Carotenoids, immunity, and integumentary coloration in Red Junglefowl (Gallus gallus)

Kevin McGraw, Kirk C. Klasing

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


There is widespread interest in the roles that carotenoids play as yolk and shank pigments, antioxidants, and immune-system regulators in chickens, but nothing is known of such functions in the wild ancestors of chickens-the Red Junglefowl (Gallus gallus). We manipulated carotenoid access in the diet of captive male and female Red Junglefowl to investigate its effects on the coloration of the red comb and buff-brown legs and beak as well as on several indices of immunocompetence. Comb, leg, and beak did not differ in coloration between control and carotenoid-supplemented groups; in fact, biochemical analyses showed that, unlike in chickens, leg and beak tissue contained no carotenoids. Carotenoids showed variable effects on immunological performance, boosting the potency of whole blood in males to kill bacterial colonies, while inhibiting the ability of macrophages to phagocytize bacterial cells and having no significant effect on the accumulation of haptoglobin-an acute-phase protein whose production was induced by a simulated infectious challenge with lipopolysaccharide. These results bring into question interpretations of the evolutionary significance of carotenoid-based and sexually dichromatic shank coloration in domestic chickens, which was apparently derived through artificial selection, and suggest that carotenoids can exert different, mechanism-specific actions on the many lines of immune defense in birds.

Original languageEnglish (US)
Pages (from-to)1161-1171
Number of pages11
Issue number4
StatePublished - Oct 2006


  • Carotenoid pigmentation
  • Chickens
  • Diet
  • Gallus gallus
  • Immunocompetence
  • Red Junglefowl
  • Sexual selection

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology


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