By Frank Hart*
A large range of additives are used in animal feed, including,
but not limited to, antibiotics; vitamins; antioxidants; amino
acids; enzymes; acidifiers; probiotics and minerals.
The term minerals can be used to
describe salt and metal compounds, which provide trace elements
such as zinc and selenium. To distinguish between laboratory
and factory-produced chemicals such as these and naturally
occurring minerals, FEMAS (Feed Materials Assurance Scheme, UK)
defined the latter as: “Limestone, salt, clays (bentonite,
kaolinite, etc.) and other minerals which undergo no further
processing beyond extraction, crushing, washing, drying and
grading.’’
Global compound animal feed
production is estimated by the IFIF (International Feed
Industry Federation) to be almost 1bn tpa and worth
approximately $400 bn. In addition, there is a further 300m
tonnes of feed produced directly on site by farmers.
The total number of feed mills
globally is estimated at approximately 28,000 with production
by species split approximately as; 46% poultry; 25% swine; 21%
ruminants; 4% aquatics; 2% pets and 2% equine.
Feed is produced in purpose built
mills where bulk raw materials are stored in silos, while
additives might be stored in plastic sacks or containers. Loss
in weight screw feeders control the required blend proportions,
which are thoroughly mixed and extruded as pellets through a
stainless steel die.
Naturally occurring minerals can be
sold directly to the feed producers or indirectly to specialist
additive suppliers, who might sell a broad range of additives
or blend various additives to produce more efficient
composites. Some suppliers are major international companies
operating with global distribution networks and offering
detailed technical advice, examples being Alltech, Nutreco,
BASF, Biomin and Special Nutrients. As farms become larger the
role of distributors will diminish and direct sales will
increase.
Legislation
Legislation governing the quality
of additives for use in animal feed is provided in most parts
of the world, preventing adverse health affects to both the
animals and consumers of meat and dairy products.
The IFIF comprises of national and
regional feed associations to represent the global feed
industry. Current membership accounts for more than 80% of
global animal feed production and includes the US, Canada,
Europe, China, India, South Africa, Japan and New Zealand.
Although this brings some consistency to legislation there are
still variations across the globe, particularly between
established and emerging economies. The 300m tpa of feedstuff
produced directly by farmers presents a problem because they
are not regularly audited by food safety authorities.
In the US, the Center for
Veterinary Medicine (CVA), part of the Federal Food Drug and
Cosmetic Act (FFDCA), which falls under the umbrella of the
FDA, controls animal feed.
In the European Union (EU), the
European Food Safety Authority (EFSA) is in control. The
all-important document is ‘Regulation (EC)
1831/2003’. This is regularly updated, with the latest
revision of Appendix 1, the list of approved additives, issued
on 12 May this year. Other institutions include FEFANA Ñ
an interface between suppliers and the EU and FAMI/QS and FEMAS
Ñ which administers quality control schemes for additive
and feed manufacturers, emphasising prevention of contamination
through HACCP (Hazard Analysis Critical Control Points).
In China, the Ministry of
Agriculture takes control of the inspection and monitoring of
feedstuffs.
Health scares resulting from minerals
There have been numerous health
scares in recent years associated with contamination of animal
feedstuffs and subsequent progression into the human food
chain, either as meat or dairy products. The BSE outbreak in
the UK in 2009 was caused by feeding cattle (which are
herbivorous) infected meat and bone meal derived from sheep.
Between 2006 and 2008 it became common practice in China to add
powdered melamine, which is rich in nitrogen, to pet foods,
milk and other feedstuffs, to make the protein content appear
higher.
Both incidents led to fatalities
and illness on a large scale.
Very few problems have been traced
to naturally occurring minerals. However, there are two notable
exceptions. The first was in 1996 in the southern US, where
chickens for human consumption were found to contain high
dioxin levels. The source was traced to local ball clay added
to soymeal chicken feed as an anti-caking agent.
