Laboratory Animals

This narrative review summarizes and synthesizes the current literature regarding the comparative anatomy of pigs and humans, focusing on organ systems commonly involved in abdominal transplantation with the aim of supporting the safe and effective use of porcine models in preclinical studies. It also integrates practical insights from experimental surgery to highlight key considerations in perioperative care and surgical technique in porcine models. Pigs demonstrate substantial anatomical and physiological similarities to humans, making them ideal large-animal models for transplantation research. The recent surge in reports concerning clinical porcine xenotransplantation underscores the increasing importance of comprehending this comparative anatomy in the forthcoming years. However, critical species-specific anatomical differences particularly involving the gastrointestinal tract, hepatobiliary system, genitourinary tract and vascular structures require careful understanding to avoid surgical complications. Proper handling, perioperative care and awareness of porcine-specific stress responses and arrhythmias susceptibility are also essential to prevent premature animal loss. A thorough understanding therefore of porcine comparative anatomy is essential for transplant researchers conducting large animal surgery. Such knowledge improves experimental outcomes, supports adherence to the 3Rs (Replacement, Reduction and Refinement) and enhances the translational value of porcine models in transplantation research.

Better animal welfare is essential for better animal-based science. Poor welfare induces stress (and vice versa), which in turn can affect or even severely confound research results. To ensure the validity of scientific results, those who work with laboratory animals must take responsibility for their care and welfare. A harm–benefit analysis can be used to weigh the welfare and quality of life of animals in scientific studies against the resulting benefits to other animals or humans, provided that animal welfare can be validly assessed. This review considers the identification and characterisation of stress by physiological, hormonal, immunological and behavioural measures and by assessment of the physical condition of the animal. It addresses controllability, predictability, chronicity, duration and severity, and the intrinsic and extrinsic factors that modulate animal behaviour and coping mechanisms in response to stress. EU Directive 2010/63 requires procedures to be classified as mild, moderate or severe. However, as long as some researchers use purely subjective assessments without a supporting structure and reference scales, or no assessment method at all, these terms may have limited practical value. The challenge is to understand the state of the animal from the information available. Welfare assessment tools can be used to demonstrate the true impact of research procedures and their refinement to protect animal welfare. If any doubt exists about the harm–benefit evaluation of the experiment then the welfare of the animal should take priority.

Transcranial direct current stimulation (tDCS) for painless, non-invasive brain stimulation is a promising approach to enhance recovery after stroke. However, the precise molecular and cellular mechanisms underlying the effects of tDCS remain unclear, impeding its use in humans and necessitating research in experimental animals. Unlike humans, who receive tDCS fully awake, experimental models of tDCS have so far been conducted under anaesthesia to ensure the immobility required by currently available experimental setups. The use of anaesthesia may, however, confound results, decreasing their translational value. To address this problem, we developed a refined method enabling tDCS in awake and freely moving mice. A tube attached to the skull contains the stimulation electrode, whose position can be adapted flexibly to the target brain region; the reference electrode is implanted subcutaneously at the contralateral chest. Here, we report n = 135 awake mice that underwent tDCS in their home cage for up to 15 minutes per session over 10 consecutive days. None of those animals showed any adverse effects, neither regarding their general wellbeing, body weight, and behavioural activity, nor in ex vivo histology and immunohistochemistry. We suggest using this refined approach in future experimental studies of neuropsychological disorders.

Light is presumed to be highly aversive to laboratory rodents. It can change their physiological responses and activity. Much behavioral experimentation is conducted under dim light, though even dim light may alter the behavior of animals. Some research facilities use a reversed light regimen and provide darkness during routine and experimental procedures. However, there are no unified guidelines of light intensity during behavioral testing, and “dim light” is being understood very broadly. It can be suggested that testing in darkness can be ethologically relevant for mice, rats, and other rodents who are known for nocturnality in laboratory conditions. We hypothesized that laboratory mice would be more active when being tested in a dark room than in an illuminated one regardless of the circadian phase. To test our hypotheses we conducted an experiment to evaluate male outbred mice behavior in four standard tests widely used in preclinical studies: the open field test, the hole-board test, the tail suspension test, and the elevated plus maze test. Locomotion in the open field test increased in darkness. The hole-board test revealed significantly reduced exploratory activity when performed in a dark room. In the elevated plus maze, mice tested in darkness behave less anxiously than those tested in light. Illumination did not affect mobility of mice in the tail suspension test. We suppose that darkness reduces anxiety and, hence, induces locomotion and exploration in mice in tests that are provided to study these traits. The tail suspension test is aversive itself, so it may mask any environmental effects.

