Page 86 - Hand rearing birds second

Incubation 69

If the embryo has failed to internally pip and is either losing strength or becoming frantic, it
may be necessary to manually provide an internal pip. A larger hole can be made in the shell
nearer the tip of the beak and a hole made through the membranes over the beak and nares,
using blunt dissection technique to minimize bleeding. The level of blood flow to the CAM and
location of large vessels can be checked by moistening a sterile swab with sterile water (or nor -
mal saline or lactated Ringer’s solution) and gently pressing or rubbing the area. If necessary,
repeating this process will eventually reduce the refill rate of the vessels, making it safer to
break the membranes.
Once this is done, it is most often necessary to fully assist the embryo from the shell when it
is ready. Both the retraction of the yolk sac and the shutdown of the chorioallantoic vessels
take time. Ensure both these have occurred before the shell is completely removed. Candling
all areas of the egg is helpful in monitoring vessels. It is difficult and sometimes impossible to
see whether the yolk sac is exposed, but removing too much shell will allow the embryo to
push out prematurely. In the meantime, the hole in the shell should be covered with cello -
phane tape or a dressing material such as Tegaderm that is perforated or loose around the
edges to allow air exchange while retaining moisture. Membranes usually become too dry dur -
ing a lengthy assisted hatch and can even shrink, compressing the embryo. Application of
sterile water or isotonic solutions seems to aggravate this drying, but oil‐based artificial tears
or ophthalmic ointment, used sparingly, will ensure membranes remain pliable. Ensure the tip
of the beak and the nares remain clear.
There also is a risk of infection at this stage, because both the membranes and the yolk sac are
exposed to the air and microbes in the environment. Using sterile, or at least aseptic, technique will
minimize the risk. Because California Condors have a protracted hatching period – an average of
72 hours from external pip to hatch in self‐hatching eggs – at the Los Angeles Zoo, it is routine to
treat them prophylactically with antibiotics when the egg must be opened for assistance. An anti-
biotic least likely to cause kidney damage, such as Rocephin (Roche Pharmaceuticals), is dripped
onto the inner surface of the CAM.
Malpositioned embryos with the beak not near the air cell are more difficult to assist.
Radiographs can determine the position of the beak and an air hole made directly over the beak.
This is certain to result in some bleeding but usually not enough to be life threatening. Because
it has not pipped into the air cell, the embryo will not have that additional space to allow move -
ment and yolk sac retraction. An additional small hole should be drilled at the apex of the air cell
and the egg positioned such that the weight of the embryo will gradually push out the air at that
end, gaining more room to move. This is also a good technique for embryos that externally pip
on their own away from the air cell. These may even hatch without further assistance, although
they warrant frequent checks.
Most chicks, even those requiring hatching assistance, will have fully retracted their yolk sacs
and tightly closed their umbilical seals. A few, however, may have partially or fully unretracted
yolk sacs. If there is a small amount exposed and the seal is slightly open, it may be possible to
ease the yolk sac into the body cavity and suture the seal closed. If the seal has tightened around
a small knob of yolk, the chick can be kept especially clean until the material dries and eventu-
ally sloughs off. If there is a large part or all of the yolk exposed, it is usually surgically ampu-
tated. Great care must be taken when tying it off as there is normally a loop of intestine external
to the body cavity until the yolk sac is retracted. Chicks that have had their yolk sacs amputated
will require supportive care, including feeding frequent small amounts as early as possible, as
well as a course of antibiotics.