EN
The aim of this study was to determine the influence of oxytetracycline given per os at a dose of 0.5 g/L in drinking water for 5 days on selected parameters of the cell-mediated immunity of 5-week-old turkeys. The research was carried out on forty turkeys divided into two groups (20 birds per group). The percentage of CD3+CD4+ and CD3+CD8+ T lymphocytes as well as IgM+ B lymphocytes were determined by flow cytometry in the blood and spleens of turkeys in the control and in the experimental group after 5 days of oxytetracycline administration and 6 days later. The results of this study show that oxytetracycline given per os (0.5 g/L) as outlined above, has no effect on the percentage of the CD3+CD4+ T lymphocyte subpopulation in the blood of turkeys. On the other hand, we were able to determine that it caused a statistically significant decrease in the percentage of CD3+CD8+ T and IgM+ B lymphocyte subpopulations in blood. The results show that six days after the administration of the antibiotic, there was a statistically significant decrease in the percentage of the CD3+CD8+ T lymphocyte subpopulation among the mononuclear cells of the spleen. A significant decrease in the CD3+CD4+ T lymphocyte subpopulation percentage and an increase in the IgM+ B lymphocyte subpopulation percentage in the spleen were recorded both after 5 days of oxytetracycline administration and 6 days later in the experimental groups of turkeys. It can be claimed that oxytetracycline given to turkeys at a dose of 0.5 g/L for five days in drinking water causes the immunosuppression of the cell-mediated mechanisms of their immune system, which can lead to infections by opportunistic pathogens, as well as weakened post-vaccination immunity.