A Review of Pain Assessment in Pigs

An injectable oleogel-based bupivacaine formulation for prolonged non-opioid post-operative analgesia

Opioid-based medications remain the mainstay of post-operative pain management, even though they are associated with a plethora of adverse effects including addiction, nausea, constipation, cognitive impairment, respiratory depression, and accidental death due to overdose. Local anesthetics are effective at controlling the intense pain after surgery but their short duration of effect limits their clinical utility in post-operative pain management. In this manuscript, an optimized injectable oleogel-based formulation of bupivacaine for multi-day post-operative pain management was characterized on the benchtop and assessed in two clinically-relevant porcine post-operative pain models. Benchtop characterization verified the optimized oleogel-based bupivacaine formulation design, demonstrating a homogenous stable oleogel with sufficient injectability due to shear-thinning properties, high drug loading capacity and first-order drug release kinetics over 5 days. In vivo assessment in two pig post-operative pain models demonstrated that the oleogel-based bupivacaine formulation can provide statistically significant multi-day analgesia in two routes of administration: local instillation directly into a surgical site and ultrasound-guided peripheral nerve block injection. Pharmacokinetic assessment of ALX005 found that Cmax values were not statistically different from the bupivacaine HCl control, with no clinical signs of local anesthetic systemic toxicity observed, when administering up to 2.7 and 8.1 times the control dose of bupivacaine HCl. This study demonstrates the pre-clinical safety and efficacy of an injectable oleogel-based bupivacaine formulation and explores its utility as a single-administration long-acting local anesthetic product for post-operative pain management that can be used in both local and regional anesthetic applications.

Part II: understanding pain in pigs-pain assessment in pigs with spontaneously occurring diseases or injuries

BACKGROUND

Pain in pigs needs to be managed and treated to the benefit of individual pigs. It is imperative for veterinarians and farmers to assure that pigs do not suffer from unnecessary pain that can be relieved. This review focusses on pain related to spontaneously occurring diseases and injuries since this topic is often neglected. The aim is to identify ways to accelerate knowledge and evidence in this area to prevent painful conditions in pigs in the future.

METHODS

A scoping review was conducted with results from a search of the electronic databases VetSearch and CABI Rxiv. The findings of selected publications are narratively synthesized and reported orienting on the PRISMA ScR guideline.

RESULTS

The results emphasize that pigs experience pain due to spontaneously occurring diseases and injuries, but systematic knowledge about this topic is scarce. More research is especially needed for rare diseases (such as UTIs). Moreover, research conducted about the topic pain in pigs should involve standardized protocols to document, analyse and share results on pain detection beyond a projects' timeframe. The findings of this review suggest that such a protocol would comprise validated pain identification measures over time and in relation to administered pain treatment.

CONCLUSION

The results of this study invite veterinary practitioners to reconsider in each pig patient whether pain and related indicators are present, how to handle the situation and document the process to ensure the welfare of individual compromised pigs.

Part I: understanding pain in pigs-basic knowledge about pain assessment, measures and therapy

BACKGROUND

Pigs can suffer from pain due to spontaneously occurring diseases, wounds, injuries, trauma, and physiological conditions such as the farrowing process; however, this pain is often neglected. To increase knowledge and awareness about this phenomenon, the current article presents a scoping review of basic and new approaches for identifying, evaluating, and treating pain in pigs.

METHODS

A scoping review was conducted with results from a search of the electronic database VetSearch and CABI. With regard to eligibility criteria, 49 out of 725 publications between 2015 and the end of March 2023 were included. The findings are narratively synthesized and reported orienting on the PRISMA ScR guideline.

RESULTS

The results of this review showed that practitioners need to consider pain not only as a sign of a disease but also as a critical aspect of welfare. If both the symptoms of pain and the underlying reasons remain unassessed, the longevity and prosperity of pigs may be at risk. In this respect, veterinarians are obliged to know about intricacies of pain and pain mechanisms and to provide adequate treatment for their patients.

CONCLUSION

It is pivotal to increase knowledge about pain mechanisms, the reasons for heterogeneity in behavioural signs of pain, and methods for evaluating whether a pig is experiencing pain. This article will help practitioners update their knowledge of this topic and discuss the implications for everyday practice.

How facial expressions reveal acute pain in domestic animals with facial pain scales as a diagnostic tool

The growing interest in managing and recognizing pain in animals has led to the search for more sensitive methods to evaluate it, especially because some species conceal any visible changes associated with pain or are not easily assessed. Research has shown that an animal's facial expression changes when exposed to painful stimuli. Thus, developing several pain scales (grimace scales) in species such as horses, cattle, pigs, sheep, donkeys, rabbits, rats, mice, and cats has helped to improve the study of pain in veterinary medicine. The possibility of using facial expression as an indicator of pain is due to the direct relationship between the activation of different regions of the Central Nervous System such as the somatosensory cortex, prefrontal cortex, amygdala, hippocampus, and hypothalamus, and their connections with the motor cortex to elicit motor responses including the movement of facial muscles. The present review aims to discuss the neurobiological association between acute pain and facial expressions in animals. It will analyze the importance of facial expression characterization and the use of grimace scales in farm, companion, and laboratory species.

Proposing a short version of the Unesp-Botucatu pig acute pain scale using a novel application of machine learning technique

Surgical castration of males is carried out on a large scale in the US swine industry and the pain resulting from this procedure can be assessed using the Unesp-Botucatu pig composite acute pain scale (UPAPS). We aim to propose a short version of UPAPS based on the behaviors best-ranked by a random forest algorithm. We used behavioral observations from databases of surgically castrated pre-weaned and weaned pigs. We trained a random forest algorithm using the pain-free (pre-castration) and painful (post-castration) conditions as target variable and the 17 UPAPS pain-altered behaviors as feature variables. We ranked the behaviors by their importance in diagnosing pain. The algorithm was refined using a backward step-up procedure, establishing the Short UPAPS. The predictive capacity of the original and short version of the UPAPS was estimated by the area under the curve (AUC). In refinement, the algorithm with the five best-ranked behaviors had the lowest complexity and predictive capacity equivalent to the algorithm with all behaviors. The AUC of Short UPAPS (89.62%) was statistically equivalent (p = 0.6828) to that of UPAPS (90.58%). In conclusion, the proposed Short UPAPS might facilitate the implementation of a standard operating procedure to monitor and diagnose acute pain post-castration in large-scale systems.

Pig tail length is associated with the prevalence of tail malformations but not with inflammation of the tail

BACKGROUND

Assuming that tail length is associated with the prevalence of tail biting, attempts are being made to shorten tails by genetic selection in order to avoid the painful procedure of docking. However, undesirable side effects such as kinky tails and inflammatory changes may occur. The aim of the present study was to clinically quantify in a population with known segregation of tail length, i) its variability, ii) possible associations with kinked tails and iii) possible associations of tail length and kinks with inflammation of the tail using 348 piglets at day 3 (undocked) and 39 (docked tails) of life.

RESULTS

The relative tail length (tail tip to tail base/tail tip to ear base × 100) varied between 20.3 and 31.3%. A reduced tail length was associated with kinked tails. Piglets with the shortest tails had 28% kinked tails, 5.6 times more than the piglets with the longest tails. The tails showed high prevalence of inflammation both on day 3 and on the docked tails on day 39. Overall, these were not associated with tail length or kinked tails. Only necrosis of the tail was significantly more frequent in the kinked tails than in the normal tails. Sow line, sow ID and boar ID significantly affected relative tail length, which may suggest a genetic cause.

CONCLUSION

Based on the phenotypic variation found in the present study, it seems possible to influence tail length through breeding. It remains to be seen whether the available potential is sufficient to actually reduce tail biting. At the same time, a higher incidence of kinked tails and necrosis is to be expected.

Active immunization against gonadotropin-releasing hormone enhances the generation of B cells but does not affect their colonization in peripheral immune organs in male rats

Active immunization against gonadotropin-releasing hormone (GnRH) affects the immune system by inhibiting testosterone production. Our previous study investigated the effects of GnRH immunization on thymic T-cell generation, migration, and colonization in peripheral immune organs. However, the mechanisms by which GnRH immunization influences B cell generation and the characteristics of B cell colonization in peripheral immune organs remain unclear. Herein, GnRH immunization enhanced B cell generation by reducing apoptosis. GnRH immunization did not markedly affect the cell cycle of bone marrow cells, B cell development-related signaling molecules, or the percentage of B cells in the blood, spleen, or inguinal lymph nodes. After testosterone supplementation in GnRH-immunocastrated rats, the generation of B cells in the bone marrow was significantly reduced, and the apoptosis of B cells was remarkably increased. Testosterone did not significantly affect the cell cycle of bone marrow cells or the proportion of B cells in the blood, spleen, or inguinal lymph nodes of the GnRH-immunocastrated rats. Overall, these results clarify the mechanisms related to B cell expansion in the bone marrow and the settlement characteristics of B cells in peripheral immune organs after GnRH immunization.

