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Management of Aflatoxins in Maize
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P Lava Kumar, S Veera Reddy, and F Waliyar
ICRISAT
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They are natural by-products produced by the Aspergillus flavus and related fungi
The fungus invades several crop species and under certain environmental conditions produce aflatoxins in standing crop and also in harvested crop
- Maize, groundnuts, chilies, millets, milk, coffee, etc.
Contaminated grain and food/feed is toxic to humans and animals (cattle, small ruminants, poultry, especially young ones) and result in serious health problems
- Liver cirrhosis, liver cancer, immunosupression, malnutrition syndrome
- Lactating animals fed with contaminated feed result in aflatoxin contamination in milk
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Why Aflatoxins are Important!
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They cause illness to humans and animals
- They cause liver cancer, affects body's immune system and cause growth retardation.
- They are also associated with malnutrition syndrome, and can lead to many other disorders and even death
They cause economic losses
- Humans and animals fed on aflatoxin contaminated food result in ill health and lowered animal production
- Commodities contaminated with aflatoxins lower its market value and export potential
- Add to the management and monitoring costs
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| Aflatoxins are problematic when they occur in food products above the levels established for human and animal consumption
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| Aflatoxin concentration
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Affects on animal health
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| 20 ppb
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Highest level allowed for humans
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| 50 ppb
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Highest level allowed for animals
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| 100 ppb
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Slowed growth of young ones
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| 200-400 ppb
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Slowed growth of adults
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| >400 ppb
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Liver damage and cancer
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| PPB = parts per billion
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Accumulation of toxins in human and animal bodies takes place when aflatoxin contaminated food products are consumed
Toxin accumulation beyond certain level inside the body results in various illnesses
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Aflatoxins in maize are of greatest concern
The climate under which maize is grown favors fungal infestation and aflatoxin production
Aflatoxins can accumulate in maize seeds and stover. They can occur in standing crop and also after crop harvest
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A. flavus infested maize
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Maize seeds infested by fungi: Note that infestation near damaged areas.
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| Fungal Infestation and Toxin Production
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The A. flavus fungus present in the soil and air, can infect maize at any stage from preharvest to postharvest storage
Preharvest contamination:
- Growth cracks, mechanical injury and damage by pests to the plant parts or seeds leads to infestation by fungi
- Toxins are produced under high temperatures, drought, and terminal water stress prior to harvest.
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Postharvest contamination:
- Fungi continue to grow and produce aflatoxins under high moisture and warm temperatures.
- This process is enhanced if drying is delayed. Damage by insect or rats can also facilitate mold invasion and toxin production during storage.
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Aflatoxins in Maize in Andhra Pradesh
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Maize is a major crop in rainfed northern AP. State government encouraging farmers in this region to shift to maize crop with subsidized seed, which is contributing to rapid increase in cropping area.
Northern AP climatic conditions favour aflatoxin contamination, especially during years with high-temperature coupled with water-stress
A. flavus is ubiquitous in AP. Fungal spores survive in soil on plant residues. It can infest maize by air-borne spores in the field during grain filling or during storage and handling.
Kernel infection may occur through the silk, cob or direct contact.
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Maize stretching up to horizon
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Aflatoxins in Maize in Andhra Pradesh
Outcomes from Pilot Studies
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Surveys for phytosanitary aspects in Kharimnagar, Medak, Nizamabad and Ranga Reddy Districts
Hybrids are grown in kharif and rabi under rainfed and irrigated conditions
No major diseases, in some areas pod borer infestation noted
Drought, terminal water-stress are major problems under rainfed conditions
Differences in harvesting methods and post-harvest processing
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Aflatoxins in Maize in Andhra Pradesh
Outcomes from Pilot Studies
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Weather data (temperature and humidity at crop height) in maize fields in various locations recorded
Over 1000 samples collected from different regions from standing crop and harvested and analyzed for aflatoxins
Little awareness among farmers about aflatoxins
Risks are mostly felt at buyer level. Certain companies are not interested to purchase contaminated stocks. When they refuse, traders are moving to other buyers who would not bother with toxin contamination
Traders are willing to offer premium price for aflatoxin free commodities
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Opportunities for A. flavus infestation
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Aflatoxins in Maize in Andhra Pradesh
What is required!
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Impart awareness about aflatoxins among relevant communities through training programmes (Phase 1)
Assess various maize hybrids for aflatoxin tolerance/ resistance (Phase II)
Develop appropriate crop management practices (pre-harvest and post-harvest) to minimize fungal infestation, aflatoxin contamination, end-of-the season drought (Phase II)
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Aflatoxin Management
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Phase I
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Training Programmes to farmers in major maize growing areas
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Good agronomic practices
Proper storing and drying of grain
Maintaining grain quality
Sanitizing grain handing equipment
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Reducing the Risk of Aflatoxin Contamination in Maize
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Preharvest
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Plant maize hybrids with first possible rains and harvest crop at correct maturity.
Remove dead plants and plants showing severe stress due to pest or pathogen attack.
Remove weeds and protect crop from corn borer damage.
Avoid continuous planting of maize under conservation tillage.
Avoid excessively high plant populations and excessive application of nitrogen.
Visually inspect cobs for fungal infections/damage on the grain and discard the affected cobs.
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Reducing the Risk of Aflatoxin Contamination in Maize
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Postharvest
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- Avoid mechanical damage to seed during harvesting, drying and storage.
- Rapidly dry the grain down to 13.5% moisture content and store the seeds.
- Clean grain bins/storage areas before putting the new crop.
- Stock cobs or seeds in bags on wooden plank and store them in well aerated waterproof area.
- Avoid stacking of harvested crop with cobs intact.
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Aflatoxin management practices not only minimizes the contamination, but also contributes to increased yields
Fetches higher remuneration
Safe to eat aflatoxin free food
Potential for direct buying by export oriented industries
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