02498nas a2200301   4500000000100000000000100001008004100002260001200043653002100055653001500076100001600091700002000107700001900127700002000146700001600166700002100182700002800203700001400231700002300245700002300268700001800291245011800309856005500427300001000482490000700492520168300499022001402182       2024                            d  c2024-0110aAnimal behaviour10aRobustness1 aIvana Jaric1 aBernhard Voelkl1 aIrmgard Amrein1 aDavid P. Wolfer1 aJanja Novak1 aCarlotta Detotto1 aUlrike Weber-Stadlbauer1 aUrs Meyer1 aFrancesca Manuella1 aIsabelle M. Mansuy1 aHanno Würbel00aUsing mice from different breeding sites fails to improve replicability of results from single-laboratory studies  uhttps://www.nature.com/articles/s41684-023-01307-w  a18-220 v533 aTheoretical 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.  a1548-4475