Effects of a Multimodal Pain Control Protocol Using 2% Lidocaine Intradermal and Meloxicam Intramuscular on Mitigating Behavioral Castration Pain in Piglets Using a Needleless System

Mitigating piglet castration pain is critical to minimize negative experiences and contribute to a positive affective state. A multimodal pain control protocol (needleless 2% lidocaine intradermal/0.4 mg/kg meloxicam intramuscular) was evaluated. Males were administered one of four treatments: (1) needleless lidocaine/meloxicam intramuscular (LM), (2) needleless lidocaine/saline intramuscular (LS), (3) needleless saline/meloxicam intramuscular (SM), and (4) needleless saline/saline intramuscular (SS). Females were sham castrated (SH). Piglets were recorded 24h pre-castration (M1) and 15min (M2), 3h (M3), and 24h post-castration (M4). The Unesp-Botucatu Composite Acute Pain Scale (UPAPS) was used to assess pain behavior. From a treatment standpoint, scores did not differ at M1 (P = 1.00) or M4 (P ≥ 0.36). However, at M2, LS piglets had (P < 0.01) higher scores (3.4) than LM piglets (1.6) and SH piglets had (P ≤ 0.01) the lowest scores (0.02). From a timepoint standpoint, piglets in the LS, LM, SM, and SS groups had (P ≤ 0.05) higher scores at M2 compared with their baseline scores at M1. These results indicate that needleless lidocaine and intramuscular meloxicam offered no analgesic benefit.

Nociceptive and Transcriptomic Responses in a Swine Diabetic Wound Model Treated With a Topical Angiotensin 1 Receptor Antagonist

BACKGROUND

Painful, treatment-resistant wounds are prevalent among diabetic patients and significantly affect health-related quality of life (HRQOL). Topical treatments may help alleviate pain without risk of dependence or side effects. However, there is a lack of topical wound compounds targeting pain-specific receptors. One possible target is proinflammatory angiotensin 1 receptor (AT1R), which is upregulated in diabetic skin and has been implicated in nociception.

OBJECTIVES

We investigated the effects of topical valsartan, an AT1R antagonist, on pain (nociceptive thresholds) and gene expression changes (transcriptomics) in a swine model of diabetic wounds.

METHODS

Eight wounds were surgically induced in diabetic, hyperglycemic Yucatan miniature swine ( n = 4). Topical AT1R antagonist was applied to wounds on one side and vehicle on the other side. Nocifensive testing was conducted at baseline and then weekly, beginning 7 days after wound induction. Mechanical and thermal stimuli were applied to the wound margins until a nocifensive reaction was elicited or a predetermined cutoff was reached. After 7 weeks of testing, tissue from the dorsal horn, dorsal root ganglion, and wounds were sequenced and analyzed with DESeq2. Unbiased pathway analyses using Metascape were conducted on differentially expressed genes.

RESULTS

There was no significant difference in mechanical tolerance threshold between AT1R antagonist-treated and vehicle-treated wounds ( p = .106). Thermal tolerance was significantly higher in AT1R antagonist-treated wounds compared to vehicle-treated ( p = .015). Analysis of differentially expressed genes revealed enriched pathways of interest: interleukin-18 signaling in dorsal horn laminae IV-V and sensory perception of mechanical stimulus in wound tissue.

DISCUSSION

In this study, wounds modeling diabetic ulcers were created in hyperglycemic swine and treated with a topical AT1R antagonist. AT1R-antagonist-treated wounds had a higher tolerance threshold than vehicle-treated wounds for thermal hyperalgesia, but not mechanical allodynia. Pathway analyses of differentially expressed genes revealed several pathways of interest for future pain research. Although further studies are needed to confirm the findings, this study can improve nursing care by providing information about a potential future treatment that may be used to decrease pain and improve HRQOL in patients with diabetic wounds.

Simplified assessment of castration-induced pain in pigs using lower complexity algorithms

Pigs are raised on a global scale for commercial or research purposes and often experience pain as a by product of management practices and procedures performed. Therefore, ensuring pain can be effectively identified and monitored in these settings is critical to ensure appropriate pig welfare. The Unesp-Botucatu Pig Composite Acute Pain Scale (UPAPS) was validated to diagnose pain in pre-weaned and weaned pigs using a combination of six behavioral items. To date, statistical weighting of supervised and unsupervised algorithms was not compared in ranking pain-altered behaviors in swine has not been performed. Therefore, the aim of this study was to verify if supervised and unsupervised algorithms with different levels of complexity can improve UPAPS pain diagnosis in pigs undergoing castration. The predictive capacity of the algorithms was evaluated by the area under the curve (AUC). Lower complexity algorithms containing fewer pain-altered behaviors had similar AUC (90.1-90.6) than algorithms containing five (89.18-91.24) and UPAPS (90.58). In conclusion, utilizing a short version of the UPAPS did not influence the predictive capacity of the scale, and therefore it may be easier to apply and be implemented consistently to monitor pain in commercial and experimental settings.

Effects of assessment method (real-time versus video-recorded) on a validated pain-altered behavior scale used in castrated piglets

We aimed to compare two assessment methodologies (real-time vs. video-recorded) using the Unesp-Botucatu Pig Composite Acute Pain Scale (UPAPS) in piglets before and after castration. Twenty-nine male piglets were castrated. Four observers scored the UPAPS over three perioperative timepoints of castration following two assessment methodologies. In real-time assessments, the observers were in-person observing the piglets in front of the pen. After two weeks, the observers did video-recorded assessments randomizing piglets and timepoints. Modeling was conducted to compare the UPAPS and each pain-altered behavior between methodologies. Intraclass correlation coefficient (ICC), Bland-Altman, and Lin's concordance correlation coefficient (CCC) were conducted to investigate agreement between methodologies. UPAPS was statistically equivalent between methodologies (P = 0.4371). The ICC for each method was very good (0.85 to 0.91). The agreement of the UPAPS assessed between methodologies had minimal bias (- 0.04), no proportion bias, and 53% of the assessments presented a perfect agreement. However, CCC of the UPAPS was moderate (0.65), and only one pain-altered behavior ("presents difficulty in overcoming obstacles or other animals") occurred more in real-time assessments (P = 0.0444). In conclusion, piglet pain assessment by UPAPS can be conducted in real-time based on a suitable agreement between the real-time and video-recorded assessment methods.

A critical review on experimental Streptococcus suis infection in pigs with a focus on clinical monitoring and refinement strategies

Streptococcus suis (S. suis) is a major pig pathogen worldwide with zoonotic potential. Though different research groups have contributed to a better understanding of the pathogenesis of S. suis infections in recent years, there are still numerous neglected research topics requiring animal infection trials. Of note, animal experiments are crucial to develop a cross-protective vaccine which is highly needed in the field. Due to the severe clinical signs associated with S. suis pathologies such as meningitis and arthritis, implementation of refinement is very important to reduce pain and distress of experimentally infected pigs. This review highlights the great diversity of clinical signs and courses of disease after experimental S. suis pig infections. We review clinical read out parameters and refinement strategies in experimental S. suis pig infections published between 2000 and 2021. Currently, substantial differences exist in describing clinical monitoring and humane endpoints. Most of the reviewed studies set the body temperature threshold of fever as high as 40.5°C. Monitoring intervals vary mainly between daily, twice a day and three times a day. Only a few studies apply scoring systems. Published scoring systems are inconsistent in their inclusion of parameters such as body temperature, feeding behavior, and respiratory signs. Locomotion and central nervous system signs are more common clinical scoring parameters in different studies by various research groups. As the heterogenicity in clinical monitoring limits the comparability between studies we hope to initiate a discussion with this review leading to an agreement on clinical read out parameters and monitoring intervals among S. suis research groups.