In 2004 in Holland, potatoes were
graded in a dilute slurry composed of water and German ball
clay. This meant that the high starch potatoes sank whilst
lower starch potatoes floated. The heavy potatoes were peeled
and washed. The peelings plus some residual clay were added to
fodder, which was exported to Belgium and Germany and fed to
cattle, pigs, sheep and goats. The discovery of high dioxins
caused the temporary closure of hundreds of farms in all three
countries.
Dioxins are carcinogenic. They were
originally thought to occur in sedimentary ball clays due to
ancient forest fires, but current scientific opinion is that
they formed due to bio-chemical decay of wood by moulds at the
time the clays were deposited. Regulations are in place in the
EU and elsewhere, which impose strict limits on the total
quantity of dioxins and associated furans and PCBs in all
additives
Why minerals are used in animal feed
Binder
Minerals such as kaolin and
bentonite can help to bind pellets together and reduce dust
content. Very few companies will buy clay minerals purely for
use as a binder however, preferring to use organic materials
such as guar gum or pregelatinised starches, which are more
expensive but work at much lower addition rates (0.1% vs 2%).
Feed pellets provided for marine shrimp and freshwater prawns
should not disintegtrate too quickly in water as feeding rate
is slow and feed may be lost before it is ingested.
Anti-caking
The high surface area of many clay
minerals help to coat sticky ingredients such as molasses and
reduce caking of the finished pellets.
MycotoxinsMycotoxins are secondary metabolites produced by
fungi. Some are good, for example penicillin, which may be
harvested from specially grown colonies and used as an
antibiotic, whilst others are toxic.
Toxic mycotoxins originate from
contamination in crops including maize, nuts and grass and may
subsequently appear in the human food chain, either directly or
indirectly by eating contaminated animals. Mycotoxins can occur
in in standing crops in wet weather or in stored crops when too
moist. They can withstand high temperatures, well above feed
processing temperatures, and are rapidly absorbed in the
digestion system of animals and humans. When present in animal
feed, they can remain in the food chain in meat and dairy
products.
Human illness through mycotoxins is rare except in some
underdeveloped countries. For example, 125 people died in Kenya
in 2004 after eating Aflatoxin contaminated maize.
Unfortunately, problems with animals are common with lameness
in cattle and horses, reduced milk output, sickness and
diarrhoea, kidney disorders and liver disorders, all caused by
mycotoxins.There are numerous mycotoxins, all of which are
complex organic structures based on benzene rings. The most
common are: aflatoxin B1; deoxynivalenol; ochratoxin;
zearalenone and fumonisin.
Aflatoxin is the most prevalent and
presents the most problems. Like some of the other mycotoxins
it has an ionic charge. Thus clay minerals such as bentonite,
sepiolite, illite and kaolin are effective at removing it (more
than 90% efficiency). Aflatoxin bonds ionically with negative
charges on the clay and passes harmlessly through the
animal’s system.
Economically, fusarium derived mycotoxins such as
zearalenone are very important as they are oestrogenic and lead
to poor fertility and potentially miscarriages in breeding
livestock.Simple, cost effective and safe processes by which
animals may be detoxified and decontaminated are in great
demand. There is intense competition from non-mineral
substances. Bacteria and enzymes are commonly used. These break
down the mycotoxin structure into non-toxic metabolites.
Esterified glucomannan, which is obtained from the cell walls
of yeast, work in a similar manner to clays by absorption.
However, these ingredients are almost always combined with a
clay mineral, for example ‘Mycosorb’, one of
Alltech’s best selling products, which is a blend of yeast
cell wall and mineral(s).Radionuclide containment
Radioactive caesium (CS-137) and other radionuclides can
enter the food chain following disasters such as those at
Fukushima in Japan and Chernobyl in Ukraine. Radioactive
elements can travel large distances before being washed out of
the atmosphere by rain, after which they enter freshwater
systems, soil and vegetation, thus contaminating meat and dairy
products and fruit and vegetable crops. Due to the location of
Fukushima, contamination into the Pacific Ocean was another
problem due to the effect on fish and other marine life.
Zeolite and bentonite have the ability to absorb CS-137
so that some of it is excreted rather than absorbed
by the animal. EFSA has approved bentonite for emergency use in
the EU with no maximum addition rate.
