The breeding and maintenance of genetically modified laboratory animal lines with a harmful phenotype (hereafter referred to as "genetically burdened lines")-that is, lines in which pain, suffering, distress, or lasting harm may arise as an inherent consequence of the genotype-pose specific ethical and regulatory challenges for animal facilities and researchers. Within the European Union, these challenges are framed by Directive 2010/63/EU, which subjects genetically modified animals with harmful phenotypes and related breeding activities to project authorization and prospective severity assessment. Institutions responsible for such lines face recurrent practical questions: When does breeding constitute a regulated "procedure" requiring prior authorization? How should killing, tissue collection, and reuse be documented in local records and annual reports? In accordance with EU terminology, "continued use" refers to a single use consisting of multiple steps, whereas "reuse" describes the use of an animal in a new procedure after a previous one has been completed. And how should documentation differ between burdened and non-burdened phenotypes arising within the same colony? Here, we present decision trees that provide a structured and reproducible framework to support consistent decision-making for genetically burdened lines. The trees are illustrated using the German implementation of Directive 2010/63/EU (the German Animal Welfare Act, GAWA, and the German Laboratory Animal Welfare Ordinance, GLAWO) as a working example; however, the underlying decision logic is jurisdiction-neutral and could be adapted to other European and international regulatory systems by mapping national terminology to equivalent categories.

Spiny mice (Acomys spp.) are increasingly used in biomedical research owing to their unique physiological properties and ability to regenerate tissues, yet standardized laboratory housing conditions are largely based on mouse or rat models and may not adequately meet their species-specific needs. Here, we describe a practical protocol for the housing of spiny mice in large individually ventilated cages, including cage setup, diet, environmental enrichment, breeding, and health monitoring. We also provide recommendations for standard procedures used in animal research, such as identification methods, anesthesia, analgesia, and euthanasia. Last, we expand on the best laboratory practices in the context of common surgical procedures used in the field of regenerative biology, such as dorsal skin wounds and ear punch injury. Our recommendations are based on a decade of experience with routine colony management and behavioral observations at different European research sites and are intended as a practical reference for laboratories starting up Acomys colonies and as guidelines for regulatory authorities and ethics committees involved in approval processes for Acomys facilities and research.

The Federation of European Laboratory Animal Science Associations (FELASA) has played a pivotal role in ensuring high-quality education and training in laboratory animal sciences via accrediting courses. FELASA has revised its accreditation framework to reflect the evolving needs of the laboratory animal science community. This paper outlines the criteria for accrediting courses that train individuals for specific functions (A-D) (Article 23), roles (Articles 24(1)a-c; 25; 34; 38), Specialists in Laboratory Animal Sciences, and a selection of stand-alone modules. The accreditation process involves two steps: a self-assessment of the course and an on-site audit. Special attention is paid to constructive alignment, a tiered approach to skill acquisition, prioritising non-animal alternatives, ethical use of live animals, and structured assessments. FELASA's accreditation ensures that laboratory animal science education remains ethically responsible, scientifically robust and pedagogically sound.

The chytrid fungus Batrachochytrium dendrobatidis (BD) poses a serious threat to amphibian species worldwide. BD infects keratinocytes of the skin and interferes with their physiological barrier function. The African clawed frog Xenopus laevis is a species with low susceptibility to BD. Nevertheless, any infection presents a challenge to the immune system and, when combined with other stressors, carries the risk of overwhelming the body's defense. Infected animals may show greater variability in their scientific output than uninfected animals. This, in turn, means that more animals have to be used, which is not in line with the 3Rs principle. Moreover, releasing the fungus into the wastewater system should clearly be avoided to prevent infection of wild amphibians. Following confirmation of BD infection in the animals by Polymerase Chain Reaction (PCR), we decided to eradicate the fungus due to the reasons outlined above. This project involved not only the treatment of our frogs but also the timely coordinated disinfection of our entire permanently installed aquarium system. Itraconazole was applied as an immersion bath for the frogs and heat was used to disinfect the aquarium system. In this report, we outline our complex approach to a logistically demanding, labor-intensive project involving a large team of staff. We emphasize the need for straightforward planning, good communication and reporting on unexpected aspects and findings.

