We investigated the viability of Opuntia ficus indica (or cactus), as nutritional substitute for alfalfa (Medicago sativa) and orchardgrass (Dactylis glomerata) hays, assessing its effects on greenhouse gas emissions, water intake, and water footprint. Fermentation kinetics were assessed using in vitro gas production technique with two ruminally cannulated Angus steers as inoculum donors. Forage types were incubated in serum bottles over three runs for 48 h to analyze fermentation characteristics. In vitro digestion kinetics evaluated cactus forage inclusion at 40%, 60%, 80%, and 100% on a dry matter basis. Computer simulations estimated the of cactus diets on water usage. Data were analyzed as completely randomized design, with diet as fixed and runs as random effects. Results showed cactus reduced CH4 and increased CO2 production higher with cactus compared to hay (P < 0.05). Rumen pH, propionate, and digestibility increased with cactus inclusion, while acetate, isobutyrate, isovalerate, and valerate decreased in orchardgrass diets (P < 0.05). Cactus also reduced water intake and footprint (P < 0.001), offering a viable option to lower methane emissions without affecting cattle performance. Cactus fermentation enhances digestibility and propionate production and produces less methane compared to alfalfa and orchardgrass while still maintaining high dry matter digestibility.