Abstract
AIM: To explore attitudes towards and use of analgesia in horses by veterinarians in New Zealand.
METHODS: A postal questionnaire was sent out to 457 veterinarians identified as working with horses in New Zealand. Questions covered demographics and practice data; analgesic drugs available for use and used in practice; analgesic management of specific conditions including assessment of pain, drugs used, and frequency of cases; factors influencing the choice and use of analgesic agents; and attitudes and personal experience.
RESULTS: Ninety-seven questionnaires containing useable data were received, a response rate of 23%. Respondents' demographics corresponded with those of the veterinary population at the time. Phenylbutazone, flunixin, xylazine, ketamine, butorphanol, dexamethasone and lignocaine were the drugs most commonly used. Respondents allocated pain scores with a range of at least eight points (on a scale of 1 to 10) between lower and upper scores for 13/17 conditions and procedures presented. Respondents identified analgesic potency and anti-inflammatory effect as the most important factors in their choice of drug. Sixty-three percent and 59% of respondents considered their knowledge of recognition of pain and analgesia, respectively, to be adequate.
CONCLUSIONS: The results of the survey indicate that analgesia was widely used for horses amongst responding veterinarians. However, there were a number of areas where there appeared to be a lack of consensus amongst respondents in their management of pain in horses, and these included assessment of pain, administration of analgesics, and, indeed, what constitutes analgesia.
CLINICAL RELEVANCE: While analgesia of horses is widely practised in New Zealand, it would appear that a lack of consistency amongst veterinarians could indicate less than optimal pain relief in some cases and for some procedures.
| NSAID | = |
Non-steroidal anti-inflammatory drug(s) |
| NZVA | = |
New Zealand Veterinary Association |
Introduction
The management of pain associated with injury or disease is a fundamental objective of veterinary medicine. One of the roles of the veterinarian is to safeguard animal welfare (Conzemius et al. Citation1997; Hardie et al. Citation1997), so there must be an ethical obligation towards techniques that aid the recognition, evaluation and subsequent alleviation of pain and discomfort (Sawyer Citation1998). Although such techniques have been researched in various domesticated species, equids have received comparatively little attention, despite pain's fundamental significance to the welfare of horses. Most existent studies are largely based around evaluation of analgesic agents (Taylor et al. Citation2002).
In the United Kingdom (UK), a lack of consensus relating to the evaluation and management of pain in horses following castration was evidenced in the correspondence columns of the Veterinary Record in 2001 (Capner Citation2001; Flecknell et al. Citation2001; Green Citation2001 as examples). Although those letters were obviously not peer-reviewed, it was clear from the correspondence cited, and others, that there were a number of differing opinions. Later, results from two surveys conducted in the UK on attitudes to pain (Price et al. Citation2002) and current analgesic practice for castration of equids (Price et al. Citation2005) demonstrated that there was still professional disagreement about whether castration was a painful procedure for horses, with little conformity in recognition and treatment of pain.
Accurate assessment of pain in animals is fundamental for effective analgesic treatment, and a lack of agreement regarding recognition and management of pain is likely to impact negatively upon animal welfare. Knowledge of the non-specific side effects of different analgesic, anaesthetic or other drugs that have been administered is vital (Conzemius et al. Citation1997). Additionally, practitioners must also be familiar with typical (and contextual) species-specific behaviour, including any breed and individual responses, in order to be able to adequately distinguish abnormal from normal behaviour (Hansen et al. Citation1997; Dobromylskyj et al. Citation2000). Being a member of a social prey species, the horse is likely to react differently to painful stimuli compared with a predator species such as the dog (Casey Citation2002). Prey animals, such as the horse, often show few signs of pain, possibly demonstrating teleologic stoicism, to avoid appearing vulnerable to predators (Zimmerman Citation1986; Anil et al. Citation2002).
Internationally, as well as within New Zealand, horses are used for different competitive sports, each of which has the potential to result in specific types of injury (Murray et al. Citation2006), accompaniedby a greater or lesser degree of pain. Hence, there is a need to assess the veterinarian's attitude towards pain and the use of analgesia in horses, and what factors influence this.