Poultry
excrement
In large poultry production farms,
birds such as chickens and turkeys are kept in small crowded
pens where they are forced to walk in their own faeces, which
is alkaline due to the ammonia content. This gives to rise to
leg or ‘hock’ burns which are often noticeable on
chicken legs in the supermarket.
Clay minerals such as bentonite,
sepiolite or clinoptilite added to the poultry feed thickens
the faeces by absorbing moisture, helping to reduce the burns
and making it easier to clean the pens. Clinoptilite will also
aborb ammonia, reducing odours.
White fish farming When farming turbot and halibut, newly
hatched fry can be encouraged to feed by introducing green
algae but this has some disadvantages, particularly cost and
availability. Research in Scotland indicated that the
introduction of kaolin can have the same affect Ñ
without any addition, the fry turn their faces to the wall and
refuse to eat. When algae or kaolin are introduced, it will
diffuse the light passing into the water, so that the fry can
see the tiny plankton particles better.
Pest
prevention
Diatomaceous earth can help to kill
pests, such as mites, which infect grain stored in silos.
Pellet production
rate
Platy clays such as kaolin act as a lubricant for when feed
mix is extruded through a stainless steel die. Significant cost
savings can be made either by running with reduced power at the
same throughput or at normal power with increased
throughput.
Approved naturally
occurring minerals
Obtaining proof for the efficacy of
mineral additives in animal feed and covering possible
contraindications with nutrients and medications is expensive
and time-consuming. Where live testing is required, this might
involve prolonged health studies of different species,
including breeding animals. In vitro tests can also be
expensive, for example the analysis by high performance liquid
chromatography (HPLC) of mycotoxins as parts per billion
(ppbn).
In the EU additives are categorised
into the following groups:
- Technological (binders,
thickeners, preservatives)
- Sensory (flavours and
colouring)
- Nutritional (vitamins, trace
elements, etc.)
- Zootechnical (digestive, gut
flora stabilisers, favourable effects on the environment)
- Coccidiostats and
histomonostats (parasite/protozoa removal)
A closer look at some of
the main minerals
Bentonite
Calcium montmorrillonite represents
the bulk of this vast industry. Biomin, in Austria and BASF in
Germany are major global suppliers.
In 2013, Biomin achieved EU
approval for the use of bentonites for aflatoxin B1 reduction
in ruminants, poultry and pigs and the containment of
radionuclides, additional to the long-standing approval for use
in binding and anti-caking. The new approvals have stipulations
that the bentonite content must be at least 70% and opal
content no greater than 10%, caveats created by Biomin to
minimise competition.
For all applications, there are
warnings that simultaneous use with macrolides (antibiotics)
must be avoided and in the case of poultry, it should not be
used at the same time as coccidiostats. These contra
indications occur due to the high absorptive ability of
bentonite, which is characterised by a high cation exchange
capacity (CEC) and an ability to swell when hydrated.
Sepiolite
Sepiolite is a magnesium silicate
with a micro-fibrous crystal structure. It is extremely fine
with a high surface area and is non-swelling. It is used for
mycotoxin binding, anti-caking and pellet binding. The
naturally high pH is an additional benefit in helping with
acidosis in sick cattle. Additionally, sepiolite has a high
moisture absorption capacity, which can help to keep poultry
excrement drier and reduce hock burns. Tolsa is the main
supplier in Europe, operating deposits in Spain and Turkey.
Kaolin
Widely used due to its common
occurrence throughout the world, kaolin can be used as a binder
for feed pellets, for anti-caking, for prevention of diarrheal
problems and to reduce aflatoxins. Imerys in
the UK has demonstrated a commitment to quality by achieving
FEMAS accreditation earlier this year, for the production and
sale of kaolin used in binding and anti-caking.
