The aim of the study was to evaluate the influence of prolonged and interrupted stress in the form of crowding, temperature decrease and light change on levels of turkey-hen’s selected blood indices, including anti-oxidation system factors. The investigations involved a medium-heavy type of turkey-hen BUT-9, reared from 6 till 16 weeks of life. The birds were randomly divided into 3 groups consisting of 60 turkey-hens each (2 replications of 30 birds each). Group I was the control. Groups II and III were subjected to the experimental factor: stress in the form of crowding, as well as temperature and light changes. The stress exposure frequency was the differentiating factor. Birds from group II were exposed to the stress for a 28-day-period every 2 days for one hour daily. Turkey-hens of group III were stressed for a 28-day period everyday for an hour daily. A three-week break with no stress was applied after 28 days of the experiment. After that period the experimental factors were applied once more for 28 days. Blood for the tests was taken from the birds’ wing vein at the end of 9th, 12th and 16th week of life. Corticosterone and malonic dialdehyde (MDA) levels were determined in blood serum to find out if stress factors affected the birds. Quantitative ratio of heterophylls to lymphocytes (H:L) as an indicator of environmental stress was also determined. Moreover, peroxide dismutase activity, glutathione peroxidase and catalase activities in blood erythrocytes as well as zinc, copper and iron in blood serum of turkey-hens were recorded. Results indicate that except for glutathione peroxidase stress exerted a significant influence on all tested parameters of a turkey-hen’s blood. The applied experimental factor appeared to be a higher stress for intensively stressed turkey-hens, which is proved by the significant increase of corticosterone and malonic dialdehyde levels as well as the H:L ratio. A significant dependence between the activities of anti-oxidation enzymes (SOD and CAT) in blood erythrocytes and copper, zinc and iron concentrations in blood serum suggests that anti-oxidation immune mechanisms cannot efficiently protect an organism against any stress during trace element deficiencies. In consequence, it may affect the strengthening of lipid peroxidation processes of poultry exposed to stress.
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