ECONOMIC AND ENVIRONMENTAL-EFFECTS OF A NEW-PROTEIN EVALUATION SYSTEM IN DAIRY FARMING

In this paper, we consider the possible effects of a new protein evaluation system on labor income and N losses on grassland dairy farms situated on sandy soil in The Netherlands. The objective function of the linear programming model used maximizes labor income of some typical dairy farms. The model includes various constraints on energy and protein intake in summer and winter as well as different fodders to fulfill the necessary dietary requirements. The N balance of the farm is also included to record N losses. The results show that use of the new protein evaluation system and, in particular, a constraint on the surplus of rumen-degradable protein in summer affect labor income and N losses. When no surplus is allowed in summer or winter, the labor income on a farm with an average herd density is reduced by Dfl. 288/ha (14%), and N losses are reduced by 141 kg/ha (37%). Sensitivity analysis on herd density shows that N losses on farms with a high density can be reduced far more than N losses on farms with a low density, but the income effects do not differ very much.