Pain In Sheep Research Articles

USING SHEEP FACIAL GRIMACE SCALE, INFRARED THERMOGRAPHY AND CORTISOL HORMONE TO MEASURE PAIN IN SHEEP INFECTED WITH MASTITIS DISEASE

The purpose of this study was to apply sheep pain facial expression scales (SPFES) to sheep infected with mastitis, measuring peripheral temperatures and serum cortisol hormone. Twenty-three healthy ewes and 23 infected ewes with clinical mastitis were included in this research from January 2022 to April 2023. Images were taken from each ewe to detect facial grimace scales of ewes. Nasal, eye and ear temperatures were collected using infrared thermal imaging camera. Moreover, serum cortisol hormone was collected from the blood. It was found that there was a significant decrease (p<0.01) in nasal, eye and ear temperatures of infected ewes in comparison to healthy ewes. Additionally, cortisol hormone was found significantly (p<0.01) higher in infected ewes at day 1 and day 7 compared to non-infected animals. The changes in facial expressions for all the determined five regions were significantly (p<0.01) different than healthy ewes. The total pain score was significantly (p<0.05) higher on day 1 and day 7, compared to healthy ewes. It was concluded that sheep facial grimace scale was a useful and practical tool for measuring pain in sheep. In addition, cortisol from the serum and peripheral temperatures were found to be useful pain indicators.

Pain in Sheep

Abstract Pain in sheep can occur for a variety of reasons, including disease, injury, and naturally through parturition. Sheep, as a prey species, do not overtly express pain making it challenging for owners and veterinarians to recognise and thus effectively treat pain. By observing facial expressions, it is possible to recognise and quantify the pain a sheep may be experiencing. This enables the provision of treatment and the prevention of any further suffering. Information © The Author 2024

Postoperative Severity Assessment in Sheep

Introduction: Sheep are frequently used in translational surgical orthopedic studies. Naturally, a good pain management is mandatory for animal welfare, although it is also important with regard to data quality. However, methods for adequate severity assessment, especially considering pain, are rather rare regarding large animal models. Therefore, in the present study, accompanying a surgical pilot study, telemetry and the Sheep Grimace Scale (SGS) were used in addition to clinical scoring for severity assessment after surgical interventions in sheep. Methods: Telemetric devices were implanted in a first surgery subcutaneously into four German black-headed mutton ewes (4–5 years, 77–115 kg). After 3–4 weeks of recovery, sheep underwent tendon ablation of the left M. infraspinatus. Clinical scoring and video recordings for SGS analysis were performed after both surgeries, and the heart rate (HR) and general activity were monitored by telemetry. Results: Immediately after surgery, clinical score and HR were slightly increased, and activity was decreased in individual sheep after both surgeries. The SGS mildly elevated directly after transmitter implantation but increased to higher levels after tendon ablation immediately after surgery and on the following day. Conclusion: In summary, SGS- and telemetry-derived data were suitable to detect postoperative pain in sheep with the potential to improve individual pain recognition and postoperative management, which consequently contributes to refinement.

Preliminary Investigation into a Novel Sustained-Release Formulation of Meloxicam in Sheep (Ovis aries)-Pharmacokinetic Profile.

