The Importance of Providing Clean Eggs

By Eduardo Costa, Hatchery Specialist, World Technical Support Team

The performance of a hatchery and the quality of a day-old chick are directly related to the quality of the raw material that comes into a hatchery,  the fertile egg. It is important to appreciate that a hatching egg is as much alive as a baby chick — we just can’t see it.

One of the most perplexing problems facing hatching egg producers is getting the hens to use the nests provided. Egg collection management directly influences bird behavior and egg quality.
At the start of the egg production phase we need to concentrate our efforts into teaching the hens to lay eggs in the nest boxes and avoid floor eggs.
When the eggs are laid the cuticle will take up to three minutes to dry and protect the pores, and this is the moment where the egg is most vulnerable to contamination. If the egg is laid on a contaminated surface, the bacteria will most probably penetrate the shell.
Bear in mind that a floor egg might look clean, but clean floor eggs do not exist; these eggs will have up to 100 times more bacteria per square centimeter of shell surface than a clean nest egg. All floor eggs need to be identified so the hatchery can manage them properly.
The shell is a permeable structure; gases and water that move in and out of the egg need to pass through the pores, and when the pores are partially obstructed by feces, litter material, yolk or albumen, gas exchange and moisture loss will be compromised and hatchability will suffer.
The graph above shows four identical sets of houses on the same area. Farm 2 had less than 5 percent floor eggs while farm 1 had more than 30 percent at the same age. Even with low numbers of floor eggs, litter quality is crucial for egg quality since wet litter equates to a dirty nest.
Embryos cannot combat bacteria, so we need to concentrate on killing bacteria before they penetrate the egg. After that anything we do to try to kill the bacteria will also kill or hurt the embryo.
The eggs should be disinfected within two hours of being laid. Egg collection frequency needs to be controlled, with nest eggs collected at least six to eight times per day. Fertilization occurs five to 15 minutes after the yolk is released on the oviduct, and the egg will only be laid 24 to 26 hours after this moment.
Since the hen’s body temperature is around 40.5 degrees C this means that when the egg is laid it has already had ‘one day of incubation’ and this embryonic development must to be stopped by cooling the eggs. When the eggs are cooled down, carbon dioxide is released and albumen pH will increase from ~7.5 to ~9.0, liquefying the albumen which will help in gas diffusion and nutrient transfer. This event will take up to 72 hours to occur.
The poultry market is very sensitive and often, for commercial reasons, we need to hold eggs for longer periods. Egg holding starts on the farm at the moment the hen lays the egg and transportation is an important part of this process where conditions need to be controlled. Holding temperature needs to be adjusted according to storage time.

1 to 6 days — 19-21 degrees C

7 to 10 days — 18-19 degrees C

11 days — < 17 degrees C
The key of success is achieving a perfect “V” shape on egg temperature, where the coolest temperature is when the egg arrives at the hatchery. However, even with perfect holding conditions hatchability will drop 0.5 percent to 1 percent every day after seven days.
Heat treatment on the eggs during holding period can also be practiced. However, unless the hatchery has ideal facilities to heat and cool down the eggs in a uniform way, this procedure is not recommended. Egg condensation normally occurs when cooled eggs are moved to a warmer environment with high humidity; when condensation occurs it damages the cuticle and increases contamination.

Egg Uniformity

With high levels of automation in the industry, especially in processing plants, flock uniformity is becoming more important. Knowing that the weight of a baby chick is around 67 percent of the initial egg weight, it would seem that setting eggs by weight, will give us the best uniformity independent of the breeder flock age.

That might sound logical, as graded egg will hatch more uniform chicks. This is true at hatch time, but this uniformity won’t last long due to the differences of egg composition, so we need to concentrate our energy on raising uniform breeder flocks to produce uniform eggs.

If more than one breeder flock is needed to make up an order for broilers, the ages need to be as close as possible; flocks younger than 40 weeks should have less than five weeks’ difference and older flocks can have up to 10 weeks since the growth of yolk slows down.


Manage the breeder flock to produce clean and uniform eggs, and keep the pores clear. Once the bacteria are inside the egg, there is not much we can do to help. When an egg is laid it has no protection against bacterial invasion, so it needs to be laid on the cleanest possible surface — the nest. Clean floor eggs don’t exist. Control storage and transportation temperature from chicken house to hatchery setter. Any fluctuation will harm the embryo and cause condensation, damaging the cuticle and increasing the number of eggs that will explode.

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