Effects of two dietary fiber levels on nutrient digestibility and intestinal fermentation products in captive brown howler monkeys (Alouatta guariba).

Herbivorous primates present a selective consumption profile and morphological adaptations to use the fibrous fraction of their diets. Brown howler monkeys (Alouatta guariba) are generalist herbivores; however, when kept under human care, they usually receive diets rich in fruits and with insufficient amounts of fiber. Thus, the objective of this study was to evaluate the effects of two levels of neutral detergent fiber (NDF) in howlers on apparent total tract digestibility coefficients (ATTDC), fecal consistency, and intestinal fermentation products. A group of 26 adult howler monkeys, 13 males and 13 females, were fed two diets formulated to have 33% or 40% NDF for 11 days, according to a randomized block design (N = 26). The block factor was the enclosures with one, two, or three individuals (each enclosure corresponded to an experimental unit), totaling in eight replicates per treatment. There were no differences in dry matter and nutrients intake between treatments (p > 0.05). The diet with 33% NDF resulted in higher (p < 0.05) ATTDC of crude protein and crude energy. However, lower fecal concentrations of short-chain fatty acids (SCFA) and dry matter were observed in the treatment with 33% NDF in contrast to the 40% NDF group (p < 0.05). We recommend the inclusion of higher fiber levels (40% NDF) in the diet of howler monkeys since there is evidence of greater production of SCFA and improvement in fecal consistency.