EN
Metabolic activity of neutrophilic granulocytes of carp (Cyprinus carpio L.) aged from 2 months - 5 years determined by the Nitrotetrazolium blue reduction test (NBT) has been rendered as the percentage of NBT⁺ cells, NBT index and quantity of formazane (g/l). A decrease of the percentage of NBT⁺ cells from the 5th months and the NBT index from the 10 month of the carps lives was discovered. The highest percentage of the NBT⁺ cells and NBT index was found in carps 2 months old, the lowest in the carps at the age of 5 years and 25 months, respectively. Sex did not affect these parameters. Age and sex of the carp did not affect the quantity of formazane in the blood.