In New Zealand, a survey conducted in 1997 and reported in conference proceedings explored the practice of anaesthesia for horses (Machon Citation1999), but there appears to be have been no survey relating to veterinary attitudes towards management of pain in this species. A recent study in New Zealand of veterinarians' attitudes towards and use of peri-operative analgesia in cats and dogs (Williams et al. Citation2005) demonstrated disparities in the provision of analgesia for different species. Despite giving similar pain scores to cats and dogs for equivalent procedures, cats were routinely given pain relief less frequently. In order to fully address the issue of effective pain management for horses, it is therefore necessary to investigate current attitudes and practice amongst equine veterinarians in New Zealand. Here, we aimed to identify attitudes towards pain and analgesic protocols used by veterinarians in New Zealand for common painful conditions and surgical procedures in horses, and to determine the role that other factors might play in decisions on the use of analgesia. Such factors included record-keeping, availability of information, cost, availability of drugs, analgesic potency, withholding times, potential side effects, and anti-inflammatory effects.
Materials and methods
Questionnaires were posted, with a covering letter, to the 457 individual practising veterinarians whose names had been provided by the New Zealand Veterinary Association (NZVA) as having identified themselves on their annual membership applications as working with horses. Veterinarians who had been incorrectly targeted were asked to indicate this by ticking a box, and to return the questionnaire uncompleted in the enclosed free-post envelope.
The questionnaire was adapted from a survey questionnaire previously used to collect similar data in the UK (Price et al. Citation2002, Citation2005), and was tailored to New Zealand conditions through consultation with the then President of the Equine Branch of the NZVA. The questionnaire was designed to be completed within 15 minutes, and was sent out in November 2005.
The questionnaire consisted of five sections (see Supplementary Table ). Section A covered demographic data, including the respondent's age, gender and year of graduation, veterinary school attended, any post-graduate qualifications achieved, and the type of practice worked in. Veterinarians who indicated that they worked within a mixed practice were also asked to specify what approximate percentage of their individual caseloads consisted of horses . Each respondent was also required to provide an approximate breakdown of their individual equine workload in terms of the percentage of horses that were Thoroughbred racehorses, Standardbred racehorses, performance horses, hacks and ponies, or breeding horses.
In Section B, respondents were asked to identify the analgesic drugs that were both available for use, and used by them. Respondents indicated their responses from a list of non-steroidal anti-inflammatory drugs (NSAID), opioids, corticosteroids, local anaesthetics, ‘other’ analgesic drugs, or any other drug or procedure.
In Section C, veterinarians were asked for information regarding the actual use of analgesics by them in practice. Within this section, veterinarians were first asked to indicate the severity of pain they considered horses might experience across a variety of procedures and conditions, including acute abdominal pain, lameness, routine surgery (including Caslick's procedure, i.e. surgical closure of the dorsal portion of the vulva to correct faulty conformation of the vulva of the mare, a frequent cause of low-grade vaginitis and infertility), orthopaedic surgery, and surgery of the upper respiratory tract. For each of the procedures and conditions specified, veterinarians were also required to indicate whether analgesics would be used, and, if so, which analgesic agents and additional analgesic therapy were used. The frequency of cases of each type of procedure and condition in horses per year for each veterinarian was also determined.
Section D concerned factors that influenced the veterinarian's choice and decision to use certain categories of analgesic agent, namely NSAID, opioids and corticosteroids. For each category of analgesic agent, respondents were asked to classify the factors of availability of information, analgesic potency, and the withholding times as not important, fairly important or extremely important, by circling the appropriate number from 1 to 5 on a Likert-type scale. For the NSAID and opioid categories, veterinarians were also asked to classify the factors of cost and potential gastrointestinal side effects. In the same manner, for the NSAID category veterinarians were asked to classify anti-inflammatory effects, and for the opioid category veterinarians were asked to classify requirement for record-keeping and potential behavioural side effects. Finally, for the corticosteroid category veterinarians were asked to classify the factor of potential side effects.
