Undernutrition and Serum and Urinary Urea Nitrogen of White-Tailed Deer during Winter

Direct, practical means of assessing undernutrition in deer (Odocoileus spp.) and other ungulates during winter are needed in areas of research and management. We examined the relationship between mass loss and serum urea nitrogen (SUN) and urinary urea nitrogen: creatinine (U:C) in captive white-tailed deer (O. virginianus). During 4 February-5 May 1988, we maintained 7 adult white-tailed deer on various feeding regimes to simulate natural nutritional restriction during winter. Mass loss was greater (P = 0.037) in deer (17.0-32.2%) fed restricted amounts of a low protein-low energy diet versus control deer (7.0-17.4%) fed the same diet ad libitum. Serum triiodothyronine (T 3 ) concentrations did not differ (P = 0.191) between groups, but declined (P = 0.001) as nutrition declined