Kaolin, bentonite, and zeolites as feed supplements for animals: health advantages and risks

Feeding kaolin as a supplement to pigs for prevention of diarrheal diseases has been introduced into some farms in the CzechRepublic. Peat was used in the 1990s for a similar purpose; however, most farmers ceased feeding peat as a supplement because of its frequent contamination with conditionally pathogenic mycobacteria, esp. with Mycobacterium avium subsp. hominissuis. The aim of the present paper is to review available literature from the standpoint of the advantages and disadvantages related to feeding kaolin as a supplement to animals. Its positive effects exerted through the diet primarily consist in its adsorbent capability which may be useful for detoxification of the organism and for prevention of diarrheal diseases in pigs. Because the mechanism of action of kaolin fed as a supplement is unknown, a risk related to its potential interactions with other nutrient compounds of the diet exists. Therefore, it is necessary to investigate the effectiveness and safety of feeding kaolin in detail with regard to the health status and performance of each farm animal species. The disadvantage of kaolin use is its potential toxicity, provided it has been mined from the environment with natural or anthropogenic occurrence of toxic compounds. Another risk factor is a potential contamination of originally sterile kaolin with conditionally pathogenic mycobacteria from surface water, dust, soil, and other constituents of the environment in the mines during kaolin extraction, processing and storage.