The purpose of the present study was to evaluate the effects of spineless cactus species in diets of feedlot lambs on intake, apparent absorption and retention of macrominerals. Thirty-six uncastrated male Santa Ines lambs presenting an average body weight of 22.0 +/- 2.87 kg were distributed in a completely randomized design with three treatments [diet containing Tifton-85 hay as exclusive roughage (control), Miuda cactus cladodes-based diet or Orelha de Elefante Mexicana (OEM) cactus cladodes-based diet] and twelve replicates. The calcium (Ca) and magnesium (Mg) intakes (from feed and total) were higher (P=0.001) for animals fed diets supplemented with Miuda spineless cactus. The spineless cactus, regardless of species, caused a mean decrease of 45.4% in sodium intake (P=0.001). There was a net loss of Ca by lambs fed OEM spineless cactus (P=0.001). The absorption and retention of P was higher in control diet compared to the OEM diet (P<0.05). The amount apparently absorbed, and body retention of Mg were higher for lambs fed Miuda spineless cactus-diet (P=0.001). Therefore, the diet containing Miuda spineless cactus increases the intake and body retention of Ca and Mg in lambs. However, the use of OEM spineless cactus may be unsuitable for a long-term.