SEASONAL CHANGE IN FEED-INTAKE, BODY-COMPOSITION, AND METABOLIC-RATE OF WHITE-TAILED DEER

Winter is a critical time of year for white-tailed deer (Odocoileus vi rginianus) in northern regions because their food consumption does not meet their daily energy demands. We measured feed intake, fasting met abolic rate (FMR), and body composition of five captive adult female w hite-tailed deer from September 1991 through March 1992 in New Hampshi re to investigate the relationships between FMR and feed intake to fat deposition and mobilization. Deuterium oxide dilution was used to est imate monthly body composition, indirect respiration calorimetry was u sed to measure monthly FMR, and metabolizable energy intake (MEI) was calculated from daily feed intake. Mean percent body fat increased fro m 9.1 +/- 1.5 to 24.9 +/- 4.4% from September to December, and then de clined through March. Mean percent body protein did not change during the study (range 20-21%). Mean MEI peaked during September and October (171.9 +/- 8.1 and 168.7 +/- 10.3 kcal . kg body mass(-0.75) . d(-1), respectively), and declined 54% by February. Mean FMR ranged from 79 to 90 from October through March. Correlations between MEI or FMR and change in body fat were weak. It was estimated that intake rates of fr ee-ranging deer were only 90-110% of winter FMR, and that deer with 20 % body fat could balance their daily energy expenditure (1.7 x FMR) wi th fat stores for about 3 months, or the period of time during which M EI was depressed in captive deer.