Study Investigates Link between Range Cover and Feather Damage in Free-Range Hens

Providing a minimum of five per cent tree cover offers egg producers a practical way to improve feathering of free-range laying hen flocks, according to new research from the UK.
calendar icon 20 June 2012
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Dr Ashleigh Bright of FAI Farms Ltd in Oxford and co-authors in the UK have reported a study from which they concluded that providing a minimum of five per cent tree cover, planted close to the house and with good canopy coverage is a feasible and practical method enabling producers to reduce feather damage due to injurious feather pecking in their free-range laying hen flocks.

They added that tree cover provision may also provide environmental benefits such as soil stabilisation, reduced nutrient leaching and carbon sequestration.

The objective of the study, published in the journal, Animal Welfare, was to investigate, in a commercial situation, the correlation between 1) the proportion of range cover and 2) the proportion of canopy cover, with feather damage of end-of-lay hens.

Background to the Study

Explaining the background to the study, Bright and co-authors said that McDonald’s moved to a policy of using free-range eggs 12 years ago. There was recognition of the need to look at ways of improving the welfare of free-range laying hens because although the system has the potential for good welfare, it is not always achieved.

Injurious feather pecking is one of biggest welfare issues for free-range laying hens, i.e. hens often peck each other and cause damage which can lead to high levels of mortality and poor feather cover at end of lay. In the UK, laying hen range is often a barren grass area with limited overhead cover. Overhead cover is very important to domestic poultry which have evolved from a jungle species and the birds are very aware of aerial predators. Vegetation providing overhead cover also provides variety of habitat and resources.

There is scientific evidence that flocks that utilise the range have a lower incidence of feather pecking than flocks that do not. There is also evidence that tree cover on the range encourages birds outside. The obvious next step, which this study addressed, was to ascertain whether providing tree/canopy cover on the range was directly associated with less injurious feather pecking.


In preparation for the study, the researchers said that a working group was set up by McDonald’s comprising McDonalds, FAI, Noble Foods and the Lakes Free Range Egg Company to design the project and decisions were based on scientific and practical evidence. Through their suppliers, McDonald’s supported the producers, enabling them to invest in tree planting.

Specifications were agreed for tree planting, i.e. a minimum of five per cent canopy coverage of the range equivalent to 500 square metres of cover per 1,000 hens, no more than 50 per cent of trees to be fast growing with the edge of the canopy to be no more than 20 metres from the house; close enough to encourage birds out of the house but not too close to impede machinery movement or issues with tree root growth.

A new scoring system for measuring canopy cover was developed and the feather score damage scoring system was adapted for commercial use from previous research. At the end of lay for each flock – around 70 weeks of age – farmers were asked to record the percentage of tree cover on the range, the percentage of canopy cover provided by the trees and the feather damage of the birds.

Bright and co-authors stressed a clear distinction between percentage tree cover and percentage canopy cover. Tree cover is the amount of range area planted in trees; canopy cover is the amount of tree planted area covered by branches. A farmer could have five per cent of the range planted in trees, mature trees planted according to planting instructions would have 100 per cent canopy cover, immature trees planted according to planting instructions may only have five to 10 per cent cover.

Feather damage is an indicator of injurious feather pecking, the group explained. To be sure that the farmers were being accurate in their assessment of feather damage, a comparison of producer feather damage scores was carried out with those from a random sample of birds of the same flock (carried out through video recordings of flocks at the abattoir).


Feather damage at end-of-lay was positively correlated with mortality, they found. Flocks at end of lay in summer had less plumage damage at end of lay than flocks depleted in autumn or winter, possibly because of leaf cover conditions at the time of placement, i.e. there is a seasonal variation.

There was no correlation between the proportion (five to 90 per cent) of range cover and feather damage at the end of lay. However, feather damage was negatively correlated with the percentage of canopy cover within tree planted areas, i.e. less canopy cover more feather damage.


Providing a minimum of five per cent tree cover, planted close to the house and with good canopy coverage is a feasible and practical method enabling producers to reduce feather damage due to injurious feather pecking in their laying hen flocks, according to Bright and co-authors. They added that tree cover provision may also provide environmental benefits such as soil stabilisation, reduced nutrient leaching and carbon sequestration.

Novel Aspects of the Study

The researchers outlined four novel aspects of their work.

Firstly, there was direct collaboration between a retailer and egg producers aimed at implementing animal welfare improvements on a commercial scale within a supply chain facilitated by a scientist. The project looked at practical measures to improve bird welfare and engaged farmers in the process, encouraging them to look closely at the birds and provide the data.

Second, information was collected on quantity and quality of tree cover.

Third, while there are many studies on laying hens that have been carried out on commercial farms, it is usually the scientists that collect the information. This can be limiting in terms of number of farms/flocks able to be visited and the amount of data captured and is costly. However, the data is collected in a very rigorous manner and detailed.

In this study, the researchers had access to a large number of farms and, by simplifying scoring protocols, the measures were carried out by farmers, requiring little extra time out of their day to day job, so ensuring it was always achieved. The information is not as detailed as that collected in some other studies but it did provide the answers needed to answer the question posed by this project, i.e. whether canopy cover is directly associated with reduced feather pecking. As long as monitoring of the data takes place, there can be confidence of the validity.

Finally, on-line or video imaging for assessment was developed during this project. It was demonstrated that feather scoring by video image analysis at the abattoir is feasible and can be directly related to the welfare of the birds on farm. Feather scoring is an animal-based measure, i.e. a measure of welfare taken directly from the animal, monitored at slaughter, which directly correlates to welfare of the bird at farm.

Proposal for Future Work

This was a three-year study and the group emphasised it was just coming to end of three years of data collection. The future proposal is to look at the relationship between tree cover and feather score as the tree stands mature over three years on the same farm. There is also the possibility of looking at additional benefits of planting trees, such as those to the environment.


Bright A., D. Brass, J. Clachan, K.A. Drake and A.D. Joret. 2011. Canopy cover is correlated with reduced injurious feather pecking in commercial flocks of free-range laying hens. Animal Welfare, 20:329-338.

Further Reading

- You can view the full report by clicking here.

June 2012
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