Simple SummaryMeloxicam is an effective non-steroidal anti-inflammatory drug (NSAID) suitable for ameliorating pain in sheep. Pain caused by husbandry procedures and other inflammatory conditions in sheep can persist for an extended time beyond the duration of action of currently available formulations of NSAIDs. This study investigates a novel sustained-release formulation of meloxicam to determine its potential for extended pain alleviation. Compared to a conventional formulation of meloxicam, the sustained-release formulation provided extended half-life making it a suitable candidate for providing extended pain relief.This study is a preliminary investigation describing the pharmacokinetic profile of a novel subcutaneous sustained-release meloxicam formulation (SRMF) in sheep. Six merino ewe hoggets (41.5 ± 4.6 kg) were treated with a novel subcutaneous SRMF at 2 mg/kg bodyweight (BW). Blood samples were collected at t = 0, 2, 4, 6, 8, 10, 12, 24, 48, 96, 144, 168, 192, and 336 h following treatment, and interstitial (ISF) fluid samples were collected at periods of 8 to 12 h, 12 to 24 h, 24 to 48 h, 48 to 52 h, and 92 to 96 h following treatment. High-pressure liquid chromatography (HPLC) analysis with ultraviolet detection was utilised to determine the concentration of meloxicam in plasma and ISF. The SRMF exhibited the following mean (±SD) pharmacokinetic indices: Cmax of 1.58 μg/mL (±0.82 μg/mL) at a Tmax of 10.0 h (±1.79 h), and half life (t1/2) of 31.4 h (±13.17 h) in sheep plasma. Interstitial fluid samples were collected from three of the six sheep, with a decrease in meloxicam concentration exhibited over 52 h. This study demonstrates a variable extended t1/2, a delayed Tmax, and a lower Cmax of the SRMF, as compared to that of a conventional meloxicam formulation (CMF) in sheep, as previously referenced (t1/2: 14.28 h; Tmax: 5 h; Cmax: 15.94 μg/mL). Further research to determine the clinical efficacy and safety of the SRMF in sheep is warranted.

Pain, Pathophysiological Mechanisms, and New Therapeutic Options for Alternative Analgesic Agents in Sheep: A Review and Investigation.

Simple SummaryThe purpose of this review is to provide current data on the definition and types of pain, describe its neuropharmacological and pathological mechanisms, and present a comparative analysis of the results obtained after intracerebroventricular (ICV) infusion of voltage-gated calcium channel inhibitors (VGCCIs) such as diltiazem, nifedipine, and verapamil, cholecystokinin receptor antagonists (PD, proglumide), and glutamatergic receptor antagonists (L-AP3, DL-AP3) during experimental distension of the duodenal and/or descending colonic wall. This method was used as a model for suppressing pain in sheep based on viscero-visceral inhibitory reflex, measured by the inhibition of behavioral symptoms of stress, degree of reticulo-ruminal motility, and changes in plasma cortisol and catecholamine concentration. After ICV infusion, all tested substances suppressed, to varying degrees, the viscero-visceral inhibitory reflex, tachycardia, hyperventilation, bleating, and gnashing of the teeth, whereas they increased the levels of cortisol and plasma catecholamines in sheep. These substances could be potential non-narcotic agents for the treatment of visceral intestinal pain (intestinal colic) in sheep, but clinical confirmation of the substances’ efficacy for treating intestinal colic is needed.Relief from suffering is the guiding principle of medical and veterinary ethics. Medical care for animals should be carried out to meet all welfare conditions. The need for pain management is demonstrated by recent monographs devoting attention to this urgent ethical need. Little data, however, are available on the prevention and attenuation of pain in sheep. After administration of narcotic analgesics used for severe visceral pain, sheep react with a state of excitement. Therefore, it was decided to experimentally investigate the usefulness of potential non-narcotic drugs to relieve pain in sheep with intestinal colic caused by 10 min of mechanical distension of their duodenal and/or descending colonic wall. The results indicate the potential usefulness of VGCCIs (diltiazem, nifedipine, verapamil), cholecystokinin receptor antagonists (PD, proglumide), and metabotropic glutaminergic receptor antagonists (mGluRAs), such as L-AP3, DL-AP3. As a premedication, these substances prevented the occurrence of symptoms of acute intestinal pain including atony of reticulo-rumen, tachycardia, hyperventilation, moaning, gnashing of teeth, hypercortisolemia, and catecholaminemia; hence, these substances are considered potential agents in the treatment of sheep visceral pain.

Evaluation of Electroencephalography, Behaviour and Eye Temperature in Response to Surgical Castration in Sheep.

