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Attapulgite: A unique clay for better digestion

Attapulgite: A unique clay for better digestion
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Clays are known for their layered structure and surface properties, making them ideal 'sponges' for unwanted molecules. The same applies to attapulgite clay. This clay is recognised for its ability to strongly interact with bacterial toxigenic strains of E. coli and Clostridium perfringens. Products containing this type of clay can therefore be seen as natural alternatives for a healthy and efficient production, mainly because they benefit the animal by protecting the intestinal epithelium cells and a better digestion.

 Different than other clays

This type of clay is different than other clays (e.g. montmorillonite or bentonite) . The difference is in the structure, but also in physicochemistry.

Montmorillonite belongs to the phyllo-silicates smectite group with 2:1 struc-ture (2 tetrahedral sheets of Silicon, sandwiching a central octahedral sheet of aluminium). Such lamellar structure opens up and swells in presence of water. Attapulgite has a nano tubular structure (Figure 1

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with tubules having a 2:1 structure connected in the four edges and forming a stable non- swella-ble 3d network, leaving between the nanotubules 4-5 A wide channels, offering to the mineral a great internal porosity 200-300 m2/g responsible for the very important water absorption capability of attapulgite. Therefore during the digestion process (intestinal tractus), attapulgite is absorbing internally and stabilising excess produced water whereas montmorillonite is traps water externally between lamellas and swells creating a muddy mass. Surface properties of the two minerals do differ (presence of Si-OH groups on the surfaces of tetrahedral sheets of silicon that are interacting with toxins) due to different stereochemistry and different isomorphous substitutions of Mg for Al creating different surface charges in the two minerals.

 Extrusion techniques

Attapulgite has been used in several industries for many years because the clay has a broad spectrum of uses. Major deposits exist in regions, including the state of Georgia in the United States, but also in Greece. Companies can extract it with surface mining techniques and process it in a variety of ways, depending on how it will be used. the clay can be divided into three different generation. 

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At Geohellas in Greece, the industrial production process involves exfoliation of the bulk structure of the clay by using extrusion techniques. 

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This way the internal specific surface of the mineral is increased, hence increasing the water absorbing capacity (anti-diarrhoeal effect). At the same time, thermal activation of the clay by using temperatures higher than 250 degrees Celsius creates a dry structural acidity level and enhances the surface organophilicity/oleophilicity. This is the affinity of a surface to interact with organics such organic molecules (aflatoxins, mycotoxins etc). Oleophilicity is the opposite of hydro-phylicity, means that a highly hydrophilic surface has a minimum oleophilic effect and also a highly oleophilic surface has a minimum hydrophilicity). In the case of attapulgite, there are internal porous surfaces that are hydrophilic and are trapping water, whereas external particle surfaces through short thermal treatment are becoming oleophilic to bind the toxins and bacterial toxigens. The reason that a non excessive temperature and a short treatment time is used is to keep the hydrophilic behaviour in attapulgite channels. This improves interactivity of the mineral with molecules such as mycotoxins and microbial pathogens.

Healthier gut in piglets

To test the ability to increase health and microbial infestation in piglets, a trial was
carried out. Piglets were inoculated with E. coli 0157:H7. Some animals received
the feed with attapulgite (corresponding to a dosage in feed of 3 kg/MT), at several dilutions (10, 102, 104 and 106). Some piglets were given the normal feed, without the clay minerals. It was shown that attapulgite appears to have a protective action in comparison to the control group, shown in a 21% increase in the number of surviving intestinal cells in the presence of E. coli (10/ml) and a 13% increase at the highest concentration (106/ml). Similarly, the number of surviving cells in the presence of Clostridium perfringens increased by 13% at the lowest concentration (10/ml) and 9% at the highest (106/ml).

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Less diarrhoea 

The Veterinary School of University of Bologna looked at the anti-diarrhoea effects of the clay in weaning piglets. Attapulgite, like other clays, are used to improve the technological characteris- tics of feed e.g. pellet hardness and durability or free flowing properties. They made two different...

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