Anastomotic leakage following intestinal surgery in a murine Roux-en-Y gastric bypass (RYGB) model is usually fatal. Carprofen, a commonly used non-steroidal anti-inflammatory drug (NSAID) for postoperative analgesia in rodents, has been linked to negative effects on intestinal wound healing. The postoperative use of the non-opioid analgesic metamizole in this setting is rare. Here, we compared the potential effects of carprofen and metamizole on intestinal anastomotic healing in a murine RYGB model in order to optimize perioperative care in this animal model. A total of 38 mice underwent RYGB surgery as part of an in-house surgical training programme and received either carprofen (n = 17) or metamizole (n = 21) postoperatively. Within three postoperative days, anastomotic leakage occurred in 82% of carprofen-treated mice (14 of 17), mainly at the lower jejunal anastomosis (n = 12). The incidence of anastomotic leakage in the metamizole group was remarkably lower, occurring in four of 21 mice (19%) during the same period with three cases at the lower and one at the upper anastomosis. This is the first study demonstrating the detrimental effect of carprofen on jejunal anastomotic healing in a murine RYGB model. These findings underscore the critical importance of selecting appropriate analgesics for intestinal anastomosis surgery.

Antimicrobial resistance (AMR) is a major global threat to human health, animal welfare and sustainable development. Whilst resistance can arise naturally, inappropriate antimicrobial exposure accelerates its emergence. Recognizing this risk, international One Health initiatives emphasize reducing antimicrobial use, especially of drugs considered critical for human medicine. Much of the evidence guiding these efforts comes from food-producing and companion animals, but antimicrobial use in laboratory animals, particularly rodents, remains poorly described. To address this gap, we surveyed all veterinarians certified by the American College of Laboratory Animal Medicine in the United States (921) and Canada (10). A total of 157 veterinarians completed the survey, resulting in a 16.9% overall response rate. The response rate was 16.6% for participants in the United States and 40.0% for those in Canada. Despite a strong response, the small number of eligible veterinarians restricts data extrapolation in the Canadian context. Survey results showed that antimicrobial use is common and routine in rodent vivaria. Overall, 91.7% of respondents reported regular antimicrobial use. Applications included both clinical treatment and research purposes such as induction of microbiome dysbiosis, prophylaxis in immunocompromised rodents and gene induction. Reported drug classes included fluoroquinolones and third-generation cephalosporins, with some use of glycopeptides and carbapenems, all considered critically important to human health. Disposal practices often involved release into sewerage or landfill without inactivation, raising environmental concerns. These findings suggest that antimicrobial use in laboratory rodents may represent an underrecognized contributor to AMR and highlight the importance of targeted stewardship.

Researchers need training to develop adequate competence before using animals in experimental procedures. In contrast to medical training, there has been almost no scholarly attention to questions of methodology for teaching practical skills with laboratory animals. In this paper, we explore how the experience of laboratory animal trainers can be combined with existing scholarship on learning and teaching practical skills in related fields. Data were collected through facilitated group discussions in a series of workshops involving a total of 72 participants from 18 countries. Participants identified the ‘See one, Do one’ method as their preferred teaching approach in practical classes, and recognised the importance of strategies for progressive and adapted learning. They also acknowledged different types of challenging situations, including trainees who have previously developed proficiency with incorrect techniques, trainees who appear uninterested, trainees expressing aversion to animals and trainees who are reluctant to subject animals to harmful procedures. Although participants presented strategies for overcoming the majority of these challenges, they also highlighted specific scenarios where they felt unable to provide adequate support or overcome the challenges within the training environment. This work represents a first systematic scholarly effort to capture and describe teaching strategies used by practical laboratory animal science trainers, an essential step for education and competency development research and practice in the field.

We evaluated the convergence between the facial vein and the submental/labialis-inferior as an alternative site to the facial vein in the submental region for blood collection in mice. Three groups of CD1 female mice (n = 10 mice/group) were used for three blood collection occasions from the convergence site. A fourth blood collection was performed from the convergence site for one group and the facial vein for the other two. Total blood removed, collection success rate, and clinical signs were evaluated. Total blood removed, and collection success rate was stable across collection occasions at the convergence site. When compared with the facial vein, the convergence site showed milder tissue damage, a higher collection success rate and a larger amount of total blood removed. Results indicate that the convergence site is more effective than the facial vein site for bleeding mice, but has an increased risk of overcollection, thus is recommended for a target volume of less than 10% of circulating blood volume.

No systematic procedures exist to ensure that differences in animal sensory capacities are accounted for in experimental design and ethical review processes. This oversight can compromise both scientific validity and animal welfare. This review presents three practical methodologies to address this gap: incorporation of specialist expertise through consultation frameworks, voluntary certification schemes modeled on Open Science practices, and mandatory sensory capacity review integrated into existing ethics committee processes. We provide a concrete tool—a sensory modality survey—that can be implemented by institutional review committees to evaluate sensory considerations in research proposals systematically. These approaches align with the 3Rs principles by enhancing experimental refinement and potentially reducing animal use through improved study design.