In the final section of the questionnaire (Section E), a series of questions sought respondents' views on the adequacy and sources of their knowledge of the recognition and analgesic treatment of pain in horses. Their level of interest in continuing education focussing on the management of pain in horses was measured. Additionally, the respondents were asked to rate the degree to which their use of analgesic drugs for horses was constrained because of the practice's policy, by use of a scale of 1 (not at all) to 10 (totally).
Questionnaires were returned anonymously in the pre-paid envelopes provided, and were assigned a number on receipt.
Statistical analysis
All data were recorded in and analysed using SPSS v11.5 for Windows (SPSS Inc, Chicago IL, USA). If questions were not answered or answered ambiguously they were registered as missing data. If respondents gave a range when a numerical classification was called for, the average of the range, e.g. 2 for 1–3, or the lower number, e.g. 1 for 1–2, was routinely taken. For the purposes of comparing pain scores, three categories of scores, viz 1–3, 4–7, and 8–10, were assigned values of 1, 2 and 3, respectively. Simple descriptive statistics were produced for all variables in the dataset. Cross-tabulations were used to examine the effect of gender, years since graduation, and the frequency with which the procedures were carried out on assessment of pain and use of analgesia for castration and Caslick's procedure. Cross-tabulations were also used to find combinations of drugs chosen by those respondents who used more than one analgesic drug for a procedure. Depending on the number of groups, differences in scores and proportions were tested using the non-parametric Kruskal Wallis or Mann-Whitney U-tests. Statistical associations were considered significant if p≤0.05.
Results
Demographics
Of the 457 questionnaires sent out, 40 were returned by veterinarians who considered themselves incorrectly identified as involved in clinical practice involving horses. Of the remaining 417, 97 questionnaires contained useable data, a response rate of 23%. Discrepancies in total numbers reported through the results relate to occasional missing data.
Details of demographic data are summarised in Table . Male respondents outnumbered females by almost two to one. Two-thirds of the respondents had graduated after 1980. Twenty-six of the 97 (27%) respondents had post-graduate qualifications; 13 (13%) worked in referral practices and five (5%) worked in a university setting.
Use of analgesics in practice
Details of the availability and use of drugs are given in Table .
The pain scores assigned by respondents to different conditions and procedures are detailed in Table . A variable percentage of respondents gave a range rather than a specific number when assigning pain scores.
Table 1. Demographic data from 97 veterinarians in New Zealand who responded to a questionnaire on attitudes to and use of analgesia in horses, compared with data from the New Zealand Veterinary Association (NZVA) and Veterinary Council of New Zealand (VCNZ).
Details on the use of analgesia by respondents for various conditions and procedures are given in Table . For foot abscess, pedal bone fracture and septic synovial cavity, seven, one and two respondents, respectively, scored pain in the highest category (8–10) but did not give analgesia, and 14 respondents scored pain for these procedures in the moderate category (4–7) but did not give analgesia.
Of the 58 respondents who carried out castrations on horses and who provided analgesia for the procedure, six said that provision was variable. Seven (29%) and 23 (88%) of the 26 respondents who were solely equine practitioners classed castration in the most painful category (8–10) and provided analgesia for the procedure, respectively, compared with 9/71 (13%) and 46/71 (65%), respectively, of those who were not solely equine practitioners.
A total of 78 veterinarians answered the question on the frequency with which they carried out castrations, seven of whom did not perform this procedure. Of the four who performed fewer than five castrations per year, three (75%) used analgesia and one (25%) did not. Of the 17 who performed five to 10 per year, nine (53%) used analgesia. Of the five who performed 11–15 per year, all (100%) used analgesia. Of the nine who performed 16–20 per year, seven (78%) used analgesia, although the use by two of these was variable. Of the 12 who performed 21–30 per year, 10 (83%) used analgesia, although the use by one of these was variable. Of the 14 who performed 31–50 per year, nine (64%) used analgesia, although the use by two of these was variable. Of the 10 who performed >50 per year, five (50%) used analgesia, although the use by one of these was variable. This indicated that those respondents who carried out the greatest number of castrations per year used analgesia less frequently than those carrying out fewer of these procedures (χ2=77; df=21; p≤0.001).
