MJ1023 GB Issue 01
10
8
Humidity and Ventilation
Short term variations in humidity are not important. The average humidity over the incubation period needs
to be near optimum to achieve the ideal weight loss. High humidity for the day or two of hatching is also
important. Beware chronic, excessive humidity.
Two main factors affect incubation humidity: water evaporation within the cabinet (from eggs as well as from
additional water) and levels of ventilation. The water content of the air being drawn through the incubator will
also have an effect.
There are two methods available to bird breeders to achieve correct humidity levels in the Ova-Easy
Advance:
8.1
Monitor humidity levels and adjust to match published guidelines for different species.
Generally accepted incubation RH levels for species groups:
During incubation
Poultry
40-50% RH
Waterfowl
45-55% RH
Hatching
All species
60% RH or more
For more specific information on particular species’ requirements check the relevant literature.
8.2
Monitor egg weight loss which varies as a direct result of humidity and correct against published
weight loss figures for the species.
Eggs lose moisture through their shells and the rate of evaporation depends on the humidity levels
around the eggs and the shell porosity. During incubation eggs need to lose a fixed amount of water
which corresponds to a loss in weight of around 13-16% depending on species. By weighing eggs
periodically during incubation it is possible to monitor and, if necessary, correct humidity levels to
achieve the correct weight loss.
Weigh the eggs on the day they are set in the incubator, take the average weight and plot this on a
graph (see example below). The ideal weight loss line can be plotted by joining the point representing
initial average weight with the ideal hatch weight (13-16% less depending on species) with the x-axis
representing the incubation period (in days).
By measuring actual average weights every few days the actual weight loss can be plotted and
compared to the ideal weight loss line and corrections can be made. For example if the actual weight
loss was greater than ideal (see graph over page) then the air has been too dry and humidity levels
need to be increased to compensate.
Typical ideal weight losses for species groups:
Poultry
13%
Waterfowl
14%
54.0
56.0
58.0
60.0
62.0
64.0
66.0
68.0
A
v
e
ra
ge
e
gg
w
e
ight
(
gra
ms)
Incubation period (days)
Egg weight loss chart
Ideal weight (grams)
Measured weight
(grams)