The Effects of Stress on Animals

It's ironic that I'm about to talk to you about the effects of stress on animals because I currently look like this:

On a more serious note.. stress can be a very important measure of animal welfare. Stress can potentially show that there is a problem with the animal's welfare, particularly in captive environments. For example in a zoo with a monorail going over an enclosure, if an animal becomes stressed every time the monorail goes over it can indicate that the monorail is having a significant detrimental effect on their welfare.Stress is an important process as it allows the body to adapt to change. The stress response is triggered by a threat such as a decrease in temperature. This causes the hypothalamus in the brain to release corticotropin-releasing hormone (CRF) which travels to the anterior pituitary. CRF controls the release of adrenocorticotropic hormone which stimulates the adrenal cortex to secrete cortisol.

Cortisol is responsible for the body's response to stress. The cells which are not needed for what we call the "fight or flight" response are stimulated by cortisol so that they decrease their use of blood glucose and start using fats and proteins for energy instead. Processes such as immune system reactions are also turned off as they are not needed to cope with the stress. Metabolic rate is therefore increased and life-sustaining processes have more energy. Cortisol is a type of Corticosteroid which are used in stressful circumstances. Corticosteroids stimulate glucose production from fat (as mentioned above), break down the tissue protein, increase the sensitivity of the blood vessels to adrenaline (to allow fight or flight), increase the rate of urine formation, make muscles function for longer, affect brain excitability, increase gastric acid and pepsin secretion, act as an anti-inflammatory and suppress the immune system (as mentioned above). Once the stress response has served its purpose cortisol effects the cells of the brain which causes a decrease in the release of CRF in a negative feedback loop.

The effect of stress on the body has three different stages depending on the length of time the stress is present. The first stage is called the Alarm Stage. This is when the body first reacts to the stress and it's response is in a state of alarm. At this point adrenaline is produced so that the fight or flight response can be used. There is also some activation of the HPA axis, producing cortisol. If the stressor persists then the body begins to adapt to the change and this is called the Adaptation Stage. However, if the stressor persists for too long then the body enters the Exhaustion Stage and it's resources become depleted. This can cause long term damage to the individual with effects such as ulcers, depression, diabetes or cardiovascular problems and it must therefore be avoided at all costs.

The physiological processes which occur when an organism is stressed allow us to measure welfare effectively by taking measurements of cortisol or other corticosteroids. This allows for improvements to be made to a captive animals environment using enrichment. It can also be combined with behavioural welfare assessments to get a better result.

Animal Welfare

Animals have had a bad run of it haven't they? I'm deep in revision at the moment so you will probably get lots of posts from me while I'm doing my extra reading. Yesterday I was revising a lecture about Animal Welfare in general and Legislation. I decided to look up the history of animal welfare and some other bits and I thought they'd make an interesting blog post.

The first ideas on the moral status of animals probably came from the bible. Indeed, in Genesis (1:20-28) you can read about how Adam was given "dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth". Other religions at this time did respect animals, an example of this was in buddhism where not only was there are deep respect for the animal kingdom but there was also a belief in reincarnation which was often not in human form. However, focussing on the Christian view of animals it is probably unsurprising that people such as the philosopher René Descartes (1596-1650) had the view that animals had no souls, mind or reason and therefore could not suffer pain. Nicolas Malebranche (1638-1715) had a similar view and was quoted as saying "animals eat without pleasure, cry without pain, grow without knowing it; they desire nothing, fear nothing, know nothing". Thankfully as time wore on people such as Jeremy Bentham and Jean-Jacques Rousseau argued for animal rights. In the 18th century Rousseau argued that animals were sentiant and Bentham argued that it was the ability to suffer, not to reason, which should influence the decision on whether animals had rights. In the 20th century the situation detiorated rapidly as the second world war came to an end and the industrialisation of farming meant that more animals were being killed for meat than ever before.

Now animal welfare is in the spotlight all the time and there are a huge variety of legislations and laws which can be read about on the DEFRA website. However the definition of welfare is still discussed and debated over. The most popular definitions are that welfare is "the state of an animal as it attempts to cope with its environment (Fraser & Broom, 1990) and "animal welfare is a state of physical and psychological harmony between the animal with itself and its surroundings". In spite of this the five freedoms from the UK Animal Welfare Council (FAWC) are widely accepted and list as follows:

1. Freedom from thirst, hunger and malnutrition
2. Freedom from discomfort
3. Freedom from pain, injury and disease
4. Freedom from fear and distress
5. Freedom to express normal behaviour

 Extrinsic and intrinsic values of animals have a large effect on how people percieve animal welfare. Verhoog (1992) argues that scientists percieve animals as "analytic" beings rather than "naturalistic" like most people and that this may cloud their judgement when they are considering whether an animal's welfare is compromised. As well as this, it could be argued that scientists only take an interest in the welfare of an animal if they think its welfare should be respected. I know from experience that there is much less objection to the dissection of a locust than there is to that of a rat. Resistance to certain areas of animal research, such as genetic engineering, is often found to be for intrinsic reasons (such as it's not fair on the animal) rather than extrinsic reasons (such as risks of the experiment to the animal). Because of this, Rollin (1986) proposed the zoocentric bioethical theory which says that only higher animals with some form of consciousness are morally relevent and should be protected. Sentient animals have more intrinsic value to people as feelings of happiness are considered to be of value to the animals.

References
www.defra.gov.uk
Fraser, D. & Broom, D.B. 1990. Farm animal behaviour and welfare. CAB International, Wallingford, Oxon
Rollin, B.E. 1986. "The Frankenstein Thing": the moral impact of genetic engineering of animals, In: Verhoog, H. 2007. The tension between common sense and scientific perception of animals: recent developments in research on animal integrity. NJAS. 54(4) 361-373
Verhoog, H. 2007. The tension between common sense and scientific perception of animals: recent developments in research on animal integrity. NJAS. 54(4) 361-373