Submitted to: Avian Biology Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/23/2014
Publication Date: 6/11/2014
Citation: Bakst, M.R., Wade, A.J. 2014. New observations regarding staging turkey embryos from oviposition through primitive streak formation. Avian Biology Research. 7(2):99-105. Interpretive Summary: When fertilized turkey eggs are stored in a cool room for longer than a week, which is a common industry practice, embryo mortality will rise. Longer periods of egg storage produce correspondingly higher rates of embryo mortality. In the course of determining the stage of development of turkey embryos isolated from fresh and stored eggs before and after incubation, we observed that descriptions of turkey embryos proposed 20 years ago did not correspond to our observations with eggs from modern day turkey breeders. Our observations of embryos from fresh, unincubated eggs revealed embryos less advanced developmentally than those observed 20 years ago. Differences in embryo development were also observed after incubation at different time intervals. Based on our new observations, a revised table describing the step-wise development of the turkey embryo was presented. This research will benefit other poultry scientists attempting to reduce embryo mortality associated with egg storage and embryologists interested in defining what genes are associated with each sequential stage of embryo development.
Technical Abstract: The normal developmental sequence of the turkey embryo from the initial cleavage divisions through hypoblast formation has been described previously in eleven separate stages based on the progressive morphological differentiation of the embryo (Gupta and Bakst, 1993). However, in recent preliminary studies, our attempts to apply their staging procedure to describe the stages of embryo development were not successful. Therefore, we re-evaluated the development sequence of the turkey using eggs obtained from modern day commercial lines. Embryos from unincubated eggs and eggs incubated at different time intervals up to 25 hr were examined. In contrast to observations by Gupta and Bakst (1993), embryos from unincubated eggs lacked an area pellucida (AP) but were characterized by dense clusters of cells that did not begin to dissipate and begin forming the AP until after 3-4 hr of incubation. We also found that Koller’s sickle may or may not be present prior to and during hypoblast formation. Based on these new observations, a revised development table including the above observations was presented that more accurately reflects the morpho-differentiation of the modern commercial turkey embryo.