Association between the levels of serum cortisol and the presence of gastric ulcers in working mules

The relationship between stress and gastric ulceration has been described in laboratory animals and human peptic ulcer disease. In horses, high levels of cortisol have been associated with ulcerations in the glandular mucosa but not in the squamous mucosa. However, currently, there are no data on gastric ulceration and cortisol concentrations in working mules. The objective of this study was to assess the association between serum cortisol levels and the presence of ulcers in both types of gastric mucosa. Blood samples of 97 clinically healthy mules of both sexes, with an average age of 8.7 ± 4.4 years, mean body weight (BW) of 290.5 ± 37.6 kg, and a body condition score (BCS) of 5 ± 0.8, were subjected to a gastroscopic study to evaluate and classify the lesions found in both gastric mucosa. In addition, blood samples were taken to measure the concentration of serum cortisol through commercial sandwich ELISA kit (AccuBind®, Monobind Inc., CA, USA). Mule gastric ulcerative syndrome (MGUS) was identified in 44.6%, 27.8% and 19.6% for mule squamous gastric disease (MSGD) and mule glandular gastric disease (MGGD), respectively. The mean cortisol concentration was 10.59 ± 4.06 μg/dL, with very similar concentrations between the ulcerated and non-ulcerated mule groups. The association analysis did not show statistical significance between the serum cortisol and the degree of ulceration in either type of gastric mucosa, differing from what has been reported in horses, possibly due to adaptive differences that these hybrids may have when compared to other equids.