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Controlling
Your Incubator’s Humidity by
Monitoring Egg Weight Loss
By
Linda Harrison
Depending on the humidity levels in the incubator and around
the eggs, more or less moisture is lost through the shells by evaporation
during the 21 days of incubation and hatching.
The suggested humidity range of 40% - 50% takes into fact many variables
in the incubator as well as the individual differences in shell porosity
between one egg and another laid by the same or different chickens. All eggshells
are not equal.
Taking all of the possible mechanical and biological variables into account, it
becomes a guessing game at best, and sometimes wrong guesses are made and eggs
fail to hatch under the exact conditions that worked last time.
Many articles indicate that the most common reason for hatch failures is too
much humidity... not enough moisture has evaporated out of the egg over the 21
days of incubation. Eggs that don't loose enough moisture produce chicks that
are too large and are unable to maneuver inside the egg when trying to pip. The
final air space created as moisture evaporates plays an important role in the
survival of the emerging chick. From
the correct amount of air space, the chick gets its first breath of air and
enough room to maneuver as it pips it's way around the shell.
Too little air and it may drown in it's own moisture or be unable to rotate
within the egg or suffocate if it is unable to penetrate and break the membrane
between it and the shell. The result could be a fully formed chick that dies in
the shell. That's a sad moment. Eggs
that lose too much moisture (low humidity levels) produce small chicks with
large air spaces. These chicks are often weak and may die before or during
hatching. Slightly lower humidity
levels are more likely to be less disastrous than slightly higher humidity
levels.
Since so much depends on a specific loss of moisture or in other words a
precise loss of weight from an egg at day 21 for a successful hatch. Weighing the egg at specific intervals can
give a very good indication of the moisture loss at any point in the process
and make it possible to monitor and correct humidity levels to achieve the
correct weight loss.
Chicken eggs need to lose 13% moisture over 21 days. Weigh all the eggs simultaneously on the first day, just before
you put them into the incubator.
Calculate the average weight of the eggs (weight in grams) and plot this
on a graph. You will create an Ideal
Weight Loss Line on a graph. The ideal
weight loss line will be a line plotted by joining the first point representing
the first average weight calculated from the total weight of all of the eggs at
day one (y-axis, weight in grams), with the second point, the ideal hatch
weight, which is the average weight loss of all of the eggs at day 21 (x-axis
representing the incubation period in days, 21 days). The goal is to lose 13% weight over the 21-day period.
Here is a graph
on which you can record your eggs’ weights.
By measuring actual average weights every three or four
days, the actual weight loss can be plotted and compared to the ideal weight
loss line. If the actual average readings from the eggs in the incubator falls
away from the ideal weight loss line (above or below), small corrections can be
made immediately. An example: If the
actual weight loss is greater than ideal (below the line), then the air has
been too dry and humidity levels need to be increased to compensate.
For more accuracy, a digital scale should be used which can weigh in grams.
Don't forget to subtract the weight of the container holding the eggs from the
total weight when calculating the average egg weight.
Do not weigh the eggs from day 19 on and keep the incubator closed. Raise the humidity to at least 65% and
resist opening, and only do so very quickly with 6-8 hours between openings. Humidity will fall dramatically when the
incubator is opened.
Good luck
hatching!
Editor’s note: You can safely track your eggs’ weight if you:
(the weight in 3) – (the weight in 1)
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