Fungi in feed

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


Rye, Triticale, Barley,

Oats, Cultivated & Wild

Oats

• Pathogen: Claviceps

purpurea, Claviceps

paspalli and Claviceps

fusiformis.

Ergot Sclerotia (GIPSA)

Fusarium Ear Rot


• Pathogen: Fusarium

moniliforme

Gibberella Ear Rot



graminarum, Fusarium

roseum (sexual stage),

Gibberella zeae

Karnal Bunt


Triticales and Rye

• Pathogen: Tilletia indica

Scab (Head Blight)


Barley


graminarum, Gibberella

zeae, Zearalenone

Wheat Scab

Barley Blight

TCK Smut (Dwarf Bunt)


Rye, Barley, Wild &

Cultivated Grasses

• Pathogen: Tilletia

controversa

Smut Balls

Tilletia controversa

THANK YOU

Vishnu Vardhan Reddy.PTVM/2015-029

Education

Fungi in feed