FIBER DIGESTIBILITY BY THE ORANGUTAN (PONGO ABELII): IN VITRO AND IN VIVO

Abstract Limited nutritional information exists on diets of free-ranging orangutans, Pongo abelii and P. pygmaeus. Although they are classified as frugivores, the chemical composition of their diet and their gastrointestinal anatomy suggest that they rely on fiber fermentation for a substantial portion of energy. However, the extent to which they can ferment fiber is not known. Continuous culture systems, inoculated with orangutan fecal bacteria, were established to determine the fiber-digesting capacity of orangutan hindgut microflora. The cultures received one of four treatments: soybean hulls, ground corncobs, corn starch, or no food. Neither dry matter nor neutral detergent fiber digestibilities differed significantly among treatments. However, neutral detergent fiber digestibilities were high for both the soybean hull (88.4%) and ground corncob (86.1%) treatments, indicating that the microflora had a strong fibrolytic capability. To determine whether the same fiber-degrading capacity occurred in vivo...