Page 83 - Hand rearing birds second

66 Hand-Rearing Birds

expected egg weight loss;
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fresh weight (egg weight on lay date, actual or estimated);
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incubator and hatcher (identify individual machines);
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temperature and humidity settings prescribed.
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Each time the egg is handled for weighing, candling, or moving to a different machine, the fol-
lowing data should be recorded:
day of incubation (lay date = day 0);
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date and time;
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actual temperature and humidity;
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current egg weight;
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candling observations, changes to the incubation environment, and other comments;
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initials of the person recording data.
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These data may be recorded directly into a spreadsheet or egg management software program for
egg management during incubation, including monitoring of egg weight loss, and later analysis of
overall hatchery results.
In addition to egg incubation records, data on individual incubators and hatchers should be
recorded. Subtle problems with individual machines may only become obvious through poor
hatchability. Records will help identify specific problems, such as excessive temperature fluctua-
tion or failed turning mechanisms, and indicate needed repairs or other solutions. The following
information should be recorded on each machine:
make, model, serial number, and local identification;
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date, time, temperature, humidity, and egg tray position at least twice daily and whenever the
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machine is opened;
type of event, including routine monitoring, servicing the machine (adding water, cleaning res-
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ervoirs, etc.), adjustments to parameters, weighing, candling, or movement of eggs, and seasonal
cleaning or repair;
initials of the person recording data.
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Similarly, monitoring room temperature and humidity on an ongoing basis will aid in manage-
ment of the hatchery.

­ The­Hatching­Process

As the time of hatching nears, the embryo approaches its maximum size, occupying nearly all the
space within the egg except for the air cell. The gas exchange capacity of the chorioallantois
becomes insufficient, causing the onset of hypoxia (low O 2 in blood) and hypercapnia (high CO 2 in
blood). The embryo consumes the remaining fluids while positioning for hatching. The spine is
aligned with long axis of egg, with the dorsal side corresponding to “highest” edge of air cell, and
the head is between the thighs in the small end of the egg. The head gradually moves up alongside
the body to under the right wing, positioning the egg tooth under the air cell (inner shell mem-
brane) (Figure 3.2). The hatching muscle along the back of the neck engorges with lymph to
enhance leverage. At this stage, the entire head may be edematous despite normal egg weight loss,
but pulmonary respiration will normally dissipate this edema. Correct positioning is correlated
with adequate egg weight loss, incubation position (on side versus air cell up), and adequate ven-
tilation (excess CO 2 often causes upside down embryos).