Harmonisation of welfare indicators for macaques and marmosets used or bred for research [version 1; peer review: 1 approved with reservations]

Background: Accurate assessment of the welfare of non-human primates (NHPs) used and bred for scientific purposes is essential for effective implementation of obligations to optimise their well-being, for validation of refinement techniques and novel welfare indicators, and for ensuring the highest quality data is obtained from these animals. Despite the importance of welfare assessment in NHP research, there is little consensus on what should be measured. Greater harmonisation of welfare indicators between facilities would enable greater collaboration and data sharing to address welfare-related questions in the management and use of NHPs. Methods: A Delphi consultation was used to survey attendees of the 2019 NC3Rs Primate Welfare Meeting (73 respondents) to build consensus on which welfare indicators for macaques and marmosets are reliable, valid, and practicable, and how these can be measured. Results: Self-harm behaviour, social enrichment, cage dimensions, body weight, a health monitoring programme, appetite, staff training, and positive reinforcement training were considered valid, reliable, and practicable indicators for macaques ( ≥70% consensus) within a hypothetical scenario context involving 500 animals. Indicators ranked important for assessing marmoset welfare were body weight, NHP induced and environmentally induced injuries, cage furniture, huddled posture, mortality, blood in excreta, and physical enrichment. Participants working with considered critical for the assessment of macaque welfare. Alsoexceeding or approaching the 70% threshold in Phase1 were a behavioural management programme, physical enrichment, and food enrichment, suggesting their consideration as well. Social enrichment was rated the top indicator in Phase 1 (>94% of respondents), reflecting the importance of companionship for psychological well-being in these animals. Social enrichment and self-harm behaviour are well known as important indicators of good and poor welfare, respectively, in NHPs, and there is a large literature on their incidence and relevance to macaque well-being, so it is not surprising that there was consensus agreement on their importance in both Delphi consultations. Fewer than two-thirds of respondents felt a humane euthanasia programme, hearing other NHPs, cage furniture, and ventilation could be used to assess welfare. Opinion was split on how practical cage furniture and ventilation are as welfare indices for macaques. Agreement scores for practicability were generally higher in Truelove et al . (2020) than in the current study, possibly reflecting differences in expert demographics, sample size, and methodology. The aim of this paper is to identify shared indicators for the level of welfare of macaques and marmosets in research laboratories, using a Delphi consultation during a NC3Rs meeting on primate welfare. The results pointed out at some reliable indicators for both species, with some interesting differences: self-harm behaviour and social enrichment were chosen as being important for macaques, whereas body weight for marmosets. I found the paper very informative and very relevant. These are the kind of studies which are really needed to improve the conditions of NHP in captivity, so I really applaud the authors' efforts. However, I have some concern about part of the article's content. In particular, although it is very informative and important for the macaques, less so for the marmosets. I don't feel that the authors have enough responses from the marmoset community to draw conclusions. There is in this paper a real unbalance when it comes to deal with the two species. I understand that this is a big ask, but I would feel more comfortable with this paper if the marmosets would be left to develop in another time, with more data available.