First of all, let’s briefly explain what hatcheries are: they are specialized production units that, imitating hatching, bring fertile eggs to generate day-old chicks, thus starting the entire poultry production chain.
There are essentially two different egg incubation processes, but it is not so much the hatchery (the building or the machine) that is structurally different, but rather the operating protocols (temperature, humidity, duration) and the rigorous separation of the genetic lines (layers and broilers).
The distinction occurs mainly for two reasons:
Genetic differences and incubation requirements
Eggs from genetic lines intended for meat production (broilers, or meat chickens) and those intended for egg production (layers) have slightly different embryonic development profiles:
Different needs: may require slightly modified temperature and humidity parameters, especially during the more advanced incubation stages or hatching.
Heat production: Broiler embryos (selected for rapid growth) tend to produce more metabolic heat in the final phase of incubation than layer embryos, requiring more careful ventilation and cooling management in incubators.
Duration: Although the standard incubation is 21 days, actual hatching times can vary slightly between lines.
Biosafety and health management
The most important reason for maintaining separation, even when using machines of the same model, is biosafety.
Strict Separation: In modern hatcheries, the principle of strictly separating batches of eggs and chicks based on their origin (the breeder farm) and, above all, their destination (broiler vs. layer) is adopted.
Cross-Breeding Prevention: Keeping genetic lines separate minimizes the risk of cross-contamination and the spread of any specific diseases between different poultry populations.
In summary and in practice, large companies:
They can use the same model of incubator machine, but load it with protocols (management modes) specific for layers or broilers.
They may have completely separate buildings or hatching areas within the same complex to manage the two types of genetic lines (physical separation), ensuring optimal health and operational control.
In the case of Hy -Line, being a leading company in layer genetics, their hatcheries are obviously dedicated to laying hen lines, such as Hy -Line Brown, and not to broiler lines.
That said: The topic of hatcheries is a very specific and extremely efficiency-oriented one, which we will be dealing with soon.
So let’s address the issue of “cleaning” eggs.
Eggs destined for hatcheries should never be dirty. Let’s see why and how hatchery workers proceed to prevent this from happening.
Clean eggs are the foundation of an incubation operation that must strive for perfection.
However, it’s not uncommon to find people underestimating how a single dirty egg can compromise hatching, chick quality, and the profitability of the farm. Let’s explore the reasons why dirty eggs should always be avoided and what can be done to prevent them.
- Dirty eggs have a high microbial load – Feces, litter, dust, and other contaminants on eggshells aren’t just surface dirt, they harbor harmful bacteria, fungi, and viruses. Microbes such as E. coli, Pseudomonas, Salmonella, and Aspergillus can easily penetrate the shell through pores or small cracks, causing infection of the embryo and early mortality.
- Risk of cross-contamination – Inside a hatchery or brooder, a single dirty egg can spread contamination to many clean eggs. Bacteria multiply rapidly in the warm, humid conditions of the incubator, increasing the overall microbial load and infecting nearby eggs. This not only reduces hatching, but also compromises the hygiene of the entire incubation system.
- Dirt clogs the tiny pores of the eggshell, limiting the exchange of oxygen and carbon dioxide – As a result, the embryos receive less oxygen and accumulate more carbon dioxide, slowing their development and reducing hatching success.
- Microbial infections are most dangerous during the early stages of incubation – They often cause embryos to die before they have fully developed, contributing to increased early mortality rates and overall hatchery loss.
Placing dirty eggs in the hatchery is essentially a critical error in breeding and incubation management, and must be strictly avoided for reasons of health, hatching efficiency and chick quality.
The main reasons for avoiding dirty eggs (especially if contaminated by feces) are related to the risk of bacterial contamination in an environment that favors their proliferation.
Here are the main reasons:
Risk of bacterial contamination (especially salmonella)
The shell is porous – Although the egg has a protective outer cuticle (“bloom”), the shell is naturally porous. Dirt, especially feces, contains a high bacterial load (such as Salmonella or Escherichia coli).
Hatchery conditions – The incubator is a warm, humid environment (about 37-38 degrees Celsius and high relative humidity). These are ideal conditions for the multiplication and proliferation of bacteria, fungi, and molds present in the dirt.
Bacterial aspiration – When a dirty egg, which is cooler than the incubator environment, is introduced, condensation (or “sweating”) can form on the shell. This moisture facilitates the passage of bacteria through the pores of the shell, where they can infect the embryo.
Cross-contamination (the explosion)
Spread – A contaminated egg can contaminate other healthy eggs, the air, the hands of operators, and the walls of the incubator itself.
Risk of ” Explosion ” – A severely infected egg, especially if the embryo dies, can become such a powerful bacterial breeding ground that it explodes due to the accumulation of gases generated by putrefaction. This immediately releases a huge amount of bacteria and infectious fluids into the hatchery, compromising the entire hatching batch.
Poor chick quality and mortality
Early embryonic mortality – Bacteria that penetrate the shell can kill the embryo in the early stages of incubation, dramatically reducing the hatching rate.
Weak Chicks – Even if the infected embryo manages to hatch, the chick will be born with an infection (e.g., omphalitis or septicemia) or will be extremely weak and susceptible to disease, leading to increased mortality in the first week of life.
In other words, depositing dirty eggs increases the risk of massive infection in the hatching batch, reduces production efficiency and compromises the health of the hatched chicks.
For this reason, eggs intended for incubation must be clean, intact, and frequently disinfected (without damaging the cuticle, for example by washing with water, which is not recommended in most protocols, or with dry/steam disinfectants).
But how can we avoid introducing dirty eggs into the hatchery?
You may be wondering how to prevent dirty eggs from entering a hatchery.
