Evaluation of different types of enrichment - their usage and effect on home cage behavior in female mice

Numerous studies ascertained positive effects of enriched environments on the well-being of laboratory animals including behavioral, physiological and neurochemical parameters. Conversely, such conclusions imply impaired animal welfare and health in barren husbandry conditions. Moreover, inappropriate housing of laboratory animals may deteriorate the quality of scientific data. Recommendations for housing laboratory animals stipulate that cages should be enriched to mitigate adverse effects of barren housing. In this context, it is not only unclear what exactly is meant by enrichment, but also how the animals themselves interact with the various items on offer. Focal animal observation of female C57BL/6J mice either housed in conventional (CON) or enriched (ENR) conditions served to analyze the impact of enriching housing on welfare related behavior patterns including stereotypical, maintenance, active social, and inactive behaviors. CON conditions resembled current usual housing of laboratory mice, whereas ENR mice received varying enrichment items including foraging, housing and structural elements, and a running disc. Active and inactive use of these elements was quantitatively assessed. CON mice showed significantly more inactive and stereotypical behavior than ENR mice. ENR mice frequently engaged with all enrichment elements, whereby riddles to obtain food reward and the running disc preferably served for active interactions. Offering a second level resulted in high active and inactive interactions. Structural elements fixed at the cagetop were least attractive for the mice. Overall, the presented data underline the positive welfare benefits of enrichment and that mice clearly differentiate between distinct enrichment types, demonstrating that the perspective of the animals themselves should also be taken into account when specifying laboratory housing conditions. This is particularly important, as the ensuring of animal welfare is an essential prerequisite for reliable, reproducible, and scientifically meaningful results

Effects of more natural housing conditions on the muscular and skeletal characteristics of female C57BL/6J mice

Background Enrichment of home cages in laboratory experiments offers clear advantages, but has been criticized in some respects. First, there is a lack of definition, which makes methodological uniformity difficult. Second, there is concern that the enrichment of home cages may increase the variance of results in experiments. Here, the influence of more natural housing conditions on physiological parameters of female C57BL/6J mice was investigated from an animal welfare point of view. For this purpose, the animals were kept in three different housing conditions: conventional cage housing, enriched housing and the semi naturalistic environment. The focus was on musculoskeletal changes after long-term environmental enrichment. Results The housing conditions had a long-term effect on the body weight of the test animals. The more complex and natural the home cage, the heavier the animals. This was associated with increased adipose deposits in the animals. There were no significant changes in muscle and bone characteristics except for single clues (femur diameter, bone resorption marker CTX-1). Additionally, the animals in the semi naturalistic environment (SNE) were found to have the fewest bone anomalies. Housing in the SNE appears to have the least effect on stress hormone concentrations. The lowest oxygen uptake was observed in enriched cage housing. Conclusions Despite increasing values, observed body weights were in the normal and strain-typical range. Overall, musculoskeletal parameters were slightly improved and age-related effects appear to have been attenuated. The variances in the results were not increased by more natural housing. This confirms the suitability of the applied housing conditions to ensure and increase animal welfare in laboratory experiments

Bored at home?—A systematic review on the effect of environmental enrichment on the welfare of laboratory rats and mice

Boredom is an emotional state that occurs when an individual has nothing to do, is not interested in the surrounding, and feels dreary and in a monotony. While this condition is usually defined for humans, it may very well describe the lives of many laboratory animals housed in small, barren cages. To make the cages less monotonous, environmental enrichment is often proposed. Although housing in a stimulating environment is still used predominantly as a luxury good and for treatment in preclinical research, enrichment is increasingly recognized to improve animal welfare. To gain insight into how stimulating environments influence the welfare of laboratory rodents, we conducted a systematic review of studies that analyzed the effect of enriched environment on behavioral parameters of animal well–being. Remarkably, a considerable number of these parameters can be associated with symptoms of boredom. Our findings show that a stimulating living environment is essential for the development of natural behavior and animal welfare of laboratory rats and mice alike, regardless of age and sex. Conversely, confinement and under-stimulation has potentially detrimental effects on the mental and physical health of laboratory rodents. We show that boredom in experimental animals is measurable and does not have to be accepted as inevitable

Cage design elements as environmental enrichment for laboratory mice - influence on home cage behavior and their suitability from an animal perspective

