Assessment of Vitamin D Status in Great Apes in Human Care

Reliably assessing vitamin D status in nonhuman great apes presents unique challenges, including the optimal collection, handling and storage of appropriate samples, assay selection, and interpretation of results. In recent decades, significant scientific evidence accumulated on these matters in humans, but a comprehensive overview of this topic in nonhuman great apes is currently lacking. This paper provides a review of the various sample types, storage and transport considerations, the wide range of available assays and their respective advantages and disadvantages, as well as important considerations for the reporting and interpretation of results, including environmental and individual animal-related factors. A thorough discussion of the reasons behind inter- and intra-assay variability of vitamin D metabolite concentration measurement is provided with the intent to support those caring for great apes to be able to reliably assess vitamin D status and interpret results. We also highlight the limitations of current human reference intervals, cover the existing literature on nonhuman great apes, and the importance of standardization across institutions to improve animal welfare and facilitate robust research. Finally, we provide a set of recommendations based on primarily current human literature to support zoo and sanctuary practitioners.