Except for conventional cages, the most common housing systems for laying hens comprise deep litter, aviaries and more recently furnished cages. Layers in floor systems may also include out-door keeping. Furnished cages will be the only legal form of cages in the EU from 2012 (1999 EU-directive) but have as yet only been installed in significant numbers in Sweden and partly in Norway, Germany and Great Britain. Climate, feed, bird genotype, group size as well as the legal possibility to beak trim or to use certain medical treatments (mainly against endo- and ectoparasites) or not, are all conditions affecting results with different housing systems in different countries. Offering benefits to the bird as regards increase in behavioural repertoire as well as providing more space, all alternatives to conventional cages, require new orspecial knowledge of management. This is due to the fact that these systems often include higher potential risks in production and health of layers. This especially applies to non-cage systems (Petermann, 2003). The main issues to control in largergroup floorhousing are parasitic disorders, outbreak and spreading of cannibalistic pecking, increased feed intake, misplaced eggs, catching of spent hens and airquality (dust and ammonia levels). Many management practices to reduce some of these risks have been presented including rearing method, medication, vaccination, light intensity, genotype, feed composition, beak trimming and – for improved air quality – the use of spraying/fogging with water or oil as well as more frequent manure removal at closerintervals have been practised. Coming in a wide range of models and group sizes, the furnished cages attempt to combine the benefits and reduce the disadvantages of floorkeeping and conventional cages. The most developed models of furnished cages provide similar production results to conventional cages. However, differences still exists e.g. in egg quality traits between models. Design and location of nests, perches and litter are all important factors.
In conclusion, future trends in investments forhousing system in egg production will have to take into account several factors apart from the degree of success from technical development of each system. These will probably involve national directives regarding beak trimming, stocking densities, directives of withdrawal times of medication and occupational safety on one side and national markets and trades fordifferent categories of eggs on the other.
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