information on the recognition of behavioural responses to pain in these species has
led to a much better understanding of appropriate treatments and dosage regimens
(Roughan and Flecknell 2003 ). An important aspect is that these small rodents and
lagomorphs show specific pain related behaviours which are not always apparent
during casual observation (Roughan and Flecknell 2006 ), as distinct from the overt
avoidance responses commonly used for analgesic drug testing. The relatively high
basal heart and respiratory rates in these small mammals have presented technical
difficulties in their use as physiological indices. Therefore, alternatives such as food
and water intake and weight loss have been used for the evaluation of potential
chronic pain, but these measures lack precision. The use of video recording, in
combination with computer programme developments, has allowed for a much
wider range of more specific behaviours to be assessed, and hence has facilitated the
development of improved analgesic protocols (Wright-Williams et al. 2007 ). In
laboratory animals, the behaviours associated with pain lend themselves to compu-
terised video analysis and hence the effects of analgesics on the various behaviours
associated with pain have been monitored (Roughan and Flecknell 2004 ). Initially,
analysis of video studies was undertaken manually and while these were effective,
using such systems as “Observer”, they were very time-consuming and prone to
error. There have been considerable advances in technology for monitoring auto-
matic behaviour recognition programs such as “HomeCageScan”. This has allowed
a more rapid and bias-free approach to laboratory animal behaviour monitoring
associated with pain syndromes and their alleviation with analgesics (Roughan
2008 ).
3.2 Dogs and Cats
Due to its close association with humans and access to veterinary treatment, the dog
is a species in which pain responses have been appreciated, particularly when
owners are attuned to slight variations in behaviour, appetite, weight loss, etc.
Not all of these indices have been reliably interpreted. However, the various pain
conditions in the dog, acute, chronic and neuropathic, have been recorded and
treated. In fact, with the exception of laboratory animal studies, most of the pain
treatments and preventative strategies have been developed for dogs and cats.
In the dog, as in man, pain responses are potentially modified by peripheral
inputs. Thus, dogs experiencing pain post-operatively in a veterinarian’s recovery
room may not exhibit the same behaviours as they do within their household
environment. This led to the development of the first sophisticated VAS (Holton
et al. 1998 ). The concept of the VAS is not new, but the introduction of the
multifactorial scale for the dog was a significant advance. A problem with all
forms of behavioural scale has been that of quantification, and scales for pain,
whether human or animal, are no exception.
Behavioural scales, irrespective of their range or complexity, are non-arithmetic.
Therefore, either doubling or halving the pain experience will not be reflected in
168 A. Livingston