Transparent reporting of animal research is both a scientific and ethical imperative and is linked to both research quality and the principles of Replacement, Reduction, and Refinement (3Rs). Persistent concerns about poor reproducibility, limited translation and research waste have driven reforms in reporting standards and data-sharing requirements. However, despite considerable progress over the past 60 years, substantial gaps remain. Many published studies still lack essential methodological detail, such as animal characteristics, welfare measures, bias minimization methods (such as randomization and blinding), and sample size justification. Non-reporting of negative or null results further distorts the evidence base. A major barrier to change has been inadequate training of researchers in best practices for experimental design and statistical analysis. We describe how standardized reporting frameworks can promote research quality and highlight tools available to assist the researcher in implementing best practices in study design, reporting, and data accessibility. Over the next decade, emerging applications such as automated compliance tools and AI-assisted screening will offer scalable approaches to adoption of reporting standards. Preclinical science itself will be profoundly altered by advances in alternative models, open data, and linked machine-readable research outputs that will shift the research culture from isolated studies to an integrated cumulative evidence ecosystem. However, an expanded evidence base will be of value only if methodological quality is prioritized over novelty. Embedding best practices at study inception coupled with transparency will enhance reproducibility, reduce waste, and strengthen the reliability and translational value of animal research.

Complete Freund's adjuvant (CFA) is used in laboratory animals to stimulate strong immune responses. However, it can cause persistent local inflammation and tissue damage, raising welfare concerns. This scoping review aimed to (i) assess how frequently welfare-relevant outcomes are reported in CFA immunisation and antibody-production studies in mice, rats and rabbits; (ii) describe reported welfare-relevant outcomes and the methods used to assess them; (iii) chart CFA regimen details across studies; and (iv) summarise reported alternatives to CFA, including welfare comparisons where available. We followed a protocol registered in Systematic Reviews for Animals and Food and reported in accordance with PRISMA-ScR. We searched PubMed and Embase from 2015 onwards. Screening was conducted in two phases (title/abstract; full text) by one reviewer, with uncertainties resolved by a second reviewer. Data were charted on animal characteristics, CFA regimen details, welfare monitoring, reported local/systemic outcomes, analgesia/humane endpoints and comparator adjuvants. Of 1608 records screened, 689 were assessed at full-text level and 43 met inclusion criteria by reporting a welfare-relevant outcome (including 'no adverse effects'): local outcomes were reported in 24/43 and systemic in 8/43; structured pain or behaviour monitoring occurred in 4/43 and formal scoring in 1/43 studies. Alternatives were evaluated in 32/43; in studies involving head-to-head comparisons with CFA (28/32), alternatives were more often better tolerated (22/28) than similar (6/28), with efficacy usually comparable or higher (31/32). Despite well-recognised welfare concerns with CFA, welfare-relevant outcomes are rarely reported. Standardised reporting of CFA regimens, welfare assessment methods and results is needed to support evidence-based refinement and comparison with alternatives.

This pilot study investigates whether trained behavioral tasks may serve as early, non-invasive indicators of distress in high-severity disease models in laboratory rats. Therefore, six Wistar rats in a diethylnitrosamine-induced hepatocellular carcinoma model, were trained to perform two tasks: lockbox solving and scale climbing. They were assessed over 18 weeks by body weight, hair corticosterone (hCORT), and Grimace Scale. Changes in task performance time and hCORT levels were observed and revealed a three-phase pattern. Initially, poor task performance (mean lockbox solving time 22 s) and elevated hCORT (mean 10.8 pg/mg) indicated a process of adaptation to the experiment. This was followed by improved performance (mean lockbox solving time 2 s) and reduced hCORT (mean 7.9 pg/mg), suggesting acclimatization. Later, performance declined again (mean lockbox solving time 9 s), accompanied by rising hCORT (mean 8.3 pg/mg), likely reflecting tumor progression and repeated anesthesia exposure. Lockbox solving appeared more variable than scale climbing. Acute stressors, such as room changes and prolonged anesthesia, had an impact on lockbox solving and scale climbing. After the initial housing room change lockbox solving time increased from 20 s to 49 s while scale climbing time rose from 12 s to 26 s. Case observations confirmed that task performance deficits coincided with illness or larger tumor burden. These findings support the use of trained behavior as a sensitive tool to detect distress. This approach could improve welfare monitoring in long-term or high-severity animal studies.

