What a Feeling! The challenges of measuring how an animal feels
Updated: Jan 8, 2021
Think about your dog or cat at home... or your chickens. What are some of the things you give them to ensure their wellbeing? ... Food, water, long walks, toys, a safe place likely come to mind. How do you know how they feel, or that you are doing the right thing? As an animal welfare scientist, that's my job.
If defining animal welfare is like a bunch of blind mice describing an elephant, then measuring animal welfare can be ... difficult. There is no one single thing we can measure that will tell us if the welfare of an animal is good – there is no “smoking gun” (sidenote: the indicators of poor welfare are a little easier to determine, so historically they have been used more often). Instead, we need to measure a number of different things and together they can tell us about the welfare of an individual animal or group of animals. Deciding what and when to measure are crucial. These factors can significantly affect how an animal's state of being is interpreted.
Animal-Based vs. Resource Based Measures
Some measures look at the environment as a proxy for animal welfare, like the amount of space provided. These are called resource-based measures. There is an underlying assumption that animals provided a certain amount of space will have good welfare (e.g. X amount of perch space per bird). Many animal welfare schemes or audits have featured these types of measures because they are associated with objectivity and may not require as much training as animal-based measures, which are traditionally more subjective (though this is not always the case, see section below).
Animal-based measures, also called outcome-based measures, look at the individual animal or group of animals directly. They do pose some challenges: they take more time to score/measure, are more subjective (i.e. require some interpretation), and are not as repeatable between scorers. However, they are much more direct measures of animal welfare.
Let's say you want to know whether chickens are using an area that you have provided for dustbathing -- see the video below. The most direct measure would be to quantify the behaviour itself, so maybe score the behaviour from the video or quantify the number of birds using the area to dustbathe. In contrast, a resource-based measure would be to calculate whether the amount of litter space provided meets the standard (e.g. in the Canadian Code of Practice, birds in aviaries must have 33% of the usable space be litter). Timing is also key: it would make the more sense to observe the area in the afternoon, since that is when dustbathing occurs most often, than in the morning when the birds are busy looking for a nest.
"Asking" Animals how they Feel
The best that we can do is choose measures that have been shown to accurately reflect a particular state (also known as measures that have been “validated”). For example, if I want to know if a bird is in pain, I can’t ask them like I would a person. But there are other ways to “ask” how they are feeling. We can look at their behaviour – are they walking normally? Do they sound like they usually do? Are they alert or are they hunched over with their feathers ruffled (this is a pain behaviour)? A resource-based measure would instead look at the environment and ask whether the equipment is in good repair.
We can also look at the bird directly – do they have any wounds? Are there any sores on their feet? Does their comb look healthy? Does a blood sample show indicators of stress? We can also test them to see if they would consume pain medication, and if that changes their behaviour. Some of these “measures” are more feasible than others in different contexts.
We can also conduct behaviour tests, either in a lab environment or in situ. These usually involve observing how an animal responds to a particular stimulus, such as a novel object or a human observer. Sometimes that stimulus may be the environment itself, such as seeing what an animal does when placed into an open arena. This post explores a couple behaviour tests that are used to determine the human-animal-relationship.
Subjective vs. Objective Measures of Welfare
Measures of animal welfare can also objective or subjective. Some examples of objective animal-based measures would be growth rate, livability (i.e. mortality), or the presence of infectious disease (i.e. morbidity). These measures are still outcome or animal based, but are considered objective because there is little room for interpretation; the numbers speak for themselves.
Subjective measures are more open to interpretation and therefore may be prone to error. This can be overcome by having clear definitions of what is being measured (also known as operationalized definitions) followed by some rigorous training and achieving good observer reliability. An example of a subjective measure would be to score an animal’s ability to walk on a scale from 0 to 5. The scorer would need to be able to consistently and accurately interpret how each animal walks, so there is more potential for error. This is called gait scoring and has been incorporated into some animal welfare audits (e.g. ProAction for dairy cows in Canada).
Both objective and subjective measures have their strengths and weaknesses in terms of how easy they are to measure, how much time they take, whether they require extra training etc. Arguably, the best thing is to use a combination of both types of measures to get a more comprehensive picture of animal welfare.
Group vs. Individual Welfare
The last challenge I will touch on is the difficulty of measuring the welfare of groups of animals. Many measures of animal welfare that I have described are based on observing and scoring one particular animal. This can be difficult or impossible to do with larger group sizes. But we still want to make sure we are providing good welfare, so what do we do? We have to adapt our method.
Some farmers are outfitting their animals with wearable technology that helps monitor their health and welfare (both the dairy and beef industries are doing cool things with wearables). Or instead of measuring and scoring every animal, we might measure a sub-set of animals, randomly selected throughout the barn, so their scores would be used to represent the overall welfare of the population. For chickens, this might be measuring body weight as well as something like feather condition.
You can only manage what you measure! So measuring good, well-validated indicators of animal welfare is essential regardless of whether you are a pet owner or a farmer.