Three controlled experiments were conducted on captive white-tailed deer (Odocoileus virginianus) to determine the response of blood levels of nonesterified fatty acids (NEFA), individual ketone bodies, and cholesterol to differences in dietary energy intake. In two long-term experiments (>30 days), deer on restricted energy intake exhibited declining 3-hydroxybutyrate levels over time that were usually lower than those of deer fed at a higher rate of energy intake. Deer fasted for 10 days had higher NEFA, cholesterol, and acetone and lower f-hydroxybutyrate concentrations than ad libitum-fed deer. Only j-hydroxybutyrate tended to vary consistently with dietary energy intake. J. WILDL. MANAGE. 49(2):380-385 Considerable research has been conducted on the use of physiological characteristics to determine nutritional status of wild cervids. Blood urea nitrogen has been shown to vary directly with protein intake when energy intake is constant (Kirkpatrick et al. 1975), but indices of energy intake suitable for use in the field have not been found. The purpose of this study was to determine the relationship between relative energy status and resulting concentrations of nonesterified fatty acids (NEFA), cholesterol, and individual ketone bodies in white-tailed deer. We hypothesized that with limited energy intake, fat would be mobilized, fatty acids would become the main oxidative substrate, and metabolites from fatty acid oxidation would This content downloaded from 157.55.39.163 on Wed, 23 Nov 2016 04:31:49 UTC All use subject to http://about.jstor.org/terms