Conventional linear programming practice in least-cost feed formulation is to introduce a "bulk constraint" row of 100 units and a diet specified in percentage terms. This procedure places an arbitrary density or concentration level on the available nutrients and metabolizable energy within the resultant feedmixes, which is not necessarily consistent with the birds' consumption capacity. In fact, animals and birds have quite flexible consumption patterns and capacities. Growing pullets fed "low-energy" feedmixes can, in pursuit of their energy requirements, consume up to 150 per cent of their "normal" feed intake. Diet specification for growing birds should be in terms of so many ounces of nutrients per day or week rather than in conventional terms of the percentage nutrient composition of the diet.