The cacti species Opuntia fícus-indica and Nopalea cochenillifera originated in México and are nowadays cultivated in Brazil and other countries. They have several uses: human and animal food, medicine, pharmaceutical industry, dye production and soils conservation. In the Brazilian semiarid region, they are almost exclusively used as in natura ruminant fodder, wasting part of their production potential. These species are considered strategic fodder reserves for milk production from Paraíba to Alagoas states. Their high biomass productivities and water use efficiencies indicate that they could be na option to supply the increasing demand for renewable energy sources in semiarid areas. The water use efficiency is highest where nights are cool with high relative humidity, when the stomata open. High productivities imply high nutrient extraction and these cacti species are highly demanding in nutrients especially K and Ca; therefore, they have to be fertilized. They are sensitive to weed competition and the control of these plants has to consider the superficial root system of the cacti. Planting of dense stands (1.0 x 0.25 m) are more productive but the selection of the planting system depends on the projected use and on social and economical conditions of the producer.
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