Submitted to: Workshop on Fundamental Biology and Perinatal Development in Poultry
Publication Type: Abstract only
Publication Acceptance Date: 9/2/2005
Publication Date: 9/23/2005
Citation: Bakst, M.R. 2005. The why's and how's of staging avian embryos [abstract]. The 2nd Combined Workshop of Fundamental Physiology and Perinatal Development in Poultry, WPSA European Working Group of Physiology and the Working Group Perinatal Adaptation, Humboldt-University of Berlin, Germany. Workshop on Fundamental Biology and Perinatal Development in Poultry. p.11. Interpretive Summary: THIS IS AN ABSTRACT. NO INTERPRETIVE SUMMARY REQUIRED.
Technical Abstract: The staging of embryos involves the classification of their normal development from the first cleavage divisions through hatching. Individual stages are based on discrete yet often quite subtle developmental changes in embryo morphology. The collective sequence of stages describing embryo development is referred to as a “normal table”. Normal tables are not only important for research on the development of the avian embryo, but it is also useful for investigators in the poultry industry attempting to discover the basis of fertility and hatchability problems. The normal-table of Hamburger and Hamilton (HH) stages chicken embryo development during incubation is the most well known. It consists of 45 morphologically discrete stages. After the introduction of the normal-table of HH, Eyal-Giladi and Kochav (EGK) devised a 14-stage normal-table of the development of the chicken embryo during the pre-oviposition, oviducal period. The Stage XIV (EGK) blastoderm, which signified the completion of hypoblast formation, coincided with Stage 1 of HH. Normal-tables similar to the EGK for the chicken have been more recently been described by others for the turkey and duck. Why should those of us interested in reproductive efficiency in poultry be interested staging embryos? Only with the standardized detailed descriptions of the normal course of development of the embryo provided in normal-tables can we obtain accurate, consistent and repeatable data between laboratories. While staging can be done by any trained individual it is usually left to the research laboratory personnel and not hatchery personnel primarily due to the substantial time investment in the preparation of each embryo. Notwithstanding, normal-tables can be applied to the following activities: defining normal versus abnormal embryo development; to differentiate an early dead, from a fertilized ovum, from an unfertilized GD; to evaluate the impact of egg handling and egg-storage conditions on preincubation development; to evaluate the impact of hen age, strain, oviposition time, and shell quality relative to blastoderm development after oviposition, egg storage, and incubation; and to determine the comparative role and function of the morphogenetic processes on further embryonic development and survival. The application of the normal table of chicken embryo development to describe embryo development of other birds of commercial and research was recently examined in our respective laboratories. Chicken, turkey, Japanese quail, and Pekin duck blastoderms from oviducal eggs showed differences in the rate of development which was inversely correlated with egg size. Oviposited eggs from these and additional species (goose, Muscovy and mule ducks, and Guinea fowl) were examined after 24-72 hr of storage and at 6 hr intervals up to 72 hr of incubation. At the time of oviposition, there was considerable variation in the developmental stages of the blastoderm both between and within the species/strains examined. While an inverse correlation between eggs size and rate of blastoderm development was observed in oviducal eggs such a relationship was not evident during incubation.