Introduction:
The current state-of the art points to a positive impact of copper (Cu) supplements on the general health status in poultry. Copper induces beneficial changes in the haematological and biochemical blood parameters. It also displays immunostimulating properties and helps maintain a proper microbiological balance in the digestive tract.

Objective:
The objective of this study was to investigate the impact of Cu at the dose of 50 mg/kg BW, administered in organic and inorganic form, on the haematological and biochemical blood parameters and level of Cu bioaccumulation in the liver and pectoral muscle.

Material and Methods:
The study was carried out on 45 BUT-9 turkeys which had been were reared for 16 weeks. They were divided into 3 experimental groups: I – the control group; II – fed with CuSO₄ at the dose of 50 mg Cu•dm^-3 H₂O; III – received a Cu chelate with lysine at the same dose.

Results:
The administration of Cu at the dose exceeding the nutritional recommendations did not induce beneficial changes in the examined birds. This indicates that it is not necessary to administer Cu doses higher than the recommended levels. The extent of Cu accumulation in the pectoral muscle increased by 40% compared to the control group, whereas in the liver it was higher by 30–35% than in the birds without Cu administration. The level of Cu in tissues does not pose a risk to consumers.

Conclusions:
The supplementation of Cu at the dose of 50 mg has a negative impact on the level of the analyzed parameters. The results of the presented study indicate that the administered Cu dose exceeds birds’ demand for this element.