Date of Award

2020

Degree Type

Thesis

Degree Name

Master of Science in Biological and Environmental Sciences (MSBES)

Specialization

Environmental and Earth Sciences (EES)

First Advisor

Scott R. McWilliams

Abstract

Migratory birds engage in two periods of endurance flight as they travel from summer breeding to overwintering grounds, and these flights likely increase the production of reactive species that can degrade biologically important molecules. Fall and spring likely represent different oxidative challenges, as many females prepare to breed shortly after spring migration, and antioxidant-rich fruits are plentiful in fall but not spring. I examined the effects of season, anthocyanin supplementation, and flight training on the antioxidant system of female European starlings (Sturnus vulgaris) to determine how each of these factors effects enzymatic antioxidant activity, non-enzymatic antioxidant capacity, and levels of oxidative damage. We fed females a diet that was either supplemented with dietary anthocyanin or not supplemented. We then flew females each day in a wind-tunnel for two weeks in both fall and spring, concluding with a long-duration flight on day 15. This study is one of the most comprehensive examinations of the antioxidant system of a migratory bird to date.

In Chapter I, I compared birds flown in fall or spring to study seasonal differences, the effects of anthocyanin supplementation, and the impact of flight training on the antioxidant system. I analyzed red blood cells and plasma to assess circulating uric acid, circulating non-enzymatic antioxidant capacity (OXY), glutathione peroxidase (GPx) activity, and levels of lipid oxidation (d-ROMs). We blood-sampled females at three timepoints: prior to flight training, immediately after the longest-duration flight on day 15, and after a two-day recovery period. Enzymatic antioxidant capacity and oxidative damage were lower in spring compared to fall. Circulating uric acid was higher in females fed the low antioxidant diet compared to the high antioxidant diet, and females fed the high antioxidant diet had a greater decrease in non-enzymatic antioxidant capacity after flight training than females fed the low antioxidant diet. Flight training had acute and chronic effects on one measure of non-enzymatic antioxidant capacity and GPx activity.

In Chapter II, I compared birds flown in the spring to determine how flight training and dietary anthocyanin supplementation impact the antioxidant system. I analyzed tissue from two muscles (leg and pectoralis), heart, and liver to assess three enzymatic antioxidants (catalase (CAT), superoxide dismutase (SOD), and GPx), two measures of oxidative damage (protein carbonyls and lipid peroxides), and one measure of non-enzymatic antioxidant capacity (ORAC). The effects of dietary antioxidants and training were tissue specific. Dietary antioxidant supplementation decreased GPx activity in the heart, decreased non-enzymatic antioxidant capacity in the pectoralis, and increased protein damage in the leg. Flight training affected SOD activity in the liver, and we found significant diet x training interactions for enzymatic antioxidants in the liver, leg, and heart.

The results reported in Chapters I and II suggest that flight training may help to condition the antioxidant system and so allow birds to prevent oxidative damage. Dietary anthocyanin had mixed effects on enzymatic antioxidants, and both complemented and inhibited the activity of antioxidant enzymes. Furthermore, females appear to prioritize reducing oxidative damage during spring migration. In general, similar flights during fall and spring represent unique oxidative challenges for female birds, and dietary antioxidant supplementation can both complement and attenuate key components of the antioxidant system.

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