Evaluation of tissue depth, captive bolt penetration force and energy, and potential for bolt-thalamus contact in cadaver heads from physically castrated market barrows and immunocastrated boars

The main objective of this study was to describe tissue thicknesses of cadaver heads from physically castrated market barrows (PC MARKET BARROWS) and immunocastrated boars (IC BOARS) at the frontal penetrating captive bolt (PCB) placement. Other objectives were to describe differences in bolt force and energy requirements to penetrate and describe potential for bolt-thalamus contact. Forty-four heads were obtained from PC MARKET BARROWS (n = 22) and IC BOARS (n = 22) of similar age and size that were rendered insensible with CO2. Mean HCW was 117.32 ± 3.52 kg. Snout to poll distance (cm) and maximum deflection distance (cm) were collected in duplicate. Heads were split at midline with a bandsaw and soft tissue and cranial thicknesses were measured with a digital caliper. Images of each cut surface were collected to evaluate the potential for thalamic damage. Tissue samples were retained from each half of each head and a universal tester was used to determine maximum force and energy of bolt penetration. There was no evidence to support a significant difference (P > 0.05) in tissue thicknesses between PC MARKET BARROWS and IC BOARS. Maximum deflection distance (maximum distance from a straight edge that was placed from the tip of the snout to the poll of the head) was not different (P = 0.10) between PC MARKET BARROWS (3.31 ± 0.10 cm) and IC BOARS (3.08 ± 0.10 cm). There was no evidence to support a difference (P = 0.77) in maximum force between PC MARKET BARROWS (7130.32 ± 483.23 N) and IC BOARS (6974.60 ± 463.70 N). There was also no evidence to support a difference (P = 0.62) in maximum energy between PC MARKET BARROWS (33.37 ± 2.77 J) and IC BOARS (32.04 ± 2.50 J). For PC MARKET BARROWS, there was a difference (P = 0.05) between the number of heads where the thalamus was located within the theoretical plane of bolt travel for market placement (21/21) versus mature placement (16/21). For IC BOARS, the number of heads where the thalamus was located within the plane of theoretical bolt path was not different between the two PCB placements (19/21 each). Overall, the data suggest that tissue profiles of PC MARKET BARROWS and IC BOARS do not differ at the frontal PCB placement site and the mechanical tools that are effective for PC MARKET BARROWS should also be effective for IC BOARS.

Continuous fluid infusion per rectum compared with intravenous fluid infusion in pigs

BACKGROUND

Peripheral blood vessels in pigs are not easily accessible, making placement of intravenous catheters difficult. Alternative methods to intravenous administration of fluids, such as administering fluids via the rectum (proctoclysis), are warranted in pigs.

HYPOTHESIS

Administration of polyionic crystalloid fluids via proctoclysis results in hemodilution changes similar to intravenous administration. The objectives of this study were to evaluate the tolerance for proctoclysis in pigs and compare analytes before and after intravenous or proctoclysis therapy.

ANIMALS

Six healthy, growing, academic institution-owned pigs.

METHODS

Randomized, cross-over design clinical trial, with 3 treatments (control, intravenous, and proctoclysis) with a 3-day washout period. The pigs were anesthetized and jugular catheters were placed. A polyionic fluid (Plasma-Lyte A 148) was administered at 4.4 mL/kg/h during the intravenous and proctoclysis treatments. Laboratory analytes, including PCV, plasma, and serum total solids, albumin, and electrolytes were measured over 12 h at T0 , T3 , T6 , T9 , and T12 . Effects of treatment and time on analytes were determined by analysis of variance.

RESULTS

Proctoclysis was tolerated by pigs. Albumin concentrations decreased during the IV treatment between T0 and T6 (least square mean of 4.2 vs 3.9 g/dL; 95% CI of mean difference = -0.42, -0.06; P = .03). Proctoclysis did not significantly affect any laboratory analytes at any time points (P > .05).

CONCLUSIONS AND CLINICAL IMPORTANCE

Proctoclysis did not demonstrate hemodilution similar to intravenous administration of polyionic fluids. Proctoclysis might not be an effective alternative to the intravenous administration of polyionic fluids in healthy euvolemic pigs.

Lameness in Pregnant Sows Alters Placental Stress Response

Pregnant sows from commercial pig farms may experience painful states, such as lameness, an essential indicator in assessing sow welfare. We investigated the effect of lameness during the last third of pregnancy on reproductive performance and placental glucocorticoid concentrations in sows. Periodic locomotion assessments were carried out on two commercial pig farms using a validated 0-5 scoring system (from 0: normal locomotion; to 5: a downer animal). Sows from both farms (N = 511) were grouped based on their average locomotion scores. On Farm 1, 30 sows were selected and grouped as either Not Lame (NL = 16; X¯ = 0-1) or Lame (L = 14; X¯ > 1). On Farm 2, 39 sows were selected and grouped as either Not Lame (G1 = 12; X¯ = 0-1), Moderately Lame (G2 = 13; X¯ = 1.1-2), or Severely Lame (G3 = 14; X¯ ≥ 2.1). Reproductive data (gestation length, litter weight, average piglet weight, litter size, and the number of piglets born alive/mummified/stillborn) were recorded on both farms. Moreover, on Farm 2, piglet intrauterine growth restriction score and the number of piglets dead during the first week were also recorded, and placenta samples were collected to determine their cortisol/cortisone concentrations. A linear mixed model was used to analyze the data. The proportion of lameness in pregnant sows (N = 511) was >40%, and the gestation length tended to decrease with the presence of lameness (p < 0.1) in both farms. G2 sows had a higher placental cortisol/cortisone ratio than G1 and G3 sows (p < 0.01). In conclusion, lameness was high in the sows assessed, which may decrease sow gestation length and reduce placental efficiency in protecting the offspring from the sows' stress response.

Behavior of Piglets in an Observation Arena before and after Surgical Castration with Local Anesthesia

Surgical castration of piglets is generally recognized as a painful procedure, but there is currently no gold standard for the assessment of pain behavior in piglets. However, pain assessment is essential for evaluating the effectiveness of local anesthetics. In this study, we investigated the efficacy of four local anesthetics in terms of pain relief during and after surgical castration in three sequential study parts. To do so, we filmed 178 piglets before the applied procedures, after injection of the local anesthetic, and up to 24 h after castration (five observation times in total) in an observation arena and compared their behavior before and after castration and between treatments and control groups. The results showed significant differences in the behavior of the piglets before and after castration and between the sham-castrated control group and the control group castrated without anesthesia. The different local anesthesia treatment groups showed diverging differences to the control groups. The most frequently shown pain-associated behaviors of the piglets were changes in tail position and hunched back posture. We observed a reduction but no complete elimination of the expressed pain-associated behaviors after local anesthesia. Several behavioral changes-such as changes in tail position, hunched back posture or tail wagging-persisted until the day after castration. Owing to the limited duration of the effects of the local anesthetics, local anesthesia did not influence long-term pain.

A new S. suis serotype 3 infection model in pigs: lack of effect of buprenorphine treatment to reduce distress

BACKGROUND

Streptoccocus suis (S. suis) is a major porcine pathogen causing meningitis, septicemia, arthritis and endocarditis. These diseases severely impair welfare of pigs. Experimental studies in pigs are important to better understand the pathogenesis and to identify protective antigens, as so far there is no vaccine available protecting against various serotypes (cps). Due to the severity of disease, application of appropriate refinement strategies in experimental S. suis infections is essential to reduce distress imposed on the piglets without jeopardizing the scientific output. The objectives of this study were to evaluate buprenorphine treatment as a refinement measure and serum cortisol levels as a distress read out parameter in a new S. suis cps3 infection model in pigs.

RESULTS

Intravenous application of 2 × 10⁸ CFU of S. suis cps3 (sly⁺, mrp⁺) to 6-week-old piglets led to severe morbidity in approximately 50% of the animals. Main pathological findings included suppurative meningoencephalitis and arthritis as well as fibrinosuppurative endocarditis. Buprenorphine treatment (0.05 mg/kg every 8 h) did not prevent signs of severe pain, high clinical scores, moderate to severe pathologies or high levels of serum cortisol in single severely affected piglets. Significant differences in the course of leukocytosis, induction of specific antibodies and bactericidal immunity were not recorded between groups with or w/o buprenorphine treatment. Of note, clinically unobtrusive piglets showed serum cortisol levels at 2 and 5 days post infectionem (dpi) comparable to the levels prior to infection with cps3. Cortisol levels in serum were significantly increased in piglets euthanized due to severe disease in comparison to clinically unobtrusive pigs.

CONCLUSIONS

Different clinical courses and pathologies are induced after intravenous challenge of piglets with 2 × 10⁸ CFU of this S. suis cps3 strain. The chosen protocol of buprenorphine application does not prevent severe distress in this infection model. Important parameters of the humoral immune response, such as the level of IgM binding to S. suis cps3, do not appear to be affected by buprenorphine treatment. Serum cortisol is a meaningful parameter to measure distress in piglets experimentally infected with S. suis and to evaluate refinement strategies. In this intravenous model, which includes close clinical monitoring and different humane endpoints, clinics and cortisol levels suggest convalescence in surviving piglets within 5 days following experimental infection.

Consumers' Attitudes towards Animal Suffering: A Systematic Review on Awareness, Willingness and Dietary Change

Planetary and human health depend on Westerners' ability to reduce meat consumption. Meat production degrades the environment while excessive meat intake is associated with cancer and cardiovascular disease, among others. Effective reasons and motivations are needed for consumers to change their diet. The fact that modern animal agriculture inflicts a great deal of pain on animals from their birth to their slaughter, animal welfare/suffering may drive consumers to curtail their meat consumption. This systematic review examined a total of 90 papers to ascertain consumers' awareness of the pain animals experience in animal agriculture, as well as consumer attitudes towards meat reduction due to animal welfare. Results show that consumers have low awareness of animal agriculture. Awareness of animal agricultural practices and animal sentience is associated with increased negative attitudes towards animal suffering. Animal suffering due to farming practices, transportation, slaughter, and animal sentience are factors that may encourage a reduction in meat consumption, and even dietary change in the short term. There is also evidence that animal suffering may be a more compelling motivation for consumers' willingness to change their diet than for health or environmental reasons. Therefore, increasing consumers' awareness of animal suffering in meat production is paramount to contributing to reduced pressure on the environment and improved human health.

