Using light to prevent floor eggs in cage free production

With the rise of cage free egg production, aviary systems have become the standard housing type in many markets globally. Over the years, much experience was gained with these production systems, but as birds are now free to move around the barn, the occasion of floor egg remains an attention point for farm managers.  

The occurrence of floor eggs can have large financial impact on cage free egg facilities. Under optimal circumstances, the number of floor eggs should not be higher then 0.5%, but under less optimal conditions this can easily increase to 3-4% of eggs produced. Next to the extra work that is needed to collect the floor eggs, floor eggs will also impact farm income, as these eggs might need to be sold as second quality. ONCE has calculated that the financial impact of in increase by 2% floor eggs on a farm with 100.000 layers could be as high as 82.000 USD per flock.  

In this whitepaper we will first dive into possible root causes of floor eggs, and secondly zoom in on how proper lighting systems can help to prevent floor eggs. Throughout the whitepaper, we will refer to the definition of floor eggs as all eggs that are not produced in the nest. This also includes egg produced on the slats of aviary systems.  

Potential root causes of floor eggs 

There are many possible causes that make hens decide not to use the laying nest as their preferred nesting site. We will split the possible root causes in three main themes: 1) housing design, 2) rearing of layers and 3) management in the production barn.  

Housing design 

To make the production of cage free eggs economically viable, aviary systems have been introduced to the market, and have become the standard housing type for cage free egg layers. As the design of the aviary defines how birds move through the house, this obviously has high impact. Below a few points of attention, that could potentially lead to increased floor egg numbers.  

• Nest design – the laying nest should be the most preferred location for egg production. Hens are typically looking for a dark, safe, and comfortable place to lay her egg. Research has shown that different flooring types, tilting angles and materials used can have an impact on the nesting behavior of laying hens. Bright light, cold draft and possibly loud noises should be prevented, to provide the comfort that the hen is looking for when laying an egg.  
   
• Nest position - the position of laying nests in the aviary could lead to improper nesting behavior. For example, when nests are placed on different levels, an uneven nest occupation should be considered, where some breeds might prefer higher positioned nests over the lower nests.  

• Ramps and platforms – moving through aviary systems should be made as easy as possible for hens. Anticipating worst case scenario, where birds have not been properly trained in the rearing period, they should still be able to get into the system, finding their way to feed, water, nest, and perches. Sloping ramps can help birds to move up in the system. 

• Perches - perches are best placed in the higher levels of the aviary system. As egg production typically take place in the morning, you want the hen to easily reach nest area, after waking up on the perch. 
    
• Separation walls – separation walls are used to prevent unequal distribution of birds over the length of the house, blocking birds to move front to back of the barn. These separation walls are typically an attention point for floor eggs, as they create corners where there is less movement and birds can sit at ease. Use open separation walls (made of wire mesh), ensure sufficient lighting near the separation walls, and prevent high litter levels. Nests near the separation walls are typically prone to gregarious nesting behavior, and can cause floor eggs.  
  
  
• Under system floor space – the floor space under the aviary is one of the most common locations for floor eggs. To prevent under system floor eggs, egg producers should consider maintaining sufficient height under the system, provide equal light distribution, and maintain low litter levels. Some aviary systems have the possibility to close the floor area under the system for the first weeks of production. This can help to reduce floor eggs, but when birds are post-peak, floor surface should be opened to prevent overstocking issues in the system.  
  
  
• Climate – cold drafts should be prevented near the nest box, as this has negative impact on nesting. Additionally, cold drafts can lead to unequal distribution of birds in the barn, which leads to local overcrowding and unequal use of laying nests.  
  
  
• Light distribution – light plays an important role in the prevention of floor eggs and should certainly be mentioned in the considerations around housing design. In the last chapter of this whitepaper, we will further map out which considerations to make related to lighting.  
  

Rearing of laying hens 

During the rearing phase, young layers are conditioned for optimum egg production, and transfer to the production barn. From their placement as a day-old, until their maturity stage, these birds go through different development stages. An important element of this development is to get birds susceptible for photostimulation. It is common practice to let birds go through an artificial wintertime, with reduced photoperiods and often reduced light intensity. 

