Joanna C. Murrell

Do Fish Perceive Anaesthetics as Aversive

This study addresses a fundamental question in fish welfare: are the anaesthetics used for fish aversive? Despite years of routine general use of many agents, within both scientific research and aquaculture, there is a paucity of information regarding their tolerance and associated behavioural responses by fish. This study examined nine of the most commonly used fish anaesthetic agents, and performed preference tests using adult mixed sex zebrafish (Danio rerio), the most commonly held laboratory fish. Video tracking software quantified swimming behaviour related to aversion for each anaesthetic at 50% of its standard recommended dose compared with clean water in a flow-through chemotaxic choice chamber. Results suggest that several commonly used anaesthetics were aversive, including two of the most commonly recommended and used: MS222 (ethyl 3-aminobenzoate methanesulphate) and benzocaine. For ethical best practice, it is recommended that compounds that are aversive, even at low concentration, should no longer be used routinely for anaesthesia or indeed the first step of humane euthanasia of adult zebrafish. Two agents were found not to induce aversive behavioural responses: etomidate and 2,2,2 tribromoethanol. For the millions of adult zebrafish used in laboratories and breeding worldwide, etomidate appears best suited for future routine humane use.

Do Laying Hens with Keel Bone Fractures Experience Pain

The European ban on battery cages has forced a change towards the use of non-cage or furnished cage systems, but unexpectedly this has been associated with an increased prevalence of keel bone fractures in laying hens. Bone fractures are acutely painful in mammals, but the effect of fractures on bird welfare is unclear. We recently reported that keel bone fractures have an effect on bird mobility. One possible explanation for this is that flying becomes mechanically impaired. However it is also possible that if birds have a capacity to feel pain, then ongoing pain resulting from the fracture could contribute to decreased mobility. The aim was to provide proof of concept that administration of appropriate analgesic drugs improves mobility in birds with keel fracture; thereby contributing to the debate about the capacity of birds to experience pain and whether fractures are associated with pain in laying hens. In hens with keel fractures, butorphanol decreased the latency to land from perches compared with latencies recorded for these hens following saline (mean (SEM) landing time (seconds) birds with keel fractures treated with butorphanol and saline from the 50, 100 and 150 cm perch heights respectively 1.7 (0.3), 2.2 (0.3), pu200a=u200a0.05, 50 cm; 12.5 (6.6), 16.9 (6.7), pu200a=u200a0.03, 100 cm; 20.6 (7.4), 26.3 (7.6), pu200a=u200a0.02 150 cm). Mobility indices were largely unchanged in birds without keel fractures following butorphanol. Critically, butorphanol can be considered analgesic in our study because it improved the ability of birds to perform a complex behaviour that requires both motivation and higher cognitive processing. This is the first study to provide a solid evidential base that birds with keel fractures experience pain, a finding that has significant implications for the welfare of laying hens that are housed in non-cage or furnished caged systems.

Combination of dexmedetomidine with buprenorphine enhances the antinociceptive effect to a thermal stimulus in the cat compared with either agent alone

OBJECTIVEnTo evaluate the sedative and antinociceptive effects of combinations of dexmedetomidine and buprenorphine in cats.nnnSTUDY DESIGNnExperimental randomized study.nnnANIMALSnTwelve purpose-bred neutered domestic short-hair cats (4 male and 8 female) weighing 4.6 kg (range 3.7-5.5 kg) aged from 2 to 5 years.nnnMETHODSnSix cats per group were administered buprenorphine (B) at 10 (B10) or 20 microg kg(-1) (B20) or dexmedetomidine (D) at 20 (D20) or 40 microg kg(-1) (D40) or a combination of B10/D20. A feline thermal nociceptive threshold testing device was used to evaluate the antinociceptive effects of the drugs before and up to 24 hours after drug treatment. Sedation was scored using a 100 mm visual analogue scale (VAS).nnnRESULTSnThermal thresholds increased significantly after administration of all but D20. Area under the curve (AUC, hours degrees C) for the first 6 hours (mean +/- SD) for B20 (281 +/- 17.8) was significantly greater than B10 (260 +/- 11.4), D20 (250 +/- 7.9) and D40 (255 +/- 11.4). The AUC for B10/D20 (273 +/- 12.2) was significantly greater than D20 but not the other treatments. No sedation was seen after administration of B10 or B20 and maximal sedation was seen for all animals in the D40 and B10/D20 groups and most animals in the D20 group.nnnCONCLUSIONSnD20 alone had the smallest analgesic effect; B10 alone provided no sedation but their combination gave good sedation with analgesia comparable with B20.nnnCLINICAL RELEVANCEnThis combination could be a useful multimodal sedative/analgesic regimen in cats.

