Pica behavior of laboratory rats (Rattus norvegicus domestica): Nauseated animals ingest kaolin, zeolite, bentonite, but not calcium carbonate chalk

"Pica" refers to the ingestion of non-nutritive substances by animals that would not typically consume them. The pica behavior can be utilized to investigate the internal conditions of animals' bodies. For example, rats, due to neuroanatomical reasons, cannot vomit; nevertheless, when nauseated, they ingest kaolin clay. This renders the ingestion of kaolin a practical proxy for measuring nausea in rats. The question of whether rats consume minerals other than kaolin during nauseous episodes remains unanswered. This study aims to identify a mineral better suited for detecting nausea in rats. In two experiments, nausea was induced in laboratory rats by a single dose of lithium chloride (0.15 M, 2% bw), and their mineral consumption over the 24-hour period was measured. Experiment 1 compared three minerals between rat groups: kaolin sold for nausea detection (kaolin A), kaolin for ceramics (kaolin B), and zeolite. Nauseated rats consumed all minerals, with the highest consumption occurring with kaolin B. In Experiment 2, three commercially available health soils were compared: edible kaolin, edible bentonite, and edible chalk. The most significant consumption was observed in the kaolin group, followed by the bentonite group, while nauseated rats did not consume edible chalk. These findings underscore the suitability of kaolin for nausea detection, although the extent of consumption may vary depending on the product.