Characterizing candidate decompression rates for hypobaric hypoxic stunning of pigs. Part 2: Pathological consequences

Pigs are commonly stunned pre-slaughter by exposure to carbon dioxide (CO2), but this approach is associated with significant welfare concerns. Hypobaric hypoxia, achieved with gradual decompression (also known as Low Atmospheric Pressure Stunning or LAPS) may be an alternative, allowing the retention of welfare friendly handling approaches and group stunning. Although validated in poultry, the feasibility and welfare consequences of gradual decompression for pigs are unknown. Here, we characterize pathological changes in 60 pigs resulting from exposure to a range of candidate decompression curves (ranging from 40 to 100 ms-1 ascent equivalent, with two cycle durations 480 and 720 s). To protect welfare, we worked on unconscious, terminally anesthetized pigs which were subject to detailed post-mortem examinations by a specialized porcine veterinary pathologist. All pigs were killed as a result of exposure to decompression, irrespective of cycle rate or length. Pigs showed no external injuries during ante-mortem inspections. Exposing pigs to decompression and the unavoidable subsequent recompression resulted in generalized congestion of the carcass, organs and body cavities including the ears, oral cavity, conjunctivae and sclera, mucosa of other external orifices (anus and vulva), nasal planum, nasal cavities including nasal conchae, frontal sinuses, cranium, meninges, brain, larynx, trachea, lungs, heart, parietal pleura of the thoracic cavity, peritoneum of the abdominal cavity, stomach, small intestine, caecum, colon, liver, spleen and kidneys and representative joint cavities in the limbs (stifles and elbows). Various severities of hemorrhage were observed in the conjunctivae and sclera, mucosa of other external orifices (anus and vulva), nasal cavities including nasal conchae, frontal sinuses, cranium, meninges, brain, larynx, tracheal lumen, lungs, parietal pleura of the thoracic cavity, liver, spleen and kidneys and representative joint cavities in the limbs (stifles and elbows). In general, faster decompression rates produced higher scores, but in the conjunctivae, sclera and kidneys, faster decompression rates were associated with marginally lower congestion scores. There was considerable individual variation in pathological scores across all body regions. The congestion and hemorrhage observed could translate into welfare harms in conscious pigs undergoing this type of stunning, depending when in the cycle the damage is occurring, but no welfare related conclusions can be drawn from the responses of unconscious pigs. Since recompression is always required, its effects cannot be separated from decompression, however cessation of cardiac activity several minutes before recompression should have eliminated any haemodynamic effects relating to cardiac function and blood pressure. This study represents the first systematic attempt to identify candidate rate profiles to underpin future explorations of decompression as a stunning method for pigs. These pathological findings also inform discussions about the likely carcass quality implications of this novel stunning method.

Comparative Study of Pain-Related Responses of Male Piglets up to Seven Days of Age to the Application of Different Local Anaesthetics and Subsequent Castration

Simple Summary

Since 2021, surgical piglet castration must be performed with complete pain elimination according to the Animal Protection Law in Germany. General anaesthesia by isoflurane inhalation, which can be performed by the farmer, or by injection of ketamine and azaperone, which must be performed by a veterinarian, are the options available. At present, local anaesthesia is still under debate because of the lack of proof of complete pain elimination and the pain on injection. We tested three local anaesthetics (procaine, lidocaine, and mepivacaine) at two different doses each. Because pain responses can be masked by reactions caused by handling, the piglets were given superficial isoflurane anaesthesia. The pain on injection to the testes was compared with intramuscular injection, and the effectiveness during castration was compared among the local anaesthetics. Nocifensive movements, respiratory rate, blood pressure, heart rate and its variability as well as electroencephalography (EEG) changes were studied in relation to the painful interventions. Most indicators of nociception point to testicular injection pain being beyond intramuscular injection pain when an effective amount of local anaesthetic was used. However, complete pain elimination could not be achieved during castration under local anaesthesia.

Abstract

To evaluate pain responses to intratesticular and subscrotal injection of three local anaesthetics and their efficacy during castration a randomized controlled study was conducted. In groups of 20 piglets, procaine (2%), lidocaine (2%), or mepivacaine (2%) were administered subscrotal and intratesticularly in two different dosages: 0.5 mL of the original substances or the maximum recommended dosage according to body weight diluted with isotonic saline to a volume of 0.3 mL per each injection site. Two placebo groups received the equivalent volume of isotonic saline. A control group was injected intramuscularly with 0.5 mL isotonic saline for injection pain comparison. Electroencephalographic changes, respiratory rate, heart rate and its variability, blood pressure, and nocifensive movements were assessed in superficial isoflurane anaesthesia. While EEG-changes and linear measures of heart rate variability did not appear conclusive, the low frequency/high frequency (LF/HF) ratio corresponded best with the other pain indicators recorded. The injection of 0.3 mL diluted local anaesthetic per injection site elicited significant fewer signs of pain compared to intramuscular injection of saline. However, pain reduction, but not complete pain elimination, during castration could only be achieved with 0.5 mL of the 2% local anaesthetics per injection site, whereby lidocaine and mepivacaine were the most effective.

Defining "Normal" in Pig Parturition

Simple Summary

The dual considerations of efficient food production and good animal welfare have never been so important nor under such strong public scrutiny as they are in current times. Intensive animal production industries play an important role in feeding an ever-growing, increasingly affluent population that is hungry for animal proteins. The efforts to improve efficiency in these production systems must not come at the cost of animal welfare. One pain point in pig production is that of parturition, where factors such as litter size and sow-housing type have been shown to influence the process and outcome. However, there are still many gaps in knowledge surrounding the normal physiology and endocrinology in a farrowing and this review seeks to summarise what is known and highlight areas where further work is required.

Abstract

Animal production industries rely on efficient and successful reproductive outcomes, with pigs being no exception. The process of parturition in pigs (farrowing) can be especially prolonged, due to the large numbers of piglets being born (on average, approximately 13 piglets per litter in Australian conditions). Difficulties in farrowing (dystocia) lead to poor piglet outcomes and health problems in sows, in turn, causing economic loss for producers and welfare concerns for the animals. Despite the importance of this topic and publications in the area stretching back nearly 50 years, there is still no consensus on the prevalence of dystocia in pigs nor on how to identify a pig experiencing the condition. Understanding the process of parturition and the factors that influence its success is a crucial step towards the early identification of sows undergoing dystocia and development of best practices to assist them. This article describes the key factors that contribute to successful farrowing and identifies areas in which more research is required before the parturition process in the pig can be fully understood.

Navigating regulatory pathways for translation of biologic cartilage repair products

Long-term clinical repair of articular cartilage remains elusive despite advances in cartilage tissue engineering. Only one cartilage repair therapy classified as a "cellular and gene therapy product" has obtained Food and Drug Administration (FDA) approval within the past decade although more than 200 large animal cartilage repair studies were published. Here, we identify the challenges impeding translation of strategies and technologies for cell-based cartilage repair, such as the disconnect between university funding and regulatory requirements. Understanding the barriers to translation and developing solutions to address them will be critical for advancing cell therapy products for cartilage repair to clinical use.

The Application of 3D Landmark-Based Geometric Morphometrics towards Refinement of the Piglet Grimace Scale

Proper methods of assessment to objectively identify pain are essential for welfare improvements of piglets undergoing surgical castration on commercial farms. The Piglet Grimace Scale (PGS) is used to identify changes in facial expressions caused by acute pain in piglets undergoing tail docking and castration. However, subjective scoring methods are a concern for the validation of the PGS. The objectives of this study were to evaluate and refine the PGS through 3D landmark geometric morphometrics. Male piglets (n = 88) were randomly allocated to one of two treatments: castration and sham-castration. Piglet facial images were taken at four time points (before treatment, immediately post-treatment, 1 h post-treatment, and 4 h post-treatment) using a photogrammetry rig. Images were scored by four raters using five facial action units (FAUs): orbital tightening, ear position, temporal tension, lip contraction, and nose bulge/cheek tension. Three-dimensional facial models were generated and landmarked denoting 3 FAUs (orbital tightening, lip contraction, and nose bulge/cheek tension). Results suggest that orbital tightening and ear position may be reliable FAUs for the PGS. However, neither the PGS nor 3D landmark-based geometric morphometrics were able (both p > 0.10) to reliably identify facial indicators of pain in piglets undergoing castration.

