Controlling mycotoxins in pig and poultry feeds

Mycotoxins are a recurrent problem in many parts of the world, affecting millions of animals. Today, the majority of public attention is focused on how to neutralize the effect of mycotoxins after they have been produced and are already in the animal feed; basically by using suitable mycotoxin-control agents (additives).

At minimum, silos should be completely emptied a few times each year. (istockphoto.com)
At minimum, silos should be completely emptied a few times each year. (istockphoto.com)

Mycotoxins are a recurrent problem in many parts of the world, affecting millions of animals. Today, the majority of public attention is focused on how to neutralize the effect of mycotoxins after they have been produced and are already in the animal feed; basically by using suitable mycotoxin-control agents (additives).

Although this is a valid approach, it should be noted that a more comprehensive control program begins right before the seed is placed in the soil. Such an integral approach includes the steps of (1) prevention, (2) control, and (3) neutralization. Successful implementation of appropriate measures in each step will reduce the effort required for success on the next step. Below is but a short list on how to handle the issue of mycotoxins from the field, to the storage facilities and finally, in the animal feeds.

Prevention

The first step should be the selection of varieties of cereals that are known to possess increased resistance to mycotoxin accumulation on the surface of the maturing seed. Although varieties with total resistance are still the focus of much research internationally, some existing varieties are known, at least locally, to be more resistant than others. This has to do mostly with the hardness of the pericarp (outer seed layer) because fungi (molds) require an entrance point to feed and multiply before they start producing mycotoxins. Cereal seeds with extra-hard pericarp have been shown to be resistant to mycotoxin accumulation on their surface (see Table 1).

In addition, it is well known that molds require high atmospheric humidity to grow and produce mycotoxins. If the period around harvest is especially humid, then it would be advisable either to delay harvesting until humidity drops, or to dry-heat the cereals before storage. It is also common knowledge that a combination of hot weather and high humidity benefit molds and enhance mycotoxin accumulation. Cool temperatures and humid weather also benefit molds because the cool temperatures delay seed maturation, giving molds more time to produce mycotoxins.

Control

Once the crops have been deemed ready to be harvested, then control of mycotoxin production becomes important. This involves two main areas of attention. First, during harvest and storage, handling (transportation from silo to silo) should be minimal to avoid breakage of the seeds. As mentioned above, molds find it difficult to multiply without first penetrating the outer layer of the seed. Second, before storage, seed humidity should be minimal either by controlling harvesting time or by dry-heating the seeds to an average moisture content around 12-14 percent. Seeds with humidity below 10 percent are quite prone to breaking and the cost to dry heat them to such low humidity levels is rather prohibitive.

There is one more measure that can be taken to ensure molds do not find the opportunity to infect cereals with mycotoxins. This is by frequently cleaning the storage silos with pressure water (if possible), at least once or, preferably, twice per year. At minimum, silos should be completely emptied a few times each year. This prevents pockets of “caked” material from remaining “glued” to the internal surfaces of the silos. Such “hot” pockets are harboring a huge population of molds because internal temperature and humidity remain very high. Such residual material is often dislodged and mixed with incoming fresh cereals, acting as an innoculant for the multiplication of molds.

In terms of additives used to control mold growth, sodium and calcium propionate salts are quite effective (among other similar products). A typical dosage of 0.2 percent is recommended for mild cases of mold infection, reaching 0.5 percent in heavily infected batches. Organic acids are mixed in with the cereals usually during loading of the silos. It should be noted here that organic acids are effective against the molds, and not against any mycotoxins already present in the cereals.

Neutralization

This is the final stage of attention that has received considerable publicity due to the nature of the methods applied to neutralize mycotoxins. Whilst the previous two steps involved measures against the molds that produce the mycotoxins, this step focuses on the already produced mycotoxins. As such, any molds already present in the feed continue to multiply (if they find enough humidity) and produce new mycotoxins. Thus, a mold inhibitor is also recommended if the final feed is going to remain in storage for a long time under unfavorable conditions.

Today, there are two major ways of neutralizing the effect of mycotoxins in feed. One is by adding a binding agent that prevents mycotoxins from interacting with the animal. Examples of such agents are bentonite, sepiolite, aluminosilicate and yeast cell-wall fragments. In the case of clays, up to 2 percent might be required to completely detoxify a heavily infected batch of feed.

The second method is that of destruction by means of enzymatic action or ammoniation. The first is quite common as it involves a commercial additive being used in the final feed. The second method is very effective, but it requires special facilities and as such, it is best suited for treatment in volume and in areas with persistent mycotoxin problems.

Here it should be mentioned that all agents are not equally effective against all mycotoxins. Matching the right anti-mycotoxin additive with the predominant mycotoxin problem is quite a challenge, but it is the only way to effectively control mycotoxins.

Dilution

Before the advent of mold inhibitors and anti-mycotoxin agents, the most common method to neutralize (or at least minimize) the effect of mycotoxins in a batch of cereals (or any other ingredient, or complete feed) was to dilute the infected batch. This involved the use of a part of the contaminated batch in conjunction with a larger part of non-contaminated material. As the effects of mycotoxins are dosage related, reducing their concentration in feed by the simple method of dilution offers a less-expensive, albeit labor-intensive, method of handling this problem. In some countries, such as Germany, this remains the main method of addressing the issue of mycotoxins in raw materials. This method finds also good acceptance in many small-size operations.

Under the same logic of dosage-related effects, quite often, contaminated raw materials and/or feeds are reserved to be fed to growing-finishing pigs (after dilution – depending on the mycotoxin levels). That is, piglets and sows are fed only with non-contaminated feeds because these animals are more sensitive to mycotoxins.

Testing

Quite often, large operations that buy raw materials and/or feed from a large number of distinct vendors do not know what kind of mycotoxins will be present and at what levels. If the volume is quite large and several truckloads from different destinations are mixed in the same mega-silo, then it is quite difficult to measure the ever-changing level of mycotoxins. As such, these operations are forced to apply a universal dosage of an anti-mycotoxin agent – frequently at a high inclusion rate – as a general precautionary measure. This is a costly way to handle the issue of mycotoxins and quite often negates any cost benefits from the purchase of raw materials at bargain prices from unknown sources. This becomes even worse when the applied agent proves ineffective in neutralizing the existing mycotoxins. Quite often problems are detected only due to reduced animal performance!

In contrast, a well-thought out prevention and neutralization program, coupled with controls at the purchasing entity, can reduce the overall impact of molds and mycotoxins on the final cost of production. For this, a vigorous testing program is required to be established in association with a laboratory that can offer timely and reliable analytical services.

Page 1 of 65
Next Page