Use of digestible amino acids and the concept of ideal protein in feed formulation for broilers

The objective of this study was to evaluate diet formulation based on digestible amino acids (DAA), the formulation of low protein diets supplemented with synthetic amino acids, and L-Thr supplementation to increase the Thr:Lys ratio from 67:100 to 70:100. Two experiments were carried out with Hubbard male broilers from 3 to 6 wk of age. In experiment 1, corn-soybean meal diets containing 20% CP were used. In experiment 2, 20% CP diets were formulated with corn, soybean meal, wheat bran, feather meal, and meat meal. In both experiments, body weight gain and economic evaluations were better for broilers fed diets formulated on DAA. Carcass yields and carcass composition were not significantly affected by formulation procedures. In experiment 2, birds fed diets based on DAA had improved feed efficiency compared with those fed total amino acids (TAA). In experiment 1, a reduction of CP from 20 to 18.2% did not affect broiler performance. It did, however, result in fatter carcasses, lower percentages of breast meat, and lower economic evaluation. In both experiments, performance and economic evaluation were not affected by the Thr:Lys ratio. In experiment 1, however, abdominal fat and carcass fatness were reduced, and, in both experiments, carcass protein level was higher with a Thr:Lys ratio of 70:100 than with 67:100 ratio (P<0.05).