What is pain?
How is pain produced?
How can pain be assessed?
How is pain relieved?
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What is Animal Pain?

PAIN is a word used by humans to represent one of their experiences.  They know what it is without needing to define it.

Animal pain should not be confused with human pain.  However, it is helpful to use definitions of human pain to understand animal pain.  Animal pain probably serves the same purposes as human pain and is as important to the animal as pain is to humans.  However, animal and human experiences of pain, in response to the same stimulus, may not be identical.

(Human) pain is:
“An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage
” (IASP, 1979).

Two definitions of animal pain are:

  • Pain in animals is an aversive sensory experience that elicits protective motor actions, results in learned avoidance and may modify species specific traits of behaviour, including social behaviour

  • Animal pain is an aversive, sensory experience representing  awareness by the animal of damage or threat to the integrity of its tissues; (note that there might not be any damage).  It changes the animal’s physiology and behaviour to reduce or avoid the damage, to reduce the likelihood of its recurrence and to promote recovery.  Non-functional (non-useful) pain occurs when the intensity or duration of the experience is not appropriate for damage sustained (especially if none exists) and when physiological and behavioural responses are unsuccessful in alleviating it (Molony, 1997)

Sites of Origin of Pain:

  • Somatic pain originates from the body including skin, bone, muscles, tendons and other tissues.

  • Horse showing stretching with acute visceral pain

  • Visceral pain originates from the internal organs e.g. heart, lungs, alimentary canal and reproductive organs.     

  • Neuropathic pain originates from nerves, the spinal cord and brain because of abnormal processing of nervous activity.

The pain from internal organs can be localised to superficial sites (Referred pain)

Duration of Pain:

Acute pain immediately follows injury and disappears when the injury heals.  It is usually associated with quantifiable changes to processes providing the body with protection from damage (defensive body processes).

Chronic pain is prolonged, however, there is little agreement as to when recurring bouts of acute pain become chronic pain or for how long pain must persist to be considered chronic. Quantifiable changes to the functioning of defensive body processes may NOT be seen.

Chronic inflammatory pain: occurs when healing  persists beyond the expected time, due to infection or other inflammatory processors.

Lame sheep, with foot rot, a chronic inflammatory condition, showing  grazing on knees

Chronic neuropathic pain: may not have a well-defined onset and may not respond to treatments that are effective against acute or chronic inflammatory pain.  It is sometimes described as "intractable" pain.                 

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                                            Revised: 20-10-08