Blood can only be red because of hemoglobin (a molecule inside blood that transports oxygen). When hemoglobin is saturated with oxygen, it swells and turns various shades of red. When it is depleted of oxygen, hemoglobin will be pale and look "blueish" under the skin. So no black blood. Sorry everyone.Ayam Cemani do not have black blood. It's just a rumor that no one has been able to prove in their own bird. The only thing special about the blood is that sometimes the red color is a darker red. Where did you get your stock?
Update: After reading my post, I was reminded by a friend that technically there is also a blue "blood" based upon hemocyanin (a copper based molecule). When oxygenated, it will turn blue-green. The famous Maryland Blue Crab has this blue "blood".
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