Is the Cystine Content of the Diet of Concern for Broilers from 0 to 21 Days of Age

Abstract Three experiments were conducted to determine whether Cystine (Cys) was of concern for the broiler chick from 0 to 21 days of age. Chicks received various levels of methionine (DL-Met) both with and without supplemental Cys. A basal diet containing 0.30% Cys was used in Experiment 1; another containing 0.25% was used in Experiments 2 and 3. The addition of supplemental DL-Met significantly improved weight gain (WG), feed intake (FI), and feed efficiency (FE) of broilers to 21 days of age. However, supplemental Cys did not affect these parameters. These data indicate that the NRC recommendation of 0.40% Cys for the female broiler from 0 to 21 days of age is too high.