Infection pressure
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Correct blood vessel development. The blood vessels in the empty eggshells must cover the inner surface. This shows that the egg was turned well during the first week of the incubation process. The blood vessels must be visible but fine in structure. The eggshell should be very clean.
A new critical phase begins when the chicks emerge from the eggs. The embryo was in a protected environment. Now the chicks are exposed to external factors: ambient temperature, RH, wind, bacteria, etc. And they need enough reserves to survive through the time until they can eat and drink. The bacterial count in the hatcher rises as the chicks hatch. Every time an eggshell breaks open, bacteria are released. So, if the hatch window is 36 hours, bacteria are released during all that time. These bacteria reproduce very quickly. The longer the hatch window, the greater the infection risk, especially if there are a lot of riskeggs (many bangers or floor eggs). The chicks become infected through their beaks or poorly sealed navels. The incubation time (between contamination and infection) is 3 to 5 days. Infection can be fatal for the chicks (resulting in increased mortality between day 3 and 5 in the house).
Bacteria on an egg
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Eggshell condition
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Here, you can see that the Chorioallantoic Membrane (CAM) is not well closed at the base of the egg. Around day 10-12, it is normally closed into the point of the egg. If you see this phenomenon in many eggs, it is a signal that the eggs were not turned properly. The blood vessels have ‘sunk’ downwards and a clot of albumen is left in the point (unused reserve). You also see this if the chick lost insufficient moisture (and therefore weight) through evaporation.
Left: a clean eggshell. Right: an eggshell stained with meconium. This can be a source of an E. coli infection.
152
Clean
Bacteria count per mm2
Of which coli-type bacteria
Mortality within 14 days
600
123
0.9%
Stained
20,000
904
2.3%
Dirty
80,000
1,307
4.1%
The dirtier the eggs, the higher the mortality within 14 days. Once hatched, the chicks come into contact with the dirty eggshells. And the longer they spend in the hatcher, the greater the risk of infection.
Sometimes you see membranes between the chicks that have come loose from the shell (popcorn membranes). This is a sign that hatching went well and chick quality is good. You see it more often in winter with dry air (cold, dry incoming air is warmed up, so RH is very low). Residue of these membranes can also be sucked up and clog the vacuum hoses during down extraction.
Ha tc he ry S i gnal s
