Flight training and dietary antioxidants have mixed effects on the oxidative status of multiple tissues in a female migratory songbird

Birds, like other vertebrates, rely on a robust antioxidant system to
protect themselves against oxidative imbalance caused by energy-intensive
activities such as flying. Such oxidative challenges may be especially
acute for females during spring migration, since they must pay the
oxidative costs of flight while preparing for reproduction; however,
little previous work has examined how the antioxidant system of female
spring migrants responds to dietary antioxidants and the oxidative
challenges of regular flying. We fed two diets to female European
starlings, one supplemented with a dietary antioxidant and one without,
and then flew them daily in a windtunnel for two weeks during the fall and
spring migration periods. We measured the activity of enzymatic
antioxidants (GPx, SOD, CAT), non-enzymatic antioxidant capacity (ORAC),
and markers of oxidative damage (protein carbonyls and lipid
hydroperoxides) in four tissues: pectoralis, leg, liver, and heart.
Dietary antioxidants affected enzymatic antioxidant activity and lipid
damage in the heart, and non-enzymatic antioxidant capacity in the
pectoralis and protein damage in leg muscle. In general, birds fed less
antioxidants appear to incur increased oxidative damage while upregulating
non-enzymatic and enzymatic antioxidant activity, though these effects
were strongly tissue-specific. We also found a significant diet x training
interaction for enzymatic antioxidant activity in the leg, and strong
trends for diet x training interactions for enzymatic antioxidant activity
in the heart and liver. Flight-training may condition the antioxidant
system of females to dynamically respond to oxidative challenges, and
females during spring migration may shift antioxidant allocation to reduce
oxidative damage.