Alfaxalone for total intravenous anaesthesia in dogs undergoing ovariohysterectomy: a comparison of premedication with acepromazine or dexmedetomidine

OBJECTIVEnTo describe alfaxalone total intravenous anaesthesia (TIVA) following premedication with buprenorphine and either acepromazine (ACP) or dexmedetomidine (DEX) in bitches undergoing ovariohysterectomy.nnnSTUDY DESIGNnProspective, randomised, clinical study.nnnANIMALSnThirty-eight healthy female dogs.nnnMETHODSnFollowing intramuscular buprenorphine (20 μg kg(-1) ) and acepromazine (0.05 mg kg(-1) ) or dexmedetomidine (approximately 10 μg kg(-1) , adjusted for body surface area), anaesthesia was induced and maintained with intravenous alfaxalone. Oxygen was administered via a suitable anaesthetic circuit. Alfaxalone infusion rate (initially 0.07 mg kg(-1) minute(-1) ) was adjusted to maintain adequate anaesthetic depth based on clinical assessment. Alfaxalone boluses were given if required. Ventilation was assisted if necessary. Alfaxalone dose and physiologic parameters were recorded every 5 minutes. Depth of sedation after premedication, induction quality and recovery duration and quality were scored. A Students t-test, Mann-Whitney U and Chi-squared tests determined the significance of differences between groups. Data are presented as mean ± SD or median (range). Significance was defined as p < 0.05.nnnRESULTSnThere were no differences between groups in demographics; induction quality; induction (1.5 ± 0.57 mg kg(-1) ) and total bolus doses [1.2 (0 - 6.3) mg kg(-1) ] of alfaxalone; anaesthesia duration (131 ± 18 minutes); or time to extubation [16.6 (3-50) minutes]. DEX dogs were more sedated than ACP dogs. Alfaxalone infusion rate was significantly lower in DEX [0.08 (0.06-0.19) mg kg(-1) minute(-1) ] than ACP dogs [0.11 (0.07-0.33) mg kg(-1) minute(-1) ]. Cardiovascular variables increased significantly during ovarian and cervical ligation and wound closure compared to baseline values in both groups. Apnoea and hypoventilation were common and not significantly different between groups. Arterial haemoglobin oxygen saturation remained above 95% in all animals. Recovery quality scores were significantly poorer for DEX than for ACP dogs.nnnCONCLUSIONS AND CLINICAL RELEVANCEnAlfaxalone TIVA is an effective anaesthetic for surgical procedures but, in the protocol of this study, causes respiratory depression at infusion rates required for surgery.

Sedative and analgesic effects of buprenorphine, combined with either acepromazine or dexmedetomidine, for premedication prior to elective surgery in cats and dogs

