The Antioxidant System in Broilers Is Altered under Free-range Conditions and Fed Restrictedly

Free-range birds exert substantial physical activity and are prone to adverse weather; these might increase the burden of reactive species in the body and hence initiate oxidative stress. Thirty-six one-day-old Ross 308 broilers were divided in 3 groups (12 birds each). The first group (I42) was kept indoors according to common rearing practices, and received a commercial feed ad libitum. The second group (O42) was reared in identical way as I42 until day 21, when they were transferred to a grass pasture and fed 50% of the ad libitum intake of weightmatched indoor birds in order to stimulate grass intake. At 42 days, 8 birds from each group were euthanized and sampled. The third group (O70) was reared similar to O42 but sampled at 70 days, with approximately the same final weight as birds I42. Compared to I42 birds, the O42 birds showed a higher and lower concentration of malondialdehyde and α-tocopherol in plasma, respectively. Even though not significant, the glutathione-peroxidase activity was 12.9% higher in plasma. The ferric reducing ability of plasma was not affected. Confronting O70 with O42, it was seen that the concentration of reduced glutathione in erythrocytes was considerably increased (+281%). In plasma, the glutathione-peroxidase activity (-49%) and the malondialdehyde level were decreased while α-tocopherol levels remained unaffected but still lower than in I42 broilers. Three weeks of free-range conditions elicited a moderate oxidative stress but after 7 weeks the antioxidant system appeared to have adapted with the glutathione system having a more prominent role.