Theoretical and empirical evidence indicates that low external validity due to rigorous standardization of study populations is a cause of poor replicability in animal research. Here we report a multi-laboratory study aimed at investigating whether heterogenization of study populations by using animals from different breeding sites increases the replicability of results from single-laboratory studies. We used male C57BL/6J mice from six different breeding sites to test a standardized against a heterogenized (HET) study design in six independent replicate test laboratories. For the standardized design, each laboratory ordered mice from a single breeding site (each laboratory from a different one), while for the HET design, each laboratory ordered proportionate numbers of mice from the five remaining breeding sites. To test our hypothesis, we assessed 14 outcome variables, including body weight, behavioral measures obtained from a single session on an elevated plus maze, and clinical blood parameters. Both breeding site and test laboratory affected variation in outcome variables, but the effect of test laboratory was more pronounced for most outcome variables. Moreover, heterogenization of study populations by breeding site (HET) did not reduce variation in outcome variables between test laboratories, which was most likely due to the fact that breeding site had only little effect on variation in outcome variables, thereby limiting the scope for HET to reduce between-lab variation. We conclude that heterogenization of study populations by breeding site has limited capacity for improving the replicability of results from single-laboratory animal studies.

理论和经验证据表明，由于研究群体严格标准化而导致的外部效度低是动物研究可重复性差的一个原因。在这里，我们报告了一项多实验室研究，旨在调查通过使用来自不同繁殖地点的动物对研究群体进行异质化是否会增加单实验室研究结果的可重复性。我们使用来自六个不同繁殖地点的雄性 C57BL/6J 小鼠，在六个独立的重复测试实验室中测试标准化与异质化 (HET) 研究设计。对于标准化设计，每个实验室从一个饲养点订购小鼠（每个实验室从不同的饲养点订购小鼠），而对于 HET 设计，每个实验室从其余五个饲养点订购按比例数量的小鼠。为了检验我们的假设，我们评估了 14 个结果变量，包括体重、在高架十字迷宫上单次进行的行为测量以及临床血液参数。繁殖地点和测试实验室都会影响结果变量的变化，但测试实验室对大多数结果变量的影响更为明显。此外，按繁殖地（HET）划分的研究群体的异质化并没有减少测试实验室之间结果变量的差异，这很可能是由于繁殖地对结果变量的变化影响很小，从而限制了HET的范围以减少实验室之间的差异。我们的结论是，按繁殖地划分的研究群体的异质化对于提高单一实验室动物研究结果的可重复性的能力有限。