Overcrowding in Poultry Houses: Technical Protocol for Prevention from Rearing Through the Peak Laying Period
INTRODUCTION
Overcrowding and suffocation in poultry systems should not be viewed as a problem limited to the laying phase.
In most cases, they result from incomplete adaptation to the system, an irregular distribution of the flock, or management practices that do not properly accommodate the birds’ peak activity periods.
The critical factor is not only the overall stocking density of the house, but also local density: the number of hens that gather in the same nest, on the same platform, in a corner, or in an area of litter for a few minutes. A facility may have sufficient capacity and still experience suffocation incidents if the flock does not use all available resources evenly.
Prevention must be addressed in three phases:
Rearing
Placement in the laying house
Daily monitoring of behavior
1Rearing determines the birds’ ability to use the aviary
A pullet destined for an alternative system must arrive at the laying house knowing how to move vertically. Adequate weight and good uniformity are not enough: the pullet must be able to move up and down, find water and feed at different heights, and settle evenly throughout the system at night.
If pullets do not develop this habit, several risks increase in the laying house:
Birds crowding on the first level when settling for the night.
Insufficient use of the upper levels.
More floor eggs.
Difficulty for the flock in finding and using the nests correctly.
Stronger reactions to stimuli, changes in management practices, or staff entering the house.
The goal at the end of rearing is clear: when the light goes out, the birds must spread out among platforms and perches, without a significant group remaining on the ground.
Gradual access to the floor during rearing is a learning opportunity. From that point onward, pullets should routinely move up and down between the different levels.
Ramps, perches, and platforms should facilitate this movement, not become bottlenecks.
Management practices should also encourage movement. Providing water and feed at different heights in alternation, guiding the flock as it moves, and conducting daily walkthroughs of the house help the birds develop agility and use the entire system.
Indicator
Objective
Vertical movement
Pullets move up and down without crowding or bottlenecks
Use of the system
Birds occupy the different levels
Lay down
No pullets remain sleeping on the floor
Uniformity
Flock uniform in weight and physical development
Familiarization
Regular access to feed, water, perches, and platforms
Response to staff
Birds accustomed to routine staff walkthroughs
A flock that arrives without this preparation will require more intervention during the first weeks of lay and will have a greater likelihood of developing uneven distribution.
2The first weeks of lay are critical
The period between placement and the start of production shapes many subsequent behaviors. During these weeks, the birds must learn where to eat, drink, rest, and lay their eggs.
Once a group becomes accustomed to sleeping on the floor or always laying eggs in a corner, changing that behavior becomes much more difficult.
Monitoring must therefore be particularly intensive from arrival until the flock stabilizes in production.
Staff walkthroughs of the house should not be limited to checking equipment or removing dead birds. They should be used to observe behavior, encourage the use of different levels, and identify where the flock is congregating.
These management walkthroughs are especially useful during the first few weeks after the birds gain access to the floor. Staff should walk through the poultry house at different times, encouraging the birds to use less occupied levels and preventing them from consistently congregating in the same areas.
Intervention should be calm. The aim is not to startle the birds into fleeing, but to encourage them to spread out and become accustomed to human presence.
Handling that is too rapid or unpredictable can have the opposite effect and increase flock reactivity.
3Settling for the night: the best time to assess distribution
Settling for the night is probably the most useful time to check whether the flock is using the aviary properly. Before the lights go out, the producer should be able to observe how the birds occupy the different levels.
When most of the birds congregate on the first level, on low platforms, or in a particular section of the poultry house, there is a clear risk of nighttime crowding. This concentration may increase if the lights go out abruptly, if there are poorly managed dark areas, or if access to the upper levels is difficult.
The lighting program should help guide the birds’ movement. Rather than lighting the entire poultry house uniformly, it is necessary to consider the desired behavior in each area.
During adaptation, reference light levels of 20–30 lux in the upper areas and 5–10 lux in the feeding and resting areas may be used, always adjusted to the facility, the birds’ genetics, the condition of the flock, and the overall lighting program.
20–30 lux in the upper areas and 5–10 lux in the feeding and resting areas.
The lights should also be switched on and off gradually. A zone-by-zone lighting sequence allows the hens to move toward the aviary system before the light goes out completely. The lights should be switched off in a way that prevents birds from becoming stranded on the floor or crowding on the lower levels.
Incoming light from outside is another factor that should be monitored. Doors, ventilation openings, windows, or inadequate blackout can disrupt the settling sequence and attract birds to undesirable areas.
4Nest boxes: preventing crowding during egg-laying hours
Crowding in nest boxes is most frequently observed at the start of production and during the first hours of the day.
