Digestive Capabilities in Elk Compared to White-Tailed Deer

Abstract

Digestive capabilities of elk (Cervus elaphus nelsoni) were determined during 15 feeding trials of singleand multiple-component rations. These results were compared to digestibilities by whitetailed deer (Odocoileus virginianus). Neutral-detergent-solubles (NDS) digestible amount was linearly related to feed content in both elk and deer. Soluble phenolics depressed NDS digestibility but not fiber digestibility. Fiber digestibility decreased curvilinearly with increasing lignin-cutin content in both elk and deer. Elk digested more of the less lignified cell walls than did deer. Equations for estimating drymatter and energy digestibility in both elk and deer are presented. J. WILDL. MANAGE. 46(1):22-29 The understanding of digestion forms an important link in relating the nutritional requirements of wildlife to their available food resources. Because it is impossible to measure the in vivo digestibilities of all forages and combinations consumed by free-ranging ungulates, digestibilities ultimately must be predicted from either summative equations developed from the comparison of feed composition and in vivo digestibility, or in vitro trials if the relationship between in vivo and in vitro digestibilities is known. The estimation of digestibilities must be species specific if larger ruminants digest feed more completely than do smaller species (Hungate et al. 1959). Because digestion measurements for elk have been limited to only a few feeds (Thorne, unpubl. rep., Wyo. Fed. Aid Proj., FW-3R-20, 1973; Westra 1978), summative equations and in vivo-in vitro comparisons have not been previously generated. In addition, earlier summative equations for deer (Robbins et al. 1975) must be reevaluated in light of recent analytical changes (Van Soest and Robertson 1980, Mould and Robbins 1981b). Consequently, the following study was undertaken to (1) compare the digestive capabilities of elk and white-tailed deer, (2) evaluate the role of various feed constituents in reducing digestive efficiencies, (3) generate summative equations for estimating digestibility in the 2 ungulates, and (4) compare in vivo and in vitro dry-matter digestibilities. We acknowledge support from the Washington Department of Game, National Science Foundation (DEB 7624329), and Washington State University. The assistance of M. Reisenauer, B. DeWaard, A. Pfister, M. Radenberg, S. Knick, and D. K. Hulbert is appreciated.