Recognizing Post-Castration Pain in Piglets: A Survey of Swine Industry Stakeholders and the General Public

We need validated, practical methods for pain assessment in piglets. Pain assessment can help researchers, veterinarians and industry professionals identify the need for analgesia or other pain management approaches when applying painful procedures, such as surgical castration. A pain assessment tool, the Piglet Grimace Scale (PGS), was previously validated in this context, but it is not widely applied. It is important that the PGS can be applied by a range of people, not just pain assessment experts. Our objective was to study the validity and reliability of PGS ratings applied by swine industry professionals and the general public, to assess its potential utility in non-research applications. To do so, we conducted an online Qualtrics survey in which, after completing a brief online training module and a practice test, 119 respondents were asked to rate 9 piglet images showing facial expressions immediately after surgical castration or sham-handling. Respondents were provided information on the castration treatment for each image and had continuous access to the scale throughout the survey. The survey also contained demographic questions. Industry respondents were recruited through networking, and participants from the general public were recruited through Amazon Mechanical Turk. Four trained experts scored each image, and these scores were averaged to produce gold standard scores. Intraclass correlations indicated strong internal consistency among experts, industry and public. ANOVA demonstrated scoring to be moderately comparable between groups. Campbell and Fiske’s Multi-Trait Multi-Method framework provided qualified support for the internal validity and reliability of the PGS scale, even applied by non-experts (industry and public). Both response groups were able to recognize pain in castrated piglets. However, public respondents attributed higher levels of pain to sham-handled piglets than industry respondents (2.83 vs. 2.35; p=0.047), and both response groups systematically overestimated pain experience compared to the experts, suggesting more training may be necessary before using the scale in a diagnostic capacity. Nevertheless, overall findings support wide applicability of PGS, even with minimal training, to improve awareness, recognition and monitoring of swine pain among veterinarians, industry professionals and even members of the public.

Pharmacokinetic/pharmacodynamic modeling of ketoprofen and flunixin at piglet castration and tail-docking

This study performed population‐pharmacokinetic/pharmacodynamic (pop‐PK/PD) modeling of ketoprofen and flunixin in piglets undergoing routine castration and tail‐docking, utilizing previously published data. Six‐day‐old male piglets (8/group) received either ketoprofen (3.0 mg/kg) or flunixin (2.2 mg/kg) intramuscularly. Two hours post‐dose, piglets were castrated and tail docked. Inhibitory indirect response models were developed utilizing plasma cortisol or interstitial fluid prostaglandin E2 (PGE2) concentration data. Plasma IC50 for ketoprofen utilizing PGE2 as a biomarker was 1.2 μg/ml, and ED50 for was 5.83 mg/kg. The ED50 calculated using cortisol was 4.36 mg/kg; however, the IC50 was high, at 2.56 μg/ml. A large degree of inter‐individual variability (124.08%) was also associated with the cortisol IC50 following ketoprofen administration. IC50 for flunixin utilizing cortisol as a biomarker was 0.06 μg/ml, and ED50 was 0.51 mg/kg. The results show that the currently marketed doses of ketoprofen (3.0 mg/kg) and flunixin (2.2 mg/kg) correspond to drug responses of 33.97% (ketoprofen‐PGE2), 40.75% (ketoprofen‐cortisol), and 81.05% (flunixin‐cortisol) of the maximal possible responses. Given this information, flunixin may be the best NSAID to use in mitigating castration and tail‐docking pain at the current label dose.

The Connection Between Stress and Immune Status in Pigs: A First Salivary Analytical Panel for Disease Differentiation

This paper analyzes the association between stress and immune response activations in different diseases, based on the salivary analytics. Moreover, a first attempt to discriminate between diseases was performed by principal component analysis. The salivary analytics consisted of the measurement of psychosocial stress (cortisol and salivary alpha-amylase) indicators, innate (acute phase proteins: C-reactive protein and haptoglobin), and adaptive immune (adenosine deaminase, Cu and Zn) markers and oxidative stress parameters (antioxidant capacity and oxidative status). A total of 107 commercial growing pigs in the field were divided into six groups according to the signs of disease after proper veterinary clinical examination, especially, healthy pigs, pigs with rectal prolapse, tail-biting lesions, diarrhea, lameness, or dyspnea. Associations between stress and immune markers were observed with different intensities. High associations (r = 0.61) were observed between oxidative stress markers and adaptive immune markers. On the other hand, moderate associations (r = 0.31–0.48) between psychosocial stress markers with both innate and adaptive immune markers were observed. All pathological conditions showed statistically significant differences in at least 4 out of the 11 salivary markers studied, with no individual marker dysregulated in all the diseases. Moreover, each disease condition showed differences in the degree of activation of the analyzed systems which could be used to create different salivary profiles. A total of two dimensions were selected through the principal component analysis to explain the 48.3% of the variance of our data. Lameness and rectal prolapse were the two pathological conditions most distant from the healthy condition followed by dyspnea. Tail-biting lesions and diarrhea were also far from the other diseases but near to healthy animals. There is still room for improvements, but these preliminary results displayed a great potential for disease detection and characterization using salivary biomarkers profiling in the near future.

Animal Welfare and the Acknowledgment of Cultural Differences

Pigs are considered sentient beings that have a mental capability that warrants attention to their welfare. Cultural values towards animal welfare differ in world regions. Still, authors have argued for worldwide harmonization of animal welfare rules. At the same time, the focus of many animal welfare rules do not address the most significant problems on modern commercial pig farms. The foci of animal welfare rules are often on space (quantity and quality), acute painful practices, equipment, and caretaker behavior. However, most serious animal welfare issues are related to episodic events such as compromised pigs, lack of appropriately skilled staff, and human behavior (or lack thereof) towards animals. Modern technologies such as image, sound, and building oversight by automated systems can potentially provide better individual pig care. The future should bring us solutions to identify and resolve episodic negative animal welfare events. The other issues of space and painful practices are best improved by using science-based solutions. We propose that science be the key resource to making animal welfare decisions, but with a healthy appreciation and respect for cultural differences in our views of animals and the economic impact of rules. Colonialism is not viewed positively today, and economic neo-colonialism should not be allowed to replace it. Respect for cultural differences should play a role in animal welfare rules within and among countries.

Linking Animal Welfare and Antibiotic Use in Pig Farming-A Review

Preventative measures, such as biosecurity and vaccinations, are essential but not sufficient to ensure high standards of health in pig production systems. Restrictive, barren housing and many widely used management practices that cause pain and stress predispose high-performance pigs reared in intensive systems to disease. In this context, antibiotics are used as part of the infrastructure that sustains health and high levels of production in pig farms. Antimicrobial resistance (AMR) is a global emergency affecting human and animal health, and the use of antibiotics (AMU) in intensive livestock farming is considered an important risk factor for the emergence and spread of resistant bacteria from animals to humans. Tackling the issue of AMR demands profound changes in AMU, e.g., reducing their use for prophylaxis and ending it for growth promotion. In support of such recommendations, we revise the link between animal welfare and AMU and argue that it is crucial to sustainably reduce AMU while ensuring that pigs can live happy lives. In support of such recommendations, we aimed to revise the link between animal welfare and AMU in pigs by analysing stress factors related to housing and management and their impact on pig welfare. In particular, we reviewed critical management practices that increase stress and, therefore, pigs' susceptibility to disease and reduce the quality of life of pigs. We also reviewed some alternatives that can be adopted in pig farms to improve animal welfare and that go beyond the reduction in stress. By minimising environmental and management stressors, pigs can become more immunocompetent and prepared to overcome pathogenic challenges. This outcome can contribute to reducing AMU and the risk of AMR while simultaneously improving the quality of life of pigs and, ultimately, maintaining the pig industry's social license.

Alteration in Activity Patterns of Cows as a Result of Pain Due to Health Conditions

Simple Summary

There are several conditions and diseases considered painful to cattle. One reason for the inconsistency in pain recognition and thus pain relief in cattle is the inadequate ability to identify and assess pain. In fact, both increased and/or reduced daily lying time can be indicative of pain in cattle. This review helps to properly interpret pain in cows through behavioural activity patterns and explores whether pain relief is capable to restore their normal activity.

Abstract

The main conditions and diseases considered painful in dairy cows are mastitis, lameness, calving (including dystocia and caesarean section) and metritis. The cattle literature reports that deviation from normal daily activity patterns (both increased and/or reduced daily lying time) can be indicative of painful conditions and diseases in cows. This narrative review discusses on how pain due to several health conditions in dairy cows modifies its activity pattern and explores if non-steroidal anti-inflammatory drugs (NSAIDs) are capable of restoring it. Divergent outcomes may differ depending upon the painful cause, the severity and the moment, and consequently its interpretation should be properly explained. For instance, cows with clinical mastitis reduced their time lying and increased the number of lying bouts and stepping due to pain caused by the swollen udder when cows are lying. However, lame cows show longer lying times, with a lower number of lying bouts and longer and more variable lying bouts duration, as compared to non-lame cows. When the relationship between painful disorders and daily activity patterns is studied, factors such as parity, bedding type and severity of disease are important factors to take into consideration. The potential benefits of the NSAIDs treatment in painful health disorders depend upon the type of drug administered, its dosage and administration mode, and the time of administration relative to the painful health disorder. This narrative review can be used as a tool to properly interpret and grade pain in cows through behavioural activity patterns and proposes directions for future investigations.

