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摘要
En 中文
Jungle fowl have many behavioural adaptations that fit them to their environment, and laying hens show almost all of them. But only a few of these behaviour patterns actually require a physical resource to perform them. Thus there is little discussion on the importance of being able to lie down or stand up, or even preen, in laying hens, but there is discussion about nesting behaviour, perching and dustbathing. From 2012 all systems for laying hens will be required to provide a nestbox, a perch and a litter area. This chapter reviews the evidence for that decision, and highlights those areas where research is still needed if this requirement is to be satisfied in a practical way in commercial housing conditions, while at the same time upholding the intention of the law to improve hen welfare. The functions of nesting, perching and dustbathing under natural conditions would be to increase the number of offspring surviving to the next generation. Initially it was argued that because the eggs laid by hens kept commercially are not fertile, are removed every day, and the hens are protected from predators or extremes of cold, then they do not need to perform these behaviour patterns in captivity. However, there is a large body of scientific research demonstrating the importance to the hen of being able to perform these behaviour patterns. In general it has been shown that given the choice, hens choose to use the resource when it is available, will show an operant response, and will work to get access to the resource at certain times of the day or after being deprived of the resource for some time. When the resource is not available, the appetitive pare: of the behaviour is often prolonged and hens may show signs thought to be indicative of frustration. For nest-building and dustbathing, sham behaviours are seen, i.e. the hen goes through the motions of the behaviour despite the lack of the necessary resource. In combination, this evidence clearly indicates that hens are highly motivated to perform nesting, perching and dustbathing and that the decision to require the provision of these resources is justified. It is, however, necessary to provide the resource in such a way and in such a form that it does indeed improve the welfare of hens. Simply adding the resource without due consideration to the hen's ability to use it or the additional welfare problems it may cause is not in keeping with the intention of EC Directive 1999/74/EU. It is in this area that more work is needed if practical solutions are to be reached within the time-frame available. There is a considerable amount of work on nestbox design to make nestboxes that are both attractive to hens as well as feasible to construct and include in loose or cage housing systems. There is even a reliable body of work on perch form, design and placing within housing systems. The remaining most critical problem area seems to be in relation to the requirement for provisions to be provided for dustbathing. In loose housing systems this is not usually an issue, since a part of the floor is converted to litter and the total available area is large. However it is a topic of debate in cage systems, since it has been clearly demonstrated that many hens do not use the litter area when it is provided. Given the experimental work showing the importance of litter-directed behaviours and the clear link between access to litter and feather pecking, the onus is on the farmer to provide the litter in an appropriate way so that liens use it and so experience the welfare benefits of its presence.
Keyword:
MODIFIED BATTERY CAGES
LAYING HENS
FEATHER PECKING
DOMESTIC-FOWL
PRELAYING BEHAVIOR
FURNISHED CAGES
INDIVIDUAL VARIATION
COMMERCIAL FLOCKS
AVIARY SYSTEMS
FLOOR EGGS
