DIGESTION OF LOW-PROTEIN GRASS HAY BY MUSKOXEN AND CATTLE

Because nutritional requirements of muskoxen (Ovibos moschatus) in winter are poorly understood, we compared voluntary intake and apparent digestibility of low-protein grass hay by 5 mature muskoxen and 3 mature Hereford cows during late winter 1993. We hypothesized that muskoxen would digest poor quality graminoid forage more completely and maintain mass at lower rates of intake than would cattle, on the basis of evidence of relatively low intake and relatively complete digestion of good quality diets by captive muskoxen during winter (White et al. 1984, Adamczewski et al. 1994). Hay was 6% crude protein and 74% neutral detergent fiber and was similar in composition to sedge (Carex spp.) and grass (e.g., Kobresia spp.) samples from feeding craters of muskoxen on Banks and Victoria islands, Northwest Territories (NWT). Both species maintained body mass on the experimental diet but daily intake of dry matter by muskoxen was only 1/3 that by cattle (32 +/- 2 [SE] vs. 96 +/- 3 g/kg0.75; P < 0.001). Apparent digestibility of organic matter, measured using chromic oxide, was higher in muskoxen than in cattle (58 +/- 2 [SE] vs. 50 +/- 3%; P = 0.03). Muskoxen are well adapted to digesting low quality graminoid forage and maintaining mass at low rates of intake, and these traits likely contribute to their success in surviving long arctic winters.