Iberian pig is, at the moment, the most important livestock subsector in Extremadura. In 1995, more than 130.000 Tm. real live weight were produced, they were evaluated at more than 20.000 million pesetas, which meant more than 30 per cent of the total final livestock production in Extremadura. The economic outcomes of the exploitation are up to now, in most cases, satisfactory, due to the good prices at the fatstock market. But the Iberian pig production may already have lost part of its extensive character. This work analyzes monthly distribution of energy needs, supplemented feed and potentially grazed resources in four Iberian pig herds during three years. We estimated that carrying capacity of the environment is overcome nowadays.