Methods of In Ovo and Ex Ovo Ostrich Embryo Culture with Observations on the Development and Maturation of the Chorioallantoic Membrane

Abstract

Culture of shell-free and windowed eggs for drug testing and other experiments has been perfected for smaller eggs such as those of chickens, where the developing blood vessels of the chorioallantoic membrane (CAM) become accessible for manipulative studies. However, due to the thickness and hardness of the ostrich egg shell, such techniques are not applicable. Using a tork craft mini rotary and a drill bit, we established windowed egg, in-shell-membrane windowed egg, and in-shell-membrane shell-free methods in the ostrich egg, depending on whether the shell membranes were retained or not. Concomitant study of the developing CAM revealed that at embryonic day 16 (E16), the three layers of the CAM were clearly delineated and at E25, the chorionic capillaries had fused with the epithelium while the CAM at E37 had reached maturity and the chorion and the allantois were both 3-4 times thicker and villous cavity (VC) and capillary-covering cells were well delineated. Both intussusceptive and sprouting angiogenesis were found to be the predominant modes of vascular growth in the ostrich CAM. Development and maturation of the ostrich CAM are similar to those of the well-studied chicken egg, albeit its incubation time being twice in duration.