A total of 2881-d-old Ross x Ross chicks was used in a 4 x 3 factorial arrangement of treatments that included 0, 400, 600, or 800 mg/kg Fe as reagent grade (RG) FeS04-7H20 added to a basal diet (Table 1) containing 188 mg/kg Fe (DM basis, by analysis) and fed for 1,2, or 3 wk. The diet was formulated to meet requirements for starting