Competing interests: We have read and understood BMJ policy on declaration of interests and declare that MR-H is a member of the council of management of the UK registered company Laboratory Animals Ltd (LAL). LAL issues the journal Laboratory Animals. The position is unpaid but travel to LAL meetings is reimbursed. The journal’s profits are used for charitable purposes, subsidising educational projects in laboratory animal science and welfare. The systematic review of animal studies (ref 3) and two other related articles (ref 4 and 6) were coauthored by Emily Sena, who is the editor of BMJ Open Science (openscience.bmj.com). Provenance and peer review: Commissioned; externally peer reviewed.