The article presents the results of studies of morphological and biochemical parameters of blood of broiler chickens KOBB-500, patients with ornithobacteriosis, who were not treated, and sick birds, for the treatment of which were used drugs "Poledoxin" (active substance - doxycycline hyclate) and "Tilmox 25%" (active substance - tilmicosin phosphate). Studies have shown that ornithobacteriosis in broiler chickens is characterized by erythrocytopenia, hypohemoglobinemia and decreased hematocrit. In the birds of the experimental groups, which in accordance with the treatment regimen used poledoxin and tilmox 25% erythrocyte count, hemoglobin content in the blood and hematocrit at 216 h of the experiment were higher than in the control: erythrocyte count - 19 and 36%, respectively; hemoglobin content - by 17% in poultry of both experimental groups; hematocrit - by 19 and 23%, respectively (p≤0.05). In the serum proteins of patients with ornithobacteriosis of broiler chickens of the control group was found dysproteinemia, in which at 216 h of the experiment there was a decrease in total protein and albumin by 12 and 34%, respectively. At the same time there was an increase in the content of globulins by 32%. The content of total protein and albumin in the serum of poultry 2 and 3 experimental groups increased and by 216 h exceeded the control index by 24 and 33% (p≤0.05), respectively, albumin - by 56% in poultry of both experimental groups. The content of globulins in the serum of poultry of the experimental groups for the period from 24 to 216 h of the experiment was in the range of 10.72 - 11.98 g / l, while in the control - 11.32 - 15.21 g / l. In the serum of broiler chickens of the control group for the period from 24 to 216 h increased the activity of alanine aminotransferase by 14%, while in the serum of poultry of experimental groups treated with poledoxin and tilmox 25% its activity decreased by 96, 120 and 216 h was probably less than in the control. Hypocalcemia was observed in the control group of broiler chickens ornithobacteriosis, whereas in the serum of poultry 2 and 3 experimental groups treated, the total calcium content in the period from 24 to 216 h was probably higher than in the control. Hypophosphatemia was observed in the control and 2 experimental birds (poledoxine), and the inorganic phosphorus content in their serum was 216 h lower than in the experimental group 3 birds (tilmox 25% was used) by 43 and 23%, respectively.

Key words: doxycycline, tilmicosin, respiratory diseases of poultry, O. Rhinotracheale, antibiotics, bioavailability.