Estimation of Dry Matter Intake of Free-Ranging Moose

Abstract

Two free-ranging moose (Alces alces) cows were used to study seasonal changes in voluntary intake between December 1982 and January 1984. Observations of each animal were made during a continuous 24-hour period every 6-8 weeks. Dry matter intake was estimated from the ratio of total dry matter in the feces to the percent indigestibility of dietary dry matter and from the bite-count technique. During the 1-year period, dry matter intake ranged from 37.8 g/kg BWo075 in January to 128.5 g/kg BW0-75 during July. The bite-count technique estimated voluntary intakes which were within 6% of those calculated from total fecal collections. Dry matter digestibility of selected diets ranged from 71% in late May to 44% in late January as estimated by the in situ nylon bag technique. Crude protein content in the feces was correlated (P < 0.05) with digestible dry matter intake (r2 = 0.88) and with the nitrogen content of simulated diets (r2 = 0.95). Nylon bag dry matter digestibility of simulated diets was highly correlated (P < 0.001) with diet dry matter (r2 = 0.73), crude protein (r2 = 0.69), and neutral detergent fiber (r2 = 0.90). The maintenance energy requirement for a free-ranging moose cow, estimated by least squares linear regression, was 399 KJ/ kg BW075 daily. J. WILDL. MANAGE. 49(3):785-792 Seasonal variations in forage intake by freeranging ungulates express the interactions of animal requirements and wide fluctuations in diet quality and availability. Schwartz et al. (1981) showed that penned Alaska moose fed a pelleted ration reached peak intake during summer and low points during the breeding season and late winter. Miquelle (1979) reported dry matter intakes of young moose on Isle Royale during summer from pen trials with clipped browse and of free-ranging moose using the bite-count technique. Crete and Bedard (1975) and Nystr6m (1980) estimated browse consumption for moose in Quebec and Sweden, respectively, using modified versions of the twigcount technique. Approximate calculations of daily food consumption by moose were made by Gasaway and Coady (1974) based on seasonal differences in rumen fill. However, few empirical data are available on seasonal forage intake of free-ranging moose. Several methods for determining forage intake of free-ranging animals have been published. Among these, ratio and bite-count methods are most practical for studies on wild ruminants. The ratio technique (fecal excretion/indigestibility of the diet) appears most reliable for estimations of intake by grazing livestock (Cordova et al. 1978). Measures of fecal output are usually combined with an in vitro estimate of diet digestibility from esophageal samples (Allison et al. 1982, Holechek and Vavra 1982). However, fecal output also can be determined indirectly using external markers (indigestible indicators attached to diet particles) and digestibility can be estimated with indigestible internal markers such as lignin or silica (Langlands 1975, Engdahl 1976). The bitecount technique, a useful alternative for less tractable animals, has been used to estimate feeding rates and daily intake by wapiti (Cervus elaphus nelsoni) (Collins 1977, Hobbs 1979, Ni tfeld 1983, Wickstrom 1983), mule deer (Odocoileus hemionus) (Wickstrom 1983), and moose (Miquelle 1979). Accurate measurement of bite rate, simulated bite size, and total foraging time are required for a reliable predictio of voluntary intake. This study determined seasonal changes in dry matter consumption by habituated freeranging moose using both ratio and bite-count methods. We acknowledge the financial support of Alberta Recreation, Parks and Wildl. Found., Agric. Res. Counc. of Alberta, The Alberta Env ron. Trust, and the Nat. Sci. and Eng. Res. Counc. We wish to thank D. M. Renecker, D. M. Bayne, M. T. Nietfeld, C. D. Olsen, L. R. Griffith, M. H. Griffith, A. J. Keith, K. L. Risenhoover, and D. A. Welch for their skillful assistance in data collection. Special thanks to D. M. Renecker and C. D. Olsen for their helpful comments on the manuscript.