The effect of diet on energy partitioning in moose

Abstract

Moose (Alces alces) have dynamic seasonal patterns of food intake and body weight changes. Body weight may vary by 35% from winter lows to summer highs. Food intake levels during summer may exceed winter levels by up to a factor of 5. Forage quality and availability are thought to drive the seasonal patterns of food intake and weight loss. Changes in digestive strategy of moose in winter and spring were analyzed in this thesis. During December, the total mean retention time (TMRT) of food in the alimentary tract increased as dry matter intake decreased, while alimentary fill remained constant. In contrast, during April TMRT did not increase with increased intake; rather, alimentary fill increased. There appeared to be a seasonal digestive strategy for optimizing nutrient intake. True basal metabolic rate (TBM) was estimated using regression analysis of heat production on metabolizable energy intake. TBM was estimated at 68.8, close to the interspecies mean of 70 (kcal/kg BW$\sp{0.75}$/d). However, differences in TBM noted during December, February, and April were not significant. Paper birch (Betula papyrifera) twigs were collected during winter and cut from the tip to 8 specific diameters (2-9 mm), and analyzed for neutral detergent fiber, acid detergent fiber, crude protein, acid detergent lignin, ash, and in vitro dry matter disappearance. Results indicated that dietary quality decreased with increasing diameter. Moose subjected to 4 different stocking rates (23, 31, 41, and 66% utilization of paper birch) showed no difference in the diameter of paper birch (mean = 2.66 mm) harvested. A simulation model was presented in which food intake by moose was controlled by both physiological demands and alimentary capacity. Seasonal estimates of food intake changed with energy demands. The model proved useful in estimating seasonal energy requirements of moose.