Effects of Winter Fasting and Refeeding on White-Tailed Deer Blood Profiles

Abstract

This study examined the effects of dietary protein, fasting, and refeeding on blood characteristics of 9 nonpregnant, female white-tailed deer (Odocoileus virginianus) in captivity from 23 February to 3 May 1984. Percent weight loss was greater in fasted deer than in deer fed diets of 2 crude protein levels. Fasting effects were also observed for hemoglobin (Hb), red blood cell (RBC) counts, packed cell volume (PCV), cholesterol, triglycerides, serum urea nitrogen (SUN), potassium (K), glucose, phosphorus (P), insulin, thyroxine (T4), and total protein (TP). Refeeding influenced cholesterol, sodium (Na), and calcium (Ca). Hemoglobin, PCV, Ca, P, and albumin varied with time in fasted deer. Changes over time in the fed deer occurred for several hematological and serum characteristics. Data are presented to serve as reference values for better understanding of data collected from free-ranging deer under less known conditions. J. WILDL. MANAGE. 51(4):865-873 Winter nutrition is most influential on whitetailed deer survival and reproductive success in the northern portions of their range. Artificial feeding in late winter has not always reduced starvation losses, perhaps due to the tardiness of such efforts and the irreversibility of moribund deer (deCalesta et al. 1977). Therefore, more sensitive evaluations of deer nutritional status that anticipate irreversible deterioration of body condition are needed. Numerous studies document the effects of varying dietary protein and energy levels on blood characteristics of captive deer (Seal et al. 1981, Warren et al. 1982, Card et al. 1985). Several examinations of free-ranging deer on northern and southern ranges have described effects of habitat quality and seasonality on blood characteristics (Anderson et al. 1972, White and Cook 1974, Coblentz 1975, Seal et al. 1978a, Kie et al. 1983, Waid and Warren 1984). Results of these studies have varied, depending on the treatment and environmental conditions. Serum urea nitrogen has been the most thoroughly tested and consistent indicator of nutritional condition; however, it has limitations (Warren et al. 1982). Thus, supportive indicators have been sought and examined. Furthermore, research into the potential effects of chemical immobilization and physical restraint on blood characteristics of deer has permitted more accurate interpretations of data relative to nutritional status (Seal et al. 1972a, Mautz et al. 1980). Few deer studies, however, have focussed on the blood effects of complete nutritional deprivation. Only work by deCalesta et al. (1975, 1977) noted the effects of early and prolonged fasting on SUN, glucose, and non-esterified fatty acids (NEFA) in Rocky Mountain mule deer (0. hemionus), whereas Card et al. (1985) examined the influence of short-term fasting in whitetailed deer on serum cholesterol, ketones, and NEFA's. To identify additional indicators of starvation, we studied the effects of dietary protein and fasting during mid-late winter and recovery in early spring on blood and urine characteristics. Here we describe our findings relative to extensive blood profiles; the urinalysis information is reported separately (DelGiudice et al. 1987). We appreciate the financial support of the Spec. Projs. Found., Minneapolis Big Game Club; the Natl. Rifle Assoc.; the U.S. Fish and Wildl. Serv.; the Res. Serv., Veterans Adm.; the Minn. Zool. Soc.; R. Shelton; the James Ford Bell Found.; Safari Club Int.; and the Minn. Dep. Nat. Resour. We thank F. B. Martin for statistical consultation, and M. D. Lewis, N. I. Manning, M. K. Twite, K. D. Kerr, W. J. Paul, S. H. Fritts, E. H. Stege, K. Johnson, J. Lazar, and R. J. Welters for technical assistance. 'Mailing address: North Central Forest Experiment Station, 1992 Folwell Avenue, St. Paul, MN 55108.