Abstract
Physiological challenges during one part of the annual cycle can carry over and affect performance at a subsequent phase, and antioxidants could be one mediator of trade-offs between phases. We performed a controlled experiment with zebra finches to examine how songbirds use nutrition to manage trade-offs in antioxidant allocation between endurance flight and subsequent reproduction. Our treatment groups included (1) a non-supplemented, non-exercised group (control group) fed a standard diet with no exercise beyond that experienced during normal activity in an aviary; (2) a supplemented non-exercised group fed a water- and lipid-soluble antioxidant-supplemented diet with no exercise; (3) a non-supplemented exercised group fed a standard diet and trained to perform daily endurance flight for 6 weeks; and (4) a supplemented exercised group fed an antioxidant-supplemented diet and trained to perform daily flight for 6 weeks. After flight training, birds were paired within treatment groups for breeding. We analyzed eggs for lutein and vitamin E concentrations and the plasma of parents throughout the experiment for non-enzymatic antioxidant capacity and oxidative damage. Exercised birds had higher oxidative damage levels than non-exercised birds after flight training, despite supplementation with dietary antioxidants. Supplementation with water-soluble antioxidants decreased the deposition of lipid-soluble antioxidants into eggs and decreased yolk size. Flight exercise also lowered deposition of lutein, but not vitamin E, to eggs. These findings have important implications for future studies of wild birds during migration and other oxidative challenges.
Highlights
Physiological challenges during part of the annual cycle can carry over and affect performance at subsequent phases, the mechanisms that produce these carry-over effects are only rarely understood (Harrison et al, 2011)
Effect of diet and exercise on circulating oxidative status Oxidative damage Oxidative damage did not vary with experiment phase, but was higher in males than in females (35.95±1.69 mmol l−1 H2O2 equivalents; sex, F1,25=4.14, P=0.0525). dROMs values for birds in the exercised group (40.25±1.51 mmol l−1 H2O2 equivalents) were on average slightly higher than those of unexercised birds (36.23± 1.63 mmol l−1 H2O2 equivalents; exercise, F1,25=3.27, P=0.0826), the only time period for which the difference between groups was statistically significant was after the flight phase
Hypothesis 3: do flight and diet affect subsequent egg composition? Our experiment revealed for the first time that flight exercise and supplementation with a combination of water- and lipid-soluble dietary antioxidants affect the allocation of lipid-soluble antioxidants in eggs by female songbirds
Summary
Physiological challenges during part of the annual cycle (e.g. spring migration) can carry over and affect performance at subsequent phases (e.g. reproduction; Ebbinge and Spaans, 1995; Bauchinger et al, 2009; Legagneux et al, 2012), the mechanisms that produce these carry-over effects are only rarely understood (Harrison et al, 2011). Plasma levels of carotenoids can relate to dietary intake (Koutsos et al, 2003), and vitamin E is considered especially important to embryos (Surai, 2002) Watersoluble polyphenolic compounds such as anthocyanins, are powerful antioxidants with high concentrations in fruits consumed by wild birds (Alan et al, 2013; Bolser et al, 2013), and their contribution to avian antioxidant capacity is emerging as an important area of research (Catoni et al, 2008; Schaefer et al, 2008; Beaulieu and Schaefer, 2013, 2014). Dietary anthocyanins circulate in avian plasma and can help songbirds mount an immune response (Catoni et al, 2008); birds may even select fruits based on their anthocyanin content (Schaefer et al, 2008; Bolser et al, 2013)
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