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We evaluated fecal nitrogen (FN) and fecal phosphorus (FP) concentrations as indicators of different dietary nitrogen (DN) and dietary phosphorus (DP) levels fed to 11 penned, white-tailed deer does (Odocoileus virginianus) during summer 1985. We fed deer pelleted rations containing 2 levels of DN (2.64 and 1.18%) or DP (0.49 and 0.30%) during 2 consecutive, 16-day trials. We collected fecal pellets from each animal during the last 6 days of each trial. Pooled mean FN concentrations for corresponding high and low DN levels were as follows: total FN = 2.26 and 1.45% (P = 0.003), neutral detergent FN = 0.60 and 0.39% (P = 0.019), and metabolic FN = 1.67 and 1.06% (P = 0.001). Pooled mean FP concentrations for corresponding high and medium DP levels were as follows: total FP = 1.23 and 0.44% (P = 0.002), neutral detergent FP = 0.12 and 0.10% (P = 0.022), and endogenous FP = 1.11 and 0.33% (P = 0.002). Under controlled conditions FN and FP concentrations can be used to discern relatively large differences in DN and DP levels of whitetailed deer. J. WILDL. MANAGE. 54(3):383-389 Nutrient levels of hand-collected forages have been used as indicators of dietary quality (Cook 1964), but this is generally an unreliable method for determining diet quality of free-ranging ungulates (Theurer et al. 1976) due to the apparent ability of ungulates to select the most nutritious forage available (Swift 1948). Esophageal fistulization is usually impractical for studying diet quality of free-ranging wild ungulates (Leslie and Starkey 1985) and, moreover, is unsuitable for DP assessment due to salivary phosphorus (P) contamination (Holechek et al. 1985). Blood samples require manual restraint or death of animals and, given the complex effects of homeostatic regulation of mineral metabolism, blood P concentrations may not be sufficiently sensitive to assess P status (Underwood 1981). The use of fecal nutrient levels to study diet quality may be a feasible noninvasive alternative to other techniques that require disturbance, stress, or death of wild ungulates (Leslie and Starkey 1985). Researchers have used fecal nutrient levels to predict dietary nutrient levels in elk (Cervus elaphus) (Mould and Robbins 1981, Leslie and Starkey 1985), black-tailed deer (Odocoileus hemionus columbianus) (Leslie and Starkey 1985, Mubanga et al. 1985), white-tailed deer (Jenks et al. 1989, Leslie et al. 1989), moose (Alces alces) (Leslie et al. 1989), and domestic livestock (Belonje and Van den Berg 1980a,b; Holechek et al. 1982, 1985). The advantages (Leslie and Starkey 1987) and disadvantages (Hobbs 1987) of FN as an indicator of DN in free-ranging deer diets have been discussed, but little controlled research has been conducted to determine the utility of using fecal indices for nutrient assessment of wild ungulate diets, particularly for white-tailed deer. Leslie and Starkey (1987) argued for continued research toward refining the use of fecal indices to measure the quality of wild ungulate diets. We conducted a controlled study involving 2 consecutive feeding trials to determine whether FN and FP concentrations could be used to detect differences in DN and DP levels fed to penned, white-tailed deer does. We thank C. Schreiner IV and the Y. O. Ranch employees of Mountain Home, Texas, for their kindness, cooperation, and generous use of study pens and other facilities. Critically constructive comments on the manuscript were provided by T. J. DeLiberto, S. Demarais, and F. C. Bryant. We are grateful to E. A. Howery for assistance with data collection and tabulation and to G. R. Scott and N. C. Jordan for lab assistance. Financial support was provided by the Caesar Kleberg Foundation for Wildlife Conservation and Texas Tech University. This is publication T-9577 of The College of Agricultural Sciences, Texas Tech University, Lubbock. 'Present address: Range Science Department, Utah State University, Logan, UT 84322-5230.