fungi in feed
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Role of fungi and it’s tolerance limits and
measures to check them in stored products
Vishnu Vardhan Reddy.PTVM/2015-029
Department of Animal nutritionCollege of Veterinary Science, TirupatiSri Venkateswara Veterinary University
Introduction
Fungi are a subdivision of the subkingdom Thallophyta.
Fungi impair feed quality in at least two ways.
• They may alter the nutritional quality of feeds by
destroying important nutri ents such as vitamins.
• They may produce mycotoxins that are harmful to
animals.
Toxigenic fungi in crops have been historically divided
into two distinct groups.
• The first includes those which invade and produce
their toxins before harvest which are often rather
loosely called 'field fungi'.
• The second group, which becomes a problem after
harvest, is known as ‘storage fungi’.
Store fungi include all species of Aspergillus, Fusarium
and Penicillium.
The growth of fungi in storage is governed by the
following factors:
• Composition of nutrients in the grain
• Moisture and temperature conditions
• Biotic factors like competition or the presence of
stored product insects.
Fungus species Feed affectedAlternaria alternate Rice, Sorghum, Soybeans
A. longissima Rice, Sorghum
A. padwickii Rice
Aspergillus flavus Cashews, Copra, Maize, Groundnuts, Sorghum, Soybeans
Fusarium moniliforme Maize, Sorghum, Soybeans
F. semitectum Maize
Penicillium citrinum Sorghum, Soybeans
Factors governing growth of fungi in stored products
1. Water activity
2. Hydrogen ion concentration
3. Temperature
4. Gas tensions, specifically of oxygen and carbon dioxide
5. Consistency that is, liquid or solid state
6. Nutrient status
7. Specific solute effects
8. Preservatives (Pin and Hocking, 1985).
9. Other factors like damaged grain during harvest, handling, threshing or drying,
penetration of water (leakage).
Water activity• Water activity is numerically equal to equilibrium
relative humidity (ERH) expressed as a decimal.
• Water activity is defined as a ratio: aw=p/po
• Where p is the partial pressure of water vapour in the
test material and po is the saturation vapour pressure of
pure water under the same conditions.
• Feed stored at humidity between 75 and 85% ERH are
susceptible to attack by xerophilic fungi
Temperature
• Temperatures below 20°C tend to favor cold-tolerant
fungi, such as Penicillium and Cladosporiwn, while
higher storage temperatures favor Aspergillus
species.
• Under tropical conditions, stored products are more
susceptible to Aspergillus species than other fungi.
Gas tension• Both reduction in oxygen tension and increase in
carbon dioxide concentrations can have profound
effects on the growth of fungi.
• Animal feeds may sometimes contain weak acid
preservatives such as propionates usually sold as
proprietary chemicals will prevent fungal growth in
stored feeds.
Preservatives
Damages caused by storage fungus• Loss of nutrients
• Discoloration of grain
• Reduction in germination ability
• Caking of grains
• Moldy smell and taste
• Production of mycotoxins
• Creation of environment for the development of
special insect species
MycotoxinsThe most common mycotoxins known to cause health problems in and
livestock are:
• Aflatoxin
• Fumonisins
• Tricothecenes, especially T-2 toxin also known as vomitoxin,
deoxynivalenol (DON)
• Ochratoxin, especially ochratoxin A (OTA)
• Ergot toxins
• Zearalenone
Ergot:
Ergot alkaloids are very potent toxins produced
by the fungi ergot (Claviceps purpurea).
Triticale and rye are the most susceptible grains, but
wheat, barley, oats and corn can also become infected.
They impair blood flow to the extremities, affecting
tissues such as the kidney and uterus. Reduced blood
flow to the reproductive tissues can result in
spontaneous abortions.
Ochratoxin A:
Ochratoxin infects many crops
including barley, oats, wheat, corn and soybean meal.
It is produced by the fungi Aspergillus and Penicillium
and is generally restricted to areas of temperate
climate.
Ochratoxin affects the kidneys and can cause birth
defects. Immunosuppression has also been associated
with Ochratoxin A.
