A016 GB Issue 02
9
b)
If measuring humidity levels directly be cautious of readings from low cost analogue or digital
hygrometers.
Generally accepted incubation RH levels for species groups:
During
incubation Poultry
40-50%
RH
Waterfowl
45-55%
RH
Parrots
35-45%
RH
Hatching
All species
65% RH or more
For more specific information on particular species’ requirements check the relevant literature.
c)
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 below) 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%
Parrots
16%
Waterfowl
14%
Egg weight loss chart
54
56
58
60
62
64
66
68
2
5
8
11
14
17
20
Incubation period (days)
Average egg weight
(grams)
Ideal weight (grams)
Measured weight
(grams)
8.3
Of the three methods given above the most reliable is egg weight method and is recommended –
particularly where poor hatch rates are experienced or if eggs of high value are being incubated.
8.4
Have water in neither, one or both of the water pots to change the humidity level. Humidity levels are
further increased by maintaining the water level above the divider between the pots.
8.5
In all cases the humidity for hatching needs to be high. Because of the short duration involved
water/weight loss will not be significantly affected. High humidity is necessary to prevent membranes