Simple SummaryAustralian sheep undergo several surgical procedures as per industry standard lamb marking, including surgical castration. Electroencephalography (EEG) has been used successfully to assess pain in sheep previously. In this study, the EEG was measured over time to assess castration pain and analgesic efficacy in conscious lambs in combination with behaviour observations and eye temperature. A combination of lignocaine and meloxicam was used as the gold-standard approach to pain relief (CML), compared to castrated but untreated (C) and sham castrated (SC) lambs. Changes in EEG and behaviour were observed in all treatment groups. Lambs in CML and C groups showed more abnormal behaviours and immediate increases in eye temperature, indicative of pain. However, little differences between these groups suggest that analgesia was not successful in removing perceived pain of the procedure in this study. Changes in EEG for SC groups suggests the effect of handling and restraint, in addition to the pain of castration, impacted all results, not singularly the pain of castration.Castration has been demonstrated to cause pain in sheep. However, it is routinely performed for management purposes. Electroencephalography (EEG) has been used successfully to measure pain in lambs in response to castration and other husbandry procedures in livestock. The aim of this study was to evaluate the use of EEG as a measure of pain and analgesia in conscious lambs undergoing castration on farm over a 24 h period. EEG responses were compared to behavioural observations and changes in ocular temperature via infrared thermography. Twenty-four merino ram lambs (18.63 ± 2.06 kg) were used in this study. Lambs were randomly allocated to one of the following treatment groups: (1) castration with pre-surgical administration of meloxicam (0.5 mg/kg Metacam 20 mg/mL injected subcutaneously into the skin of the neck 15 min prior to recording) and lignocaine (applied via intra-testicular injection five minutes prior to castration, 2 mL lignocaine hydrochloride 20 mg/mL, Troy/Ilium) (CML, n = 8); (2) castration only (C, n = 8); (3) sham castration, handling only (SC, n = 8). EEG was recorded for 5 mins pre-procedure (prior to any intervention), and for 5 mins post-procedure at 0, 1, 4 and 24 h. Behavioural reactions to the procedure were scored, and behaviours were scan sampled at 5 min intervals at the above time points, by blinded observers. Eye temperature was measured for five-minute intervals at each time point. EEG decreased from baseline to 0 h for CML and C groups (p < 0.001), C group values returned similar to baseline at 24 h. Eye temperature increased post-castration at 0 h for C group, no initial change was seen for CML or SC groups. CML and C groups were more likely to have higher reaction scores and showed more abnormal behaviours (p = 0.017). CML and C groups had similar results, indicating minimal effect of analgesic intervention. Lambs in SC group showed significant EEG changes, suggesting that stress from handling also impacted EEG results.

Analgesic Comparison of Flunixin Meglumine or Meloxicam for Soft-Tissue Surgery in Sheep: A Pilot Study.

Simple SummaryPain management is lacking in U.S. commercial sheep production systems. This is, in part, due to the limited amount of scientific data evaluating sheep pain responses after analgesia treatment. Non-steroidal anti-inflammatory drugs (NSAIDs), such as meloxicam (MEL) and flunixin meglumine (FLU), are the most common drug class provided to livestock species to manage pain. Pain assessment tools, such as facial grimace scales, which use changes in facial expression to monitor pain, are also needed to improve pain management and sheep welfare. In this study, sheep undergoing a laparotomy (a surgical procedure where an incision is made into the abdominal cavity) were treated with either MEL or FLU to manage pain. A third group of ewes did not undergo surgery and served as study controls (CON). Behavior and physiologic outcome measures were collected pre-procedure and up to 48 h post-procedure. The results suggest that MEL and FLU were equally effective at providing post-operative analgesia; however, even with NSAID administration, acute pain and inflammation were still present in surgical sheep compared to non-surgical controls. The facial grimace scale results were not consistent with the other outcome measures taken in this study and it should not be used as a stand-alone pain assessment tool.The amount of scientific data evaluating sheep pain responses after analgesia treatment is limited. The aims of this study were to compare the efficacy of flunixin meglumine (FLU) and meloxicam (MEL) at relieving post-surgical pain in sheep and to evaluate the utility of the Sheep Grimace Scale (SGS). Thirty ewes were assigned to one of three treatment groups: oral MEL or intravenous FLU to manage pain associated with a laparotomy procedure, or a non-surgical control (CON) group. Behavior and physiologic outcome measures were collected pre-procedure and up to 48 h post-procedure. There were no significant differences in behavior, gait, degree of inflammation or pain around the surgical site when MEL and FLU sheep were compared, suggesting that both drugs provided similar levels of analgesia. Significant differences in behavior, gait, abdominal inflammation and pain were found when surgical sheep were compared to non-surgical controls. More work is needed to characterize the amount of pain relief provided by MEL and FLU. The SGS had moderate reliability between scorers; however, the results were inconsistent with the other study outcome measures. The SGS may have some utility as a pain assessment tool but should be used in conjunction with other pain measures.

