Protein Requirement of White-Tailed Deer Fawns

Abstract

Eight hand-reared white-tailed deer (Odocoileus virginianus) fawns were randomly paired and pairs were randomly assigned to 1 of 4 isocaloric diets containing 11, 15, 20, and 25 percent crude protein (dry matter basis) to study their protein requirement. Thirty-two complete digestibility, nitro- gen balance, and energy balance trials were carried out. Partition of dietary energy was not signifi- cantly affected by protein level in the diet, except that proportion of energy lost in urine, presumably ketones, increased significantly (P < 0.05) with increasing dietary crude protein. Apparent digestibility of protein increased significantly up to 20 percent ration crude protein, but most of this difference was attributable to decreasing proportion of metabolic nitrogen (0.37 g/100 g diet dry matter) in feces; proportion of ingested nitrogen lost in urine increased with increasing nitrogen intake. The fawn's re- quirement for maximum growth (body retention of dietary protein), estimated by regression analysis, was 19 g digestible crude protein per kilogram of metabolic body weight (W075) daily. J. WILDL. MANAGE. 39(3):582-589 White-tailed deer, an aesthetically and economically valuable resource, are increas- ingly threatened by the effects of urban- ization in many areas. Their survival in optimum quantity and quality will depend largely on intensive management based on biologically sound principles. Deer man- agers will need information on the nutri- tional requirements of different age classes of deer throughout the year, and on the value of natural foods in meeting these re- quirements. Fawns probably are the age class most vulnerable to undernutrition during the winter. Certainly the food consumed dur- ing the preceding fall contributes greatly to winter survival. Thompson et al. (1973: 307) reported that the metabolizable energy required for maintenance of fawns is higher (38 percent, our calculation) during pe- riods of weight gain than in winter. They also found that the component of growth described by deposition of body protein may continue despite body weight loss and negative energy balance during the winter. Although energy generally is the most crit- ical factor in deer nutrition, the work of Murphy and Coates (1966) suggested that low protein content of foods may account for low productivity and suboptimum phys- ical development as in most other species.