Table 2. Number (and percentage) of 97 veterinarians in New Zealand who responded to a questionnaire on attitudes to and use of analgesia in horses that stated the availability and use of different analgesic drugs.
There was no relationship between age or gender of respondent and pain scores attributed to castration. Of the 68 respondents who performed Caslick's procedure, 21 (31%) were female. Thirty-two (68%) of the 47 males scored pain for this procedure in the lowest category (1–3) compared with 5/21 (24%) females; 14/47 (30%) males scored it in the medium category (4–7) compared with 15/21 (71%) females; and one each of the males and females (2% and 5%, respectively) scored it in the highest category (8–10). This indicated a significant gender difference, with females using higher pain scores more frequently than males (χ2=12; df=3; p≤0.007), but this was not the case for provision of analgesia, where there was no difference between the genders.
Table 3. Number (and percentage) of 97 veterinarians in New Zealand who responded to a questionnaire on attitudes to and use of analgesia in horses that assigned a pain score on a scale of 1–10, those that assigned scores as a range, and the overall range of scores assigned.
Table 4. Number (and percentage) of 97 veterinarians in New Zealand who responded to a questionnaire on attitudes to and use of analgesia in horses that claimed provision of analgesia to some extent for different procedures and conditions, and the pain score, on a scale of 1–10, attributed by those not giving analgesia. Discrepancies in the data are due to inconsistent responses, e.g. no pain score given but analgesia used.
The range of drugs and combinations detailed as providing analgesia for castration are given in Table . Just over half of the 69 respondents to this question included an opioid or NSAID, while the remaining used various combinations of local anaesthetic and sedation. Nine of the 53 respondents who performed Caslick's procedure on horses and provided analgesia for the procedure used either an opioid or an NSAID, and the majority of the remainder used local anaesthetic alone.
Table 5. Drugs specified as used, or designated as appropriate for use, for analgesia for castration by 69 of 97 veterinarians in New Zealand who responded to a questionnaire on attitudes to and use of analgesia in horses.
Table 6. Median and interquartile range for the factors influencing choice and use of analgesic agents, where 1 = not important, and 5 = extremely important, by 97 veterinarians in New Zealand who responded to a questionnaire on attitudes to and use of analgesia in horses.
Factors influencing choice and use of analgesic agents
The factors identified by respondents as influencing the choice and use of analgesic agents are detailed in Table .
Attitudes and personal experience
Knowledge of recognition of pain and analgesic treatments was considered to be adequate by 61/97 (63%) and 57/96 (59%) respondents, respectively. A total of 80/95 (84%) respondents expressed interest in continuing education which focuses on the management of pain in horses. Seventy-one of 96 (74%) respondents felt no constraint at all from the practice's policy on their use of analgesic drugs for horses. Of the remaining 25, four (4%) placed the degree of constraint at ≥6 on a scale of 1 to 10, where 1 was not at all constrained, and 10 was totally constrained.
Discussion
A greater response to the survey would have been preferable, but the population surveyed had a similar distribution of males and females, and year of graduation, compared with the veterinary population at the time (Table ). The response rate of 23% is comparable with the 25% recorded for an epidemiological study by Price et al. (Citation2002), on which this study was based, and is only a little lower than the 28% response rate recorded in a similar survey conducted in New Zealand on peri-operative pain management in cats and dogs (Williams et al. Citation2005). It must be noted that the voluntary nature of the survey does introduce the possibility of bias, and the results need to be considered in light of this.
The results of the survey indicated that analgesia was widely used for horses amongst responding veterinarians. However, there were a number of areas where there appeared to be a lack of agreement amongst respondents in their management of pain, and these included assessment of pain and administration of analgesics. There also appeared to be confusion regarding the common descriptors and definitions applicable to the use of analgesia.
