Data_Sheet_1_Structural enrichment for laboratory mice: exploring the effects of novelty and complexity.pdf

Providing structural enrichment is a widespread refinement method for laboratory rodents and other animals in captivity. So far, animal welfare research has mostly focused on the effect of increased complexity either by accumulating or combining different enrichment items. However, increasing complexity is not the only possibility to refine housing conditions. Another refinement option is to increase novelty by regularly exchanging known enrichment items with new ones. In the present study, we used pair-housed non-breeding female C57BL/6J and DBA/2N mice to investigate the effect of novelty when applying structural enrichment. We used a double cage system, in which one cage served as home cage and the other as extra cage. While the home cage was furnished in the same way for all mice, in the extra cage we either provided only space with no additional enrichment items (space), a fixed set of enrichment items (complexity), or a changing set of enrichment items (novelty). Over 5 weeks, we assessed spontaneous behaviors, body weight, and extra cage usage as indicators of welfare and preference. Our main results showed that mice with access to structurally enriched extra cages (complexity and novelty) spent more time in their extra cages and complexity mice had lower latencies to enter their extra cages than mice with access to the extra cages without any structural enrichment (space). This indicates that the mice preferred the structurally enriched extra cages over the structurally non-enriched space cages. We found only one statistically significant difference between the novelty and complexity condition: during week 3, novelty mice spent more time in their extra cages than complexity mice. Although we did not detect any other significant differences between the novelty and complexity condition in the present study, more research is required to further explore the potential benefits of novelty beyond complexity.为圈养实验啮齿类及其他动物提供结构型环境丰容（structural enrichment），是当前广泛使用的饲养优化手段。迄今为止，动物福利领域的研究大多聚焦于通过累积或组合不同丰容物品来提升环境复杂度所产生的效应。不过，提升环境复杂度并非优化饲养条件的唯一路径。另一种优化方案是通过定期将已使用的丰容物品更换为全新物品，以此提升环境新颖性（novelty）。本研究中，我们以成对饲养的未繁育雌性C57BL/6J与DBA/2N小鼠为实验对象，探究施加结构型环境丰容时，环境新颖性对动物的影响。我们采用双笼系统：一个笼盒作为主笼（home cage），另一个作为备用笼（extra cage）。所有小鼠的主笼均采用统一陈设配置，而备用笼则分为三种实验条件：仅提供空置空间且无额外丰容物品（space）、配置固定组合的丰容物品（complexity）、以及定期更换丰容物品组合的新颖性组（novelty）。在为期5周的实验周期内，我们以自发行为、体重及备用笼使用情况作为动物福利与偏好的评估指标，对小鼠进行观测。主要实验结果显示：相较于仅可使用空置备用笼的空笼组小鼠，可使用结构丰容备用笼的固定复杂度组与新颖性组小鼠在备用笼中停留的时长更长；且固定复杂度组小鼠进入备用笼的潜伏期显著短于空笼组小鼠。这表明小鼠更偏爱带有结构丰容的备用笼，而非无结构丰容的空置备用笼。我们仅在新颖性组与固定复杂度组之间发现了一处具有统计学显著性的差异：在实验第3周，新颖性组小鼠在备用笼中的停留时长显著长于固定复杂度组小鼠。尽管本研究未在新颖性组与固定复杂度组之间发现其他显著性差异，但仍需开展更多相关研究，以进一步探究相较于单纯提升环境复杂度，环境新颖性所具备的额外潜在福利增益。