This study aimed to evaluate the intake and digestibility of nutrients, nitrogen use, performance and blood metabolic profile of lambs in finishing fed with urea supplemented alternative feeds. Forty Santa Ines lambs, uncastrated males, with an average body weight of 22.8 +/- 2.1 kg, were used in a completely randomized design. Four diets were tested, with Tifton-85 hay as forage (580 g/kg of dry matter) and corn + soybean meal (CSM), corn + urea (CU), cassava scraping + urea (CSU), and spineless cactus + urea (SCU). The lambs fed with SCU diet had lower (P < 0.05) intake of dry matter (DM), organic matter (OM), lignin, total carbohydrates (TCH), non-fibrous carbohydrates, and energy; lower (P < 0.05) apparent digestibility of DM, OM, and TCH, as well as lower (P < 0.05) final body weight and mean daily gain (g day(-1)). However, they presented a higher (P < 0.05) serum concentration of magnesium, higher urinary volume, and higher microbial efficiency (relationship between microbial N flux (g day(-1)) and digestible organic matter fermented in the rumen in kg day(-1); DOMR). Plasma concentrations of glucose were higher (P < 0.05) in lambs fed CSM concerning to CSU and SCU lambs. Diets containing corn resulted in higher (P < 0.05) serum concentrations of cholesterol, triglycerides, and phosphorus. Serum albumin concentration was affected (P < 0.05) by soybean meal replacement. The carbohydrate sources corn, cassava scraping, or spineless cactus, in association with urea, in diets for finishing lambs did not allow the same performance compared to that of animals feed CSM. The SCU diet use can reduce freshwater intake and allow reasonable body weight gain. So, this diet may be more sustainable option in Arid and Semiarid livestock production. Diets containing spineless cactus allow a better efficiency (g N kg(-1) DOMR) of the use of non-protein nitrogen in the rumen.