Describing the Relation Between Dietary Protein and Energy Levels and Chick Performance by Mathematical Equations

Chicks were fed diets with 36 energy-protein combinations for 19 days. A mixture of corn, soybean, and fish meals with methionine replaced glucose to produce diets ranging from 15 to 28.5% protein. Vegetable oil levels ranging from 1 to 15%, also replacing glucose, varied energy level. Equations were found that expressed each of the following as a function of dietary protein and metabolizable energy levels: body weight gain, gain/feed ratio, protein gain, lipid gain, percent carcass moisture, and percent protein and percent chloroform-methanol extract in the carcass dry matter. The ratio of gross energy gained to metabolizable energy consumed decreased as dietary protein level increased from 16.5 to 27%. Increasing the dietary fat level from 1 to 3% increased this ratio. Mean gross energy in the chloroform-methanol extracts from 12 chicks was 35.3 kJ/g.