Use of quadratic growth responses to select protein or amino acid concentrations for production feeds is used to formulate poultry feeds. Arraes (1983) showed that feeds derived from quadratic programming constraints produced market-size broiler chickens for 5% to 15% less cost than linear programming that used NRC nutrient requirements. The NRC requirements are for a fixed, usually maximum, rate of growth. Quadratic programming takes into account diminishing productivity with increasing nutrient inputs. It also considers changes in value of growth produced as well as changes in cost of production.