In “A Series of Normal Stages in th

In “A Series of Normal Stages in the Development of
the Chick Embryo” (1951), Hamburger and Hamilton
developed and defined specific stages of morphogenetic
progression from the first cleavage divisions through
hatching. The classical Hamburger and Hamilton
(HH) Staging Table is widely used in classifying development of the chick embryo into 45 stages (Hamburger and Hamilton, 1992). In their scheme, Hamburger
and Hamilton used different prominent morphological
changes and developmental features to classify different phases of development. The initial stages (1 to 6)
are characterized by the development of the primitive
streak. The middle stages (7 to 14) are defined primarily by the number of somites and related features. The
late developmental stages (15 to 45) are identified by
several typical morphological features and grouped by
a series of standard measurable features. The morphological changes of limbs and visceral arches are used to
determine stages 18 to 40. However, toward the end of
development, the chick does not undergo further morphological changes and only increases in size; therefore, these late stages require identification by objective
measurements (such as the length of beak and third
toe).
Eyal-Giladi and Kochav (1976) provided the first
stage-by-stage procedure to describe the morphogenetic
development of the early chicken embryo during preoviposition. In the Eyal-Giladi and Kochav 14-stage procedure (Eyal-Giladi and Kochav, 1976), a stage I embryo
is a blastodisc with less than 5 or so cleavage divisions
and a stage XIV embryo has a completed hypoblast
that is generally equivalent to stage 1 in the HH Staging Table. Thus, combining these 2 staging schemes
gives a complete and comprehensive staging reference
throughout chick development.
Although we recognize that the temporal rate of development differs among different species, strains, and
even individuals, the external features of any embryo
within any given stage will be almost identical (Sellier
et al., 2006). With the detailed descriptions of a normal
table as a reference, it is possible to identify the actual
stage at which prenatal activation of functional systems
occurs and the proper time of embryonic response. This
knowledge can be applied not only to scientific research
but also in the poultry industry for evaluating the effect of preincubation handling on embryo development;
estimation of embryonic mortality at different stages
when performing fresh egg and candling breakouts; defining normal and abnormal embryo development; and
evaluating the impact of other factors (hen age, strain,
and shell quality) on fertility and hatchability. These
reference tables ensure that accurate, consistent, and
repeatable data are obtained among laboratories and
represent a standard for industry quality assessment.