Evaluating Pain and Analgesia Effectiveness Following Routine Castration in Rabbits Using Behavior and Facial Expressions

Prevention of pain in rabbits is a priority for both welfare and validity of scientific data. We aimed to determine if the rabbit grimace scale (RbtGS) could be used as a viable, rapid assessment tool in two breeds of rabbit, Dutch belted (DB) and New Zealand white (NZW), following orchidectomy, as an adjunct to behavioral analysis. All animals received analgesia. Rabbits were filmed and their behavior was recorded at multiple time points pre- and post-orchidectomy. Observers then scored specific pain associated behaviors for analysis. Time matched footage was also scored using the rabbit grimace scale (RbtGS). Following surgery, rabbits showed significant increases in the duration spent displaying key pain associated behaviors at 1 and 5 h post-surgery. DB rabbits that received low dose meloxicam (0.2 mg/kg) showed significantly more pain behaviors at 1 and 5 h post-surgery compared to those administered a combination of higher dose meloxicam (0.6 mg/kg) and a lidocaine/bupivacaine local infusion. DB rabbits showed an increase in RbtGS score at both 1 and 5 h post-surgery. In the NZW rabbits, an increase in RbtGS score was only observed at 1 h post-surgery. Using behavioral analysis as the gold standard for comparison, the RbtGS was an effective means of determining when rabbits are painful following orchidectomy. Higher dose meloxicam (0.6 mg/kg) combined with local anesthetic was a more effective method of reducing pain, compared to lower dose meloxicam (0.2 mg/kg) alone.

Proposed multidimensional pain outcome methodology to demonstrate analgesic drug efficacy and facilitate future drug approval for piglet castration

Castration of male piglets in the United States is conducted without analgesics because no Food and Drug Administration (FDA) approved products are labeled for pain control in swine. The absence of approved products is primarily due to a wide variation in how pain is measured in suckling piglets and the lack of validated pain-specific outcomes individually indistinct from other biological responses, such as general stress or inflammation responses with cortisol. Simply put, to measure pain mitigation, measurement of pain must be specific, quantifiable, and defined. Therefore, given the need for mitigating castration pain, a consortium of researchers, veterinarians, industry, and regulatory agencies was formed to identify potential animal-based outcomes and develop a methodology, based on the known scientific research, to measure pain and the efficacy of mitigation strategies. The outcome-based measures included physiological, neuroendocrine, behavioral, and production parameters. Ultimately, this consortium aims to provide a validated multimodal methodology to demonstrate analgesic drug efficacy for piglet castration.Measurable outcomes were selected based on published studies suggesting their validity, reliability, and sensitivity for the direct or indirect measurement of pain associated with surgical castration in piglets. Outcomes to be considered are observation of pain behaviors (i.e. ethogram defined behaviors and piglet grimace scale), gait parameters measured with a pressure mat, infrared thermography of skin temperature of the cranium and periphery of the eye, and blood biomarkers. Other measures include body weight and mortality rate.This standardized measurement of the outcome variable's primary goal is to facilitate consistency and rigor by developing a research methodology utilizing endpoints that are well-defined and reliably measure pain in piglets. The resulting methodology will facilitate and guide the evaluation of the effectiveness of comprehensive analgesic interventions for 3- to 5-day-old piglets following surgical castration.

Comparison of two injectable anaesthetic techniques on induction and subsequent anaesthesia in pigs

Pig experiments often require anaesthesia, and a rapid stress-free induction is desired. Induction drugs may alter the subsequent anaesthesia. Therefore, the aim of the present study was to compare, in pigs, the effects of two different injectable anaesthetic techniques on the induction and on the physiological variables in a subsequent eight hours of total intravenous anaesthesia (TIVA). Twelve domestic castrates (Swedish Landrace/Yorkshire) 27‒31 kg were used. The pigs were randomly assigned to different induction drug combinations of zolazepam-tiletamine and medetomidine intramuscularly (ZTMe) or midazolam, ketamine intramuscularly and fentanyl intravenously (MiKF). Time from injection to unconsciousness was recorded and the ease of endotracheal intubation assessed. The TIVA infusion rate was adjusted according to the response exhibited from the nociceptive stimulus delivered by mechanically clamping the dewclaw. The time from injection to unconsciousness was briefer and intubation was easier in the ZTMe group. Results from the recorded heart rate, cardiac index and arterial blood pressure variables were satisfactorily preserved and cardiovascular function was maintained in both groups. Shivering was not observed in the ZTMe group, but was observed in four of the pigs in the MiKF group. The requirement of TIVA was lower in the ZTMe group. In conclusion, ZTMe had better results than MiKF in areas such as shorter induction time, better intubation scoring results and less adjustment and amount of TIVA required up to six hours of anaesthesia. The results may have been due to a greater depth of anaesthesia achieved with the ZTMe combination at the dose used.

Technical contribution: use of continuous recording video monitoring of maintenance and pain behaviors in piglets after surgical castration to validate six continuous time sampling periods for behavior scoring

Castration is a painful procedure routinely performed on piglets. Specific periods relative to castration and time sampling rules are used widely to quantify deviations in piglet's behavior associated with castration rather than assessing behavior for the entire trial period. However, very limited work has evaluated time sampling recording rules to quantify behavioral changes to piglets undergoing castration. Therefore, the objective of this study was to validate the accuracy of six continuous time sampling periods (5, 10, 15, 20, 30, and 45 min), to quantify piglet behavior post-castration when compared with a full 60-min observation period. Sixteen Yorkshire-Landrace x Duroc piglets were surgically castrated. Data were collected using continuous observation (recording rule) of each individual male piglet per litter for 60-min post-castration. The 60-min continuous behavioral data set was then subdivided into six data subsets for each defined continuous time sampling period (5, 10, 15, 20, 30, and 45 min). Data from each continuous time sampling period and the full period data were analyzed using both a generalized linear mixed model and linear regression analysis. For the generalized linear mixed model, 30- and 45-min continuous time sampling periods were not different (P > 0.05) when compared with the full observation period data for all behaviors. For the linear regression analysis, affiliative interaction, sitting, walking, huddled up, prostrated, scratching, spasms, and trembling behaviors met the pairwise comparison accuracy criteria: [1) the coefficient of determination (R2) was > 0.90, 2) the intercept did not differ from 0 (P > 0.05), and 3) the slope did not differ from 1 (P > 0.05)] at the 45-min continuous time sampling period compared to full observation period. Results from this study suggest that a 45-min continuous time sampling period would be necessary to accurately investigate piglet behavior during the acute pain sensitivity time post-castration when considering both maintenance and pain-associated behaviors.

A systematic review of porcine models in translational pain research

Translating basic pain research from rodents to humans has proven to be a challenging task. Efforts have been made to develop preclinical large animal models of pain, such as the pig. However, no consistent overview and comparison of pig models of pain are currently available. Therefore, in this review, our primary aim was to identify the available pig models in pain research and compare these models in terms of intensity and duration. First, we systematically searched Proquest, Scopus and Web of Science and compared the duration for which the pigs were significantly sensitized as well as the intensity of mechanical sensitization. We searched models within the specific field of pain and adjacent fields in which pain induction or assessment is relevant, such as pig production. Second, we compared assessment methodologies in surrogate pain models in humans and pigs to identify areas of overlap and possible improvement. Based on the literature search, 23 types of porcine pain models were identified; 13 of which could be compared quantitatively. The induced sensitization lasted from hours to months and intensities ranged from insignificant to the maximum attainable. We also found a near to complete overlap of assessment methodologies between human and pig models within the area of peripheral neurophysiology, which allows for direct comparison of results obtained in the two species. In spite of this overlap, further development of pain assessment methodologies is still needed. We suggest that central nervous system electrophysiology, such as electroencephalography, electrocorticography or intracortical recordings, may pave the way for future objective pain assessment.

Parturition in Mammals: Animal Models, Pain and Distress

Parturition is a complex physiological process and involves many hormonal, morphological, physiological, and behavioural changes. Labour is a crucial moment for numerous species and is usually the most painful experience in females. Contrary to the extensive research in humans, there are limited pain studies associated with the birth process in domestic animals. Nonetheless, awareness of parturition has increased among the public, owners, and the scientific community during recent years. Dystocia is a significant factor that increases the level of parturition pain. It is considered less common in polytocous species because newborns' number and small size might lead to the belief that the parturition process is less painful than in monotocous animal species and humans. This review aims to provide elements of the current knowledge about human labour pain (monotocous species), the relevant contribution of the rat model to human labour pain, and the current clinical and experimental knowledge of parturition pain mechanisms in domestic animals that support the fact that domestic polytocous species also experience pain. Moreover, both for women and domestic animal species, parturition's pain represents a potential welfare concern, and information on pain indicators and the appropriate analgesic therapy are discussed.