Temporomandibular disorders affect about 12% of the industrialized population, and their complex management often results in recurrence or treatment failure. Among animal models, the pig is particularly relevant owing to its anatomical similarity to humans, although specific differences in the zygomatic arch and mandibular fossa require adapted surgical approaches. We describe and validate a standardized surgical approach to the porcine temporomandibular joint (TMJ) suitable for translational research. Eleven cadavers of Sus scrofa domestica were dissected to identify key anatomical structures. A high condylectomy was performed to establish a reproducible surgical pathway, and the caudal intra-articular injection technique was tested using methylene blue to assess its feasibility. The pig's TMJ area consists of superficial muscles such as the platysma and parotidoauricularis, with deeper structures such as the parotid gland, facial nerve and major vessels, while the bony anatomy includes a large condylar head and a superficial zygomatic arch. The proposed surgical approach to the pig TMJ involves a retromandibular incision with preauricular extension, subperiostal dissection to expose the zygomatic arch and articular capsule, followed by an incision to access the condyle, disc and mandibular fossa, allowing for condylectomy with careful preservation of the facial nerve and surrounding structures. This study highlights the anatomical differences with humans, such as the presence of the parotidoauricularis muscle, which lies superficially to the facial nerve and serves as a useful landmark for a safe dissection. The described approach provides a reliable and reproducible technique for future TMJ surgical studies in the pig model.

The use of animals as a model for humans has a long history. This paper describes in a bird's eye view the main developments from the ancient period until recent times. Although animal models have been used since the early Greek and Roman civilizations, the main increase in their use dates from the end of the Second World War. Not only did the number of animals used in experiments increase dramatically in this period, but also the variety of species, as well as the purposes for which animals were used. However, from the 1970s onwards, the number of animal experiments has decreased. The reasons for this decrease are briefly explored.

Although overeating is the root cause of many diseases and even premature death in laboratory animals, ad libitum feeding is still the prevailing practice in rodent husbandry. There is a need for practical methods of food restriction compatible with group housing. The diet board was developed as a mechanical solution to food restriction of group-housed rats. It tightly embeds food pellets in grooves cut into aspen boards, forcing the rats to gnaw wood to reach their food. In this two-year experiment, 146 nine-week-old outbred Hsd:Sprague Dawley[®] rats were divided into four equal groups: diet board-fed males and females, and ad libitum-fed males and females. Blood samples for clinical chemistry were collected at regular intervals during the study, and times of spontaneous death or euthanasia were recorded. Triglyceride and cholesterol values were significantly lower in diet board males than ad libitum males. The restriction of food intake via a diet board significantly increased the 24-month survival rate for both female and male groups. The better observed survival rates amongst diet board-fed rats makes it possible to start long-term studies with far fewer rats than with ad libitum feeding. Thus, using a diet board appears to be a promising method for the reduction of animal numbers in long-term rat studies that is compatible with group housing.

Successfully implementing the 3R principles relies on a range of interdependent factors operating across multiple levels. As such, any effort to advance the 3Rs must engage with this complexity and incorporate the lived experiences of stakeholders to inform policy advancements. In an interview-based study, we gathered insights from 35 Swiss researchers on the implementation of the 3Rs in Switzerland. Using reflexive thematic analysis, we identified two overarching categories of facilitation: originative facilitation, referring to the collective meaning-making of the 3Rs, and executive facilitation, encompassing politico-institutional conditions that support their implementation. The present paper focusses on the latter domain, in which key themes include political support fostering a pro-3R research environment, the cultivation of a 3R culture within research institutions, clearer 3R guidance from cantonal commissions on animal experimentation, and strategic use of the Swiss 3R Competence Centre as a leading national 3R intermediary. These themes detail major institutional stakeholders that could further promote the implementation of the 3Rs from the perspective of researchers. Accordingly, the results showed that advancing the 3Rs is not just a matter of niche innovations but should also be orchestrated from a broader institutional perspective and with specific objectives to achieve. While these findings are specific to the Swiss context, they provide valuable information for countries with similar regulations on animal experimentation or a similar political structure.

