Digestible lysine requirements of male and female broilers from fourteen to twenty-eight days of age.

There is little research data available on the digestible Lys requirement of broilers from 2 to 4 wk of age. Two experiments were conducted to determine the digestible Lys requirements of male and female Ross x Ross TP16 broilers from 14 to 28 d. Two diets (dilution and summit) consisting of corn, soybean meal, poultry by-product meal, and peanut meal were formulated to be adequate in all other amino acids. The dilution and summit diets were blended to create 9 titration diets. A control diet containing adequate Lys was used for comparison with the titration diets. A true Lys digestibility assay was conducted with cecectomized roosters to determine the values for the dilution (low) and summit (high) diets. True digestible Lys of the low and high dose-response diets were determined to be 0.84 and 1.21%, respectively. Body weight gain, feed intake, digestible Lys intake, digestible Lys intake:BW gain, feed conversion, and mortality were assessed during experimentation. Digestible Lys requirements were estimated using a quadratic broken-line model and a quadratic regression equation based on 95% of the optimum response. In experiment 1, the digestible Lys requirement for male Ross x Ross TP16 broilers was determined to be between 1.07 and 1.09% and 1.10 and 1.15%, for BW gain and feed conversion, respectively. In experiment 2, the digestible Lys requirement for female Ross x Ross TP16 broilers was estimated as 0.98% for BW gain determined with a quadratic broken-line model and 1.03 and 0.99% for feed conversion, respectively, using a quadratic regression equation based on 95% of the optimum response and the quadratic broken-line model. Digestible Lys requirements for male and female Ross x Ross TP16 broilers were estimated at 1.10 and 1.00%, respectively, based upon BW gain and feed conversion averaged for both statistical models.