Purpose of ventilation At the start of the incubation process, ventilation is determined by the relative humidity. When more CO2 is produced, ventilation is determined by the CO2 concentration. Moisture production does not depend on the fertility, but the CO2 production of course does. You can calculate the ventilation requirement based on the number of eggs, egg weight and heat production.
Oxygen Oxygen consumption varies according to the type of bird. You cannot incubate broilers and layers together and expect to create the ideal conditions for both types. Broilers eggs require higher levels of ventilation. They contain larger embryos that need more oxygen. They also pip the eggshell earlier than layers. Differences also occur between breeds: for example, Ross can utilise more oxygen than Cobb and Hubbard. Consequently, these embryos also cope better with temperature increases. Ventilation requirement for moisture and carbon dioxide
Required ventilation to maintain CO2 levels A setter contains 57,600 fertile eggs that each produce 18.5 ml CO2 per hour at day 18. The incoming air contains 400 ppm CO2 (0.4 l/m3) and the exhaust air is set at max. 4,000 ppm CO2 (4.0 l/m3). So per cubic metre 4.0 - 0.4 = 3.6 l is exhausted. In one hour 57,600 * 18.5 = 1,066 l of CO2 has to be removed. Therefore a capacity of 1,066/3.6 = 296 m3/h is required.
3. P r in c i p l e s o f a r t i f i c i al i n cu bati o n
ventilation requirement for CO2 (VCO2)
d
250
ec
0
3
6
pr ot
0
te
ventilation requirement for H2O (VH2O)
9
12
15
18
21
Incubation time (days)
ht
py
co
CALCULATION EXAMPLE
500
Here, until day 11, ventilation is based on RH, then based on CO2. To maintain a constant RH after day 11, you need to add extra moisture to the air (using sprayers or water rollers). However, this often has a side effect of creating cold spots near the humidifiers. It is better to treat the incoming air, so you don’t have to intervene with humidification in the incubator.
Heat production and CO2 production of broiler embryos
rig
Too much moisture removal To maintain relative humidity at a constant level, you should realise that this moisture comes partly from the hatching eggs and partly from artificial humidification. In the previous example, with exhaust air at 37°C and 55% RH and inlet air of 25°C and 55% RH ventilation of 80 m3/h was required to remove sufficient moisture. But to remove the CO2, the ventilation on day 18 is set to 305 m3/h. This will remove too much moisture (for a linear moisture profile). The difference in absolute moisture content between the incoming and exhaust air is 12.6 g/m3. So you are removing 305-80 = 222 * 12.6 = 2.8 litres of moisture per hour too much that you will then have to add to maintain a constant RH (and therefore removal of moisture). Another option is to use a non-linear weight loss program and reduce the relative humidity in the second phase of setting, without using a sprayer. This will benefit the uniformity of the eggshell temperatures! Do not let the RH become too low. This can negatively affect uniformity or hatchability in incubators with an insufficient cooling capacity.
Ventilation (m 3/hour)
CALCULATION EXAMPLE
Heat production (mW/60g egg)
CO2 production (ml/hour)
1
0
0.0
2
2
0.2
3
4
0.4
4
6
0.7
5
8
0.9
6
10
1.2
7
12
1.5
8
15
1.9
9
20
2.5
10
32
3.9
11
44
5.4
12
65
8.0
13
95
11.7
14
113
13.9
15
132
16.3
16
140
17.3
17
145
17.9
18
150
18.5
Day
When the heat production and therefore the CO2 production are known, you can calculate the ventilation requirements based on the CO2 levels. Multiply these values by the number of fertile eggs in the incubator and apply a correction factor for egg weight or differences between breeds (broiler eggs +10%). 39
