Abstract
An animal's antioxidant system is fundamentally complex aiming at finding a balance between pro-oxidative and anti-oxidative stressors in the body. To further unravel the animal's response to oxidative stressors we used free-range broilers combined with severe feed restriction as opposed to conventional broilers as a reference. At 21 days of age, 36 Ross 308 broilers were divided into three groups. The first group (I42) was raised indoors according to common practices and fed ad libitum. The second group (O42) was transferred to outdoors on a grass pasture and fed once daily 50% ad libitum. At 42 days of age, eight birds from each group were sampled. The third group (O70) was reared similar to O42 but was sampled at 70 days, having 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 their plasma, respectively; indicating oxidative stress after 3 weeks of free-ranging and feed restriction. As a response, the glutathione synthesis was up-regulated as manifested by increased levels of glutathione in the liver in O42 compared with I42, and in the jejunal mucosa in O42 and O70 compared with I42, and by a three- to four-fold increase in erythrocytes in O70 compared with the other groups. Regarding meat quality, the outdoor birds showed a darker and yellower colour of breast meat as compared with those reared indoors. Muscle total fatty acid content was higher in O42 compared to I42 and O70, which was reflected in the content of individual fatty acids (mg/100g meat), whereas differences in fatty acid profile (% of total fatty acids) between groups were marginal. To conclude, free-ranging together with feed restriction elicited remarkable changes in the animal's antioxidant system, while changes in meat oxidative stability were less pronounced and more difficult to interpret.
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