Effect of Dietary Carotenoid Supplementation on Food Intake and Immune Function in a Songbird with no Carotenoid Coloration

Abstract

Studies of ornamental carotenoid coloration suggest that animals may have evolved specialized mechanisms for maximizing color expression and advertising their potential worth as a mate. For example, when given a choice of foods, many carotenoid‐pigmented fishes and birds select the more colorful, presumably carotenoid‐rich foods, and then accumulate these pigments at high levels in both the integument and systemically, in order to boost their immune system and hence directly advertise their health state with their colors. The majority of animals, however, do not exhibit sexually selected carotenoid coloration, which raises the question of whether they still optimize pigment intake and allocation in ways that boost endogenous accumulation and health. We tested the effect of carotenoid supplementation on food intake, carotenoid accumulation in blood, and both innate and adaptive immunity in male society finches (Lonchura domestica) – a non‐carotenoid‐colored estrildid finch relative of the zebra finch (Taeniopygia guttata; a species in which males do display sexually attractive and health‐revealing carotenoid color). Males fed a carotenoid‐rich diet for 2 wk did not consume more food than control males. Still, consumption of the carotenoid‐rich diet for 2 wk significantly elevated circulating levels of carotenoids in blood in male society finches, yielding the potential for immune enhancement. In fact, carotenoid‐enriched finches performed significantly better than control birds in our assay of constitutive innate immunity (bacterial‐killing activity of whole blood), although not in our test of inducible adaptive immunity (response to a mitogenic challenge with phytohemagglutinin). These results suggest that affinities for carotenoid‐rich foods may be particular to species with sexually selected carotenoid pigmentation, but that, as in humans and other mammals (e.g. mice, rats) without carotenoid color, the immune‐boosting action of carotenoids is conserved regardless of the strength of sexual selection on pigment use.

Carotenoids in nature: insights from plants and beyond

“…Fish and birds accumulate dietary carotenoids, which boost their immune system and advertise health, often leading to preferential selection by the sexual partner (McGraw et al 2006b; Baron et al 2008). Animals typically place different priorities on fitness-enhancing activities (e.g.…”

Carotenoids modulate the effect of coccidian infection on the condition and immune response in moulting house sparrows

“…Birds were allowed to keep visual and acoustic contact held in individual cages in order to maintain interactions between individuals in this highly social species. The next day (day 3) we randomly re-introduced the birds in the four aviaries where they were assigned to one of the four experimental groups as follows: (1) (Hill and McGraw, 2006a;McGraw et al, 2006). To our knowledge, no data are available quantifying carotenoid content in the diet of house sparrow, and that is why we calibrated the level of supplementation to that for granivorous songbirds.…”

“…von Schantz et al, 1999;Hill et al, 2004;Hill and McGraw, 2006a;Hill and McGraw, 2006b;Hill et al, 2009); however, the role of these biochemicals in physiological performance, defence against parasites or any measure of fitness in hosts with no carotenoid-based signal have remained less studied (McGraw et al, 2006). Because carotenoids may have important immunostimulating and immunoregulating properties (Møller et al, 2000), animals with no carotenoid-based signal in their colouration can allocate the available carotenoids exclusively toward self-maintenance, growth and reproduction (von Schantz et al, 1999;Blount et al, 2001;McGraw and Ardia, 2003;Catoni et al, 2008).…”

“…Their essential role in immune function is attributed to their immunostimulating and immunoregulating effects (Blount et al, 2003;McGraw and Ardia, 2003;Saino et al, 2003;Grether et al, 2004;Peters et al, 2004;Cucco et al, 2006;Kolluru et al, 2006;McGraw et al, 2006;Aguilera and Amat, 2007). The concentration and the availability of carotenoids in the peripheral blood are often negatively related to parasite infestation (e.g.…”

Unpredictable food availability induces metabolic and hormonal changes independent of food intake in a sedentary songbird

“…food quantity and quality) is a primary limiting factor influencing many physiological processes including reproduction (Fernandez-Fernandez et al, 2006;dos Santos et al, 2010), growth (Cox et al, 2008;Fan et al, 2008), development (Corbel et al, 2010) and the immune system (McGraw et al, 2006;Houston et al, 2007). Energetic status may also act as a proximate cue for timing reproductive activities in seasonal breeders (Hau et al, 2000;Schoech and Hahn, 2005).…”