Measures of animal well-being
There are several possible ways of measuring animal welfare, and value judgements must be as to which will be most accurate in particular cases, and the weight to be given to different measures in arriving at the final verdict.
Productivity measures
Measures of productivity include things like growth rate and reproduction rate - the idea being that high productivity shows a high state of well-being.
It's important to apply these measures to individual animals and not be deceived by high overall productivity into ignoring the suffering of individuals.
But productivity measures can be deceptive, as these examples show:
- an unhappy animal kept in bad conditions may be kept productive by the use of antibiotics
- growth rates and reproduction rates can be artificially raised by feeding the animals hormone supplements
But even if no artificial methods are used to raise productivity, the measure itself has a basic flaw. Farm animals have been selectively bred for to achieve high productivity, so productivity measures will be artificially high in comparison to non-farmed members of the species.
But breeding for productivity can compromise well-being since it promotes only certain characteristics of the animal (those important to human beings). This may be at the expense of other things that may be more important to the animals themselves.
Veterinary measures
A healthier group of animals is probably a happier group of animals, so levels of disease, injury and mortality can be used to measure well-being.
This is misleading if drugs are routinely given to keep the animals healthy.
Veterinary studies can be used to compare the health impact of different ways of keeping animals. The conditions that produce healthier animals are regarded as ethically more satisfactory.
Physiological measures
The stress a creature is suffering can be shown by certain physiological measures such as suppression of the immune system, raised heart rate, increased catecholamine secretion and so on.
Physiological measures are not reliable indicators of chronic stress in animals, and since these indicators can be affected by other things, they are not, on their own, reliable indicators of well-being.
Observing behaviour
Careful observation of behaviour can help us assess animal well-being. But in order to come to useful conclusions we need to have considerable information about the normal behaviour patterns of the species concerned.
Distressed animals usually show that they are unhappy - they cry out, move away from whatever is upsetting them or try to escape.
In the long-term, unhappy animals develop abnormal patterns of behaviour such as aggression, repetitive behaviour and avoiding contact with others of their species.
It's also possible to learn how a particular species behaves under pressure by deliberately putting animals into stressful situations.
Researchers can then look for this behaviour in captive animals of the same species.
If they find such behaviour then it's probable that action should be taken to improve the well-being of the captive animals.
Ethical question: Is it ethical to mistreat experimental animals in order to gain information that will be used to improve conditions for other animals?
Preference testing
The closest human beings have so far got to asking animals what they like is preference testing. This lets animals choose between various alternatives.
Experimenters are now also able to test just how strongly an animal prefers a particular alternative.
This sort of research enables to keep animals in the conditions that they prefer, and thus enhance their well-being.
An early experiment tested the preferences of hens for different types of flooring by housing the birds in double cages in which they could move freely between two areas with different floors.
To discover which flooring each bird preferred, the experimenters simply noted the amount of time a bird spent on each side of the cage.
But it is more complicated than it seems.
Animals don't always make the same choices - the conditions an animal will choose for one activity may not be the ones it chooses when it wants to do something else.
And animals can show one perverse human characteristic in that they may prefer something that actually isn't good for their long-term well-being (i.e. eating tasty food rather than nourishing food), so it may be sensible to limit the range of choices offered to animals.
Pain
In the past it was thought by some people that animals either did not feel pain in the same way as human beings, or that if they did, it didn't matter. This view is now unacceptable.
Because it is difficult to assess pain and distress in animals the preferred rule is to assume that animals experience and respond to pain in a similar manner to humans.
Wrongly guessing what animals want
The case of the mechanical chicken handler
Chickens preferred being caught by machine
A few years ago scientists discovered that chickens saw the world in a very different way to human beings.
When chickens need to be sent to market they have to be packed into crates for transport. This was traditionally done by human chicken-packers, but a few years ago someone invented a mechanical chicken-catcher to do the job.
This elaborate machine used conveyor belts and rubber fingers to do the job. It was obvious to everybody that this machine might be more efficient for the poultry industry, but was going to be a great deal worse for the chickens.
A research team looked into this, by comparing the stress on the birds caused by the machine and the stress caused by human catchers.
They detected statistically significant differences in the heart trace between the manually-caught and machine-caught birds. The trace in both systems rose to same levels immediately after catching; however, the trace of machine caught birds dropped quicker and the average heart rate was significantly lower than in manually 'harvested' birds.
This showed that the birds found being caught and packed by machine a great deal less stressful than being caught by human beings.
Reference: Duncan, I. J.H., Gillian, S. S., Kettlewell, P., Berry, P., and Carlisle, A. J. , "Comparison of the stressfulness of harvesting broiler chickens by machine and by hand," British Poultry Science 27 (1986)
The case of the poultry cage floor
A British government committee once recommended that hens in battery cages should not be housed on fine-gauge hexagonal 'chicken wire' floors.
But when hens were given a choice of various types of floor, they preferred the type of floor that had been criticised to any other type of floor.
Reference: Hughes, B.O. and A.J. Black. 1973. The preference of domestic hens for different types of battery cage floor. Br. Poult. Sci. 14: 615-619.