The aim of this study was to evaluate the histological alterations in the digestive and renal systems of 35 male ovines in Paraíba, Brazil, at around 16?± 1.87 kg submitted to the following treatments for 90 days (15 of adaptation +?75 of experimental period): 1- Tifton hay (TH); 2- Cassava foliage hay (CH); 3–35% TH and 35% CH; 4–35% TH and 35% forage palm (FP), and 5–35% CH and 35% FP, based on dry matter (DM). Samples of the liver, kidney, rumen, and small intestine were histomorphometrically evaluated and the data were submitted to ANOVA analysis and Tukey post test at p ≤?0.05. The use of alternative foods in the voluminous fraction (CH?+?FP) in the ovine diets did not compromise the performance of the animals; on the contrary, promoted better gain when compared with TH treatment (18.55 kg vs 9.42 kg). The CH?+?FP diet had a positive effect on papilla height. The papilla width decreased with the diets CH?+?FP and TH?+?FP. The thickness of the ruminal muscular layer were higher in the diets containing TH?+?CH and CH?+?FP. The keratinized layer of the ruminal epithelium was larger in the diet containing CH and FP. The villi of the intestinal crypts were deeper in the diets with FP and the villus/crypt ratio was the same in all diets. Goblet cells decreased with the CH or FP diet. Some renal changes were observed according to the diets, mainly when using FP. It is recommended to use CH and FP as a large fraction of the ovines diet, which will not alter animal performance.