OBJECTIVEnTo evaluate the sedative and analgesic effects of intramuscular buprenorphine with either dexmedetomidine or acepromazine, administered as premedication to cats and dogs undergoing elective surgery.nnnSTUDY DESIGNnProspective, randomized, blinded clinical study.nnnANIMALSnForty dogs and 48 cats.nnnMETHODSnAnimals were assigned to one of four groups, according to anaesthetic premedication and induction agent: buprenorphine 20 μg kg(-1) with either dexmedetomidine (dex) 250 μg m(-2) or acepromazine (acp) 0.03 mg kg(-1), followed by alfaxalone (ALF) or propofol (PRO). Meloxicam was administered preoperatively to all animals and anaesthesia was always maintained using isoflurane. Physiological measures and assessments of pain, sedation and mechanical nociceptive threshold (MNT) were made before and after premedication, intraoperatively, and for up to 24 hours after premedication. Data were analyzed with one-way, two-way and mixed between-within subjects anova, Kruskall-Wallis analyses and Chi squared tests. Results were deemed significant if p ≤ 0.05, except where multiple comparisons were performed (p ≤ 0.005).nnnRESULTSnCats premedicated with dex were more sedated than cats premedicated with acp (p < 0.001) and ALF doses were lower in dex cats (1.2 ± 1.0 mg kg(-1) ) than acp cats (2.5 ± 1.9 mg kg(-1)) (p = 0.041). There were no differences in sedation in dogs however PRO doses were lower in dex dogs (1.5 ± 0.8 mg kg(-1) ) compared to acp dogs (3.3 ± 1.1 mg kg(-1) ) (p < 0.001). There were no differences between groups with respect to pain scores or MNT for cats or dogs.nnnCONCLUSIONnChoice of dex or acp, when given with buprenorphine, caused minor, clinically detectable, differences in various characteristics of anaesthesia, but not in the level of analgesia.nnnCLINICAL RELEVANCEnA combination of buprenorphine with either acp or dex, followed by either PRO or ALF, and then isoflurane, accompanied by an NSAID, was suitable for anaesthesia in dogs and cats undergoing elective surgery. Choice of sedative agent may influence dose of anaesthetic induction agent.

A study to evaluate buprenorphine at 40 μg kg−1 compared to 20 μg kg−1 as a post-operative analgesic in the dog

OBJECTIVEnComparison of the analgesic effect of buprenorphine at 20 or 40u2003μgu2003kg(-1) .nnnSTUDY DESIGNnAn investigator blinded, randomised study.nnnANIMALSnTwenty six dogs presented for ovariohysterectomy.nnnMETHODSnDogs were premedicated intramuscularly with acepromazine 0.03u2003mgu2003kg(-1) and buprenorphine at either 20 (B20, nu2003=u200312) or 40u2003μgu2003kg(-1) (B40, nu2003=u200314) followed by anaesthetic induction with propofol and maintenance with isoflurane. During anaesthesia non invasive blood pressure, heart rate, respiratory rate, blood oxygen saturation, inspired and expired volatile agent, end-tidal carbon dioxide and ECG were recorded. Pain and sedation were assessed using interactive VAS scores; mechanical nociceptive thresholds were measured at the wound and hindlimb--all were assessed before and up to 22 hours after administration. Carprofen was used for rescue analgesia.nnnRESULTSnThere were no significant differences between the two groups for any of the parameters examined. Rescue analgesia was required around 5 hours after administration of buprenorphine in a significant number of animals. Sedation was good preoperatively and scores decreased over time postoperatively. Hock thresholds did not change over time; wound thresholds decreased significantly compared to the baseline value from 3 hours onwards.nnnCONCLUSIONSnAdministration of buprenorphine at either 20 or 40u2003μgu2003kg(-1) IM with acepromazine provided good pre-operative sedation. Cardiovascular and respiratory values remained within clinically acceptable limits during anaesthesia. There was no evidence that increasing dose increased adverse events that may be associated with opioid administration (e.g. bradycardia and respiratory depression).nnnCLINICAL RELEVANCEnIncreasing the dose of buprenorphine from 20 to 40u2003μgu2003kg(-1) did not provide any benefits with respect to analgesia after ovariohysterectomy as assessed using the VAS scoring system.OBJECTIVEnComparison of the analgesic effect of buprenorphine at 20 or 40 μg kg-1.nnnSTUDY DESIGNnAn investigator blinded, randomised study.nnnANIMALSnTwenty six dogs presented for ovariohysterectomy.nnnMETHODSnDogs were premedicated intramuscularly with acepromazine 0.03 mg kg-1 and buprenorphine at either 20 (B20, n = 12) or 40 μg kg-1 (B40, n= 14) followed by anaesthetic induction with propofol and maintenance with isoflurane. During anaesthesia non invasive blood pressure, heart rate, respiratory rate, blood oxygen saturation, inspired and expired volatile agent, end-tidal carbon dioxide and ECG were recorded. Pain and sedation were assessed using interactive VAS scores; mechanical nociceptive thresholds were measured at the wound and hindlimb - all were assessed before and up to 22 hours after administration. Carprofen was used for rescue analgesia.nnnRESULTSnThere were no significant differences between the two groups for any of the parameters examined. Rescue analgesia was required around 5 hours after administration of buprenorphine in a significant number of animals. Sedation was good preoperatively and scores decreased over time postoperatively. Hock thresholds did not change over time; wound thresholds decreased significantly compared to the baseline value from 3 hours onwards.nnnCONCLUSIONSnAdministration of buprenorphine at either 20 or 40 μg kg-1 IM with acepromazine provided good pre-operative sedation. Cardiovascular and respiratory values remained within clinically acceptable limits during anaesthesia. There was no evidence that increasing dose increased adverse events that may be associated with opioid administration (e.g. bradycardia and respiratory depression).nnnCLINICAL RELEVANCEnIncreasing the dose of buprenorphine from 20 to 40 μg kg-1 did not provide any benefits with respect to analgesia after ovariohysterectomy as assessed using the VAS scoring system.