Zearalenone:
Zearalenone, sometimes referred to as
F2 toxin, is a mycotoxin produced by the fungi
Fusarium. It is often associated with corn but can infect
many other crops including wheat. It is an estrogenic
compound; as a result, its effects on the animals are
similar to those of the natural hormone, estrogen
particularly affects reproduction.
Tricothecenes:
Tricothecenes are a group of very toxic
compounds which include deoxynivalenol (also called
DON or vomitoxin), HT-2 toxin, diacetoxyscirpenol and
T-2 toxin. They are produced by Fusarium molds and
highly toxic . tricothecenes are particularly causes
suppression of the immune system.
Aflatoxin:
Aflatoxin is produced primarily by the
fungus, Aspergillus. Ideal conditions for Aspergillus
growth include moisture content above 14%,
temperature above 25°C and the presence of oxygen. It
is known to affect many feed ingredients including
corn, rye, oats, wheat, barley, soybean meal,
sunflower meal, rapeseed and alfalfa.
Fumonisin:
• Fumonisin B, produced by E verticillioides It causes
leucoencephalomalacia in horses
• Pulmonary edema in swine and
• Hepatoxicity in rats.
Food or feedstuff Concentration (ppb)
All products, except milk, designated for humans 20
Corn for immature animals and dairy cattle 20
Corn and peanut products for breeding beef cattle, swine and mature poultry 100
Corn and peanut products for finishing swine (>100 lb.) 200
Corn and peanut products for finishing beef cattle 200
Cottonseed meal (as a feed ingredient) 300
All other feedstuffs 20
Milk 0.5
FDA action levels for total aflatoxins in food, feed
Safe levels of mycotoxins
FDA advisory levels for DON (vomitoxin) in livestock feed
Animal type Feed ingredients,Maximum diet inclusion
DON levels(ppm)
Total diet levels (ppm)
Ruminating beef and feedlot cattle
older than 4 months
Grain and grain byproducts (88% DM basis)not to exceed
50% of the diet10 or 30 10
Ruminating dairy cattle older than 4
months
Grain and grain byproducts (88% DM basis) not to exceed
50% of the diet10 or 30 5
Chickens Grain and grain byproducts not to exceed 50% of the diet 10 5
Swine Grain and grain byproducts not to exceed 20% of the diet 5 1
All other animals Grain and grain byproducts not to exceed 40% of the diet 5 2
FDA guidance for industry on fumonisin levels in foods and animal feeds
Feed Feed Ingredients (ppm)
Finished feed (ppm)
Corn and corn byproducts intended for:Equids and rabbits (no more than 20% of diet) 5 1
Swine and catfish (no more than 50% of diet) 20 10
Breeding ruminants, breeding poultry and breeding mink and including
lactating dairy cattle and hens laying eggs for human consumption (no more than 50% of diet)
30 15
Ruminants more than 3 months old being raised for slaughter and mink being raised for
pelt production (no more than 50% of diet)60 30
Poultry being raised for slaughter (no more than 50% of diet) 100 50
All other species or classes of livestock and pet animals (no more than 50% of diet) 10 5
Safety level of Zearalenone
• Hyperestrogenism occurs when contamination of ZEA
is as low as 0.1 ppm.
• Broiler chicks and laying hens are less susceptible to
ZEA, even at very high dietary concentrations.
• Turkeys, on the other hand, at the high dietary levels
of 300 ppm, develop greatly enlarged vents.
Prevention of fungi in feed
Action to take before harvest• Use certified seed or ensure seed is free of fungal, bacterial or viral infection;
• Avoid drought stress – irrigate if possible;
• If practicing minimum or zero tillage remove crop residues;
• Weed regularly;
• Control insect, mammal, bird and virus pests;
• Rotate crops;
• Avoid nutrient stress – apply appropriate amount of organic or inorganic
fertilizer;
• Plant resistant varieties where these are available.