Validation of the Unesp-Botucatu composite scale to assess acute postoperative abdominal pain in sheep (USAPS).

A scale with robust statistical validation is essential to diagnose pain and improve decision making for analgesia. This blind, randomised, prospective and opportunist study aimed to develop an ethogram to evaluate behaviour and validate a scale to assess acute ovine postoperative pain. Elective laparoscopy was performed in 48 healthy sheep, filmed at one preoperative and three postoperative moments, before and after rescue analgesia and 24 hours after. The videos were randomised and assessed twice by four evaluators, with a one-month interval between evaluations. Statistical analysis was performed using R software and differences were considered significant when p <0.05. Based on the multiple association, a unidimensional scale was adopted. The intra- and inter-observer reliability ranged from moderate to very good (intraclass correlation coefficient ≥ 0.53). The scale presented Spearman correlations > 0.80 with the numerical, simple descriptive, and visual analogue scales, and a correlation of 0.48 with the facial expression scale. According to the mixed linear model, the scale was responsive, due to the increase and decrease in pain scores of all items after surgery and analgesic intervention, respectively. All items on the scale demonstrated an acceptable Spearman item-total correlation (0.56-0.76), except for appetite (0.25). The internal consistency was excellent (Cronbach's α = 0.81) and all items presented specificity > 0.72 and sensitivity between 0.61-0.90, except for appetite. According to the Youden index, the cut-off point was ≥ 4 out of 12, with a diagnostic uncertainty zone of 4 to 5. The area under the curve > 0.95 demonstrated the excellent discriminatory capacity of the instrument. In conclusion, the Unesp-Botucatu pain scale in sheep submitted to laparoscopy is valid, reliable, specific, sensitive, with excellent internal consistency, accuracy, discriminatory capacity, and a defined cut-off point.

Preliminary Findings on a Novel Behavioural Approach for the Assessment of Pain and Analgesia in Lambs Subject to Routine Husbandry Procedures.

The identification and assessment of pain in sheep under field conditions are important, but, due to their stoic nature, are fraught with many challenges. In Australia, various husbandry procedures that are documented to cause pain are routinely performed at lamb marking, including ear tagging, castration, mulesing, and tail docking. This study evaluated the validity of a novel methodology to assess pain in lambs: qualitative behavioural assessment (QBA) was used to compare the behavioural expression of control lambs (CONTROL) with that of lambs subject to these procedures that received either a saline placebo 15 min before procedures (PLACEBO), or were administered meloxicam 15 min before procedures in addition to the standard analgesic Tri-Solfen at the time of procedures, as per the manufacturer's recommendations (ANALGESIC TREATMENT; AT). In terms of behavioural expression, it was expected that: CONTROL ≠ PLACEBO, AT = CONTROL, and PLACEBO ≠ AT. Video footage of the 6-8-week-old lambs (n = 10 for each treatment) was captured approximately 1.5 h postprocedure and was presented, in a random order, to 19 observers for assessment using the Free-Choice Profiling (FCP) approach to QBA. There was significant consensus (p < 0.001) among the observers in their assessment of the lambs, with two main dimensions of behavioural expression explaining 69.2% of the variation. As expected, observers perceived differences in the demeanour of lambs in the first dimension, scoring all lambs subject to the routine husbandry procedures as significantly more 'dull' and 'uneasy' compared to the control lambs (p < 0.05). Contrary to expectations, the results also suggested that analgesic treatment did not provide relief at the time of observation. Further investigations to validate the relationship between behavioural expression scores and pain are necessary, but these results suggest that painful husbandry procedures alter the behavioural expression of lambs and these differences can be captured using QBA methodology.