Animals used in research and testing face physical and mental challenges, which may cause mild to severe pain and distress. Pain and distress are generally considered in the context of the analogy postulate and the precautionary principle. The analogy postulate refers to (patho-)physiological similarities between humans and vertebrates, assuming that manipulations causing pain and distress in humans do so equally in vertebrates. According to the precautionary principle, animals will be considered to have pain/distress in the absence of any scientific consensus as to the presence or absence of pain. Although those principles can be useful guides for humane treatment of laboratory animals, they do not address the subjectivity involved in recognising pain/distress. A reliable estimate of animal pain and distress can be derived from both behavioural and physiological indicators. Distress and pain are biological phenomena that motivate behaviours aimed at alleviating these states. If no behaviour achieves the expected outcome, the animal may switch to other modes, such as depression or learned helplessness. Pain is regarded as a biologically adaptive mechanism, alerting organisms to possible damage or injury. The effect of experimental procedures on perceived pain/distress may depend on physical and social environmental conditions. Observation schemes can be used to assess and monitor daily for clinical signs or problems. They can help reduce pain/distress and provide adequate care. Competent observation of animals is also basic to the correct implementation of humane endpoints. AI will transform research. Intelligent systems will generate data, enable early stress detection and improve animal welfare.

Breast cancer is the most common cancer in women worldwide, underscoring the need for ethical and effective preclinical models to advance disease management. This study aimed to highlight the importance of humane endpoints in a rat model of mammary carcinogenesis undergoing ladder resistance training to evaluate and ensure the absence of animal suffering. Twenty-eight female Wistar rats were assigned randomly to four groups of seven animals per group: sedentary, sedentary induced (with N-methyl-N-nitrosourea (MNU)), exercised and exercised MNU-induced. At 7 weeks of age, the animals in the induced groups were injected intraperitoneally (i.p.) with the carcinogenic agent (N-methyl-N-nitrosourea; i.p; 50 mg/kg). The animals' welfare was monitored using a set of biological characteristics. The resistance exercise training, started at 9 weeks old and comprised climbing a ladder three times per week for 18 weeks, gradually increasing the load throughout the protocol. Of 14 MNU-induced rats, 9 (64%) developed mammary cancer. Exercised rats tended to show delayed tumor ulceration despite larger tumor volumes. No significant differences in bodyweight were observed, although weight loss appeared earlier in sedentary-induced animals. Exercised rats exhibited more stress signs, including reduced grooming and one case of chromodachryorrhea, yet had lower tumor-related humane endpoint scores. Three rats were euthanised early due to tumor-related endpoints. Minor tail wounds occurred but did not affect exercise or welfare. These results indicate that, with careful endpoint monitoring, the exercise protocol is well tolerated and may improve performance in tumour-bearing rats, supporting ethical standards while allowing accurate investigation of resistance training effects.

Rats play a crucial role in advancing scientific research and contributing to the understanding of various diseases. The striking structural similarity between the rat foot and the intricate anatomy of the human hand has drawn scientific interest to these animals. However, detailed morphometric and functional analyses of the adult Sprague-Dawley rat foot, including its dimensions, range of motion, and grip strength, remain limited in the literature. We aimed to examine the hind feet of 42 adult male Sprague-Dawley rats, each weighing 300-350 g. Using a multifaceted approach, we inspected hind paw morphology and performed descriptive statistical analyses of foot dimensions (a), measured unilateral hind foot grasping strength (b), assessed joint mobility (c), and examined the microscopic appearance of the hind foot third digit (d). One animal was additionally used to observe the hind limb skeletal architecture using microcomputed tomography. This study provides critical normative data regarding the structure and function of the hind foot in adult Sprague-Dawley rats, thereby facilitating future studies on musculoskeletal diseases.