An increasing number of laying hens is housed in alternative or non-cage housing systems. In the European Union, poultry welfare is a basic element in management and conventional cage housing was prohibited from 2012 onwards. Since then, European laying hens can only be housed in furnished cages and non-cage systems.
Advantages of these housing systems compared with conventional cages are the increased space allowance per birds and the access to perches, nests and litter. However, the larger group size and the more complex environment in furnished cages and non-cage systems also results in relatively new welfare issues, such as feather pecking, keel bone fractures and smothering. Outbreaks of feather pecking can be very difficult to control in large flocks of hens in non-cage systems, so the focus has been on prevention of the problem. Continuous access to litter for pecking and scratching and reducing stress sensitivity of the birds are key factors in the prevention of feather pecking. The incidence of keel bone fractures has also increased in recent years. Keel bone fractures are thought to occur mainly through accidents when birds navigate through the complex non-cage environment. Solutions focus on improving housing design, for instance by adding extra platforms or perches, on improving the bird’s abilities through selective breeding or modifying the rearing environment. Smothering is a relatively new problem, where birds congregate in a part of the house or even in the outdoor run. The birds at the bottom of this congregation may die due to suffocation. The reasons for this behaviour are still poorly understood, but it seems that avoiding large contrasts within the housing environment play an important role here.
Compared with conventional cage systems, furnished cages and non-cage systems are more challenging to manage regarding welfare problems and maintaining a good egg laying performance.
With the prohibition of cage systems in the European Union in 2012, large changes have occurred in laying hen housing systems. Laying hens can now only be kept in furnished cages or non-cage systems. In these systems, birds have more space compared to conventional cage and access to nests, perches and litter. On the other hand, birds are kept in much larger groups than in conventional four bird cages, ranging from 30-100 birds in furnished cages to 6,000 birds in non-cage systems. The larger group sizes and more complex housing environment also result in an increased risk of welfare problems, such as feather pecking, keel bone fractures and smothering.
Feather pecking is the pecking at and pulling out of feathers of other birds. Feather pecking is a form of redirected foraging behaviour, that is brought about by a combination of internal (high stress sensitivity) and external (poor litter availability) factors. In a recent project, we have shown that stress in the parent stock may be an important factor in the development of feather pecking. Here, we found that flocks of parent stock with high stress levels and feather damage also produced rearing flocks that were more stress sensitive and showed severe feather pecking already during the first weeks of life. Further, availability of litter during early life is of key importance: rearing flocks that experienced a disruption or a limitation in litter supply were much more likely to develop feather pecking already during rearing than flocks with continuous access to litter. Severe feather pecking early in life was also identified as a risk factor for feather damage later in life on the laying farm. Other risk factors were high fear of humans, large group sizes, a floor system rather than an aviary system and the absence of modified management. Modified management consisted of offering the birds roughage or pecking blocks and playing a radio in the house, to make the birds less sensitive to stressors. Together with innovations in breeding, such as breeding birds that are more social and less likely to show damaging behaviour, these recommendations can be used to minimise problems with feather pecking. This is especially important for countries where a ban on beak trimming is considered or already in place.
Keel bone fractures
A second emerging welfare issue is the issue of keel bone fractures.
Keel bone fractures are found in all housing systems, but are generally more prevalent in non-cage systems than in cage systems.
In cage systems, keel bone deviations and fractures may be more related to osteoporosis towards the end of the laying period, whereas in non-cage systems fractures may be more related with high-impact collisions. The presence and design of perches also has clear effects on the incidence of keel bone deviations and fractures. Hester et al. (2013) recently reported high fracture rates in cage-housed hens, with the highest fracture rates in cages fitted with perches. Fracture rates could be reduced by offering soft perches, coated in a soft plastic material or by making perch structures less rigid (allowing the perch to absorb the energy of the landing bird). Another area of importance is that of bone health and bone strength. Laying hens have to invest a large amount of calcium in the daily formation of the eggshell. In the absence of sufficient calcium they use calcium from their bones for this process. This can lead to osteoporosis if the calcium supply is insufficient. Indeed, we recently found that birds with keel bone fractures had also weaker leg bones than birds without fractures. Finally, improvement of both the rearing and laying hen housing system offers good opportunities to reduce the risk of keel bone fractures: adding extra ramps and platforms to the housing systems reducing the incidence of keel bone fractures. In early rearing, adding ramps to stimulate muscle development and 3D skills seems a promising avenue to follow.
Smothering is defined as the event when animals pile up in any part of the house or the outdoor run and where the birds at the bottom of the pile may die of suffocation. This welfare issue has received limited attention in research, partly because it is very unpredictable in time and space and is much more likely to occur in large commercial flocks than in the generally smaller groups of birds kept at research stations. However, smothering is a serious issue, associated with up to 25% of the mortality in UK organic flocks. The problem is more prominent in brown than in white commercial hybrids, which is probably linked to the fact that the brown birds are more docile and more likely to flock together. To be able to investigate a problem like smothering in more detail, sensor-based tracking methods need to be developed, that allow studying how these smothers develop and what are the key factors influencing their occurrence.
The transition from conventional cages to furnished cages and non-cage systems in the European Union has resulted in increased space per bird and access to nests, perches and litter.
These changes provide the bird with more space and more behavioural opportunities compared with the cage environment. At the same time, the increased group size results in an increased risk of welfare problems, such as feather pecking, keel bone fractures and smothering. Innovations in breeding, rearing and laying hen housing and management systems should allow the industry to reduce the negative impact of these issues on animal welfare
From the Proceedings of the Potential For Poultry Production In Developing Countries, 15 -18 October 2015 , Belek – Antalya