Agriculture Business Week

Lack of or absence of postharvest facilities… this is the perennial problem plaguing the corn industry for more than a decade. Despite technological advancements that the Philippines is able to catch up on, postharvest is apparently left behind. To this day, we still see plenty of corn and palay being dried in highways all at the mercy of the elements and even motorists. It was reported that about 4 to 25% of a given volume of corn grains are lost during and after harvest. From picking to storage, a farmer knows that every step of the way he or she is losing money. The longer it takes for farmers to bring the grains to the buying center; the higher the postharvest losses.

One of the things that very few farmers know in postharvest management is about grain quality and aflatoxin. We term aflatoxin locally as amag. Everybody is aware of amag and it can spell the difference between rejected and acceptable grain, premium and inferior grain prices. I have personally heard of an incident where a truckload of corn grains from North Luzon was rejected at the feedmill plant just because it failed the tolerable levels of aflatoxin. It was a waste of money, time and effort and to think it travelled several hundreds of kilometers only to find out that they are carrying tons of garbage.

So why is amag so important to feed processors? Why do they have to be so particular with aflatoxin levels? I came across a 2003 presentation of the Bureau of Animal Industry (BAI) showing what corn grains should be before processing into feeds. It should be (1) free from pesticide residue; (2) not moldy or insect-damaged; (3) moisture content should not exceed 14 percent; (4) aflatoxin levels should not exceed 50 ppb or parts per billion; (5) impurities not more than 2 percent; and (6) spoiled/ damaged grains not more than 3 percent. So clearly, we need to understand aflatoxin and how it impacts our grains’ end-users. While I’m not an animal nutritionist or postharvest specialist, let me share with you a few of the basics we all need to know.

PROPERTIES OF AFLATOXIN
Aflatoxins are naturally occurring toxins produced by certain fungi or molds.

There are 4 aflatoxins identified produced by different kinds of fungi in particular Aspergillus flavus and Aspergillus parasiticus. One thing about aflatoxin is that it is stable or temperature-tolerant – meaning it cannot be destroyed even during processing or heating up to 260°C. Even heating under pressure, aflatoxin can only be inactivated by 50%. While the molds can be killed by heating or irradiation; the aflatoxin may still be there. When fed to lactating cows, the toxin may find its way into the milk: Although transformed already into lesser toxic forms, the popular use of cow’s milk for infants is enough warning for stricter monitoring of aflatoxin in feeds.

Exposure of animals to aflatoxin can produce a wide range of symptoms. Even at low concentrations, it has been shown to reduce weight gain, reduce litter sizes, deform offspring, reduce egg production, and, reduce milk production. It can also lower resistance of animals to diseases, interfere with vaccination and acquired immunity. Acute signs include anorexia, depression, among others. Mycotoxicosis, in short, can lead to reduced yield and profit or death of livestock/poultry.

What if it gets into the human body? Literature s iys it is filtered and accumulates in the liver since these aflatoxins are not conv :rted to any other substance or compo,ani i needed by the body. This scenario cot Id lead’ to carcinogenesis and other ne ative effects.

CORN GRAINS ARE PREDISPOSED TO AFLATOXIN
How disease occur in plants is the same as how aflatoxin contaminates corn grains. The interaction of the host (corn grains), the fungus (Aspergellus sp.) and the environment is important in understanding this problem. Aflatoxin can only be present when the fungus finds a host that will sustain it in a favorable enviroment for its growth and development. Corn and peanuts are the preferred hosts of Aspergillus. Between yellow and white corn, it was found that the former produces higher concentrations of aflatoxins fiom harvesting up to the point of the wholesaler.

In many parts of the world, contamination of aflatoxin is a major problem in the corn industry Field infection will always be then when temperatures are high along with relative humidity. Drought conditions and insect damage on corn were also shown to aggravate this problem. There was also some evidence showing infection can also occur through the corn silk.

HOW TO MINIMIZE CONTAMINATION
An ordinary farmer can start right at his farm when tryi3 ig to isolate or minimize fungal infection that can lead to aflatoxin production.
1. Harvest your corn at the right maturity.
• Some farmers opt not to follow maturity dates; harvesting done earlier than the desired maturity of crop can lead to more contamination as grains are softer and with higher moisture content.
• Late harvesting, on the other hand, will expose mature ears to late stalk lodging and put more ears closer to the soil.
2. Manage your crops properly.
• Plant at recommended distances; too close planting promotes fungal growth.
• Keep your plants healthy by providing the right amounts and combination of nutrients.
• Plant hybrids that are tolerant to wide range of diseases.
3. Plant corn borer-tolerant or resistant varieties.
• It has been proven that Bt corn grains (30Y80, 30T80, 30T35) have far less aflatoxin levels than their conventional counterparts especially when corn borer infestation is high.
• The lesser the crop injury the better protection against infection.
4.Avoid mechanical damage to corn grains during shelling.
• Use efficient corn shellers to minimize grain damage which may pre-dispose grains to molds.
• Shell corn when moisture is from 21 % down to 18%.
• Separate good quality ears from the spoiled ones (discolored, moldy, germinated, immature ears) to avoid lowering the quality of the rest of the crop.
5. Store dried grains in a cool dry place and free from storage insect pests.
• Dry corn grains to 14% moisture content uniformly within 2 days after shelling.
• If immediate drying is not possible. store corn in corn cribs.