Study compares enrichment materials for female BALB/c mouse welfare
Bottom line
Female BALB/c mice housed with simple enrichment materials such as maple cardboard, cardboard rolls, and Kraft paper showed measurable welfare benefits over standard, unenriched housing in a new study published in Animals by Rosa De Jesús, Patricia L. Fernández, and Cesar Murillo. The authors used a multidimensional welfare assessment, rather than a single behavioral endpoint, to compare standard cages with different combinations of commercially available enrichment materials. While the abstract indicates the study focused on species-specific behavior, stress reduction, and physiological adaptation, the broader literature around mouse enrichment points in the same direction: simple nesting and shelter resources can improve welfare without necessarily undermining research quality. The study adds strain- and sex-specific evidence for female BALB/c mice, a common laboratory model, and helps narrow the question from whether enrichment matters to which low-cost materials may work best. (nc3rs.org.uk)
Why it matters: For laboratory animal veterinarians, IACUC members, and research colony managers, this is the kind of evidence that can support practical refinement decisions at the cage level. U.S. guidance already treats environmental enrichment as part of accepted standards for humane care, while also noting that enrichment should be considered an experimental variable and controlled appropriately. At the same time, both the Guide for the Care and Use of Laboratory Animals and more recent welfare literature have pushed back on the long-standing concern that enrichment automatically increases data variability. In mice, the Guide specifically cites evidence that housing can be enriched without compromising precision or reproducibility, and NC3Rs says bedding and nesting material, refuges, and gnawing resources should be provided unless there is a sound scientific reason not to. (olaw.nih.gov)
What to watch: Watch for the full paper’s detailed outcome data, including which material combinations performed best and whether facilities begin using those findings to update standard operating procedures or IACUC guidance. (nc3rs.org.uk)
A new paper in Animals examines a practical question for laboratory animal welfare programs: whether different low-cost environmental enrichment materials meaningfully improve welfare in female BALB/c mice. The study, by Rosa De Jesús, Patricia L. Fernández, and Cesar Murillo, compares standard housing with cages supplied with combinations of maple cardboard, cardboard rolls, and Kraft paper, using a multidimensional welfare framework rather than relying on a single indicator. That matters because enrichment policy in mouse facilities has increasingly shifted from broad principle to operational detail: what to provide, to whom, and with what effect. (nc3rs.org.uk)
The background is well established. Environmental enrichment is widely used as a refinement strategy in laboratory rodents because it supports species-typical behavior and can reduce stress-related responses. But implementation has never been entirely straightforward. The Guide for the Care and Use of Laboratory Animals, which underpins many U.S. institutional programs, recognizes enrichment as part of humane care while also cautioning that it may act as an experimental variable and should be standardized within study designs. The same Guide also notes that evidence in mice does not support the claim that enrichment necessarily compromises reproducibility. (olaw.nih.gov)
That tension, between welfare gains and fears about scientific noise, has shaped the field for years. NC3Rs advises that bedding and nesting material, refuges, and gnawing sticks should be present in every mouse cage unless there is a sound scientific justification not to. It also notes that mice show preferences for different materials that may vary by strain and sex, which is one reason targeted studies like this one are useful. Female BALB/c mice are especially relevant here because strain-specific responses to enrichment have been documented before, and BALB/c mice are common in immunology, oncology, and behavioral research. (nc3rs.org.uk)
Although the source abstract available here is truncated, it shows that the investigators compared unenriched housing with several combinations of commercially available materials and assessed welfare through multiple dimensions, including behavior, stress-related measures, and physiological adaptation. That design aligns with current best practice in welfare science, which increasingly favors composite assessment over one-off endpoints. It also fits with prior findings that simple resources, including nesting material and shelters, can improve behavioral well-being in mice and may do so without materially increasing outcome variability. A 2018 open-access study in female mice similarly found that enrichment improved welfare-related measures without the feared penalty in data consistency, while another study concluded that common enrichment can improve housing conditions without compromising data. (pmc.ncbi.nlm.nih.gov)
Industry and expert guidance broadly support that direction. NC3Rs says enrichment should not be added randomly, but selected based on the animals’ demonstrated preferences and overall benefit. That point is particularly relevant for a study comparing maple cardboard, cardboard rolls, and Kraft paper, because the question is no longer whether any enrichment is better than none, but which materials are most usable, most preferred, and least disruptive in routine husbandry. Earlier literature has also suggested mice often prefer paper-derived nesting materials, and that BALB/c mice can make strong use of shelters and other simple cage resources. (nc3rs.org.uk)
Why it matters: For veterinary professionals working in research settings, this paper is most useful as refinement evidence that can translate into policy. If certain low-cost materials improve welfare in female BALB/c mice, facilities may be able to strengthen enrichment standards without major capital changes, and with better strain-specific justification when protocols are reviewed by the IACUC. That could affect everything from procurement and cage-change SOPs to welfare scoring and post-approval monitoring. It also gives attending veterinarians and compliance teams more current literature to cite when balancing animal well-being with investigator concerns about study integrity. Under the Guide and PHS-linked oversight, those decisions increasingly need to be evidence-based, not just customary. (olaw.nih.gov)
There’s also a broader scientific point. Enrichment is part of refinement under the Three Rs, but it can also improve model quality if it reduces chronic stress or abnormal behavior that might otherwise confound results. The Guide explicitly notes that higher-stress conditions can themselves increase variation, which flips the old argument on its head: barren housing may not be the more neutral baseline many researchers assume. In that sense, studies like this one are not only about ethics, but also about experimental validity. (olaw.nih.gov)
What to watch: The next step is the full paper’s detailed results, especially whether one material or combination clearly outperformed the others, what endpoints changed most, and whether the findings are likely to be generalizable beyond female BALB/c mice to other strains, sexes, or facility types. If the effects are clear and operationally simple, this could feed into future husbandry guidance, local SOP revisions, and more specific enrichment expectations during protocol review. (nc3rs.org.uk)