Primate Gastrointestinal Tracts
Adaptations for hindgut fermentation are most pronounced in the highly folivorous howler monkeys (Alouatta spp.) and Indrids (Avahi, Indri, and Propithecus). In these species, the complex nature of the hindgut is demonstrated by the presence of sacculations (haustra), longitudinal bands (taeniae), and flexures that presumably trap or slow the movement of digesta (Clemens and Phillips, 1980). Increased retention of food particles in this region facilitates microbial degradation by symbiotic organisms.
Some hindgut fermenters have adaptations in the foregut. For example, the stomach of Alouatta, which consumes a diet of at least 40% leaf material by weight (Hladik and Hladik, 1972; Edwards, 1995), is the most complex among the hindgut fermenters (Figure 1-13). It is a capacious globular sac, narrowing toward the bent tubular pylorus, guarded by strong pillars running longitudinally with the body (Chivers and Hladik, 1980).
Median gut passage time for a mixed-ingredient diet, including browse plants, fed to the highly folivorous Hapalemur griseus alaotrensis was 18.21 hours (Cabre-Vent and Feistner, 1995). Three species of howler monkeys fed two manufactured diets with different fiber concentrations (15% and 30% acid-detergent fiber [ADF]) exhibited no significant difference between diets in mean transit time of solids (28.0 vs. 21.5 hours) or liquids (14.6 vs 16.1 hours) (Edwards, 1995).
When fed a manufactured diet containing 15% ADF, silvered leaf monkeys (Semnopithecus cristatus) exhibited a mean transit time of 13.6 hours for both solid and liquid phases of digesta (Sakaguchi et al., 1991). Francois’ leaf monkeys (Trachypithecus f. francoisi) fed a comparable (15% ADF) diet had a comparable transit time for liquid digesta (13.5 hours), but the mean transit time for solid digesta was 27 hours (Edwards, 1995). When the same animals were fed a diet with twice the fiber concentration (30% ADF), there was no significant effect of the dietary change on the transit time of either liquids (15.5 hours) or solids (28.5 hours) (Edwards, 1995).
Digestibility studies with the Yunan snub-nosed monkey (Rhinopithecus bieti), a foregut fermenter that feeds primarily on lichens, revealed apparent dietary dry matter digestibilities of 71 to 80%. Mean (± SD) retention time of plastic digesta markers was 47 ± 17 hr (Kirkpatrick et al., 2001).
Development of scientifically sound feeding programs for captive primates requires a balance of information on the species of concern. Gastrointestinal tract structure, natural feeding behavior, and nutrient composition of foods consumed by free-ranging individual animals are some of the items required to address dietary husbandry requirements. Identifying readily available foods to meet physio-