A mathematical programing model is built in order to measure the effects of « decoupling » cap compensation payments on three cattle farms in Pays de la Loire (a dairy intensive farm, a beef farm with suckler cows, an intensive beef farm with bull calves). The model maximizes the income under technical and administrative constraints. The object of this paper is to appreciate the adaptation of farmers and to value the impact on the extensification of changing support payments from a per capita to a per hectare basis. Globally, one can expect a redistribution of supports in favor of extensive farms, but the extensification means a complex adaptation of the farm system. The extensification is hardly incited in the intensive areas of Pays de la Loire, where crops yield are high, and the competition beetween beef products and crops is strong.