In terms of assessment of pain, the different conditions and procedures to which the respondents were required to allocate pain scores provided a cross section of situations where different types of pain would be experienced by horses, including acute pain, chronic pain, visceral pain, and somatic pain. Pain scores were revealed to have a range of at least eight points (on a scale of 1 to 10) between lower and upper scores for 13/17 conditions and procedures presented. Only moderate to severe laminitis, diagnostic arthroscopy, and surgery for septic synovial joints and on sinuses had smaller ranges. While it could be expected that the pain caused by many of the conditions specified would vary depending on the severity or stage of the condition and whether it was acute or chronic, resulting in a wider range of scores, it was interesting that elective surgical procedures, which might be expected to be relatively consistent in the degree of pain caused, were also given ranges of ≥8 points. Castration, for example, although scored between 4 and 7 by 61% of respondents, was also classed as low as 1 and as high as 10 by about 20% of respondents in each case, a marked variation in the degree of pain ascribed. This variability within the data derived from New Zealand, with castration more markedly dispersed between the range of pain scores compared with the other procedures/treatments, reflects speculation in the veterinary literature in the UK (Green Citation2001; Price et al. Citation2005) that there was a lack of professional agreement amongst veterinarians about whether castration was a painful procedure warranting the provision of analgesia. It is of interest that, in this survey, those respondents who performed castrations most frequently were least likely to use analgesia for this procedure. This could perhaps indicate a lesser degree of attention to the need for analgesia by those for whom the procedure is both familiar and routine. As with castration, respondents scored Caslick's procedure between 1 and 8, although the majority of scores were in the range of 1 to 3. Female respondents tended to score pain for Caslick's procedure higher than their male counterparts, but this did not result in correspondingly higher levels of analgesia.
It is noteworthy that although 78% of respondents scored castration in the medium to high pain categories, only 67% claimed provision of analgesia for this procedure. Only foot abscesses were given pain relief at a lower rate (66%), but given that the treatment for this condition in itself acts to relieve the pain, this is understandable.
The variability in attitudes towards and scoring of pain for routine procedures has been documented in a variety of species and in a number of countries (Dohoo and Dohoo Citation1996; Capner et al. Citation1999; Williams et al. Citation2005). However, although the variation in pain scores assigned to each procedure or condition was wide in this study, this variability was qualitative rather than quantitative. Indeed, particularly for conditions or procedures that were perceived to be associated with the highest degree of pain, e.g. colic and septic synovial cavity, there was relative consistency in the way pain scores were assigned. The lack of validated pain scales or objective measurements, however, means that it is difficult to realistically evaluate the ability to accurately assess pain, although a recent study from Canada established the value of some behavioural and physiological criteria in determining the intensity of orthopaedic pain in horses (Bussières et al. Citation2008).
There are several possible reasons for the variability between pain score and application of analgesia, not least of which must be clinical considerations in individual cases. For example, the chronic nature of osteoarthritis and mild laminitis must obviously be taken into consideration. Also, it is notable that respondents who were solely equine practitioners, who would be expected to have a higher caseload of the orthopaedic procedures where provision of analgesia was high, also assigned relatively higher pain scores to castration and demonstrated a substantially higher use of analgesia for this operation. This raises the possibility that such practitioners, having perhaps more familiarity with horses in general, are more sensitive to behavioural indicators of pain in this species. Overall, however, an inconsistency in the application of pain relief as compared with pain scores could indicate a tendency to underuse pain relief for what is seen as a routine procedure in an otherwise healthy animal.
One finding of note in this survey was a lack of consistency shown by respondents in the interpretation of analgesia as opposed to anaesthesia. This was most clearly demonstrated in responses concerning Caslick's procedure. As stated previously, only 75% of the 70 respondents who performed this operation said they used analgesia. Sixty-one percent of those cited local anaesthetic as the only analgesic used. However, it seems most improbable that those claiming not to use analgesia would perform Caslick's procedure without local anaesthetic. Indeed, one respondent who claimed not to use analgesia added “local anaesthetic only”. This issue also arose in relation to castration, where only 67% of respondents claimed to provide analgesia. While at least one veterinarian indicated that ‘general anaesthetic’ was the ‘analgesic’ used, it is also likely that veterinarians may have used ketamine, for example, concentrating on its anaesthetic rather than its analgesic properties.
