Committee composition is a recurrent theme within the literature on Institutional Animal Care and Use Committees (IACUCs). The ability of IACUCs to ensure the ethical treatment of nonhuman research subjects depends upon who makes up these committees. Non-scientists and those not affiliated with the research institution have been deemed indispensable for the democratic, objective review of protocols and, thus, for ethical treatment. IACUCs’ critics and partners alike have persistently offered suggestions for how to further optimize committee composition towards these ends. (...) This paper contributes to the ongoing conversation by advocating for the addition of holistic species experts to IACUCs, arguing that holistic species experts are as indispensable for the political and epistemic viability of protocol reviews as non-scientists and non-affiliates. Holistic species experts are defined here as members of the larger community who have extensive firsthand experience with animals living and dying under relatively ideal conditions. If we accept that non-scientists and non-affiliates are crucial for IACUCs' ethical treatment of animals, then we have every reason to embrace holistic species experts. The values, welfare expertise, and productive epistemic dissonance that these experts bring to the table would prove invaluable. (shrink)