Action to take during harvest
• Harvest as quickly as possible
• Avoid field drying
• Transport the crop to the homestead as soon as possible
• If lack of labor or time prevents removal from field then dry
on platforms raised above ground (if climate is hot and dry
crop can be left to stand in field or cut and tied into stooks) to
dry
• Bundles of stover should also be placed on platforms to dry
and not left to lie on the soil
Action to take after harvestDrying
• Crop should be spread on a (black) polythene sheet,
tarpaulin or empty sacks laid on the ground or on a concrete
plinth .
• Unthreshed crop can be laid on platform or in ventilated crib
to dry; cobs can also be tied in pairs and suspended from a
vertical frame to dry.
• In wet or humid conditions crop should be artificially dried in
a solar dryer.
Threshing, shelling , winnowing
• Handle crop carefully to avoid broken or damaged
grain.
• Use hand or pedal operated threshers if possible.
• Avoid beating the crop with sticks as this creates lots
of damage leading to mould development unless the
grain is to be used quickly and not stored.
Storage
• Store unthreshed produce or grain in suitable container which is
raised above ground level. If the crop has to be stored on the
ground ensure a suitable waterproof barrier is in place.
• Treat a crop that is to be stored for more than two months with
a suitable grain protectant to prevent insect damage. Protect
the crop against damage by rodents.
• External storage structures must have a good roof with suitable
overhang to provide shade and to take away rain. They should
be protected against rodents and termites.
• Access to the crop inside should be easily achieved by having
an opening or door in the wall or a roof that can be raised.
Sacks must be stored on a platform raised above the floor.
• Produce must be inspected regularly to ensure that it is free
of mould, insect and rodent damage; if damage is present
remedial treatment must be put into place.
• Flour and feed must only be stored for short periods to avoid
mould development. Small quantities can be kept longer in
airtight containers.
Chemical treatment• Caustic soda-treated grain swells making silo storage
impractical. Treatment offers no long-term protection
against insects or mites.
• Propionic acid allows storage of damp grain but offers
no long-term protection against insects or mites.
• Apply caustic soda solution – either 30–45 g solid, or
47% solution. Or l Apply propionic acid at 5.5 L/tonne
at 16% mc,to 14.5 L/tonne at 32% mc.
Aspergillus Ear Rot
• Grain Affected: Primarily
Corn/Corn products,
Peanuts/Peanut products;
Secondarily Pecans, Walnuts,
Almonds, Cottonseed meal,
Sorghum, Barley and Oats.
• Pathogen: Aspergillus flavus, A.
parasiticus, A. nomius, A. niger, A.
glaucus
Black Tip / Black Point
• Grain Affected: Wheat,
Barley
• Pathogen: Cochliobolus
sativus, Helminthosporium
sativum (asexual stage)
Blue-Eye Mold
• Grain Affected: Corn
• Pathogen: Penicillium
oxalicum
Blue-Eye Mold (GIPSA)
Purple Plumule (GIPSA)
Ergot
• Grain Affected: Wheat,
Rye, Triticale, Barley,
Oats, Cultivated & Wild
Oats
• Pathogen: Claviceps
purpurea, Claviceps
paspalli and Claviceps
fusiformis.
Ergot Sclerotia (GIPSA)
Fusarium Ear Rot
• Grain Affected: Corn
• Pathogen: Fusarium
moniliforme
Gibberella Ear Rot
• Grain Affected: Corn
• Pathogen: Fusarium
graminarum, Fusarium
roseum (sexual stage),
Gibberella zeae
Karnal Bunt
• Grain Affected: Wheat,
Triticales and Rye
• Pathogen: Tilletia indica
Scab (Head Blight)
• Grain Affected: Wheat,
Barley
• Pathogen: Fusarium
graminarum, Gibberella
zeae, Zearalenone
Wheat Scab
Barley Blight
TCK Smut (Dwarf Bunt)
• Grain Affected: Wheat,
Rye, Barley, Wild &
Cultivated Grasses
• Pathogen: Tilletia
controversa
Smut Balls
Tilletia controversa
THANK YOU
Vishnu Vardhan Reddy.PTVM/2015-029
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