The supply of grains associated with protein supplements ensures a better balance between energy and protein, promoting productive gains. The objective of this study was to evaluate the performance and physiological parameters of lambs fed diets based on whole corn with extruded protein supplements containing different protein levels. The project was approved by the Ethics Committee on the Use of Animals of the Federal University of Uberlândia (protocol no. 092/16). Twenty-two crossbred lambs (Dorper × Santa Inês) with an initial body weight (BW) of 21.46 ± 6.36 kg and 3 ± 1 months of age were used and were randomly distributed according to age, BW, and body condition score. The animals were housed in group pens for 62 days in a randomized block design and distributed into four experimental groups differing in the protein content of the extruded supplements (20, 24, 28, and 32% crude protein). Feeding was carried out three times a day at 8:00 AM, 12:00 PM, and 4:00 PM. The animals were weighed weekly and evaluated for average daily gain (ADG) and final weight (FW). Heart rate (HR), rectal temperature (RT), and ruminal movements (RM) were measured at 2:00 PM on days 0 (start), 6, 12, 18, 24, 30, 36, 42, 48, 54, and 60. The data were tested for variance assumptions using SAS software, and the means were compared using Tukey's test at a significance level of 5%. The protein level did not influence the variables ADG (0.284 kg day^-1), PF (39.40 kg), HR (72.57 bpm^-1), TR (39.35 °C), and MR (two movements per 5 min^-1) (p>0.05). It was concluded that lambs fed high-grain diets based on whole corn and supplemented with extruded protein sources containing varying crude protein levels maintain satisfactory growth performance and stable physiological parameters, demonstrating effective metabolic adaptation and homeostatic regulation under high-concentrate feeding systems.