Development of an Automated Pain Facial Expression Detection System for Sheep (Ovis Aries).

Simple SummaryDetecting signs of pain in sheep is a challenging problem, as they are a prey species and would usually try to hide any signs that they are unwell or injured. This means that treating ill or injured sheep and preventing any further spread of contagious diseases such as footrot can be slow. The recent development and publication of a Sheep Pain Facial Expression Scale (SPFES) has provided a tool to reliably detect pain in this species. However, due to the increase in intensification in farming and larger flock sizes being cared for by individual farmers, there is less time to spend monitoring sheep for changes in behaviour that may indicate illness or injury. Having an automated system that could detect changes in the facial expression of individual sheep would mean that farmers could receive information directly about particular individuals that need assessment. This would allow treatment to be provided in a timely and direct manner, reducing suffering. We have been developing the SPFES further in order for it to become an automated system. In this paper, we present our novel framework that integrates SPFES concepts with automatic facial expression analysis technologies.The use of technology to optimize the production and management of each individual animal is becoming key to good farming. There is a need for the real-time systematic detection and control of disease in animals in order to limit the impact on animal welfare and food supply. Diseases such as footrot and mastitis cause significant pain in sheep, and so early detection is vital to ensuring effective treatment and preventing the spread across the flock. Facial expression scoring to assess pain in humans and non-humans is now well utilized, and the Sheep Pain Facial Expression Scale (SPFES) is a tool that can reliably detect pain in this species. The SPFES currently requires manual scoring, leaving it open to observer bias, and it is also time-consuming. The ability of a computer to automatically detect and direct a producer as to where assessment and treatment are needed would increase the chances of controlling the spread of disease. It would also aid in the prevention of resistance across the individual, farm, and landscape at both national and international levels. In this paper, we present our framework for an integrated novel system based on techniques originally applied for human facial expression recognition that could be implemented at the farm level. To the authors’ knowledge, this is the first time that this technology has been applied to sheep to assess pain.

Identification of key genes and pathways involved in response to pain in goat and sheep by transcriptome sequencing

PurposeThis aim of this study was to investigate the key genes and pathways involved in the response to pain in goat and sheep by transcriptome sequencing.MethodsChronic pain was induced with the injection of the complete Freund’s adjuvant (CFA) in sheep and goats. The animals were divided into four groups: CFA-treated sheep, control sheep, CFA-treated goat, and control goat groups (n = 3 in each group). The dorsal root ganglions of these animals were isolated and used for the construction of a cDNA library and transcriptome sequencing. Differentially expressed genes (DEGs) were identified in CFA-induced sheep and goats and gene ontology (GO) enrichment analysis was performed.ResultsIn total, 1748 and 2441 DEGs were identified in CFA-treated goat and sheep, respectively. The DEGs identified in CFA-treated goats, such as C-C motif chemokine ligand 27 (CCL27), glutamate receptor 2 (GRIA2), and sodium voltage-gated channel alpha subunit 3 (SCN3A), were mainly enriched in GO functions associated with N-methyl-d-aspartate (NMDA) receptor, inflammatory response, and immune response. The DEGs identified in CFA-treated sheep, such as gamma-aminobutyric acid (GABA)-related DEGs (gamma-aminobutyric acid type A receptor gamma 3 subunit [GABRG3], GABRB2, and GABRB1), SCN9A, and transient receptor potential cation channel subfamily V member 1 (TRPV1), were mainly enriched in GO functions related to neuroactive ligand-receptor interaction, NMDA receptor, and defense response.ConclusionsOur data indicate that NMDA receptor, inflammatory response, and immune response as well as key DEGs such as CCL27, GRIA2, and SCN3A may regulate the process of pain response during chronic pain in goats. Neuroactive ligand-receptor interaction and NMDA receptor as well as GABA-related DEGs, SCN9A, and TRPV1 may modulate the process of response to pain in sheep. These DEGs may serve as drug targets for preventing chronic pain.

