Fiber enrichment of captive primate diets

Wild, herbivorous primates have adapted, anatomically and physiologically, to meet a significant proportion of their daily energy requirement through fiber fermentation. Bacteria, residing in the cecum and colon of primates, degrade fiber and in return secrete volatile fatty acids, which are absorbed by the animal and used as energy. Captive primates are fed extruded biscuits and produce. Biscuits are low in fiber compared to items consumed by free-ranging primates. Nutritional reports on produce analyses reflected portions of produce consumed by humans; animals often consume whole items, changing the nutrient content of the items. These reports used dietary fiber analyses instead of neutral detergent fiber (NDF) analyses, which is a more defined method for determining fermentable fiber. More than 80 commercially available produce items, classified as fruits, vegetables or leafy greens, were analyzed for NDF, free sugars, pectin, fructans, crude protein and fat levels. Vegetables and leafy greens had the highest level of NDF at 19%; they also had the lowest level of free sugars at 26 and 18%, respectively. Fruits averaged 13% NDF and 41% free sugars. It is impossible to meet the levels of NDF consumed by wild primates using commercially available produce. To replace the primate biscuit, an alternative diet was created using a fiber-based gel matrix manufactured by Purina Mills, Inc. Gel based diets, differing in fiber type (soybean hulls or ground corn cobs) or level (50 or 60% NDF), were fed to a pair of orangutans. Orangutans were capable of degrading significant proportions of structural fiber. The NDF digestibilities ranged from 58 to 75% for the high fiber gel diets. Continuous culture fermenters, using orangutan fecal bacteria as the inoculum, were used to measure the bacterial degradation capabilities when fed ground corn cobs, soybean hulls or starch. There were no differences in fermenter digestibility between soybean hulls and ground corn cobs. The bacteria degraded 87% of the NDF fed. Fourteen black lemurs at the St. Louis Zoo were fed the same high fiber gel diets that the orangutans received. As fiber increased in the diets, NDF digestibility decreased. They were able to degrade only 12% of the NDF from the high fiber gel diets. Although black lemurs were limited in the amount of fiber they digested, orangutans would benefit from increased levels of fermentable fiber in their diets. Increasing structural fiber and decreasing the levels of readily available carbohydrates in some herbivorous primate diets may decrease the incidence of obesity and other related health problems often seen in captive primates.