Methadone in combination with acepromazine as premedication prior to neutering in the cat

OBJECTIVEnTo investigate the safety, sedative and analgesic properties of methadone in combination with acepromazine prior to neutering in cats.nnnSTUDY DESIGNnControlled clinical, block randomized, prospective, blinded study designed for regulatory purposes.nnnANIMALSn24 female and 21 male healthy cats.nnnMETHODSnCats received one of three opioids combined with acepromazine (0.05 mg kg(-1) ) intramuscularly (IM) for premedication: Group 1: buprenorphine (0.02 mg kg(-1) ), group 2: methadone (0.5 mg kg(-1) ), group 3 butorphanol (0.4 mg kg(-1) ). Sedation was assessed 30 minutes after premedication using a visual analogue scale (VAS) and simple descriptive scale. Anaesthesia was induced with alfaxalone and maintained with isoflurane in oxygen. Surgical ovariohysterectomy or castration was performed. Pain was assessed using an interactive VAS (IVAS) and mechanical nociceptive threshold (MNT) with a pressure rate onset device. Methadone (0.5 mg kg(-1) IM) and meloxicam (0.2 mg kg(-1) subcutaneously) were provided 6 and 8 hours after premedication respectively, or together as rescue analgesia (IVAS above 50).nnnRESULTSnSedation scores, induction agent dose, pain scores at all time points and rescue analgesia were not statistically different between groups. In methadone treated cats there was no significant variation in MNT over time, suggesting a possible anti-hyperalgesic action, whereas in the other two groups lower thresholds were recorded at various time points after surgery compared to baseline. No cats required rescue analgesia after the second dose of methadone. No perioperative adverse effects occurred.nnnCONCLUSION AND CLINICAL RELEVANCEnMethadone provided comparable sedation and analgesia to both buprenorphine and butorphanol when combined with acepromazine. Differences in analgesic efficacy between opioids might have been undetectable because of the surgical model and surgeon competency. Nevertheless, methadone is an effective analgesic in cats and its administration prior to feline neutering may be advantageous.

Kinematic Analysis Quantifies Gait Abnormalities Associated with Lameness in Broiler Chickens and Identifies Evolutionary Gait Differences

This is the first time that gait characteristics of broiler (meat) chickens have been compared with their progenitor, jungle fowl, and the first kinematic study to report a link between broiler gait parameters and defined lameness scores. A commercial motion-capturing system recorded three-dimensional temporospatial information during walking. The hypothesis was that the gait characteristics of non-lame broilers (nu200a=u200a10) would be intermediate to those of lame broilers (nu200a=u200a12) and jungle fowl (nu200a=u200a10, tested at two ages: immature and adult). Data analysed using multi-level models, to define an extensive range of baseline gait parameters, revealed inter-group similarities and differences. Natural selection is likely to have made jungle fowl walking gait highly efficient. Modern broiler chickens possess an unbalanced body conformation due to intense genetic selection for additional breast muscle (pectoral hypertrophy) and whole body mass. Together with rapid growth, this promotes compensatory gait adaptations to minimise energy expenditure and triggers high lameness prevalence within commercial flocks; lameness creating further disruption to the gait cycle and being an important welfare issue. Clear differences were observed between the two lines (short stance phase, little double-support, low leg lift, and little back displacement in adult jungle fowl; much double-support, high leg lift, and substantial vertical back movement in sound broilers) presumably related to mass and body conformation. Similarities included stride length and duration. Additional modifications were also identified in lame broilers (short stride length and duration, substantial lateral back movement, reduced velocity) presumably linked to musculo-skeletal abnormalities. Reduced walking velocity suggests an attempt to minimise skeletal stress and/or discomfort, while a shorter stride length and time, together with longer stance and double-support phases, are associated with instability. We envisage a key future role for this highly quantitative methodology in pain assessment (associated with broiler lameness) including experimental examination of therapeutic agent efficacy.