Detection and assessment of acute and chronic pain in Meat Merino ewes using ethological parameters

The assessment of pain in sheep is a clinical challenge, because being a prey species, they tend to mask it. Since pain in animals cannot be measured directly, various methods are applicable to detect its effects on physiological, biochemical and ethological processes. Clinicians experienced in behavioural assessment are able to reliably determine the level of pain endured by an animal. The objective of this study was to identify behaviours that reflect acute and chronic pain as well as stress in sheep. The behaviour of 36 Meat Merino ewes with contagious footrot (contagious interdigital dermatitis) was analysed during normal activities in the flock and during footrot treatment, which included claw trimming to remove abnormal horn. The behaviour during treatment was compared with that of 12 healthy control sheep of the same breed during routine foot trimming. Grading of the observed behaviours was made using a numerical score. The occurrence of footrot was defined as, and equated with, chronic pain, and treatment was equated with acute pain. For the assessment of stress induced by the manipulative treatment, the data of the healthy sheep were taken as a comparison. The strongest indications of chronic pain were non-weight bearing lameness of an affected limb, shifting of weight and abnormal gait patterns. Additionally, sheep with footrot urinated more frequently than healthy animals. Stress-related bruxism occurred in healthy and ill sheep during foot trimming, but not during normal activities in the flock. Tail wagging and strong defensive movements of all limbs commonly occurred during footrot treatment. Head shaking appeared to be primarily stress-related in association with dorsal recumbency on the tilt table, but was exacerbated by pain elicited by hoof trimming. The behaviours selected in this study were useful for the identification of chronic and acute pain in sheep; however, correct interpretation of behavioural changes requires an experienced individual.

Development of a Pain Scoring System for Use in Sheep Surgically Implanted with Ventricular Assist Devices

ABSTRACTPurpose/Aim: In prey species, such as sheep, clinical signs of postoperative pain can manifest in subtle ways or may be concealed entirely. Previous publications describing pain assessment in ruminants focus on lameness and flock behavior, often in a farm environment. These indicators of pain may be difficult to assess in sheep housed in biomedical research settings. We have developed a novel pain scoring system for sheep undergoing thoracotomy for implantation of ventricular assist devices that are permanently housed in modified stanchions. Materials and Methods: The pain scoring system includes ruminant-specific behavioral signs of pain in addition to objective measurements that can be readily evaluated in a biomedical research setting. A numerical score is generated by the evaluator for each category. A decision tree is utilized to help guide further action following the generation of a cumulative score by the evaluator. A total score of 0–2 requires no intervention, 3–9 requires the consideration of additional analgesic administration, and a pain score ≥ 10 warrants the consideration of additional multimodal analgesia. Results: A novel pain scoring system and decision tree specifically designed for sheep undergoing thoracotomy in a biomedical research environment was developed and successfully utilized. Out of 102 postoperative pain scores measured, 86 scores were <2. There were 17/102 postoperative pain scores ≥3, which typically resulted in the administration of supplemental rescue analgesia in the immediate postoperative period. Conclusions: A novel pain scoring system was developed and utilized in a biomedical research environment for evaluating postoperative pain in sheep undergoing thoracotomy for implantation of a ventricular assist device. Further studies are necessary to validate the reliability of this novel pain scoring system.

