How can Pain be Assessed? > Objective Assessment > Behaviour

Facial Expression

Postural changes are used as a means of communication in many species. They are supplemented in some species by changes in facial expression e.g. young children.  Changes in facial expression in response to pain have not been systematically investigated for domestic animals. Many animals do not seem to wrinkle / furrow their brows as shown by humans in pain. Horses may wrinkle their noses but there has been no work specifically identifying this as a pain-related behaviour.  Long-term carers of individual animals may recognize subtle differences in facial expression but they have not been adequately described for use by others.  Some examples of facial expression in lambs after rubber ring castration and a calf with bloat are shown in the stills below. Ear position, particularly back and down, may be important in identifying animals in pain.  However, it is difficult to prove as animals frequently move their ears to pick up sounds from all around them.

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Calf with bloat showing ears back and wide open eyes	Lamb showing lip curling when in pain following rubber ring castration	Lamb vocalising after rubber ring castration and docking