It’s a process that begins long before harvest and is based on two fundamental pillars: preventing dirt on the farm and properly preparing/disinfecting the selected eggs.
Here’s what’s typically done in best practice in the poultry industry:
Prevention: Keep eggs clean in the nest
The most effective strategy to prevent the introduction of dirty eggs into the hatchery is to prevent them from becoming dirty in the first place, through careful farm management.
The main prevention actions are:
Nest hygiene: nests must always be kept clean and regularly replenished with fresh bedding (such as straw or shavings). Dirty litter is the main source of fecal contamination.
House litter hygiene: it’s crucial to keep the litter on the house floor dry. Wet litter can stick to the hens’ feet and feathers, which then contaminate the eggs in the nests.
Frequent collection: eggs should be collected several times a day (ideally every 2-3 hours). This reduces the time they remain in contact with feces or dirt and prevents further damage or contamination.
Checking the health of your hens: it is necessary to monitor the health of your birds, as dirty feathers or loose feces (often related to nutritional problems or illnesses) inevitably lead to dirty eggs.
Handling of ground eggs: all eggs laid on the ground, outside the nest, must be discarded and not used for incubation, given their high and risky contaminant load.
Selection and preparation (what to do before incubating)
After collection, the eggs are sorted in a sanitized room.
Initial Selection
First of all, you need to discard:
Very dirty eggs (with feces or mud): these should be discarded.
Broken or cracked eggs (even slightly): the damaged shell allows immediate bacterial penetration.
Eggs with shell defects: shells that are too thin or porous, offering less protection.
Treatment of slightly soiled eggs
For eggs that only have light stains, treatment is crucial and must be done correctly so as not to damage the cuticle and force bacteria to enter:
After the broken and severely soiled eggs have been selected and discarded, those with only light stains require extremely delicate treatment so as not to compromise their natural protection (cuticle).
Methods and precautions:
Dry cleaning: to remove surface dirt, proceed with extreme caution, using a dry cloth, a dry abrasive sponge, or very fine sandpaper. It’s essential to avoid using cold or hot water, scrubbing vigorously, or using hard brushes, as these actions damage the cuticle and facilitate the entry of bacteria.
Washing (in professional settings): in industrial settings, washing, if absolutely necessary, should be done exclusively with warm/hot water (the temperature must be higher than that of the egg to avoid aspirating bacteria) and specific disinfectants, followed by rapid drying. It is crucial not to immerse eggs in water colder than their interior, as cooling causes the contents to shrink and contaminants to be aspirated through the pores of the shell.
Disinfection (fumigation or alternative treatments)
In most commercial hatcheries, cleaned and sorted eggs are immediately disinfected before being placed in the incubator or stored through:
Fumigation: traditionally, formalin (formaldehyde gas), a powerful germicide, is used, although its use is subject to severe restrictions due to its dangerousness.
Alternative treatments: treatments such as spraying with disinfectants (such as hydrogen peroxide), UV treatment or ozone are increasingly being used to decontaminate the shell surface before incubation.
The objective is threefold: to prevent dirt on the farm, to discard unsalvageable eggs and to disinfect clean eggs to eliminate residual surface bacterial load.
What about eggs intended for human consumption?
There are differences in rules and practices between Europe (including Italy) and those in force in other countries (for example, the United States). In Italy and the European Union, the legislation on eggs intended for consumption (Category A, or “fresh eggs”) states that they must NOT be washed or cleaned.
The (EU) standard
Category A eggs must be clean and intact at source. The EU Regulation clearly specifies:
No washing: category A eggs are not washed or cleaned either before or after classification and do not undergo any preservation treatments.
Rationale: this ban serves to preserve the cuticle (or bloom), a thin, natural, and invisible protective layer that covers the shell. The cuticle plays a crucial role in sealing the pores of the shell, preventing the entry of external bacteria (such as Salmonella) and excessive moisture loss.
Washing risk: Washing the egg with water (especially if it is colder than the egg) removes the cuticle and can encourage bacterial penetration inside through the pores due to the difference in pressure.
What happens to dirty eggs?
Grade A eggs: eggs that are significantly soiled or damaged are removed from Grade A (fresh counter eggs) and cannot be sold directly to the consumer.
Category B eggs (industry): these dirty or non-compliant eggs (and Category A eggs that do not meet freshness requirements after a certain period of time) are intended exclusively for industrial processing (for example, for the production of liquid or powdered egg products), where they are broken, the contents pasteurized and processed.
In summary
The eggs you find on sale in Italy and Europe:
They are not cleaned with water after harvesting.
They are only transported, selected and packaged (and stamped) if they meet hygiene and quality standards directly as they came from the hen.
Any slight impurities are removed dry.
Outside the European Union, these specific rules on the prohibition of egg washing can be (and often are) disregarded or replaced by different regulations.
The best-known case is that of the United States, where the standard (and often mandatory) practice is just the opposite:
United States (and other countries): eggs are systematically washed, brushed, and disinfected (often with chlorinated solutions) immediately after collection. This process removes the natural protective layer (the cuticle).
Consequence: to compensate for the loss of the cuticle and prevent bacterial proliferation, these eggs must be stored in the refrigerator (at 4 degrees Celsius or below).
Difference in approach
The difference between Europe and the United States is based on two different approaches to food safety:
European (“natural”) model: prevent contamination by keeping the cuticle intact and ensuring strict hygienic conditions in the farm, with a ban on washing.
American (“technological”) model: remove the cuticle (and therefore surface dirt) by washing and then rely on maintaining the cold chain to prevent the growth of any bacteria that could penetrate through the open pores.
So, while in Europe washing is prohibited for fresh eggs for consumption, in many other parts of the world it is standard practice.
Writer: Rasel Ahmed – Incubation Specialist