Artificial intelligence learns to spot pain in sheep

Artificial intelligence learns to spot pain in sheep

Development of a facial expression scale using footrot and mastitis as models of pain in sheep

Management of pain in sheep is limited by the challenges of recognising and accurately quantifying pain in this species. The use of facial expression scoring to assess pain is a well-utilised, practical tool in both humans and non-human animals. The objective of this study was to develop a standardised facial expression pain scale for adult sheep, that could be used reliably and accurately to detect pain associated with naturally occurring painful diseases, such as footrot and mastitis. We also investigated whether the scale could be reliably and accurately utilised by observers after training, enabling the development of an on-farm pain assessment tool. The sheep pain facial expression scale (SPFES) was able to correctly identify sheep suffering from disease with a high degree of accuracy (AUC; footrot: 0.81, mastitis: 0.80). Diseased sheep scored higher on the scale than controls on the day of disease identification (P<0.05) and diseased sheep showed changes in their facial expression after treatment (P<0.001). The abnormal facial expressions of diseased sheep reduced over time, and at recovery were in line with control sheep. Control sheep did not change their facial expression over time. Five scorers who were trained to use the developed scale also assessed the facial expressions of sheep. The scorers were blind to treatment and session. Scorers reliably (ICC: 0.86) and accurately (α=0.86) identified changes in the facial expression of sheep with footrot over time (P<0.05), and scored control sheep consistently low over time. The SPFES offers a reliable and effective method of assessing pain in sheep after minimal training.

The bioavailability of medetomidine in eight sheep following oesophageal administration

There is sound evidence that medetomidine is an effective analgesic for acute pain in sheep. In this study, 15μgkg−1 of medetomidine was administered intravenously, and into the oesophagus, in a cross-over study, using eight sheep. Following intravenous administration, medetomidine could be detected in the plasma of these sheep for 120–180min but following oesophageal administration, medetomidine could not be detected in the plasma of any sheep at any of 17 time points over four days. It is suspected that this is due to high first pass metabolism in the liver. Consequently, we conclude that future studies investigating the use of analgesics in orally-administered osmotic pumps in sheep should consider higher doses of medetomidine (e.g. >100μgkg−1), further investigations into the barriers of medetomidine bioavailability from the sheep gut, liver-bypass drug delivery systems, or other α2-adrenergic agonists (e.g. clonidine or xylazine).

Influence of centrally administered diltiazem on behavioural responses, clinical symptoms, reticulo-ruminal contractions and plasma catecholamine level after experimentally induced duodenal distension in sheep

A different role of L-type antagonists for voltage-gated calcium channels (VGCC) has been previously identified in different types of experimental and clinical pain in man and animals. Present study examined the role of VGCC blocker – diltiazem administered icv (0.25, 0.5, 1.0 and/or 2.0 mg in toto) on the development of pain related symptoms, clinical signs, plasma catecholamine level and the inhibition of reticulo-rumen motility caused by 5 min lasting mechanical duodenum distension (DD) in the sheep. Experimental DD was conducted by insertion (during surgery) of rubber balloon into the duodenum and the distension by 40 ml of warm water. Duodenal distension resulted in a significant increase of behavioural pain responses, tachycardia, hyperventilation, inhibition of reticulo-rumen contractions rate (from 85% to 45% during 15–20 min), an increase of plasma catecholamine concentration (over sevenfold increase of epinephrine during 2 h following DD, two-times norepinephrine and 84% increase of dopamine). Diltiazem infusion given 10 min before DD decreased intensity of visceral nocifensive responses such as: behavioural changes, tachycardia, hyperventilation, reticulo-rumen motility and efficiently prevented appearance of catecholamine release. These data demonstrated that the development and persistence of acute duodenal pain depends on the activation of Ca 2+ ion flux leading to neurotransmitters release and modulation of membrane excitability. It seems that diltiazem given icv 10 min prior to DD (as a source of acute visceral pain), inhibited specific receptors α 1 subunits of VGCCs in target tissues, prevent depolarization of cell membranes and release of neurotransmitters responsible for pain sensitivity in sheep. The observed antinociceptive action of VGCCs type-L blockers suggests that these channels play a crucial role in the modulation of acute visceral pain in sheep.