Analgesics are usually considered to be drugs which abolish or reduce sensitivity to pain in the conscious animal, and local anaesthetics can certainly be regarded as analgesic (Nolan Citation2000). It is possible that, for those who claimed not to use analgesia, local anaesthetic was used for purposes of restraint (and techniques in relation to Caslick's procedure) rather than for the relief of pain, and that for those respondents provision of analgesia was viewed on a rather longer-term basis, consisting of administration of a longer-acting drug such as an opioid or NSAID as opposed to the immediate peri-operative effect provided by local anaesthetic.
This is interesting when considered in the light of work by Eager (Citation2008), who examined behaviour following castration, where castrated horses that received sedation and local anaesthetic at the time of the operation but no additional analgesia stamped more frequently 6 hours post-operatively compared with horses that were given additional analgesia. The former group was still showing various behavioural changes indicative of pain 24 hours post-operatively, e.g. increased weight-shifting, licking and chewing, compared with the latter group. The ongoing effects of castration have also been demonstrated in cattle, when liveweight gain was suppressed for the full 29 days of a trial following castration after puberty compared with bulls and steers castrated before puberty (Cosgrove et al. Citation1996).
In considering the protocols that respondents gave as their usual choice for analgesia, we have limited our comment to those used for castration. While the information given in Table must be considered in the light of the differences in interpretation by respondents of the term ‘analgesia’, it can be seen that there was a range of drugs and drug combinations given. NSAID, however, whether used alone or in combination, were the most commonly mentioned.
The data from the study presented here revealed variation in the use of analgesia for osteoarthritis, foot abscess, castration and pedal bone fractures, suggesting that veterinarians do not have consistent approaches to pain management for each specific condition and procedure. There was also some disparity between the allocation of pain scores and the actual provision of analgesia. For example, one veterinarian who scored pain associated with pedal bone fracture between 8 and 10, and two veterinarians who scored this between 4 and 7, claimed not to have provided analgesia when presented with this condition. Additionally, two veterinarians who scored pain associated with a septic synovial cavity between 8 and 10 claimed not to have provided analgesia when presented with this condition. This suggests that attitudes towards the assessment and management of pain may not reliably predict the veterinarian's actual pain management behaviour, although provision of pain relief may be influenced by factors associated with the veterinarian's assessment of the individual animal rather than the condition or procedure concerned.
The results of this study also indicate that pain management may be more influenced by factors such as the side effects of drugs, or an individual veterinarian's attitude towards pain, than by a practice's policy. Overall, 84% of the respondents expressed interest in continuing education in the management of pain in horses, a finding that could be addressed by both conference organisers and design of curricula within tertiary education in New Zealand.
In conclusion, the results of the survey indicated that amongst responding veterinarians analgesia was widely used for horses, of significance because of the importance of the use of analgesia to the welfare of horses under veterinary care. However, inconsistencies were apparent in the assessment of pain as well as in the application of analgesia. These areas, together with the lack of consistency shown by respondents in the interpretation of analgesia as opposed to anaesthesia, are noted for further education and research.
69402supplementaryinformation.pdf
Download PDF (115.8 KB)Acknowledgements
The research was financially supported by Unitec New Zealand, and the New Zealand Equine Veterinary Association, with assistance from the NZVA and the Veterinary Council of New Zealand.
References
- Anil , SA , Anil , L and Deen , J . 2002 . Challenges of pain assessment in domestic animals. . Journal of the American Veterinary Medical Association , 220 : 313 – 319 .
- Bussières , G , Jacques , C , Lainay , O , Beauchamp , G , Leblond , A , Cadoré , JL , Desmaizières , LM , Cuvelliez , SG and Troncy E . 2008 . Development of a composite orthopaedic pain scale in horses. . Research in Veterinary Science , 85 : 294 – 306 .
- Capner , CA . 2001 . Castration of horses and analgesia. . Veterinary Record , 149 : 252 – 252 .
- Capner , CA , Lascelles , BD and Waterman-Pearson , AE . 1999 . Current British veterinary attitudes to perioperative analgesia for dogs. . Veterinary Record , 145 : 95 – 99 .
