3-4 days after egg laying
||Chicken Gallus gallus
||Burggren WW. What is the purpose of the embryonic heart beat? Or how facts can ultimately prevail over physiological dogma. Physiol Biochem Zool. 2004 May-Jun77(3):333-45. DOI: 10.1086/422230 p.338 right column bottom paragraphPubMed ID15295688
||Romanoff A.L. 1967. Biochemistry of the Avian Embryo. Wiley, New York. AND Tazawa H. and P.‐C.L. Hou. 1997. Avian cardiovascular development. Pp. 193–210 in W.W. Burggren and B.B. Keller, eds. Development of Cardiovascular Systems: Molecules to Organisms. Cambridge University Press, Cambridge.
||P.338 right column bottom paragraph: "Surgical conotruncal ligation (ligation of the ventricular outflow tract) can be carried out with 10‐0 surgical silk in chicken embryos from about day 2+ until day 5–6 (after which the embryo descends too deeply into the interior of the egg for surgical access). Chicken embryos by day 3–4 have a vigorous circulation, with a rapidly expanding blood volume approaching 50–100 μL and a cardiac output of about 20–50 μL/min (primary sources)."