Diets different in crude protein (CP) and undegraded intake protein (UIP) contents were offered to sheep in a metabolism study to describe their effects on nutrient digestibility and nitrogen (N) metabolism. Six Corriedale sheep (body weight=56.2±2.3 kg) were divided in random within a Latin square design (replicated) to 1 of 3 diets: 1) a low-CP diet (LP; 12.2% CP with 35.1% UIP), 2) high CP with low UIP diet (HPLU; 14.9% CP with 33.7% UIP), and 3) high CP with high UIP diet (HPHU; 15.5% CP with 45.8% UIP). High-protein dried distillers grain and soybean meal were the main CP sources for the adjustment of UIP:DIP in the diets. No significant differences were found in feed consumption and nutrient digestibility; however, a greater proportion of CP was digested in sheep fed the HPLU diet (69.4%; P=0.04). Although N intake was greater in sheep receiving HPLU and HPHU diets, loss of N through fecal or urinary route was not different among sheep, which resulted in the highest (12.7 g/d) and lowest N retention (7.40 g/d) in HPHU- and LP-fed sheep, respectively. In conclusion, although CP or UIP content had marginal effects on feed consumption and whole-tract digestibility of the majority of nutrients, with the increased CP and UIP levels in the diet, the efficiency of N utilization was improved with regard to increased N retention with minimal differences in N excretion, which is important from an economic and environmental standpoint.