• Jump training – important in an optimum preparation for aviary systems is that birds are trained to jump to a perch, and into systems. Birds that are reared on the floor, and transferred to a production barn with avaiary systems, can be expected to prefer to stay on the floor area over the aviary system, and have higher incidence of floor eggs.  

• Time scheduling – time scheduling in the rearing barn should be adjusted to the production barn. Birds are known to develop a strong circadian rhythm, which preferably should not be disturbed. The need to adjust the circadian rhythm in the production barn could lead to birds producing eggs even before lights come on. Furthermore, proper adjustment of transfer require knowledge about daylight possible entering the production barn daylight, and if the flock will come in production in summer or wintertime.  

• Transfer – the transfer moment from rearing to production barn can be a stressful moment for the birds. Its important to get the birds perching into the aviary systems from the first day they arrive. The first weeks, all birds that remain on the floor should be manually placed in the system, to develop such habit. Birds spending the night on the floor are more prone to produce floor eggs when they get into lay.  

Management in the production barn 

With an optimum housing design, and perfectly reared birds, the first step is taken to achieve low number of floor eggs. Next up is the management of the layers in the production barn.  

• Stocking density – too high stocking densities can lead to increased floor eggs, as there might be insufficient nest space, and birds have difficulty navigating through aviaries in their search of suitable nest space.  

• Training in first weeks – from the moment the first egg is found, until around 2-3 weeks post-peak of the egg production is the most important training period, as laying hens will develop their nesting preference. If birds develop the habit of laying their eggs on the floor or onto the slat, it will be very difficult to change this behavior at later time. When eggs are not collected from the floor, other hens will start laying eggs next to them. Farm workers should collect floor eggs at least 6 times per day during the training, to ensure floor eggs are collected as soon as possible.  

• Photoperiod – some flocks might develop early laying behavior, where birds are producing their egg even before the light switches on. Therefore, it’s important to review when floor eggs are produced. If floor eggs occur during dark period, and eggs are found immediately when lights switch on, farm management should consider increasing the photoperiod. Additional hours of light should always be added to front and back of the day. If only sunrise time is adjusted, the moment of lay might shift to an even earlier time.   

• Collection and feeding times – typically most birds produce their egg 6 hours after lights switch on in the barn. In this period there should be minimum disturbances around the nest. When egg collection starts too early, birds can get disturbed in their nesting, due to the running egg belts behind the nest. Running feed tracks can also be a cause of stress for birds, and result into floor eggs. 

• Litter management – as the flock proceeds, and birds are getting older, farm management should keep a close look on the development of floor egg percentages. If the floor egg percentage increases, preventive measures should be taken. One of the most common preventive measures is the reduction of the litter height on the floor. If the litter builds up, this can become an attractive alternative for the laying nest. Automatic removal of litter from the floor with manure scrapers can be an effective prevention.   

• Bird health – sudden increase in floor eggs could also mean that there is an issue with bird health, as they could become inactive.  

Light to support prevention of floor eggs 

In the previous chapter, we have described potential root causes of floor eggs. Lighting has already been mentioned a few times here, as it has big impact on the behavior of egg layers. In the remainder part of this whitepaper, we will explain how optimum lighting can support the prevention of floor eggs. Then again, we should be reminded that lighting is not a silver bullet and cannot overcome all issues mapped out in the previous chapter.  

Perception of light by chickens 

There are two biological mechanisms in which chickens perceive light: visual perception and non-visible perception. The visual perception is facilitated by the eyes, same to humans, but with the difference that chickens are able to see a wide range of colors, which make them more sensitive in the blue and red color spectrum. Birds are even able to see part in UV-A color spectrum. This means that birds perceive their environment differently, and we should not assume that good lighting for humans is sufficiently catering for the needs of chickens.  

The non-visible perception of light happens, as light triggers hormonal processes by photoreceptors that are positioned in the hypothalamus. Research has shown that mainly the shorter wavelengths of light, in the red color spectrum, are able to penetrate to these photoreceptors.  

