Ear tattooing is a routine procedure performed on laboratory, commercial and companion rabbits for the purpose of identification. Although this procedure is potentially painful, it is usually performed without the provision of analgesia, so compromising animal welfare. Furthermore, current means to assess pain in rabbits are poor and more reliable methods are required. The objectives of this study were to assess the physiological and behavioural effects of ear tattooing on rabbits, evaluate the analgesic efficacy of topical local anaesthetic cream application prior to this procedure, and to develop a scale to assess pain in rabbits based on changes in facial expression. In a crossover study, eight New Zealand White rabbits each underwent four different treatments of actual or sham ear tattooing, with and without prior application of a topical local anaesthetic (lidocaine/prilocaine). Changes in immediate behaviour, heart rate, arterial blood pressure, serum corticosterone concentrations, facial expression and home pen behaviours were assessed. Changes in facial expression were examined to develop the Rabbit Grimace Scale in order to assess acute pain. Tattooing without EMLA cream resulted in significantly greater struggling behaviour and vocalisation, greater facial expression scores of pain, higher peak heart rate, as well as higher systolic and mean arterial blood pressure compared to all other treatments. Physiological and behavioural changes following tattooing with EMLA cream were similar to those in animals receiving sham tattoos with or without EMLA cream. Behavioural changes 1 hour post-treatment were minimal with no pain behaviours identifiable in any group. Serum corticosterone responses did not differ between sham and tattoo treatments. Ear tattooing causes transient and potentially severe pain in rabbits, which is almost completely prevented by prior application of local anaesthetic cream. The Rabbit Grimace Scale developed appears to be a reliable and accurate way to assess acute pain in rabbits.

Rat behaviour was studied to develop a reliable method of determining the severity and duration of post-laparotomy pain, and to assess analgesic effects of ketoprofen or carprofen. Behaviour was studied in groups of ten animals 1 h following subcutaneous (s/c) saline (0.2 ml/100 g), ketoprofen or carprofen (5, 10 or 15 mg/kg) given either alone, or prior to surgery. The frequency of over 150 individual behavioural acts was calculated during the first post-treatment hour, the hour immediately prior to darkness, and the first 15 min of each of 5 subsequent hours. Discriminant analysis and analysis of variance isolated several easily recognizable behaviours which were markedly altered in frequency by surgery. These were unaffected by drug administration alone and were mainly transient, easily quantifiable activities; 'cat-like' back arching, horizontal stretching followed by abdominal writhing and twitching while inactive. Reductions in the frequency of these behaviours following surgery with analgesic treatment supported the hypothesis that they reflected post-operative pain. Ketoprofen and carprofen were equipotent and no dose related effects were apparent. Analgesic activity lasted between 4 and 5 h with the 5 mg/kg dosage, this being estimated from the duration of overall and specific behaviour differences between saline and drug treated animals. The data provided substantial evidence as to the usefulness of behavioural criteria for estimating pain severity, and for the first time, the basis of a system for routine pain assessment and management in rats subjected to abdominal surgery.

A structured literature review was carried out to assess recent trends in the administration of analgesics and anaesthetics to laboratory rats and mice undergoing surgical procedures. The ScienceDirect database was used to systematically identify studies published in peer-reviewed journals over two periods (2000–2001 and 2005–2006), 86 studies from each time period were included in the review. The total number of animals that underwent surgery, species used, type of procedure, anaesthetic regimen and analgesic administration were noted for each study. There was an increase in the reported administration of systemic analgesics from 10% in 2000–2001 to 20% in 2005–2006. Buprenorphine was the most commonly reported analgesic in both periods (2000–2001: 78%, 2005–2006: 35%) and reporting the use of non-steroidal anti-inflammatory drugs increased from 11% to 53%. There was also a change in reported anaesthetic practices, notably a decrease in the use of pentobarbital and an increase in the use of isoflurane and ketamine/xylazine. Although reported administration of analgesics has increased and there has been some refinement in the selection of anaesthetic agents used, the findings of this review suggest that there is still significant scope for improvement with respect to the perioperative care of laboratory rodents.

Current behaviour-based pain assessments for laboratory rodents have significant limitations. Assessment of facial expression changes, as a novel means of pain scoring, may overcome some of these limitations. The Mouse Grimace Scale appears to offer a means of assessing post-operative pain in mice that is as effective as manual behavioural-based scoring, without the limitations of such schemes. Effective assessment of post-operative pain is not only critical for animal welfare, but also the validity of science using animal models. This study compared changes in behaviour assessed using both an automated system (“HomeCageScan”) and using manual analysis with changes in facial expressions assessed using the Mouse Grimace Scale (MGS). Mice (n = 6/group) were assessed before and after surgery (scrotal approach vasectomy) and either received saline, meloxicam or bupivacaine. Both the MGS and manual scoring of pain behaviours identified clear differences between the pre and post surgery periods and between those animals receiving analgesia (20 mg/kg meloxicam or 5 mg/kg bupivacaine) or saline post-operatively. Both of these assessments were highly correlated with those showing high MGS scores also exhibiting high frequencies of pain behaviours. Automated behavioural analysis in contrast was only able to detect differences between the pre and post surgery periods. In conclusion, both the Mouse Grimace Scale and manual scoring of pain behaviours are assessing the presence of post-surgical pain, whereas automated behavioural analysis could be detecting surgical stress and/or post-surgical pain. This study suggests that the Mouse Grimace Scale could prove to be a quick and easy means of assessing post-surgical pain, and the efficacy of analgesic treatment in mice that overcomes some of the limitations of behaviour-based assessment schemes.