Effects of feeding alfalfa hay in comparison to meadow hay on the gastric mucosa in adult Warmblood horses

Equine gastric ulcer syndrome (EGUS) is a common health problem in horses and foals. Beside the importance of forage feeding for the gastric mucosa, results of studies targeting the specific effect of alfalfa on different gastric mucosal regions are controversial. The objectives of this study were to determine the influence of the two forage types (1) meadow hay and (2) alfalfa hay with similar fiber length on different gastric mucosal regions in order to further clarify the effect of alfalfa hay on the equine gastric mucosa. It was hypothesized that feeding alfalfa hay will impair mucosal integrity of the pylorus and antrum pyloricum but may be a benefit for the squamous regions. In a randomized blinded prospective study with a cross-over design, 10 healthy adult warmblood horses were separated randomly into two groups each with five horses. Both groups were fed with 2 kg/100 kg BW/animal/day alfalfa hay or meadow hay in two feeding periods each 21 days long. A wash out period of 21 days was conducted between the feeding periods. Before and after feeding periods body condition score (BCS), body weight (BW), clinical health status, feces pH and particle size and gastroscopic findings were determined. Each region of the gastric mucosa was assessed and scored separately. Data such as BW, fecal pH and fecal particle size were analyzed for normal distribution by the Shapiro-Wilks test. BCS, gastroscopic findings and fecal pH were subjected to non-parametric statistical tests. Kruskal-Wallis ANOVA and Wilcoxon test were performed to compare the findings in gastric mucosal scores, BCS and fecal pH. The relative change in BW and fecal particle size were analyzed by one-factorial analysis of variance (ANOVA). Data are presented as medians, 25th and 75th percentiles. Relative BW changes and fecal particle size are given as means ± standard deviation (SD). Statistical significance was set at p < 0.05. Before starting the feeding trial, the prevalence of overall gastric mucosal lesions was 100 % with a median severity score of 1. After the feeding period, the median lesion score of the lesser curvature of the squamous region decreased significantly from a median of 1 to a median of 0 in the alfalfa group. The median score of 0 remained constant before and after feeding the meadow hay. Findings in the pyloric region did not differ significantly between the two feeding groups. We concluded that feeding alfalfa hay seems to have no detrimental effects on the mucosal integrity at the squamous gastric region in healthy adult horses. With respect to the glandular area, feeding alfalfa hay appears to be noncritical in healthy adult horses. Further studies are needed to investigate the effects of feeding alfalfa hay in horses suffering from severe mucosal lesions at the antrum pyloricum or pylorus. Furthermore, the longer fecal particle size in horses fed alfalfa hay needs further elucidation.