Wasted cladodes from the cactus pear (Opuntia ficus spp.) are an environmental nuisance, and alternative measures are required to utilize this product, such as utilizing it as a ruminant feedstuff. By simulating ruminal fermentation through in vitro gas production, the fermentation characteristics of dried cladodes were compared with that of lucerne hay and oat hay. A completely randomized design with six replications was used to assess the kinetic parameters of gas production (lag time, rate of gas production and maximum volume of gas (V-max)), in vitro dry matter digestibility (IVDMD), and volatile fatty acid (VFA) and ammonia nitrogen (N-NH 3 ) production during an incubation period of 96 h. Cladodes were collected from containers for organic wastes at large food stores in Mexico. The Vmax was similar between the substrates but the rate of gas production and IVDMD was higher for dried cladodes than for lucerne and oat hays, though the lag time of the cladodes was longer (9.5 vs. 6.5 and 6.7 h, respectively). Acetic and total VFA concentrations were similar during fermentation of dried cladodes and lucerne hay. These results suggested that ruminal microorganism fermented dried cladodes as well as when lucerne hay or oat hay were used as substrates in an in vitro fermentation system.