Circadian Rhythm with the right (red) light colors 

Whereas non-visible perception of light is responsible for the creation of hormones like melatonin, it are mainly the short wavelengths of light, in the red color spectrum, that are responsible for the establishment of circadian rhythms with chickens. As the reproductive system of egg layers has a strong relationship with this circadian rhythm, egg producers should always ensure sufficient light is provided in the red spectrum of light, in order to optimize daily egg production.  

Exposure of young hens to high amounts of red light, has shown to lead to an improved onset of lay. Research has shown an even stronger effect, when birds are reared under blue color spectrum.  

Uniformity in light intensity 

Light intensity is known to have an impact on laying performance of hens. Getting birds into lay goes hand in hand with an increase in photoperiod and light intensity. But research has also shown that no more then 10 lux will also get layers into production. In barns with aviary systems typical lighting intensity is often around 30 lux. Main reason for this, is the prevention of floor eggs. By increasing overall lighting intensity, the contrast between nest intensity and the rest of barn is emphasized.  

This increased intensity also brings challenges, whereas there is more risk on shadowing effects. Strong shadowing can cause local floor eggs. Lighting should therefore cater for large beam angles, as lamps with narrow beam angles will have more risk of shadowing.  

Unequal distribution of light has a similar effect as direct shadowing, and should be key concern, when designing light plans for layer barns. There should be little difference between minimum and maximum lighting levels, with extra attention to the intensity in the aisle versus under system. Under system lights are often provided by the equipment manufacturer, where there is a trend to provide high levels of light by these suppliers. When high light intensity is used under system, also the aisle lighting should be adjusted to that level to prevent floor eggs here. As such, an optimum cage free production barn has high uniformity of lighting on the full floor area.  

Light color to prevent floor eggs 

Experience with egg producers has shown that the composition of the light spectrum, and the contrast of this color composition throughout the barn, can support prevention of floor eggs. The more cooler light spectrum, with additional blue spectrum, can help to prevent floor eggs under-system. In-system, the more warm(red) spectrum of light will lead to less aggressive behavior and feather pecking.  

Lighting in the system  

Like with the under-system lighting, the in-system lighting is mainly there to ensure prevention of out-of-nest eggs. The risk here is actually biggest during morning time, when there is high pressure on the laying nests. In the afternoon, system lights can be dimmed to lower intensity, in order to promote chickens to go to the floor area for fouraging behavior. If too many birds stay in the aviary, issues like featherpecking could occur.  

Dimming at sunset 

As mentioned before in this whitepaper, its important to have birds perching in the aviary system during the night. This is known to lead to less floor eggs. Birds can be stimulated to move in the system by using a sequence in the dimming at sunset, as birds tend to move ‘towards the light’. Bird specialists relate this behavior to the natural migration of birds into a tree. As the sun goes down, they move up in the tree. Lights under the system are first to switch off, followed by the in-system lighting. All this should happen gradually but should not take more then 30 to 40 minutes. Changing color mix when dimming, like in the ONCE dim-to-red color recipe, can improve the migration of birds into the system.  

Post-peak changes in lighting 

As mentioned before, training of birds take place from the moment the first egg is produced, until about 2 weeks post-peak. During this training time, the habits around nest behavior are established. During this time, it is advisable to use high intensity lighting, to prevent favorable alternative nest areas. But once the habit is established, egg producers should consider to dim light levels, providing more comfortable light levels, that reduce possible issues like aggressive behavior and feather pecking.  

Lifetime of LED luminaires 

Whereas conventional lighting would normally ‘break’, LED luminaires will not suddenly stop working, but slowly lose their light emitting capacity. The lifetime of LED lighting is often expressed in a certain amount of hours, with an L-value behind it, expressing the expected intensity after the amount of hours. For example; 50,000 hrs L70 would mean that it is expected that the luminaire has 70% of the initial light output after 50,000 hrs in operation. Egg producers should beware of this effect, as the reduction in light emitting capacity could lead to increased floor egg percentages after a certain lifetime of the lights. To be sure that sufficient light is provided, yearly measurements can help to keep track of the light emitting capacity of the lights.