Hematological parameters of domestic chickens as stress reaction markers derived from different etiologies

We studied the stress reaction markers among blood parameters from three groups of broiler chickens (Gallus gallus domesticus) of Ross-308 breed aged 5 weeks, with a total number of 60 animals. There were 20 chickens from a private farm in an ecologically clean area; 20 chickens from a private farm in a radiation-contaminated territory; and 20 chickens were brought from a poultry farm to feed animals in the zoo. We determined numbers of erythrocytes, thrombocytes, leukocytes and their individual populations, and heterophils and lymphocytes ratio (H/L ratio). We identified morphological features of blood cells in broilers from a radiation-contaminated territory: an increased number of medium and large lymphocytes and heterophils in half-destroyed or destroyed forms ("shadow cells"). It was shown that the morphological and quantitative features of blood in broilers raised on the private farm from an ecologically clean territory met the normal parameters. Typical features of stress reaction were observed in broilers brought from the poultry farm to the zoo: the relative and absolute numbers of lymphocytes were significantly lower, and the relative and absolute numbers of heterophils were significantly higher than in chickens from the other two analyzed groups. As a result, the leading marker of stress in birds, which is the ratio of heterophils/lymphocytes, was significantly higher in broilers from the poultry farm than in the other two groups. The indicators of monocyte number were significantly lower in broilers from the radiation-contaminated territory than in birds from the private farm in an ecologically clean area. Moreover, the indicators of basophil number were significantly higher, which was an additional sign of a stress reaction. This group also revealed certain morphological features of blood cells such as the tendency of heterophils to destruction, the formation of platelet clusters, and the presence of a significant number of medium and large lymphocytes. It was found that these denoted signs of stress in chickens appeared in cases of acute stress through capture and transportation, which, presumably, was potentiated by previous rearing in industrial conditions. Stress reactions of chickens from areas with an increased radiation background require additional research. The taming effect had a positive influence on the birds’ blood parameters, reducing indications of stress. It is recommended to minimize stress in chickens whose meat is to be used in human and animal nutrition.