Copper (Cu) plays an essential role in the human and animal body system. One of the most important sources of Cu is milk. The purpose of this study was to determine the effect of different doses of injection of inorganic Cu and organic Cu as Cu-arginine and Cu-lysine on Cu concentrations of milk in the lactating Zandi’s ewes. This experimental research involved 54 lactating Zandi’s ewes collected from the department of State Organization Agriculture of Tehran province, Iran. They were allocated into three main groups included: group 1) which received inorganic form of Cu as copper chloride, groups 2 and 3) which received organic Cu as Cu-arginine or Cu-lysine (25, 50 and 100 mg kg-1 of body weight (BW)) in the chelate form, respectively. The milk samples were taken 30 min before and 6 hours after intravenous injection of Cu preparations. The Cu concentration in milk was measured using the flame atomic absorption spectrometric method. There was no significant difference among the groups in milk’s Cu concentration before administration of either inorganic or organic Cu. Data analysis showed that the administration of inorganic Cu caused a significant increase (P<0.01) of Cu concentration in the milk in a dose dependent manner. Furthermore, the administration of Cu-arginine or Cu-lysine in chelate form caused a significant increase (P<0.01) in milk Cu concentration compared to the inorganic Cu. In conclusion, administration of different forms of Cu influenced the Cu concentration in the milk. The organic forms of Cu led to a significant increase in milk Cu concentration in a dose dependent manner compared to the inorganic form of Cu. پرونده مقاله