LAUSR

Abstract This study aimed to evaluate the effects of five forage cactus genotypes (“Gigante,” “Miuda," “IPA Sertânia," “Orelha de Elefante Mexicana” [OCP], and “Orelha de Elefante Africana” [ACP]) in sheep. The goal was also to show the importance of energy content compared with other forages produced in dryland conditions. Five male sheep cannulated were randomized in a 5 × 5 Latin square design. The experimental diets contained a genotype of spineless forage cactus (440 g/kg of dry matter [DM]), alfalfa hay (585 g/kg DM), and a mineral mixture (15 g/kg DM). The “Gigante” diet promoted lower ruminal pH than the diet containing ACP. There was a lower ruminal ammonia nitrogen concentration observed in the “Gigante” and “Miuda" diets. The highest concentration was found in the “IPA Sertânia" diet. The highest levels of microbial protein synthesis and efficiency were observed for the “IPA Sertânia" diet. Except for the ACP cactus, the spineless forage cactus genotypes featured metabolizable energy content (2.29–2.39 Mcal/kg DM) that was higher than that of alfalfa hay. The spineless forage cactus is suggested to be the primary forage to adopt in semiarid areas due to its high nutritional value and its incomparable production of energy and water per area.