Efficacy of Intra-Operative Topical Wound Anaesthesia to Mitigate Piglet Castration Pain-A Large, Multi-Centred Field Trial

Simple Summary

Piglet castration causes pain and stress to the animal. Although desperately needed, there are complexities developing safe and effective methods of pain alleviation applicable for on-farm use. Topical anaesthesia, instilled to the wound during surgery, is a newly evolving on-farm method to mitigate castration pain. In the current study, we investigated the use of Tri-Solfen^® (Animal Ethics Pty Ltd, Melbourne, Australia), a topical local anaesthetic and antiseptic formulation, instilled to the wound during the procedure, to alleviate subsequent castration-related pain experienced in piglets. We performed a large, blind, multi-centred trial comparing pain in piglets castrated with or without Tri-Solfen^®. Piglets treated with wound instillation of Tri-Solfen^®, 30 s prior to subsequent castration, showed significantly lower pain-induced motor and vocal responses during the procedure. Acute post-operative pain-related behaviours, evident in piglets in the first 30 min following castration, were also significantly reduced in treated piglets compared with untreated piglets. Using this method, Tri-Solfen^® provides an effective on-farm method to mitigate acute castration-related pain in young piglets.

Abstract

Piglet castration results in acute pain and stress to the animal. There is a critical need for effective on-farm methods of pain mitigation. Local anaesthesia using Tri-Solfen^® (Animal Ethics Pty Ltd., Melbourne, Australia), a topical local anaesthetic and antiseptic formulation instilled to the wound during surgery, is a newly evolving on-farm method to mitigate castration pain. To investigate the efficacy of Tri-Solfen^®, instilled to the wound during the procedure, to alleviate subsequent castration-related pain in neonatal piglets, we performed a large, negatively controlled, randomised field trial in two commercial pig farms in Europe. Piglets (173) were enrolled and randomised to undergo castration with or without Tri-Solfen^®, instilled to the wound immediately following skin incision. A 30 s wait period was then observed prior to completing castration. Efficacy was investigated by measuring pain-induced motor and vocal responses during the subsequent procedure and post-operative pain-related behaviour in treated versus untreated piglets. There was a significant reduction in nociceptive motor and vocal response during castration and in the post-operative pain-related behaviour response in Tri-Solfen^®-treated compared to untreated piglets, in the first 30 min following castration. Although not addressing pain of skin incision, Tri-Solfen^® is effective to mitigate subsequent acute castration-related pain in piglets under commercial production conditions.

Comparison of 12 Different Animal Welfare Labeling Schemes in the Pig Sector

Simple Summary

Welfare requirements from an animal point of view are the same regardless of the country. However, differing requirements of animal welfare schemes make it hard for consumers to make informed choices. Therefore, an open and coherent labeling scheme that provides information on farm animal welfare will be beneficial from the consumer perspective. We reviewed 12 pig welfare schemes. We aimed to identify consistencies and differences in welfare requirements between these schemes. The studied welfare requirements were heterogeneous in the potential each scheme had to advance pig welfare. Certain requirements barely exceeded the minimum standards for the protection of pigs in European Union (EU) legislation, but the more demanding tiers of multitier schemes had the potential to enhance animal welfare. The most ambitious tiers could improve animal welfare substantially and, in terms of resources available to the animal, they often were convergent with organic animal farming standards. Because of variation of welfare requirements between the labels, it was challenging to compare existing labeling schemes. Adopting a harmonized labeling terminology and standard, increased use of animal-based measures, and open communication will make labeling more reliable and transparent, which will contribute to the availability of standardized animal-friendly products and will be equitable from an animal welfare perspective.

Abstract

Animal welfare labeling schemes have been developed to respond to consumers’ expectations regarding farm animal welfare. They are designed to certify that labeled products comply with certain animal welfare standards. In this study, 12 pig welfare labeling schemes were reviewed, and their criteria related to pig welfare were compared. Information regarding farrowing criteria, space allowance, outdoor access, mutilations, and provision of enrichments and bedding material were gathered from the labels’ internet pages and documentation. The results indicated a substantial variation between the labels in terms of the level of animal welfare they ensure. While certain schemes barely exceeded the minimum standards for the protection of pigs in the European Union, more demanding tiers of the multitier schemes had the potential to improve animal welfare substantially. The most ambitious tiers of multistage schemes were often comparable to organic standards providing outdoor facilities and additional space. The heterogeneity of the labels’ standards complicates the comparison of labels.

Circulating miRNome of Trachemys scripta after elective gonadectomy under general anesthesia

Post-surgical management is an important issue in veterinary medicine, requiring biomarkers with high sensitivity and specificity for timely and effective treatment. Emerging evidence suggests that miRNAs are promising stress- and pain-related markers. The aims were to profile the circulating miRNA signature in plasma of turtles (Trachemysscripta) and point out potential candidate biomarkers to assess the status of the animal. The plasma of female turtles underwent surgical gonadectomy were collected 24 h pre-surgery, and 2.5 h and 36 h post-surgery. The expression of miRNAs was profiled by Next Generation Sequencing and the dysregulated miRNAs were validated using RT-qPCR. The diagnostic value of miRNAs was calculated by ROC curves. The results showed that 14 miRNAs were differentially expressed over time. RT-qPCR validation highlighted that 2-miR-499-3p and miR-203-5p-out of 8 miRNAs tested were effectively modulated. The Area Under the Curve (AUC) of miR-203-5p was fair (AUC 0.7934) in discriminating pre- and 36 h post-surgery samples and poor for other time points; the AUC of miR-499-3p was excellent (AUC 0.944) in discriminating pre-surgery and 2.5 h post-surgery samples, and fair in discriminating pre-surgery and 36 h post-surgery (AUC 0.7292) and 2.5 h and 36 h post-surgery (AUC 0.7569) samples. In conclusion, we demonstrated for the first time that miRNAs profile changes in plasma of turtles underwent surgical oophorectomy and identified miR-203-5p and miR-499-3p as potential candidate biomarkers to assess animals' status. Further studies are necessary to confirm their diagnostic value and to investigate functional and mechanistic networks to improve our understanding of the biological processes.

The in-utero experience of piglets born from sows with lameness shapes their life trajectory

Experiences during gestation can alter the mother's behavior and physiology, thereby potentially affecting the behavioral and physiological development of the offspring. In livestock, one common challenge for pregnant animals is lameness: a multifactorial condition that causes pain, stress, resulting in poor welfare outcomes. Since maternal pain can affect offspring development, we aimed to quantify the behavioral response in 142 piglets born from sows with different degrees of lameness during pregnancy. Gait scores of 22 pregnant group-housed sows were assessed six times at 2-week intervals. Lameness scores varied from 0 (no lameness) to 5 (most severe lameness score). Saliva samples and behavior were assessed in the sows throughout pregnancy. Sows were moved to individual farrowing pens and placental tissue was collected for glucocorticoid assessment. At 28 days of age, piglets were weaned, weighed, and regrouped by body size and sex. Skin lesions were counted for each piglet on days 28, 29, and 30 after birth. During open field and novel object tests on day 30, the vocalization and activity levels were evaluated. Piglet data were grouped by the lameness score of the sows as G1 (without lameness), G2 (moderate lameness), and G3 (severe lameness). Data analysis included ANOVA or Kruskal-Wallis tests and pairwise comparisons which were performed using Tukey and Kramer (Nemenyi) test with Tukey-Dist approximation for independent samples. G2 piglets were heavier than G3 at weaning. G1 piglets had fewer skin lesions at days 28 and 29 than G2 piglets. Moreover, G1 piglets vocalized more than G2 when they were subjected to the combined open field and novel object test. We did not identify differences among sows showing different lameness scores in the concentration of placental or salivary glucocorticoids. Lameness in pregnant sows altered the offspring's weight gain, number of skin lesions and vocalizations, together showing evidence that lameness in sows affect offspring performance and behavior.

Minimizing complications in a porcine survival craniotomy model

A large craniotomy survival porcine model is useful for scientific research. The surgical approaches and complications of craniotomies in pigs have not been published before. This study describes how large craniotomies were performed in 46 pigs and how the risk of complications was minimized. The major complications were direct postoperative epidural hematomas (n = 3) and sagittal sinus rupture (n = 4). The measures taken to prevent postoperative epidural hematomas consisted of optimizing anesthesia, using bone wax to stop trabecular bleeding, increasing blood pressure before bone flap replacement, tranexamic acid administration, and postoperative recovery of the pigs in the prone position in a dedicated hammock. After these measures, no pig died from a postoperative epidural hematoma. Iatrogenic sagittal sinus rupture occurred in cases where the dura shifted into the craniotome during craniotomy. The dura was detached from the skull through drill holes with custom elevators before craniotomy to minimize the risk of a sagittal sinus rupture. In conclusion, pigs can undergo craniotomy and survive if the right measures are put in place.

