DESCRIPTION OF PROBLEM The

essentiality of copper for poultry has been well documented [1]. Moreover, copper is typically an essential supplement in poultry diets for growth promotion and antimicrobial ef-fects. Dietary concentrations to support the for-mer are higher than that established by the NRC [2]. Feeding either 125 or 250 mg/kg of copper improved growth and feed conversion rate in broilers, but supplementation of 375 mg/kg of copper was of no further benefit [3]. The inor-ganic copper sources used in poultry diets are typically copper sulfate pentahydrate (CuSO4 × 5H2O) or tribasic copper chloride [TBCC; Cu2 (OH)3 Cl]. Because of the lower hygroscopicity and solubility in water, TBCC is considered to be a less reactive and destructive form of copper compared with CuSO4. Also, TBCC is a more concentrated form of copper relative to CuSO4 (58 vs. 25%). Spears et al. [4] reported that the copper in TBCC is more bioavailable compared © 2014 Poultry Science Association, Inc. Copper and lysine amino acid density responses in commercial broiler