ABSTRACT: Pornunça (Manihot sp.) is a potential forage to feed ruminants in drylands worldwide; however, evaluations of animal diets are necessary. This study assessed intake and digestibility of dry matter and nutrients, physiological responses, ingestive behavior, water intake, as well as hematological and biochemical responses of lambs fed diets containing increasing levels of Pornunça silage (PS) replacing Tifton-85 bermudagrass hay (Cynodon spp.). Treatments consisted of 0, 33, 66, and 100 % PS considering the roughage portion of the diet (% dry matter – DM). The experimental design was completely randomized with six replicates. Cyanide acid (HCN) levels in fresh Pornunça leaves were 207.7 mg kg−1 DM and 76.78 mg kg−1 DM in PS. Intake of DM and crude protein (CP), and neutral detergent fiber corrected for ash and protein (NDFap) increased linearly with increasing levels of PS in the diet. Digestibility of DM, NDF, and CP were higher with increasing levels of PS. Idle time decreased linearly, while water balance, water intake via food, and total water in feces increased with PS. Nitrogen balance, physiological, and hematological responses were not influenced by treatments, while the final alanine aminotransferase increased for lambs fed all diets evaluated. The PS up to 100 % of the roughage portion increased DM and nutrient intake and digestibility without altering physiological responses and the hematological and biochemical parameters, resulting in greater water intake via food.