Duikers: Native food composition, micronutrient assessment, and implications for improving captive diets

Abstract

AbstractThis review summarizes and contrasts published information on the proximate chemical composition of native fruits and leaves eaten by duikers, and adds new data concerning the soluble carbohydrate, mineral, and tannin content of duiker foods. Information on circulating plasma concentrations of minerals and the fat‐soluble vitamins A and E is also summarized in relation to free‐ranging vs. zoo‐held duikers and differences in the nutrient content of their respective diets. In nature, duikers consume diets containing low starch (in general <0.1% of dry matter (DM)) and moderate‐to‐high fiber (averaging 32% DM) and protein (fruits <10%, leaves <20% DM) levels, and do not avoid foodstuffs containing tannins. Native food samples were considered low to marginal in calcium (Ca) and phosphorus (P) content compared with domestic ruminant dietary requirements, but Ca levels were generally two‐ to threefold higher than P concentrations. Diets fed to duikers in captivity are often low in fiber and tannin content, and high in starch and protein, as well as low in Ca relative to P (compared with native plants), which may lead to nutrient imbalances and health problems. Plasma alpha‐tocopherol values measured in zoo duikers ranged from 0.4 to 8.3 μg/ml, and were less variable in free‐ranging animals (1.7–7.0 μg/ml). Retinol values did not differ among duiker species or between sample populations, and were within normal ranges (0.2–0.7 μg/ml) expected for herbivores. Domestic hoofstock appear to be suitable physiological models for evaluating fat‐soluble vitamin status, but mineral homeostasis appears to differ in duikers. Free‐ranging duikers have somewhat higher Ca, and lower P concentrations compared with captive‐held individuals, and inverse Ca:P ratios and copper (Cu) deficiency have been reported in captive duikers—both conditions in which captive diet may play a key role. A frugivorous browser pellet/diet that incorporates the findings summarized here, and better duplicates the chemical complement described for native foods eaten by duikers, may provide health benefits to these small concentrate selectors. Zoo Biol 21:185–196, 2002. © 2002 Wiley‐Liss, Inc.