The Welfare of Cattle, Sheep, Goats and Pigs from the Perspective of Traumatic Injuries Detected at Slaughterhouse Postmortem Inspection

Simple Summary

The occurrence of traumatic injuries was assessed in cattle, sheep, goats and pigs reared and slaughtered in the Czech Republic. For the purposes of the study, the results of veterinary postmortem examinations at slaughterhouses in the period from 2010 to 2019 were analyzed. In the studied animal species, findings of traumatic lesions were detected at low frequency. The low frequency of traumatic lesions is favorable from the perspective of the welfare of slaughtered animals. In terms of further improvements to animal welfare, it would be desirable to focus on the prevention of trauma in cattle in particular, in which findings of trauma were more frequent than in the other species studied. The category most affected by trauma both to the limbs and body was cows.

Abstract

The welfare of cattle, pigs, sheep and goats was assessed by measuring trauma detected during veterinary postmortem inspection at slaughterhouses. The subject of this evaluation were all bovine, porcine, ovine and caprine animals slaughtered at Czech slaughterhouses in the monitored period, i.e., a total of 1,136,754 cows, 257,912 heifers, 1,015,541 bulls, 104,459 calves, 586,245 sows, 25,027,303 finisher pigs, 123,191 piglets, 22,815 ewes, 114,264 lambs, 1348 does and 5778 kids. The data on the numbers of traumatic findings were obtained retrospectively from a national veterinary database collecting data from slaughterhouse postmortem examinations. The results showed that findings of trauma were observed at a low frequency in the studied species. Injuries were detected most frequently in cows (1.71%). In contrast, no findings associated with the presence of trauma were recorded in does and kids. From the viewpoint of trauma localization, findings on the limbs were more frequent than findings on the body (p < 0.01). The only exceptions to this were lambs, does and kids, for which there was no statistically significant difference between findings on the limbs and the body (p = 1.00). The results show that housing system (bedding, the presence of slats, floor hardness), transport of animals to the slaughterhouse (moving animals to the vehicle, loading ramps, floors in transport vehicles and the transport of animals itself) and design of the slaughterhouse (unloading ramps, passageways and slaughterhouse floors) have a greater impact on the limbs than the bodies of animals in the majority of species. A difference was also demonstrated in the occurrence of findings of trauma in the limbs and body (p < 0.01) between culled adult animals and fattened animals, namely in cattle and pigs. A difference (p < 0.01) between ewes and lambs was found only in the occurrence of traumatic injury to the limbs. The results showed that fattened animals are affected by the risk of trauma to a lesser extent than both culled adult animals and young animals. Statistically significant differences (p < 0.01) were also found between the studied species and categories of animals. The category most affected from the viewpoint of injury both to the limbs and body was cows. In contrast to cows that are typically reared indoors, the low frequency of traumatic findings was found in small ruminants and in bulls, i.e., animals typically reared outdoors. Assumedly, access to pasture may be beneficial considering the risk of traumatic injury.

Recovery from discrete wound severities in side-blotched lizards (Uta stansburiana): implications for energy budget, locomotor performance, and oxidative stress

Wounding events (predation attempts, competitive combat) result in injuries and/or infections that induce integrated immune responses for the recovery process. Despite the survival benefits of immunity in this context, the costs incurred may require investment to be diverted from traits contributing to immediate and/or future survival, such as locomotor performance and oxidative status. Yet, whether trait constraints manifest likely depends on wound severity and the implications for energy budget. For this study, food intake, body mass, sprint speed, and oxidative indices (reactive oxygen metabolites, antioxidant capacity) were monitored in male side-blotched lizards (Uta stansburiana) healing from cutaneous wounds of discrete sizes (control, small, large). Results indicate that larger wounds induced faster healing, reduced food consumption, and led to greater oxidative stress over time. Granted wounding did not differentially affect body mass or sprint speed overall, small-wounded lizards with greater wound area healed had faster sprint speeds while large-wounded lizards with greater wound area healed had slower sprint speeds. During recovery from either wound severity, however, healing and sprint performance did not correspond with food consumption, body mass loss, nor oxidative status. These findings provide support that energy budget, locomotor performance, and oxidative status of a reptile are linked to wound recovery to an extent, albeit dependent on wound severity.

Walking on Tiptoes: Digital Pads Deserve Increased Attention When Scoring Footpad Dermatitis as an Animal Welfare Indicator in Turkeys

Animal welfare is one of the most challenging issues in modern farm animal husbandry. Animal welfare indicators can be used to monitor welfare on farms or at slaughterhouses, with footpad dermatitis (FPD) being one of the most important indicators used in turkeys. Up to now, the severity of FPD has been measured by evaluating the size of altered lesions on the metatarsal pad of birds. However, such lesions are not only found on the metatarsal pads, but alterations can also occur on the digital pads of the animals, the latter is not included in the European standard scoring systems for turkeys so far. The aim of the present study was to give a detailed outline of alterations on the digital pads of turkeys and associate their occurrence to a standardly used five-point scoring system, which is based on alterations of the metatarsal pad only. Therefore, pictures of 500 feet of turkeys from 16 flocks at the end of the fattening phase were taken, using an automatic camera system. Based on these pictures, alterations on the digits were scored according to different parameters (lesions, swellings, and number of affected digits). Furthermore, detailed measurements were conducted using an imaging software. Results were compared with a standardly used five-point scoring system (standard FPD scoring system), based on the metatarsal pad as reference. Results provide no equivalence in occurrence and severity of alterations on the metatarsal pads compared to those found on the digits. Pathologic alterations on the digits were already present at standard FPD scoring level 0; no differentiation became obvious between the higher scoring levels 2-4. Strong correlations were found when comparing percentage of alterations of the standard FPD scoring system to those of a system including alterations on the digits and the metatarsal pad, using the total foot as a reference (rp = 0.9, p < 0.001). This was the first study conducting a detailed analysis of alterations on the digits of turkeys. In conclusion, results of this study show that including the evaluation of alterations on digits could refine the present FPD scoring system, especially when using FPD as an animal welfare indicator.

Effect of two methods and two anaesthetics for local anaesthesia of piglets during castration

Background

Since January 2019, surgical castration of male piglets must be performed using local anaesthesia, if farmers deliver pigs to the primary exporting slaughterhouses according to the “Danish quality scheme”; a voluntary initiative taken by the Danish pig industry. The approved procedure for local anaesthesia in Denmark is a three-step injection method with procaine. A comparison of lidocaine and procaine with the same concentration and injection methods of local anaesthetics has not previously been studied. The purpose of this study was to investigate the effect of two injection methods and two local anaesthetics on piglets’ avoidance behaviour (vocalisation and resistance movements) as well as the time spent on the procedures. The study included 203 male piglets that were randomly assigned to one of five treatments: 1. Control: Sham-handling without injection of local anaesthesia, 2. Pro3: Procaine injection using a three-step method, 3. Pro2: Procaine injection using a two-step method, 4. Lid3: Lidocaine injection using a three-step method, 5. Lid2: Lidocaine injection using a two-step method. During injection of local anaesthesia and castration, vocalisation was measured using a decibel meter and resistance movements were registrated by video recordings.

Results

During castration, piglets treated with local anaesthesia showed significantly reduced vocalisation and resistance movements and time spent on castration was also significantly reduced compared to the control group. During injection of the local anaesthesia, the piglets had significantly increased vocalisation and resistance movements compared to the control group. Piglets injected with lidocaine had a significantly reduced resistance movement score and a tendency to reduced vocalisation compared to piglets injected with procaine. No differences in avoidance behaviour were found between the injection methods.

Conclusions

The use of local anaesthesia, irrespective of the method and local anaesthetic, was effective in reducing vocalisation and resistance movements during surgery as well as the time spent on castration.

Grimace Scores: Tools to Support the Identification of Pain in Mammals Used in Research

The 3Rs, Replacement, Reduction and Refinement, is a framework to ensure the ethical and justified use of animals in research. The implementation of refinements is required to alleviate and minimise the pain and suffering of animals in research. Public acceptability of animal use in research is contingent on satisfying ethical and legal obligations to provide pain relief along with humane endpoints. To fulfil this obligation, staff, researchers, veterinarians, and technicians must rapidly, accurately, efficiently and consistently identify, assess and act on signs of pain. This ability is paramount to uphold animal welfare, prevent undue suffering and mitigate possible negative impacts on research. Identification of pain may be based on indicators such as physiological, behavioural, or physical ones. Each has been used to develop different pain scoring systems with potential benefits and limitations in identifying and assessing pain. Grimace scores are a promising adjunctive behavioural technique in some mammalian species to identify and assess pain in research animals. The use of this method can be beneficial to animal welfare and research outcomes by identifying animals that may require alleviation of pain or humane intervention. This paper highlights the benefits, caveats, and potential applications of grimace scales.