The study showed that the bone structure of hens kept in furnished cages is stronger than that of hens kept in conventional cages.

Dr Valkonen explained: "In conventional cages, hens lack the opportunity for exercise, which leads to fragile bones but furnished cages improve bone mineralisation. This supports the hypothesis of improved welfare for the hens. On the other hand, perches were found to increase foot pad lesions and damages to the breastbone."

Studying animal welfare not straightforward

According to Dr Valkonen, the active use of perches and nests suggests that they allow hens to perform certain behaviours identified as being important for them.

She said: "Studying the welfare of animals is never a straightforward matter, and results are invariably ambiguous. They are always open to interpretation, at least as concerns the weighting of different welfare indicators. For example, is it more important to satisfy behavioural needs than it is to avoid the foot pad lesions?"

Despite the room for interpretation, she believes that furnished cages are better for the hen than conventional cages.

Conventional cages soon history

From the beginning of 2012, the European Union member states will adopt a Directive prohibiting the use of conventional cages for egg-laying hens. Only furnished cages will be allowed, and they must be fitted with perches, nests and litter as well as slightly more space per hen than in conventional cages.

In Dr Valkonen's dissertation, study hens were observed in three separate experiments lasting throughout the egg-laying period, i.e. one year. The experiments studied the effects of feed protein content, energy content and limestone supplement on the production and health of hens. A fourth experiment evaluated the effects of perches on feed consumption and behaviour.

The cages under comparison were conventional cages for three hens and furnished cages for eight hens. The floor area of the conventional cages was approximately 1,970 square centimetres and that of the furnished cages 6,000 square centimetres.

Production level stays the same

In her study, Dr Valkonen specifically studied the impact of furnished cages on production and feed intake. The cage type has been under development for decades, but very little research has been done on feeding and feed consumption in this production model.

The research results show that hens in furnished cages can reach the same production level as hens in conventional cages. Although minor variation was observed in feed intake, it was not significant enough to change current feeding recommendations.

Dr Valkonen added: "The key indicator in terms of production profitability is feed conversion ratio, or feed intake per one kilogramme of eggs produced. The figure was the same for both of the cage types studied."

The doctoral dissertation of M.Sc. (Agriculture & Forestry) Eija Valkonen, 'Egg production in furnished cages' was reviewed at the Faculty of Agriculture and Forestry of the University of Helsinki on 12 November 2010. The opponent will be Professor Ragnar Tauson from the Swedish University of Agricultural Sciences (SLU), with Professor Matti Näsi from the University of Helsinki as custodian.