Saturday, October 3, 2009

The Great Egg Debate - Science, Not Emotion, Shows that Caged Laying Hens have Poor Welfare

The Great Egg Debate - Science, Not Emotion, Shows that Caged Laying Hens have Poor Welfare
By Sara Shields, PhD
Tuesday, August 11, 2009 Link to full article below

Previous blog posts on Ham and Eggonomics have addressed the often-touted claim that concerns about the welfare of animals in intensive production facilities are based on emotion rather than science. However, the basis for opposition to the confinement of hens in battery cages is deeply rooted in objective scientific inquiry, and research on the topic is almost as old as the use of the battery cage itself.1

From the beginning of the debate, ethology (the study of animal behavior) has advanced understanding of the effects of cage confinement on the well-being of laying hens and, without a doubt, shown that there are very serious welfare consequences. Studies have demonstrated that there are two basic reasons for this: 1) the animals are deprived of the opportunity to express important natural behavior; and 2) the constraints of the cage prevent exercise, which has profound physical consequences for the health of the birds.

There seems to be a general lack of appreciation for the importance of behavioral expression as a component of animal well-being. Historically, it has been easier to comprehend the role of health, for example, in ensuring good welfare, while it’s sometimes been more challenging to see how behavioral restriction can reduce welfare. The science, however, tells a very compelling story.

One of the most important behavior patterns that hens are prevented from performing in a conventional cage is nesting. Observational studies of feral hens and wild Jungle Fowl (the progenitor of today’s domesticated chickens) have shown that hens will seek out a secretive, sheltered nesting site when they are about to lay an egg.2,3,4 Ethologists have investigated this behavior further in laboratory studies. They have shown that when hens do not have a nest box—as is the case when confined inside a typical battery cage—they express frustration with stereotyped, repetitive pacing movements just prior to oviposition (egg-laying),5 and make “gakel-calls,” the same types of behavior expressed in experiments with hungry hens who are able to see an expected food reward but are prevented from access by a clear Plexiglas-like cover.6,7

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