Chronic pancreatitis in farmed pigs fed excessive zinc oxide

Most of the pigs on a farm in Aichi Prefecture, Japan had chronic diarrhea and severe wasting. The pigs had consumed 8,000 ppm zinc oxide (ZnO) as a feed additive. The pancreas of each of 4 autopsied pigs was less than half the normal size. Acinar cells were considerably decreased. Epithelial duct-like cells were increased and tested positive for cytokeratin AE1/AE3, Ki67, PGP9.5, and Sox9. Pancreatic islet cells were decreased and shrunken. The α and δ cells were relatively decreased, and their distribution was abnormal. Islet cells were positive for PGP9.5. The livers and kidneys had high accumulations of zinc (Zn; 788 µg/g and 613 µg/g, respectively). Copper was deficient in the liver, likely as a result of Zn poisoning. Our immunohistologic examination suggested that the high dose of ZnO could influence the function of islet cells in addition to that of acinar cells. Given that colistin sulfate has been banned as a feed additive in order to reduce antimicrobial use in Japan, the use of ZnO in the livestock industry is expected to increase. Zn supplementation of pig feed must be monitored to prevent Zn poisoning and contamination of soil and water.