Heat and temperature under constant conditions, the embryo temperature will also increase. In order to avoid the increase in embryo temperature, the heat transfer from the egg to the air immediately surrounding the egg should increase as well.
Heat and temperature during the incubation process internal external plateau phase pipping pipping
350
104/40.0
300
103/39.4
250
102/38.9
200
d
150
ec
te
heat loss by evaporation
50 0
101/38.3
heat production
0
2
4
6
100/37.8 embryo temperature machine temperature
8 10 12 14 Incubation time (days)
16
18
20
99/37.2
Temperature (°C/°F)
growth
pr ot
Heat production or loss (mW)
development
98/36.7
The development of heat production and temperature. As soon as the heat production of the embryo increases, the machine temperature can be decreased slightly to create a cooling effect.
rig
ht
At first, the heat production of the embryo is still low, but it steadily increases. Heat and temperature are clearly different units! Hatchery managers balance the heat production with the heat loss to maintain a constant embryo temperature. They can do this by measuring the eggshell temperature (EST). At the start of the incubation process, the machine temperature should often be slightly higher than the desired eggshell temperature. This is because eggs lose water and the evaporation of water has the effect of slightly cooling the egg. On average, this effect does not exceed 0.2°C (0.4°F). As heat production increases, and consequently the eggshell temperature increases, the machine temperature is decreased to prevent an excessive increase in eggshell temperature. So, the eggshell temperature determines a good incubation result. The metabolism of the embryo is inhibited in the third phase of the incubation process by the limited O2 permeability of the eggshell. This is also called the plateau phase. An increase in the O2 concentration increases heat production further, and hence the absorption and utilisation of the yolk. If heat production increases
py
Embryo/chick temperature changes over time
co
The embryo develops optimally at an embryo temperature close to 37.8°C (100°F), with an acceptable margin of no more than 0.3°C (0.5°F) below and 0.3°C (0.5°F) above this value. Any values outside this margin will slow down the incubation process or damage the embryo. The larger and longer the deviating temperature occurs; the more damage. In the hatcher, heat production will increase more after pipping and the embryo temperature may increase further. An embryo temperature of 40.0°C (104°F) or higher is fatal, but if the chick has dried after hatching, 40.0°C (104°F) is optimal. Correctly setting the temperature in the period around hatching is especially complicated, because the hatcher contains unhatched eggs as well as newly hatched chicks.
100°F
37.8°C
2. Th e i n c u b a t i o n p ro c e s s
101°F
38.3°C
102°F
38.9°C
103°F
39.4°C
104°F
40°C
25