Exploring non-invasive methods to assess pain in sheep

The aim of this study was to determine whether changes in eye temperature, measured using infrared thermography (IRT), and heart rate variability (HRV) can detect moderate levels of pain in sheep. Six ewes received the following treatments: 1) noxious ischaemic stimulus by application of a forelimb tourniquet (S), 2) noxious ischaemic stimulus and flunixin meglumine (S + F), and 3) flunixin meglumine (F). Maximum eye temperature, HRV, mechanical nociceptive threshold, blood pressure and behaviour were recorded for up to 60 min, including 15 min of baseline, 30 min during intervention and 15 min post-intervention. There was a tendency towards a decrease in the heart rate variability parameters RMSSD (the root mean square of successive R–R intervals) and SDNN (the standard deviation of all interbeat intervals) in treatment S compared to treatment F, and a significant increase in the same parameters between test day 1 and 3. A reduction in eye temperature was detected for all treatments during intervention, but no difference was found between S and F and S + N and F during intervention. The eye temperature decreased more in test day 2 and 3 compared to test day 1 during intervention. A significant reduction for both lip licking and vocalisation was observed between test day 1 and 3, and forward facing ears was the ear posture most frequently recorded in test day 1. We suggest that HRV is a sensitive, non-invasive method to assess mild to moderate pain in sheep, whereas IRT is a less sensitive method.

Comparison of the analgesic properties of transdermally administered fentanyl and intramuscularly administered buprenorphine during and following experimental orthopedic surgery in sheep

To evaluate the analgesic properties of transdermally administered fentanyl and IM administered buprenorphine in sheep undergoing unilateral tibial osteotomy. 20 mature sheep. Fentanyl patches (n = 15 sheep) or placebo patches (5 sheep) were applied 12 hours before sheep underwent general anesthesia and a unilateral tibial osteotomy. Buprenorphine was administered to the placebo group every 6 hours commencing at time of induction. Signs of pain were assessed every 12 hours after surgery by 2 independent observers unaware of treatment groups. There were no differences in preoperative and intraoperative physiologic data between the 2 groups. Sheep treated with fentanyl required less preoperative administration of diazepam for sedation and had significantly lower postoperative pain scores, compared with those treated with buprenorphine. No complications associated with the antebrachium at the site of patch application were detected. Under the conditions of this study, transdermally administered fentanyl was a superior option to IM administered buprenorphine for alleviation of postoperative orthopedic pain in sheep. This information can be used to assist clinicians in the development of a rational analgesic regimen for research and clinical patients.

Centrally administered verapamil prevents the autonomic reaction to visceral pain in sheep

The significant role of voltage gated calcium channels (VGCC) L-type antagonists used concomitantly with opioids in attenuation of clinical pain has been confirmed. The aim of this study was to evaluate the effect of centrally administered verapamil on behavior and biochemical parameters in sheep that have undergone experimental duodenal distension (DD) and to determine whether verapamil exerts any anti-nociceptive effects under these conditions. The study was carried out using 24 mature crossbred ewes, each weighing 38–43 kg. Verapamil, a VGCC blocker, was administered through an intracerebroventricular cannula at the following doses: 0.25, 0.5, 1.0 and 2.0 mg in toto. Ten minutes later experimental DD was conducted by insertion and the distension of rubber balloon (containing 40 ml of warm water) inserted into sheep duodenum. After 5 min of mechanical DD the following reactions were then observed: the significant increase in behavioral pain responses, i.e. tachycardia, hyperventilation, inhibition of reticulo-ruminal contractions (70% approximately, during 15 min), an increase of plasma catecholamine concentration (over 7-fold increase of epinephrine during 2 h following DD, 2-times norepinephrine and ±80% increase of dopamine). Verapamil infusion administered 10 min prior to DD decreased intensity of visceral pain responses, such as: behavioral changes, tachycardia, hyperventilation, inhibition of the reticulo-rumen motility and efficiently prevented the appearance of catecholamine release. These data demonstrated that the development and persistence of duodenal hyperalgesia depends on the activation of Ca 2+ ion flux leading to neurotransmitters release and modulation of membrane excitability. The observed antinociceptive action of VGCCs type-L blockers suggests that these channels play a crucial role in the modulation of acute visceral hyperalgesia in sheep.