Background - Dietary composition may have an impact on type and number of small intestinal mucosal leucocytes. Hypothesis/Objectives – To quantify B and T lymphocytes in the duodenal and rectal mucosa of horses fed three different diets. Animals - Seven healthy mares (n = 7) were fed for six weeks consecutively a diet with 1) a higher fiber content, followed by 2) a higher protein content and 3) a higher lipid content. Methods -Duodenal and rectal biopsies were endoscopically (n= 4-6) obtained from each horse after each feeding periods. Standard HEPS slides were evaluated by a board-certified veterinary anatomic pathologist. Histomorphometry was used to count B-cells (CD20) and T-cells (CD3) using immunohistochemistry (absolute number per field). A mixed linear model and Benjamini-Hochberg (post-hoc) procedures were used to evaluate the effect of diet on B- and T-cell counts.
Results - The duodenal and rectal epithelium contains exclusively T lymphocytes (CD3) for all diets. The number of T lymphocytes in the duodenal and rectal lamina propria in horses fed diets with higher protein content was significantly greater than when fed diets with higher fiber (p = 0.025) or higher lipid content (p = 0.009). Horses fed diets with higher protein content had significantly lower numbers of B lymphocytes in the duodenal and rectal mucosa compared to horses fed diets with higher fiber (p=0.039) or higher lipid content (p = 0.039).
Conclusion and clinical importance - These data allows a more finetuned interpretation of lymphocyte numbers in duodenum and rectum biopsies in horses.
