Crib biting and equine gastric ulceration syndrome: Do horses that display oral stereotypies have altered gastric anatomy and physiology?

Abstract

Equine gastric ulceration syndrome (EGUS) and crib biting (CB) are two separate conditions suffered by horses. Previous research has hypothesized causal relationships between these two conditions, whereby the behavior is driven by a requirement to stimulate saliva production to buffer gastric juice. However, to date, there is limited empirical evidence to support this notion. To identify if the anatomy and physiology of the equid stomach differed in CB horses and non–crib-biting (N-CB) controls a two-part experiment was conducted using cadaver stomachs. Twenty-four stomachs (CB: n = 12 and N-CB: n = 12) were collected from an abattoir. Duplicate 1.5 cm squared sections were taken from the fundic and pyloric mucosa for histology and H&E staining to identify gastrin (G)-producing cells. Slides were scored using an adapted four-point scale. A further 18 stomachs, (CB: n = 9 and N-CB: n = 9) were collected to test the pH of the mucosa and digesta from the fundic and pyloric regions. G cell concentrations were analyzed by Mann Whitney U-test. Stomach content pH was analyzed by one-way ANOVA and L.S.D post hoc. Relationships between digesta and mucosal pH were evaluated by correlation. In both parts of the study, there was no difference between the G-cell concentration (P > 0.05) and pH (P > 0.05) between CB and N-CB horses. There was a positive correlation between digesta and the mucosal surface of pyloric region in CB horses (R2 0.66, P < 0.001), but not in N-CB horses. These findings suggest, from cadavers, that CB and N-CB stomachs are not anatomically or physiologically different. It is plausible that there is no direct inherent link between CB and EGUS rather that both conditions are linked to environmental and physiological stress.