Hens exhibit gregarious nesting behavior: if several birds choose the same spot, others may follow, and occupancy can increase rapidly.
The first nest boxes, the ends of nest-box rows, and areas near partitions require particular attention. If excessive occupancy is observed, action should be taken before birds crowd inside the nest box or on the access platform.
The technical assessment should focus on five points.
1. LOCATION AND MOVEMENT
The nest box should be located in a quiet area, but not one that is isolated or difficult to reach. Hens resting in front of the nest should not block those trying to enter to lay eggs. A well-designed access surface or appropriately positioned perches can improve the flow of movement.
2. LIGHTING
The entrance should be easily located and attractive. The interior, however, should provide a sheltered environment without being completely dark. If there is an excessively dark area before the entrance, birds may stop there or seek alternative laying sites on the floor.
3. DRAFTS
Direct drafts at the entrance to or inside the nest box make it less appealing to the birds. If certain sections of the line are used less than others, ventilation should be checked rather than attributing the problem solely to flock behavior.
4. CAPACITY AND DISTRIBUTION
As a guideline, individual nests should be provided at a ratio of one nest for every six or seven hens, while communal nests should provide a minimum area of 1 m² per 120 hens.
However, sufficient capacity alone does not guarantee even use. Capacity must be accompanied by accessibility. A properly sized nest with a congested entrance or located in an unattractive area will still result in eggs being laid in only a few places.
5. NIGHT-TIME CLOSURE
Automatically closing the nests at night prevents the birds from using them as resting areas. This measure reduces the risk of birds crowding inside the nests and helps keep the nest mats in better hygienic condition.
5Crowding on the litter: how to identify the trigger
When crowding occurs on the litter, usually between the end of the laying period and early afternoon, it is necessary to observe how the group forms.
Recurring crowding usually begins with a few birds. Other hens then join them, the group becomes denser, and the birds may begin to move as a group or become compressed against a partition, wall or corner.
Recording each episode is essential. For at least one week, the following should be recorded:
Time of onset.
Exact location in the poultry house.
Age of the flock.
Approximate number of birds.
Previous activity: distribution of feed, collection of eggs, passage of personnel or opening of trap doors.
Temperature, ventilation and possible drafts.
Changes in lighting or incoming daylight.
Noise from equipment, vehicles or outside.
Corners and partitions are risk areas because the group may become compressed against a barrier. In these areas, the layout should prevent birds from becoming trapped and allow them to escape sideways.
Installing structural elements can help break up an excessively open area, provided they do not create new obstacles or make cleaning and flock management more difficult.
For flocks that tend to gather on the litter, controlled distraction measures, such as distributing pecking material or encouraging exploration of other areas of the poultry house, can be used.
These measures should be taken before the group becomes densely packed.
These records will help distinguish an isolated episode from a recurring pattern.
6Panic: reducing stimuli that trigger a collective reaction
Panic-induced crowding can occur at any time and tends to develop most suddenly. The birds react collectively to a stimulus they perceive as threatening and move towards the sides of the poultry house or places of refuge.
The most common triggers are:
Unexpected noises.
Banging on doors or metal panels.
Sudden changes in lighting.
Entry of unfamiliar personnel.
Presence of wild birds or rodents.
Equipment malfunctions.
Strong drafts or sudden changes in ventilation.
Prevention involves reducing unpredictability. Work routines should be consistent, visitors should be familiar with the rules for entering the poultry house, and equipment should be maintained to prevent noise or abrupt changes in operation.
For a reactive flock, it is advisable to inspect the places where panic-driven movements tend to end: corners, partitions, the ends of equipment blocks and doors. These areas should allow the birds to disperse rather than become compressed against a barrier.
7Checklist for an episode of crowding
When birds are found crowding together, the response should follow a sequence:
Identify whether the birds are seeking a nest, a place to rest or shelter, or reacting to a fright.
Record the time and exact location.
Check access points, lighting, ventilation, and any physical barriers.
Check for eggs on the floor, birds sleeping outside the system, or unused areas.
Make one adjustment and assess the results over several days.
Avoid abrupt changes that could increase the flock’s agitation.
Monitor the flock more closely at critical times: the onset of lay, late afternoon, and roosting time.
Conclusion
Preventing overcrowding begins before the hens enter production. A rearing system that teaches pullets to use vertical space, well-designed housing, and lighting designed to guide behavior are the foundation for achieving a well-distributed flock.
The aviary design must support these efforts: easy access, movement between levels, good visibility for staff, well-designed nesting areas, and no places where birds could become compressed.
Ultimately, reducing the risk of suffocation is not simply a matter of providing more space. It means ensuring that every hen knows how to use it.
