was significant improvement in those in the squamous (non-glandular) region after eight weeks, especially for those being fed more frequent forage meals. This original study was undertaken in mainly young horses being trained for the first time. The current study evaluated the risk factors for Icelandic riding horses at various ages and stages of their training. This study found a low prevalence of gastroscopically significant squamous ulcers (grade ≥ 2/4: ~27%) in Icelandic horses being kept in training establishments and fed low starch and sugar diets. It was found that body condition, age and workload were not significantly associated with either squamous or glandular ulcer score but the region of Iceland wherein the horses were being kept did have an influence, as did their sex. Those animals showing clinical signs often associated with gastric ulcers were at increased risk of having gastroscopically significant glandular or gastroscopically severe squamous ulcers. It also highlighted the relatively high prevalence of ulcers in the glandular region (~46%) but did not identify any risk factors for such ulcers that could easily be modified. ABSTRACT: A high prevalence of both squamous (ESGD) and glandular (EGGD) ulcers was previously found in, mainly young, Icelandic horses coming into training for the first time. This study evaluated risk factors for gastric ulcers in Icelandic riding horses at various ages and stages of training. The horses (n = 211) were gastroscoped from 21 equine establishments across Iceland. A variety of morphometric, clinical, behavioural and management factors were evaluated as potential risk factors for gastroscopically significant (grade ≥ 2/4: found in 27% of horses) or gastroscopically severe (grade 3 or 4/4: found in ~10% of horses) ESGD or gastroscopically significant EGGD (grade ≥ 1/2: found in 46.4%). Body condition score (BCS), cresty neck score (CNS), stable/turnout behaviour, exercise intensity/frequency and age were not significantly associated with ESGD or EGGD ulcer score. However, having come off the pasture into training for 4 weeks or less was a significant risk factor for gastroscopically significant and severe ESGD compared to 5 weeks or more. For both EGGD and ESGD, “region” was important. Gastroscopically significant EGGD and gastroscopically severe ESGD were more prevalent in those showing clinical signs often associated with ulcers. Geldings were more likely to have gastroscopically significant ESGD than both mares and stallions and more EGGD than stallions. Being stabled, but spending >2 h/day out in the paddock, compared with <2 h paddock time or full-time turnout, was protective for gastroscopically significant ESGD as was being fed complementary feed (all fed <1 g non-structural carbohydrate (NSC)/kg/BW/meal). Being at a training establishment for >4 weeks was protective for gastroscopically significant and gastroscopically severe ESGD but not EGGD. This study confirms the relatively low prevalence of ESGD in Icelandic horses being kept in training establishments and fed low NSC diets but highlights the high prevalence of EGGD.