- Casey , R . 2002 . “ Clinical problems in performance horses ” . In The Welfare of Horses , Edited by: Waran , N . 18 – 44 . Dordrecht, , The Netherlands : Kluwer Academic Publishers .
- Conzemius , MG , Hill , CM , Sammarco , JL and Perkowski , SZ . 1997 . Correlation between subjective and objective measures used to determine severity of postoperative pain in dogs . Journal of the American Veterinary Medical Association , 210 : 1619 – 1622 .
- Cosgrove , G P , Knight , TW , Lambert , MG and Death , AF . 1996 . Effects of post-pubertal castration and diet on growth rate and meat quality of bulls . Proceedings of the New Zealand Society of Animal Production , 56 : 390 – 393 .
- Dobromylskyj , P , Flecknell , PA , Lascelles , BD , Livingston , A , Taylor , P and Waterman-Pearson , A . 2000 . “ Pain assessment ” . In Pain Management in Animals , Edited by: Flecknell , PA and Waterman-Pearson , A . 52 – 77 . London, , UK : WB Saunders .
- Dohoo , SE and Dohoo , IR . 1996 . Postoperative use of analgesics in dogs and cats by Canadian veterinarians . Canadian Veterinary Journal , 37 : 546 – 551 .
- Eager R Edinburgh University Edinburgh, , Scotland 2008
- Flecknell , PA , Raptopoulous , D , Gasthuys , F , Clarke , K , Johnston , GM and Taylor , PM . 2001 . Castration of horses and analgesia . Veterinary Record , 149 : 160 – 161 .
- Green , P . 2001 . Castration of horses and analgesia . Veterinary Record , 149 : 160 – 160 .
- Hansen , BD , Hardie , EM and Carroll , GS . 1997 . Physiological measurements after ovariohysterectomy in dogs: what's normal? . Applied Animal Behaviour Science , 51 : 101 – 109 .
- Hardie , EM , Hansen , BD and Carroll , GS . 1997 . Behaviour after ovariohysterectomy in the dog: what's normal? . Applied Animal Behaviour Science , 51 : 111 – 128 .
- Machon , R . 1999 . “ The practice of equine anaesthesia in New Zealand: preliminary results ” . In Proceedings of the Annual Seminar of the Equine Branch of the New Zealand Veterinary Association , FCE Publication Number 193 57 – 59 . Palmerston North, , NZ : Veterinary Continuing Education .
- Murray , RC , Dyson , SJ , Tranquille , C and Adams , V . 2006 . Association of type of sport and performance level with anatomical site of orthopaedic injury diagnosis . Equine Veterinary Journal , : 411 – 416 .
- Nolan , A . 2000 . “ Pharmacology of analgesic drugs ” . In Pain Management in Animals , Edited by: Flecknell , PA and Waterman-Pearson , A . 21 – 52 . London, , UK : WB Saunders .
- Price , J , Marques , JMS , Welsh , EM and Waran , N . 2002 . Pilot epidemiological study of attitudes towards pain in horses . Veterinary Record , 151 : 570 – 575 .
- Price , J , Eager , R , Welsh , E and Waran , N . 2005 . Current practice relating to equine castration in the UK . Research in Veterinary Science , 78 : 277 – 280 .
- Sawyer , DC . 1998 . Pain control in small-animal patients . Applied Animal Behavioural Science , 59 : 135 – 146 .
- Taylor , PM , Pascoe , PJ and Mama , KR . 2002 . Diagnosing and treating pain in the horse — Where are we today? . Veterinary Clinics of North America, Equine Practice , 18 : 12 – 22 .
- Williams , VM , Lascelles , BDX and Robson , M . 2005 . Current attitudes to, and use of, perioperative analgesia in dogs and cats by veterinarians in New Zealand . New Zealand Veterinary Journal , 53 : 193 – 202 .
- Zimmerman , M . 1986 . “ Behavioural investigations of pain in animals ” . In Assessing Pain in Farm Animals , Edited by: Duncan , IJH and Molony , V . 16 – 29 . Luxembourg, Luxembourg : Commission of the European Communities .