How does flight training, dietary fat, and dietary anthocyanins affect the oxidative status of the plasma and metabolic tissues in a migratory songbird?
To better understand the multifaceted antioxidant system of birds, we conducted a factorial experiment that manipulated three ecologically relevant factors (i.e. flight training, dietary fat, dietary antioxidants) to determine their effects on equivalent measures of lipid damage and antioxidant capacity in the plasma, liver, and flight-muscle of a migratory songbird. We tested the following hypotheses:
  1. Stimulatory effect of flight (H1): Acute flight and flight-training stimulate the non-enzymatic antioxidant system and protect against oxidative damage in the plasma, liver, and pectoralis.
  2. Acute-effect of a long flight : plasma antioxidant capacity decreases during a given long-duration flight and so enables circulating oxidative damage levels to remain low.
  3. Long-term effect of flight-training : a bird’s plasma non-enzymatic antioxidant capacity (OXY) increases and lipid damage (d-ROMs) decreases over the course of several weeks of daily flight training.
  4. Flight-training effect across multiple tissues : compared to untrained birds, flying regularly over several weeks increases non-enzymatic antioxidant capacity (Oxygen radical absorbance capacity, ORAC in flight muscle and liver; OXY in plasma) and decreases lipid damage (Lipid hydroperoxides, LPO, in flight muscle and liver; d-ROMs in plasma) in a consistent manner across tissues.
  5. Dietary fat effect (H2): migratory songbirds fed diets composed of more 18:2n-6 PUFA are more susceptible to oxidative damage and thus preventatively increase antioxidant capacity in the plasma, liver, and flight-muscle so as to maintain low levels of lipid damage compared to birds fed diets with less PUFA.
  6. Dietary antioxidant effect (H3): migratory songbirds fed dietary anthocyanins have increased non-enzymatic antioxidant capacity, and lower levels of lipid damage in all three tissues (i.e., liver, muscle, plasma) compared to birds not fed anthocyanins.
We also examined whether these three ecologically relevant factors (flying, fat quality of diet, dietary antioxidants) interacted to affect key components of the antioxidant system.