Auch wenn zunehmend tierfreie Alternativmethoden, im Sinne des Replacements (Vermeiden) nach dem 3R-Prinzip von Russel und Burch in der biomedizinischen Forschung und in regulatorischen Arzneimittelprüfungen entwickelt werden und zum Einsatz kommen, so sind Forschende vor allem im Bereich der Grundlagenforschung noch auf Tierversuche angewiesen. Ist ein Tierversuch zur Beantwortung der Forschungsfragestellung unerlässlich, so fordert die RL 2010/63/EU i.V.m. dem Tierschutzgesetz die konsequente Umsetzung von Reduction (Verringern) und Refinement (Verbessern) nach dem 3R-Prinzip. Dies impliziert, dass nur die notwendige Anzahl an Versuchstieren eingesetzt wird und Schmerzen, Leiden und Schäden für die Versuchstiere durch die verwendeten Verfahren auf ein geringstmögliches Minimum reduziert werden müssen. Haltungsbedingungen von Versuchstieren müssen laut RL 2010/63/EU ebenfalls konsequent reevaluiert und verbessert werden, um so den fortschreitenden Wissenszuwachs im Bereich des Animal Welfares zur Haltung von Versuchstieren zu berücksichtigen. Die Empfehlungen der EU zu Maßen und Ausgestaltung der direkten Haltungsumgebung sind dabei nur als Mindeststandard für die Haltung von Versuchstieren zu verstehen. Die direkte Haltungsumgebung muss den Versuchstieren durch eine hinreichende Komplexität und Strukturierung ermöglichen, ein breites Repertoire spezies-spezifischem Verhaltens auszuüben. Eine Möglichkeit, die Komplexität des Haltungsumgebung zu erhöhen, besteht darin, den Tieren verschiedene Käfigausgestaltungselemente in Form von beispielsweise Kletterelementen und Unterschlüpfen als sogenanntes Environmental Enrichment (EE) anzubieten. Die Ausgestaltung der Haltungsumgebung von Versuchstieren wird in der RL 2010/63/EU ausdrücklich empfohlen. Bei Labormäusen konnten bereits zahlreiche positive Auswirkungen von EE auf tierwohlbezogene Gesundheitsparameter nachgewiesen werden. Jedoch sind nicht alle aus anthropozentrischer Sichtweise dargebotenen EE Elemente mit positiven Auswirkungen für das Tierwohl verbunden. Zur Evaluierung, ob eine angebotenes Ausgestaltungselement als Refinementmaßnahme geeignet und somit als Enrichment der Haltungsumgebung gewertet werden kann, sollte daher die Sichtweise der Mäuse mit einbezogen werden. Ziel der vorliegenden Arbeit war es daher, Ausgestaltungselemente der Kategorien Strukturelemente, Hauselemente und Futtersuchelemente auf ihre Eignung für die meistverwendete Versuchstierart Maus Mus musculus, im Speziellen weibliche C57BL/6J Mäuse, zu untersuchen. Die Evaluation der Eignung der untersuchten Ausgestaltungselemente für Mäuse beinhaltete die vergleichende Auswertung des Heimatkäfigverhaltens und des Körpergewichts als tierwohlbezogene Gesundheitsparameter, von angereichert gehaltenen Mäusen mit wöchentlich wechselnden Ausgestaltungskombinationen sowie einer Laufdisc, im Vergleich zu Mäusen in einer laborpraxisüblichen reizarmen Standardhaltung. Die quantitative Auswertung des aktiven und inaktiven Nutzungsverhaltens während der Aktivitätszeit der Mäuse gab Aufschluss über die Interaktionsmöglichkeiten mit den dargebotenen Ausgestaltungselementen. Anschließend folgte die direkte Befragung der angereichert gehaltenen Mäuse in heimatkäfigbasierten binären Präferenztests zum Wert (WV) und Entscheidungskonsens (CE) der Ausgestaltungselemente aus Tiersicht. Die Mäuse konnten im Präferenzsystem, bestehend aus zwei verbundenen Heimatkäfigen, innerhalb ihrer Gruppe zur Wahlentscheidung befragt werden. Basierend auf den ermittelten WV der vergleichenden Einzelanalysen wurde eine Rangfolge der untersuchten Ausgestaltungselemente innerhalb ihrer Kategorien ermittelt. Mäuse in der Standardhaltung zeigten signifikant häufigeres inaktives und stereotypes Verhalten, verglichen mit angereichert gehaltenen Mäusen. Angereichert gehaltene Mäuse erreichten ein höheres Körpergewicht und wandten mehr Zeit für Fressverhalten auf. Alle angebotenen Ausgestaltungselemente wurden von den Mäusen häufig für aktive und inaktive Interaktionen genutzt. Für aktive Interaktionen wurden Futtersuchelemente mit enthaltener Futterbelohnung und die Laufdisc vermehrt genutzt. Mit am Käfigdeckel befestigten Strukturelementen wurde von den Mäusen am wenigstens interagiert. Dahingegen wies eine zweite Ebene aus Holz bevorzugte Nutzung der Mäuse für inaktives und aktives Verhalten auf. In der Präferenzbefragung der Mäuse konnten keine einheitlichen Rangfolgen und Positionen der Ausgestaltungselemente mit allgemeingültigem Charakter für alle individuellen Mäuse ermittelt werden. Dennoch rangierten einige Ausgestaltungselemente, wie der Gitterball und die zweite Ebene, durchgehend auf höheren Positionen in der Rangfolge. Der hohe CE der Ranglisten spiegelt die starke individuelle Wahrnehmung der untersuchten Ausgestaltungselemente für die Mäuse wider und zeigt auf, dass der regelmäßige Wechsel der Ausgestaltungselemente im Käfig dazu beitragen kann die Bedürfnisse jeder individuellen Maus im Laufe der Haltungsperiode zu befriedigen. Die in der vorliegenden Arbeit untersuchten Ausgestaltungselemente waren zusammenfassend geeignet, um tierwohlbezogene Verhaltensparameter bei C57BL/6J Mäusen im Sinne des Refinements von Tierversuchen positiv zu beeinflussen. Die individuellen Bedürfnisse der Tiere müssen bei der Planung der Haltung berücksichtigt werden. Ein Ausgestaltungskonzept, das die individuellen Bedürfnisse der Mäuse berücksichtigt, trägt durch eine Erhöhung des Tierwohls zu zuverlässigen, reproduzierbaren und somit aussagekräftigen Versuchsergebnissen bei

