In physiological conditions, an equilibrium between pro- and anti-oxidant factors exists; when the former exceed the capacity of their removal/inactivation, oxidative stress (OS) occurs. The OS levels in plasma of two bird species were assayed: blood samples were collected from 20 healthy hens ( Gallus gallus domesticus ), 10 bred with intensive and 10 with free-range farming method, and from 18 clinically healthy magpies ( Pica pica ), captured during an ornithological study. For OS biomarker assessment, the determinable-Reactive Oxygen Metabolites (d-ROMs) were measured, and the Plasmatic Antioxidant Test (PAT) was performed, using a spectrophotometric technique; the OS Index (OSI) was then calculated (d- ROMs/PATx1000) as a parameter of overall oxidative stress. Moreover, lipid peroxidation was assessed by measuring plasmatic malondialdehyde (MDA) levels; a haematological evaluation was also carried out with a haemocytometer, and on blood smear for white blood cell differential count. In hens, OSI and MDA levels were significantly higher ( P = 0.04, and P = 0.004) in subjects from intensive farming (14.7 ± 7.1, and 27.2 ± 10.4 nmol/ml) than in those bred in rural conditions (5.6 ± 10.3, and 8.2 ± 13.3 nmol/ml). In magpies, a positive correlation between white blood cell number and OS was found, and both d-ROMs and OSI were significantly higher ( P = 0.03) in subjects with WBC > median value (20.4 x 10 3 cells/dl) with respect to those with WBC < median value. Obtained results evidenced the occurrence of higher OS levels in hens bred in indoor intensive, compared to outdoor free-range conditions, and this could be related to the higher stocking density and dust levels. In addition, the correlation between OS biomarkers levels in magpies and WBC suggests that OS level is influenced by immune response, in agreement with previous studies. Collectively, present data seem to be promising for the application of OS measurement in avian medicine for health and animal welfare monitoring.
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