Ultraviolet B-induced inflammation in the rat: A model of secondary hyperalgesia?

Summary Evaluation of the occurrence of secondary hyperalgesia in the rat UV‐B inflammatory pain model, and in a new model combining UV‐B irradiation with heat rekindling. ABSTRACT Cutaneous inflammation induced by ultraviolet (UV) irradiation in the UV‐B range has received significant recent interest as a translational inflammatory pain model. Changes in thermal and mechanical sensitivities in the area of primary hyperalgesia are well documented in both the rat and human UV‐B models, but the occurrence of secondary mechanical hyperalgesia is controversial. We investigated the occurrence of secondary mechanical hyperalgesia in the rat UV‐B model. Additionally, we investigated whether secondary hyperalgesia was enhanced by heat rekindling of UV‐B‐irradiated skin as a new rat inflammatory model of sensitisation with an enhanced central contribution. UV‐B irradiation (1000 mJ/cm2) induced significant secondary mechanical hyperalgesia and allodynia that peaked at 48 h. Heat rekindling (45 °C stimulus for 5 min) of UV‐B‐irradiated skin at 24 h further enhanced and prolonged this secondary mechanical hyperalgesia and allodynia, with a peak at 72 h. Heat rekindling also induced a significant mechanical hyperalgesia and allodynia on the contralateral hind paw, further suggesting the contribution of central sensitisation. Our data provide strong evidence for a central contribution in both the rat UV‐B pain model and an enhanced contribution in the new model combining UV‐B irradiation with heat rekindling. We also elucidate potential differences in the methods used by ourselves and others to obtain mechanical withdrawal thresholds in rats, which may explain the lack of secondary hyperalgesia in the rat UV‐B model.

The influence of various confounding factors on mechanical nociceptive thresholds in the donkey

OBJECTIVEnTo evaluate a mechanical nociceptive threshold (MNT) testing device in the donkey, and to investigate the influence of potential confounders on MNTs generated.nnnSTUDY DESIGNnProspective, randomised.nnnANIMALSnSixteen castrated male donkeys aged 4-9 years, weighing 105-170 kg.nnnMETHODSnMechanical nociceptive thresholds were measured using an actuator with three pins placed on the dorsal aspect of the distal limb, connected to a force meter. The pins (surface area 15 mm(2) ) were extruded onto the limb by pressurising an air-filled syringe, until the MNT force (when foot-lift was observed) or 25 N (cut-off force) was reached. Effect on MNT of presence of a companion donkey, the limb tested, rate of application of force, testing location, level of distraction, ambient temperature and hair cover at the test site was evaluated. Long and short-term repeatability of MNT was assessed. Data were analysed using general linear models and Mann-Whitney U tests, p < 0.05 was considered significant.nnnRESULTSnIncreasing the rate of force application significantly increased the mean ± SD MNT from 9.2 ± 2.0 N when applied at 0.4 N sec(-1) to 10.6 ± 2.1 N when applied at 1.2 N sec(-1) (p = 0.001). No other factors significantly influenced MNT. Mean MNT remained stable over a 3 week period, however MNTs were significantly (p = 0.006) higher (12.8 ± 3.0 N cf 10.3 ± 1.9 N) after a 12 month interval.nnnCONCLUSIONS AND CLINICAL RELEVANCEnWhen designing studies measuring MNT in donkeys, rate of application of force must be standardised. Donkeys MNTs have good short-term stability suggesting this technique is appropriate for short-term analgesiometry studies; however variability of MNTs over the long-term is greater.