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Dry matter disappearance (DMD) of native forages collected from the Slave River Lowlands (SRL), Northwest Territories, was consistently greater in bison (Bison bison) than in Hereford cattle (Bos taurus) when measured with a nylon bag technique. Overall average DMD values were 52% and 39% for bison and cattle, respectively. Mean percent DMD values for each plant species were: willow (Salk spp.), 56; slough sedge (Carex atherodes), 50; baltic rush (Juncus balticus), 47; aleppo avens (Geum aleppicum), 44; and northern reedgrass (Calamagrostis inexpansa), 39. Dry matter disappearance was inversely correlated (P < 0.05) with crude fiber content of the sample. Dependence of DMD on crude fiber content was less (P < 0.001) in cattle than in bison. Based on relative digestibilities and data on forage intake, we concluded that slough sedge was the most important bison forage in the study area. Average DMD was 44% greater (P< 0.01) in a Hereford fed hay than in a Hereford fed hay plus a concentrate supplement. There was no difference (DO.05) hi DMD between two bison fed the hay ration and two fed hay plus the supplement. and was chosen to make these comparisons. Materials and Methods Samples of native forages were collected in the SRL in February and June, 1975. Summer samples of willow consisted of approximately equal dry weights of leaves and twigs from the terminal 12 cm of the twigs. Winter willow samples were comprised of twigs only. Herbaceous plant samples included the entire aerial portion of the plant cut at approximately 2 cm above ground. All samples were air-dried and ground through a l-mm mesh screen. Nylon bag digestibility experiments were conducted using two ruminally fistulated adult Hereford cattle and four ruminally fistulated adult bison at the Pawnee Site, International Biological Program, Nunn, Colorado, during Jaquary 1976. One Hereford and two bison were fed crested wheatgrass hay containing 6% crude protein (CP) (Table 1). One Hereford and two bison were fed

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ABSTRACT. The importance of adequate selenium in diets of native wild herbivores can only be inferred from data for beef cattle where minimum dietary concentrations range from 50 to 100 ppb. Concern about possible selenium deficiencies in wild herbivores is based on a few reports of symptoms in wildlife, a paucity of data on selenium in their forages, and the idea that excessive atmospheric sulfur may increase the incidence of selenium deficiencies in herbivores. Concentrations of selenium in sedges, Carex spp., and reedgrasses, calamagrosris spp., the main food plants of bison, Bison bison, in northwestern Canada, varied from 9 to 800 ppb in samples collected at three lowland locations. However, approximately threequarters of all the samples of plant species consumed by bison were dietarily deficient by the beef cattle standard. Key words: Carex, calamagrostis, bison, selenium concentration &UMfi. L'importance d'un quantit6 adkquate de sklbium dans les rCgimes des herbivores sauvages locaux ne peut &re infCr6e que d'apks les donnh portant sur le Mtail bovin, dans lequel les concentrations minimales varient entre 50 et 100 ppb. La question d'insuffisance possible en dlenium chez les herbivores sauvages fut lev& par rapport h quelques etudes des sympt8mes d'animaux sauvages, la p6nurie de donnh sur le dlCnium dans leur rkgime et h la hypothhe selon laquelle un ex& de souffre dans I'atmosphZxe pourrait augmenter I'incidence d'insuffisance en &lCnium chez les herbivores. Les concentrations de dlCnium dans les laiches (Carex spp.) et les gourbets ( C h g r o s t i s spp.)