PRIMATE NUTRITION: Novel Feeding Options for Folivorous Species
Mark S. Edwards, Ph.D.
Zoological Society of San Diego, P.O. Box 120551, San Diego, CA 92112-0551
Species differences in natural dietary habits and in the morphology of the gastrointestinal tract suggests that all captive primates should not be fed in the same manner (Ullrey, 1986). The specialized nutrient requirements of leaf-eating primates has been long over-looked (Edwards et al., 1989). The National Research Council mentions this group of primates only once in their Nutrient Requirements of Nonhuman Primates (1978). This may be a result, in part, to the low number of leaf-eating primates represented in laboratory research colonies.
Zoological institutions have long recognized the difficulty in maintaining these delicate feeders, yet continue to feed individuals diets similar to those offered to omnivorous primate species. The anatomical and physiological specializations which enable leaf-eating primates to effectively utilize plant materials as a principal source of nutrition place limitations on their adaptability to many commercially available foods.
Adaptations for Folivory
Primates which specialize in consuming leaves exhibit several gastrointestinal adaptations. These adaptations, which include sacculation and expansion of the gastrointestinal tract, may occur anterior to the sites of gastric digestion (foregut fermenter), or posterior (hindgut fermenter). Microbial fermentation occurs in the large sacculated forestomach of Colobidae (e.g., Colobus spp., Presbytis spp., Trachypithecus spp., Pygathrix nemaeus, Nasalis larvatus). Hindgut fermentation, in the sacculated cecum and/or colon, occurs in certain other primates (e.g., Alouatta spp., Indridae). However, the extent of herbivory demonstrated by a given species is variable.
The colobine stomach has four parts: the presaccus and saccus, the long tubus gastricus, and the short pars pylorica (Kuhn, 1964). The large, complex presaccus and saccus is distended and sacculated proximally, with a U-shaped tube distally, and sacculated along the proximal part of the greater curvature (Hill, 1958). The stomach of the mantled howler Alouatta palliata exhibits a great deal of complexity when compared with other cebids. The globular sac is capacious and narrows to the bent tubular pylorus (Chivers and Hladik, 1980). The cecum of cebids is hook-shaped, and the colon is simple and straight.
Dietary Husbandry of Folivorous Primates
Those institutions that seem to have the greatest success with long-term maintenance of captive folivorous primates are those that have addressed their specialized needs (Edwards, 1995). There are three primary methods of increasing the amount of fiber in these animals’ diets. The most widely applied, and easily implemented approach, is the replacement of commercial primate biscuits containing a low concentration of fiber (10-19% NDF, 5-7.5% ADF) with a higher-fiber product (25% NDF, 15% ADF). The lower fiber commercial primate diets were designed originally for omnivorous primates, such as macaques. The commercial production of higher fiber primate diets is a fairly recently available option, as zoo feed manufacturers respond to the scientific evidence and demands of the enlightened consumer.
Another approach includes the reduction or elimination of commercially available fruits and replacement of those items with leafy greens and higher fiber vegetable material. This method is often used in conjunction with the incorporation of the higher fiber primate biscuit.
The cultivation of plant material for supplemental feeding is also an option (Griner, 1977; Ullrey et al., 1982). This practice is not as widespread, due primarily to the variability of local growing conditions and economic considerations (Koontz et al., 1988). The types of plant material cultivated also are widely variable, from indigenous species to easily grown tropical plants. Surprisingly, no attempts have been made to cultivate widely the browse plants that are consumed by free-ranging representatives of the species held in captivity.
Special considerations should be taken when offering browse to captive primates. Nutrient contributions of the browse material should be determined, and the impact of seasonal variability and fertilization of browse plant materials should be assessed. The animals to which these plants are offered (most of which have been born in captivity) should be considered naive to such defenses and should be monitored as to the parts of the plants that are consumed. As this approach to feeding becomes more common, reports of deaths directly attributable to the consumption of browse have increased (Ensley et al., 1982; Robinson et al., 1982; Janssen, 1994; Edwards, unpublished data). This is an unfortunate demonstration of the evolutionary effectiveness of mechanisms that plants have developed to protect against herbivory, as well as the consequences of relying upon “nutritional wisdom” when offering naive animals novel foods.
An ideal approach to the feeding of captive folivorous primates appears to be a combination of the above three methods:
1. Use a higher fiber primate biscuit.
2. Reduce or eliminate fruits, and increase green leafy vegetables.
3. If browse plants are fed, ensure that they are appropriate.
4. Distribute these foods in small quantities over several feedings per day.
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Edwards, M.S. 1995. Comparative Adaptations to Folivory in Primates. Ph.D. Dissertation. Michigan State University. East Lansing, MI. USA.
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Janssen, D.L. 1994. Morbidity and mortality of douc langurs (Pygathrix nemaeus) at the San Diego Zoo. In: AAZV Annual Conference Proceedings. St. Louis, MO.
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National Research Council. 1978. Nutrient Requirements of Nonhuman Primates. Nutrient Requirements of Domestic Animals No. 14. National Academy of Sciences. Washington, D.C.
Robinson, P.T., T.A. Reichard, P.A. Whetter and D.E. Ullrey. 1982. Evaluation of diets of leaf-eating monkeys. p. 36. AAZV Annual Proceedings. New Orleans, LA.
Ullrey, D.E. 1986. Nutrition of primates in captivity. In: Primates: The Road to Self-Sustaining Populations (K. Benirschke, ed.) Pp. 823-835. Springer-Verlag, New York, NY.
Ullrey, D.E., P.T. Robinson, T.A. Reichard, P.A. Whetter, D.K. Brockman. 1982. Dietary studies with colobids at the San Diego Zoo. Unpublished Research Report. Michigan State University, East Lansing, MI.