Three years data on a ryegrass + orchardgrass + white dover pasture were used to establish, following the Anslow method, a percentual monthly distribution of dry matter production. The same was done with the requirements of cows producing 4.000 lt/year. These two monthly percentage distributions agree fairly well, when calving is programmed in September (Spring). Therefore, an economic milk production system can be developed by adjusting cow requirements to pasture production, in the southern section of Chile. The authors emphasize the importance of determining the pasture growth curve for the elaboration of animal production systems.