How Do Different Diets Affect the Horse’s Hindgut?

Four groups of resting adult horses participated in a 10-week feeding experiment. The diets of the resting group of horses (high fiber or high carbohydrate) were supplemented (or not) with a commercially available dietary yeast culture. After an adaptation period of six weeks, a four-week feeding trial and a final five-day total collection of urine and feces were conducted. Five hours after the last meal, cecum digesta samples were taken for analyses of dry matter, crude protein, crude fiber, crude fat, ash, pH, NH3, NH3-N, total organic acids, lactate, acetate, propionate, and butyrate.

The dry matter, crude protein, crude fiber, crude fat, and ash content did not differ significantly in all four diet groups. Lower pH values in all four diet groups appeared to be closely related to the substantial amount of soluble carbohydrates in the diets. Mean cecal lactic acid concentrations of high-fiber and high-carbohydrate diet groups were not significantly different. The tendency toward a higher level of lactate accumulation could be detected only in the high fiber diet group with added yeast. The ammonia concentration of cecum digesta showed a lower tendency in the high-fiber diet group without added yeast. However, the differences were not significantly different due to marked individual variations. The concentration of NH3-N showed similar patterns in all four diet groups, with the lowest concentration in the high fiber diet group without added yeast.

The concentration of total VFA in the cecum digesta was not influenced by the different diet groups or by yeast supplementation. The mean concentrations of acetate, propionate, and butyrate were consistently lower than the concentration of total organic acids in all four diet groups. The amount of acetate was found to be higher in both the high-fiber diet and high-carbohydrate diet group without added yeast, but the acetate concentration in the high-carbohydrate diet with added yeast did not show a significant lower value. Similar trends were observed in the concentration of cecal propionate. Both propionate and butyrate concentration of cecum digesta were almost the same in all four diet groups.

This report of KER’s 2001 research was published in Proceedings of the 17th Equine Nutrition and Physiology Society Symposium.

Read the entire research paper, titled Influence of High Carbohydrate and High Fiber Diet on Cecum Content of Organic Matter and Volatile Fatty Acids.