16. Testing Incubated Eggs For Embryo
it is necessary to test the incubated eggs for fertility. If
large numbers of infertile eggs are incubated, they can be found
and discarded, and the extra space used for additional eggs.
This test will not injure the young embryos and is reliable for
eliminating eggs that will not hatch.
tester or candler by placing a light bulb and fixture inside a
cardboard box. Cut a small, round hole in the top or side of the
box, and let a narrow beam of light escape from the box. You can
see the internal features of the egg by placing it against the
hole. A darkened room makes testing easier.
eggs are normally tested after 4 to 7 days of incubation. Eggs
with white shells are easier to test and can be tested earlier
than dark shelled eggs. Two classes of eggs can be removed on
the basis of this early test, "infertiles" and "dead germs."
"Infertile" refers to an unfertilized egg or an egg that started
developing but died before growth could be detected. "Dead
germs" refers to embryos that died after growing large enough to
be seen when candled.
"infertile" appears as a clear egg except for a slight shadow
cast by the yolk. A live embryo is spider-like in appearance,
with the embryo representing a spider's body and the large blood
vessels spreading out much like a spider's legs. A "dead germ"
can be distinguished by the presence of a blood ring around the
embryo. This is caused by the movement of blood away from the
embryo after death.
are not sure whether the embryo is alive, place the egg back in
the incubator and retest later. A second test can be made after
14 to 16 days of incubation. If the embryo is living, only one
or two small light spaces filled with blood vessels can be seen,
and the chick may be observed moving.