An Investigation of Protein Levels for Broiler Starter and Finisher Rations and the Time of Ration Change by Response Surface Methodology

A response surface experiment was conducted with male broilers to examine quantitatively the protein levels in starter and finisher rations and the time of ration change to optimize body weight, carcass weight, feed conversion, and net profit. Starter and finisher protein levels and time of ration change treatments were arranged in a central composite design with 15 treatment combinations. Treatment protein levels ranged for the starter rations from 13 t o 33%, finisher rations from 8 to 18%, and the time of ration change varied from 14 to 42 days. The center point of the design was at 23% protein for the starter, 18% protein for the finisher, and a time of ration change at 28 days. Results showed that the responses could be described by quadratic equations and that the plotted contour surfaces were ellipsoid. Optimal protein levels for starter and finisher rations and times of change were calculated for body weight (starter 26%, finisher 19%, and time of change 27 days), carcass weight (starter 27%, finisher 18%, and time of change 35 days), feed conversion (starter 30%, finisher 26%, and time of change 24 days), and net profit (starter 22%, finisher 19%, and time of change 24 days).