Pig International - September 2017 - 29
PigInternational ❙ 29
MINERAL CLAYS LIKE BENTONITE are natural
products with wide industrial uses.
water and plasticity - hence, mud.
In brief, earth is a natural product, and animals
are well accustomed to consuming it - but this does
not imply we should start feeding mud to our farm
livestock! In contrast, in today's modern farming
world, it is imperative to look at natural earth compounds to find suitable additives that will optimize
the quality of feeds.
Unique properties of bentonite
Such a product is bentonite, a mineral clay deriving
its name in 1898 from a natural deposit called Benton
Shale near Fort Benton in Wyoming, U.S. Of course,
bentonite is not unique to the U.S., as its counterparts
can be found all over the world. In fact, in Europe, a
similar if not identical mineral clay is called montmorillonite, after the French town Montmorillon, where
it was first discovered in 1847 (the clay, not the town).
But we will call it bentonite, if only because it is easier
to write and pronounce. It is interesting to note that
scientists still debate nomenclature of all these clays,
something that escapes the scope of this work.
Bentonite, thus, is a mineral clay, and more specifically an aluminum phyllosilicate clay. In other
words, it contains silicon dioxide (earth) and aluminum, bound with two major minerals (calcium or
sodium) that give bentonite unique industrial properties and possible applications in feeds for monogastric animals.
The major characteristic of sodium bentonite is that
it expands and absorbs water several times its mass.
This mineral clay is used as a gut "sponge" that can
absorb excess moisture from digesta, something that
can happen due to pathological disturbances (bacterial
diarrhea, for example) or nutritional imbalances (osmotic diarrhea). In either case, it helps control digesta
moisture and, along with other additives, can prevent
September 2017 ❙ www.WATTAgNet.com
or alleviate the symptoms, but not the cause, of wet
droppings (poultry) or watery fecal matter (pigs).
The usual inclusion rate for this purpose is up
to 20 kg per metric ton, or 2 percent, at which level
it can affect the plasticity of feeds being thermally
processed. Feeds that are being pelleted (most often)
or expanded (rarely) containing high levels of sodium
bentonite will have different handling characteristics
and final product traits compared to non-fortified formulas. Bentonite will absorb water usually added as
steam during thermal processing and make the conditioned mass more plastic, but it will also harden the
pellets or extrudate upon drying. We need to keep in
mind that clay is a fragile element after being baked,
and if this is the only pelleting aid, it can result in
more fines than anticipated.
Learn more: 6 unique ingredients
to lower piglet feed cost,
In contrast with sodium bentonite, the main characteristic of calcium bentonite is not that of a water
absorbent material. Instead, its main trait is the adsorption (binding) of ionic particles - such as trace
minerals, but also some mycotoxins. Thus, using
calcium bentonite is a delicate exercise. It is one of
the most widely-used additives in controlling aflatoxin
contamination (used at levels of 0.5 to 1.0 percent), but
has no effects on any other mycotoxin.
When used as an aflatoxin binder, care should be
taken to ensure diets are well fortified with all possible
ionic compounds that can be bound by calcium bentonite.
Here, it is required mentioning that in the presence of
sodium in solution (such as in the conditions found in the
gut of animals), calcium bentonite can be converted to
sodium bentonite. Thus, given enough time, calcium ben-