Physico-Chemical Properties of Clay Minerals and Their Use as a Health Promoting Feed Additive

SIMPLE SUMMARY: Feeds contaminated by mycotoxins cause organ damage, immune suppression and health disorders, limiting growth and performance of farm animals. One of the most practical approaches to minimizing the negative effect of these substances in livestock diets is by the use of different feed additives, preventing their absorption from the gastrointestinal tract. Growing interest in particular is applied to mineral additives, such as clays and clay minerals. These materials are not digested but bind toxic metabolites and mycotoxins, moving them through the digestive tract, without detrimental influence on the animal body. Apart from the binding capacity, clay minerals show other activity which could positively affect animal welfare and productivity. However, each type of clay has its own specific binding capacity that can greatly vary according to its origin deposit and treatment. Moreover, clays may bind with not only noxious substances but also some nutrients, causing a nutritional imbalance for animals. Therefore, the aim of the review was to present the available knowledge on the properties and use of clays in feedstuff decontamination as well as to discuss the resulting potential benefits for animal health and safety of human food. ABSTRACT: The contamination of feeds with microbiological or toxicological agents can affect health, productivity and safety of livestock animals and their products. The treatment of feedstuffs to lower the content of undesired substances before feeding is expensive and labor intensive, therefore an alternative is to reduce their gastrointestinal absorption. Different feed additives are available, however the use of clays and clay minerals are ideal for this purpose due to their high specific surface area, adsorption capacity, low or null toxicity for the animal and low cost. A large number of clays available to producers have different structures that are dependent on their mining source, causing difficulty in proper categorization. For this reason properties of phyllosilicates with 1:1 layers (one sheet of SiO(4) tetrahedra joined to one sheet of Al- or Mg-octahedra), 2:1 layers (one sheet of Al- or Mg-octahedra between two sheets of Si-tetrahedra), and 2:1:1 layers (a basic 2:1 structure with an interlayer brucite (with cations Mg(2+) or Fe(2+)) or gibbsite (with cation Al(3+)) sheet) and tectosilicates are described. The role of clay minerals in animal production shows a reduction in diarrhea, better feed conversion ratio, and improved health of many livestock species due to their specific adsorption potential of many feed mycotoxins. Overall, there is growing interest in the use of clays due to their beneficial characteristics, absence of primary toxicity and success in research to reduce animal disease and improve animal production and safety of animal products.