1999 SECOND -PRIZE 20-28 YEARS | BACK |
By Andrea Lord Intensive farming of hens in battery cages for eggs, and
broilers in crowded, dim sheds for meat, causes problems of its own. Chickens
evolved from red jungle fowl, which go about in small groups among dense
jungle undergrowth. Such an environment differs greatly from both free
range Despite their bodies being specialised to produce either eggs or meat, the minds of chickens and hence the way they socialise, their preferred physical environment, and what frightens them - are probably still largely adapted to jungle conditions. It's unlikely that we can ever replicate such ideal conditions on farms while the demand for omelettes and chicken korma remains, but we can find out what chickens really like or, more realistically, what they really hate. Measuring the internal experience of an animal is central to the science of animal welfare, and a tricky subject, but one that my team in the animal behaviour research group at Oxford, in collaboration with scientists from the universities of Glasgow and Washington, are tackling. Humans, chickens and other animals all release hormones known as corticosteroids when they are frightened, stressed or otherwise aroused. Corticosterone, the chicken version of the hormone, can be measured in blood samples, and shows promise in being one of the signs we can use to monitor the mental health of chickens. However, blood sampling can be pretty stressful for a chicken, and the resulting rise in corticosterone levels has interfered with the results of many previous studies. An alternative, less disturbing, way to measure hormones is in the droppings. By analysing the droppings of chickens from both intensive and free-range systems, I hope to discover whether the husbandry system influences corticosterone levels, and to relate this to the welfare of the birds. Another promising way of measuring hen happiness without harming the chicken is by looking at eggshell quality. Although hens will continue to lay even under sub-optimal conditions, certain characteristics such as shell density change when hens get a fright. By measuring eggs from different husbandry systems, my team plans to investigate whether such changes occur only in response to short-term stressors, such as vaccination, or whether they are also an indicator of long-term welfare. One problem with using corticosterone as a welfare indicator is that it is also released during times of excitement people riding a roller coaster are likely to be releasing corticosteroids like mad, yet many would classify their experience as positive. Similarly, pleasurable events may raise hormone levels in chickens, and also cause eggshell changes. To distinguish between ''good'' and ''bad'' causes
of elevated corticosterone levels and shell changes, we can ask the birds
if they enjoy the chicken equivalent of a roller coaster ride or boxing
match.
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