This paper explores how a translational research platform in Denmark uses piglets as infant models. Drawing on meanings of “public” as “open” and “visible,” we track how researchers and clinicians together and separately turn research piglets and premature infants into both public and un-public beings in laboratory and clinical settings. In these complex multispecies relationships, researchers and clinicians alike create and retain certain “zones of unknowing” in which intimate cross-species care relations are fostered. While critical social scientists call for greater public recognition of animals in accounts of human health, our study demonstrates that “zones of unknowing” enable the involved professionals to care simultaneously for neonatal beings and the greater public good. To account for the efforts involved in contributing to the greater public good, we introduce the term “publication work.” We argue that publication work relies as much on porosity between species and spaces as on actively drawing boundaries between species and between public and private spaces. Plastic pigs and public secrets are crucial to realise the ambition of more-than-human public health.