Financial losses caused by feather pecking are difficult to evaluate, but figures show that 55% of producers with non-caged birds report signs of feather pecking by the end of lay, says Professor Christine Nicol of Bristol University. However, having studied the subject for some years, she believes the figure may be as high as 80%.
"The economic effects have not been fully recognised by industry," says Prof Nicol. "Producers have become so accustomed to seeing the results of feather pecking that they view it as acceptable behaviour, rather than actively trying to manage the problem."
It is only fairly recently that researchers have found that feather pecking can be divided into two main types - gentle and severe. This relatively new observation makes it difficult to fully utilise data from past studies.
Severe feather pecking
Severe feather pecking can cause tissue damage and even escalate into cannibalism. It should not be confused with aggressive pecking, which is mainly directed at the head, says Prof Nicol. Most scientists believe feather pecking is redirected foraging, although it has also been linked to lack of dust bath provision.
"There is a misconception that feather pecking is an aggressive behaviour, but it is not connected with inter-bird competition," comments Prof Nicol. "It is caused by restricting birds to an environment that doesn't permit them to search for food in a natural way."
A correlation has been found between feather pecking and vent pecking, with flocks prone to feather pecking at higher risk of suffering from vent pecking, she adds.
Heleen Van de Weerd from ADAS Gleadthorpe has analysed research from a number of scientific trials. Evidence shows that chicks can begin severe feather pecking at an early age, but the behaviour may go unnoticed, because young birds go through several moulting periods. Once a bird has been singled out as a victim, its appearance is likely to attract other birds and make the situation worse.
Feather pecking - effects
Feather pecking causes body heat loss, which in turn can lead to increased food consumption. It may also be associated with disease, because it can affect the immune system. There is also a potential spiral effect, due to the strong possibility that birds are more likely to feather peck when they are feeling off-colour.
Prof Nicol describes the causes of feather pecking as "multifactorial." After many years of research, the behaviour is still not fully understood. However, changes to management practices may help to reduce the incidence.
The focus on selecting for high egg production levels has probably allowed unwanted behavioural traits to creep into our standard brown hybrid laying flocks. Research has revealed fewer problems with feather pecking among white hybrid flocks, but UK consumers demand brown eggs. Companies have looked at breeding out the trait, but with margins already tight, production has remained the main criteria when it comes to bird selection.
It is understood that nutrition is an influential factor. Feeding large flocks on a uniform diet means the food is unlikely to meet the dietary needs of all the individual birds. However this issue cannot easily be resolved in a commercial situation. Dietary changes may also stimulate feather pecking.
Birds denied access to loose litter at the end of lay have been found to be more likely to display feather pecking behaviour. Restricting the birds' access to litter on arrival in the laying house, by confining them to slatted areas, has been associated with feather pecking. Providing litter gives birds the freedom to behave more naturally.
Studies have shown that turning the lights up during inspections and keeping the housing temperature at below 20C will encourage feather pecking. Any form of stress on the birds is also considered to be an influential factor.
Encouraging young chicks to start foraging at an early stage can be useful, as it helps to prevent the problem from escalating in later life.
Several studies have shown that increasing the ranging area reduces feather pecking among free-range flocks, says Heleen Van de Weerd. This probably reflects the fact that range use is indirectly related to other risk factors, such as genotype (which affects temperament), stocking density and stress.
Ranging also stimulates ground pecking, which in turn reduces the bird's inclination to feather peck its own species. The risk of feather pecking increased when fewer than 50% of the birds used the outdoor area.
Trials in 2005 concluded that more than half of organic reared pullet flocks displayed signs of feather pecking during rearing. If 20% of the birds showed subtle signs of feather pecking at 16 weeks of age, the majority of the flock would be displaying bald patches due to the behavioural problem by 30 weeks.
By Wendy Short