Taken together, the findings of this research on whole oat incorporation into the equine diet support the hypothesis that a diet with a high concentration of NSC (non-structural carbohydrates) (>35%), small particle size, and no oats will result in gastrointestinal leakiness, and that inclusion of whole oats may nullify or moderate this leakiness and associated changes in other response variables. Evidence associated with each of the project objectives are as follows. Objective 1) Directly evaluate gastrointestinal permeability with sugar marker tests. Permeability was highest in the horses fed the pelleted diet that contained the smallest particle size. The treatment diets that contained whole oats moderated this increased permeability and no difference was detected between whole oat containing diets and the hay only diet. Objective 2) Characterize and quantify gastric ulceration. In this study, horses fed the hay only diet had the lowest quantity of nonglandular and glandular ulcers. While statistically significant differences were not detected, it appears that whole oats may reduce the risk of ulceration. Further work needs to be completed to confirm this hypothesis. Objective 3) Measure indicators of systemic inflammation associated with increased gut permeability. No differences in systemic markers of inflammation were detected in this study.
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There are a number of reasons why we may have been unable to detect any treatment differences. First, it may be that the dietary treatments have no effect on gastrointestinal inflammation. Second, localized inflammation at the level of the gastrointestinal tract may have been undetectable when examined at a systemic concentration. Third, the timing of sample collection may have not have been appropriate to detect changes that were occuring. For future work we are examining acute phase proteins as another way of evaluating inflammation under conditions similar to this study. Objective 4) Quantify other markers associated with hypothesized changes, including feed and fecal particle size, and fecal pH. While relatively simple to measure, these response variables were one of the unique characteristics of this study. Our original hypothesis was built around a concept of dietary physically effective fiber, a concept that is well established in dairy nutrition. We demonstrated an ability to formulate diets that have clear differences in feed particle size. Further, these differences are associated with changes in fecal particle size and fecal pH. These last two characteristics theoretically influence gastrointestinal health. Our recommendation based on the findings of this study is to examine the effects of dietary whole oats on measures of gastrointestinal health in a similar approach to this study, but with the addition of exercise. Horses in the current study were confined to stalls and runs. They had very little exercise and stress. Exercise is an important risk factor for gastric ulcers and other gastrointestinal health concerns. We suggest that differences may be more apparent if horses were exercised regularly. This would be a further improvement, as exercise is normally part of most horses normal management schedule. Further, there are some response variables that could be examined in future studies that may provide a clearer understanding of how dietary whole oats improve the health of the horse. Examples would include chewing activity and saliva production.