Clinoptilite
Clinoptilite/zeolite is
micro-porous with a very high surface area of approximately 500
metres squared per gram (m2/g). It can selectively
absorb molecules depending on their size. The maximum size is
determined by the dimension of channels in the crystal
structure, hence its description as a ‘molecular
sieve’. It is sold into the aquaculture industry, to
shrimp and fish farms and to pet aquariums, due to its ability
to absorb ammonia from water. It is also used in animal feed to
absorb mycotoxins, particularly aflatoxin as well as in poultry
feed to bulk excrement and absorb ammonia. Globally, China and
South Korea are the biggest producers.
Illite
Illite is a potassium aluminum
silicate, which often occurs as a mixture with montmorrillonite
and/or kaolinite. Special nutrients in the US sell an illitic
clay (‘Myco-Ad’) which they claim is affective
against a range of mycotoxins at a low dose rate and is
compatible with all other feed
ingredients.
Diatomaceous
earth
Diatomaceous earth is composed of
the fossilised remains of minute diatoms, some of which are
cylindrical. Deposits vary in species of diatom and in purity,
as some are mixed with clays and other minerals. It has a
strong negative charge and a Mohs hardness of seven.
It is used extensively as an
anti-caking agent and for control of mealworms and mites. in
stored grain. In controlling pest infestations, the razor sharp
edges of the diatoms cause lacerations, after which the powdery
diatomaceous earth absorbs body fluids, bringing death by
dehydration. It can also be used for control of alflatoxin,
particularly when mixed naturally or artificially with clay
minerals.
Calcium
carbonate
Calcium is essential for the
skeletal system but also important for nerve impulse
transmission, blood clotting, milk production
and eggshell development. Calcium carbonate (CaCO3)
also acts as an antacid.
Most production for feed grade is
as ground calcium carbonate (GCC) from pure limestone deposits
containing 98% or more CaCO3 content. Omya, Imerys
and Huber dominate globally.
Salt
Insufficient salt results in
reduced feed intake and subsequent reductions in animal
performance. Excessive salt in poultry leads to increased water
consumption and poor quality excrement, causing leg burns. Salt
regulates blood pH and maintains osmotic pressure, acid/base
balance and exchange mechanisms through cell membranes.
Salt occurs in most countries and
current global production (for use in all industries, including
human and animal feed and chemical) is approximately 284m tpa.
Different production methods include hard rock mining, solution
mining/mechanical evaporation and solar evaporation of
seawater.
Salt for animal feed is normally
sold in vacuum packed sacks at different sizes, ranging from
granules at 1-3mm to fine powder. Salt licks direct from the
mines are also used for cattle, horses, sheep and goats. Global
suppliers include K+S AG (Germany), Compass Minerals (US) and
China National Salt.
Poultry grits
Across the world it is common
practice to provide suitable insoluble grits, according to the
size of the bird, to help with food digestion, as poultry do
not have teeth. The grit passes through the bird into the
gizzard where it is used to grind down the food. Flint, granite
and limestone are among the rock types commonly used, crushed
and graded to a narrow particle size distribution ranging from
0.85-1.50mm for chicks to 6-12mm for turkeys. Many
end-suppliers blend in oyster shell to help with eggshell
development. In the UK, grouse grit (1-4mm) is normally
premedicated to kill nematode worms and other parasites. It is
left to gamekeepers and estate managers to remove medicated
grit at least four weeks before the shooting season starts to
prevent this medication entering the human food chain.
Conclusions
Naturally occurring minerals have
an important role to play in animal feed and the market will
grow substantially, due to our increasing world population and
the need for an adequate food supply.
The UN Food and Agricultural
Organization estimates that the world will have to produce
around 60% more food by 2050 and that animal protein production
will grow by an even larger margin, as a result of family
incomes increasing and greater urbanisation. The global market
for feed additives (all additives, including nutrients etc.)
was estimated by IFIF to be worth approximately $16m in 2012
and is expected to reach $20m by 2016.
This gives plenty of scope for
companies mining natural minerals. Those most likely to succeed
will be committed to quality and proving the efficacy of their
products.
*Frank Hart, director at First Test
Minerals Ltd., has been involved in the manufacture and quality
control of kaolin for use in animal feed at Goonvean Ltd and in
achieving FEMAS accreditation. Contact him at frank.hart7@btinternet.com