Pain is commonly considered a marker of negative welfare, and the importance of preventing pain in animals is reflected within a number of laws in the UK e.g. the Animal Welfare Act 2006 provides a duty of care on animal owners to prevent or treat pain, suffering, injury, and disease.
When we consider welfare we try to consider all aspects of the animal – not just its physical sensations, but its emotional responses and how it interacts with the environment in which it lives.
So how does pain impact welfare? And are there any strategies we can consider to modify these impacts?
We can consider three different levels of pain processing within the body. The firest level is the spinal cord, which co-ordinates reflex (unconscious) movements to avoid acutely painful stimuli.
Acute, nociceptive pain is a physical process without much emotional or cognitive processing. In fact, when we accidentally touch something dangerously hot, the nerve impulses cause our muscles to contract and pull our hand away from the source of pain before we are even consciously aware of the sensation – the “ouch!” comes later.
Some spinal cord nerve cells project toward the brain, and if pain continues these transmit information in the form of electrical signals.
At lower levels of the brain these projected pain signals activate areas associated with behavioural motivation, such as the anterior cingulate cortex and insula. These centres mediate the ‘affective’ component of pain, which can be considered as how the pain makes us feel emotionally. This activation causes an increased vigilance and alertness, recognised as the ‘fight, flight, or freeze’ response, and is associated with increased stress hormone release such as noradrenaline and cortisol. In cases of ongoing pain and continued activation of these brain centres, animals may find it difficult to regulate their emotions and exhibit behavioural issues, including increased noise sensitivity and aggression. In humans with chronic pain there is a clear association between physical pain and emotional suffering exhibited as anxiety and depression. It is the emotional unpleasantness of pain which motivates the animal experiencing it to fight, run away, or freeze. Although these behaviours might be helpful to ameliorate an acute threat of pain, in longer term pain these behaviours don’t mediate an escape from pain, and so the motivations remain.
Finally the pain signalling reaches the cerebral cortex, which mediates the conscious perception of pain, in terms of where in the body it is and how intense it is. In people with ongoing pain there are effects on learning, memory, and concentration, so It may be that ‘trainability’ and other executive functions of the dog’s mind are affected by pain.
Although it is most straightforward for us to recognise the conscious perception of pain as ‘suffering’, seeing animals directing their attention to painful areas, or limping, it is important that we recognise that the unconscious emotional aspects and resulting sympathetic nervous system activation will also impact the animal, and could also be considered suffering.
Exaggerated fight and flight responses can impact pet and owner relationships – if your dog is lunging at other dogs it can be difficult to have sympathy with them, even when we are aware that they may have a source of pain. It’s not much fun for them either, and over time the increased levels of stress hormones are likely to accelerate their aging processes.
Whilst pain can negatively impact emotions and cognitive function, evidence from people suggests that positive emotional states might be able to reduce pain, so while we cannot replace the need for effective vet-led pain management, it is probably worth considering ways in which we might be able to influence emotions in animals.
Training pain free dogs in a foraging task for food led to improvements in cognitive bias (a measure of optimism in dogs) compared to a group trained in heelwork1. Although data are not available for dogs affected by painful conditions, simple tasks such as these promote gentle movement and may have an additional emotional benefit, so seem well worth doing. Physiotherapy was reported to have a positive effect on the psychological domain within a canine quality of life scale2.
Some evidence exists of the stress relieving properties of essential oils such as lavender3 and ginger4 for dogs in kennel environments – it is possible that these effects could also occur in the home environment. These products should never be applied directly to animals but can be applied to cloths or tissues placed (out of pet’s reach) around the home. It is important to note that there are reports of toxicity associated with use of essential oils, particularly in cats5, so careful use is vital.
The mind-body connection is not purely a human phenomenon, and we are beginning to learn ways in which we can improve welfare by addressing all aspects of an animal’s experience.
1.Duranton, C. & Horowitz, A. Let me sniff! Nosework induces positive judgment bias in pet dogs. Appl Anim Behav Sci 211, 61–66 (2019).
2.Piotti, P., Albertini, M., Lavesi, E., Ferri, A. & Pirrone, F. Physiotherapy Improves Dogs’ Quality of Life Measured with the Milan Pet Quality of Life Scale: Is Pain Involved? Vet Sci 9, 335 (2022).
3.Amaya, V., Paterson, M. B. A. & Phillips, C. J. C. Effects of Olfactory and Auditory Enrichment on the Behaviour of Shelter Dogs. Animals 10, 581 (2020).
4.Binks, J., Taylor, S., Wills, A. & Montrose, V. T. The behavioural effects of olfactory stimulation on dogs at a rescue shelter. Appl Anim Behav Sci 202, 69–76 (2018).
5. Online https://www.cats.org.uk/cats-blog/cats-and-essential-oils [accessed 19th November 2022]