Rating enrichment items by female group-housed laboratory mice in multiple binary choice tests using an RFID-based tracking system

Laboratory mice spend most of their lives in cages, not experiments, so improving housing conditions is a first-choice approach to improving their welfare. Despite the increasing popularity of enrichment, little is known about the benefits from an animal perspective. For a detailed analysis, we categorized enrichment items according to their prospective use into the categories ‘structural’, ‘housing’, and ‘foraging’. In homecage-based multiple binary choice tests 12 female C57BL/6J mice chose between enrichment items within the respective categories over a 46-hour period. A new analyzing method combined the binary decisions and ranked the enrichment items within each category by calculating worth values and consensus errors. Although there was no unequivocal ranking that was true in its entire rank order for all individual mice, certain elements (e.g. lattice ball, second plane) were always among the top positions. Overall, a high consensus error in ranking positions reflects strong individual differences in preferences which could not be resolved due to the relatively small sample size. However, individual differences in the preference for enrichment items highlights the importance of a varied enrichment approach, as there does not seem to be one item that satisfies the wants and needs of all individuals to the same degree. An enrichment concept, in which the needs of the animals are central, contributes to a more specific refinement of housing conditions

Effects of more natural housing conditions on the muscular and skeletal characteristics of female C57BL/6J mice

Abstract Background Enrichment of home cages in laboratory experiments offers clear advantages, but has been criticized in some respects. First, there is a lack of definition, which makes methodological uniformity difficult. Second, there is concern that the enrichment of home cages may increase the variance of results in experiments. Here, the influence of more natural housing conditions on physiological parameters of female C57BL/6J mice was investigated from an animal welfare point of view. For this purpose, the animals were kept in three different housing conditions: conventional cage housing, enriched housing and the semi naturalistic environment. The focus was on musculoskeletal changes after long-term environmental enrichment. Results The housing conditions had a long-term effect on the body weight of the test animals. The more complex and natural the home cage, the heavier the animals. This was associated with increased adipose deposits in the animals. There were no significant changes in muscle and bone characteristics except for single clues (femur diameter, bone resorption marker CTX-1). Additionally, the animals in the semi naturalistic environment (SNE) were found to have the fewest bone anomalies. Housing in the SNE appears to have the least effect on stress hormone concentrations. The lowest oxygen uptake was observed in enriched cage housing. Conclusions Despite increasing values, observed body weights were in the normal and strain-typical range. Overall, musculoskeletal parameters were slightly improved and age-related effects appear to have been attenuated. The variances in the results were not increased by more natural housing. This confirms the suitability of the applied housing conditions to ensure and increase animal welfare in laboratory experiments

Effects of more natural housing conditions on the muscular and skeletal characteristics of female C57BL/6J mice

Enrichment of home cages in laboratory experiments offers clear advantages, but has been criticized in some respects. First, there is a lack of definition, which makes methodological uniformity difficult. Second, there is concern that the enrichment of home cages may increase the variance of results in experiments. Here, the influence of more natural housing conditions on physiological parameters of female C57BL/6J mice was investigated from an animal welfare point of view. For this purpose, the animals were kept in three different housing conditions: conventional cage housing, enriched housing and the semi naturalistic environment. The focus was on musculoskeletal changes after long-term environmental enrichment.The housing conditions had a long-term effect on the body weight of the test animals. The more complex and natural the home cage, the heavier the animals. This was associated with increased adipose deposits in the animals. There were no significant changes in muscle and bone characteristics except for single clues (femur diameter, bone resorption marker CTX-1). Additionally, the animals in the semi naturalistic environment (SNE) were found to have the fewest bone anomalies. Housing in the SNE appears to have the least effect on stress hormone concentrations. The lowest oxygen uptake was observed in enriched cage housing.Despite increasing values, observed body weights were in the normal and strain-typical range. Overall, musculoskeletal parameters were slightly improved and age-related effects appear to have been attenuated. The variances in the results were not increased by more natural housing. This confirms the suitability of the applied housing conditions to ensure and increase animal welfare in laboratory experiments