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Nutrient Requirements and Interactions

Dietary Fiber Influences Nutrient Utilization, Growth and Dry Matter Intake of Green Iguanas (Iguana iguana)1,2
David J. Baer,*†‡3 Olav T. Oftedal,* William V. Rumpler† and Duane E. Ullrey‡
*National Zoological Park, Department of Zoological Research, Washington, DC 20008; †USDA, ARS, BARC-East, Beltsville Human Nutrition Research Center, Diet and HumanPerformance Laboratory, Beltsville, MD 20705; and ‡Department of Animal Science, Comparative Nutrition Group, Michigan State University, East Lansing, MI 48824
ABSTRACT Herbivory is an uncommon feeding strategy in lizards. Appropriate diet formulations for captive lizards should be based on performance measures, yet few data are available on the effect of plant fiber on food intake, nutrientutilization and growth of captive herbivorous lizards. This study was conducted to determine the effect of three levels of dietary fiber on dry matter intake, nutrient and energy metabolizability and growth rate of the green iguana (Iguana iguana). Twenty-one captive iguanas were fed nutritionally complete diets containing three levels of dietary fiber: 19, 24, and 27% neutral detergent fiber. The iguanaswere fed each diet for at least 12 wk, and total excreta were collected for 11.3 { 4.0 d (means { SEM, range of 7 to 25 d). Diets and excreta were analyzed for dry matter, organic matter, gross energy, neutral detergent fiber, acid detergent fiber, and acid detergent lignin. The study was designed as a Latin square crossover. Across all diets, dry matter intake was proportional to body mass1.0(BM). Growth rate was greater (P õ 0.05) when iguanas were fed the low and medium fiber diets (2.2 and 2.4 g/d, respectively) than when fed the high fiber diet (1.4 g/d). However, mean daily dry matter intake of the three diets [7.2 g/(drkg BM)] was not different. In general, digestibility of fiber fractions and the metabolizability of dietary energy decreased (P õ 0.05) as the level of dietary fiberincreased. These data suggest that a diet containing less than 27% neutral detergent fiber should be fed if rapid growth is to be sustained during intensive captive production of green iguanas. J. Nutr. 127: 1501–1507, 1997. KEY WORDS: • Iguana iguana • growth rate • digestibility • neutral detergent fiber • energy intake

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Herbivory is anunusual feeding strategy in extant lizards, and it occurs primarily in two families. Of about 3750 extant lizard species (Halliday and Adler 1986), the green iguana is one of the most folivorous (Rand 1978). Reptilian herbivores may differ from mammalian herbivores in many respects, although the process of fiber digestion seems similar. Anaerobic microbial species, including cellulolytic species, thatferment plant material have been identified from the hindgut of green iguanas (McBee and McBee 1982). Volatile fatty acids (the usable end-products of anaerobic fermentation) have been identified and production rates measured in digesta samples taken from the hindgut of green iguanas (McBee and McBee 1982, Troyer 1984b). Furthermore, important morphologic adaptations have been identified that areconsistent with hindgut fermentation and digesta retention (Iverson 1980 and 1982). There are compelling reasons to determine the digestive performance and nutrient requirements of a species such as the green iguana. First, the green iguana is an increasingly
1 Partially funded by a grant from the Scholarly Studies Program of the Smithsonian Institution. 2 The costs of publication of this articlewere defrayed in part by the payment of page charges. This article must therefore be hereby marked ‘‘advertisement’’ in accordance with 18 USC section 1734 solely to indicate this fact. 3 To whom correspondence should be addressed.

popular companion animal and an important exhibit species for zoos. Appropriate diets are important for maintaining health, as well as for captive breeding. Second,...
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