Serum antioxidant levels in wild birds vary in relation to diet, season, life history strategy, and species

Abstract

Micronutrient antioxidants are thought to be generally important for health in many animals, but factors determining levels in individuals and species are not well understood. Diet and season are obvious environmental variables that might predict the degree to which species can accumulate such nutrients. We analyzed antioxidant levels [Trolox-equivalent antioxidant capacity (TEAC), uric acid (UA), vitamin E, and four carotenoids] in 95 bird species and compared these to species-level data on diet from the literature. Using compositional principal components analysis, we identified two main axes of diet variation: invertebrate consumption and seed-to-fruit ratio. We then examined associations between diet axes and antioxidant measures, with and without control for life-history variation and phylogeny. We also analyzed a subset of 13 species for which we had data on seasonality of antioxidant levels and diet, assessing the variance in antioxidant levels explained by seasonality, diet, and species. Unsurprisingly, there were strong associations between antioxidant levels and diet. TEAC and UA concentration were consistently positively associated with invertebrate consumption and seed-to-fruit ratio, and carotenoid concentrations (e.g. zeaxanthin and beta-carotene) were negatively associated with invertebrate consumption. However, vitamin E was not associated with diet as measured here. Importantly, there is much variation in antioxidants that is not explained by diet, and we are able to identify diet-independent effects of species, season/breeding stage, and life history on antioxidant levels. Circulating antioxidant concentrations within and across species can therefore be viewed as a function of multiple factors, including but not limited to diet, and antioxidant metabolism appears to differ across species and seasons irrespective of diet.

Plasma markers of oxidative stress are uncorrelated in a wild mammal

“…2007; Cohen et al. 2009). Timing of sampling is also likely to influence the direction of any correlation.…”

Effects of immune supplementation and immune challenge on oxidative status and physiology in a model bird: implications for ecologists

“…Regarding physiological functions, confounding factors are likely to be numerous, diverse and interrelated. For example, indices of immune function and antioxidant capacity may vary with life history stage (Norris and Evans, 2000;Monaghan et al, 2009), age (Lavoie, 2005;Cohen et al, 2009a), stress levels (McEwen, 1998), energy use (Saino et al, 1998;Cohen et al, 2008), nutritional state (Cohen et al, 2009b) and health status (Costantini and Møller, 2009;Monaghan et al, 2009). By controlling for such confounding factors, studies that experimentally manipulate the physiological status of captive individuals living under standardized conditions are invaluable.…”

Magellanic penguin telomeres do not shorten with age with increased reproductive effort, investment, and basal corticosterone

“…However, penguins may have a better ability to neutralize ROS through antioxidant defense than other bird species or mammals. Antioxidants present within the blood plasma are, in part, a result of the intake of prey that possess high antioxidant load (Cohen, McGraw, & Robinson, 2009). Adelie penguins ( P. adeliae ) can preferentially feed within prey assemblages that consist primarily of krill ( Euphausia superba and E. crystallorophias ), a high antioxidant prey, in response to stress (Beaulieu et al., 2010).…”