Top Mycotoxin Myths - Busted
Have you ever heard of or seen the popular television show “Myth Busters”? The premise of the series is a team of scientists test and, in many cases, debunk common myths. While the show has discredited the classic saying of being “as clumsy as a bull in a china shop” with a live bull running gracefully between shelves with china on them, there are still a number of other myths that need debunking, including myths related to mycotoxins. Below are some of the most common mycotoxin myths and the truths behind them.
Myth #1: Test results can’t lie
The Facts: On the one hand, it’s definitely true that analytical tests are much better than they used to be, they’re more accurate. BUT the problem with that is, how you sample is critically important because molds grow in pockets, you can have extremely high mycotoxin levels in one source and very low in others. As grain is handled and processed, those toxins are distributed. Tests taken on grain need be done very carefully to get an accurate representation of what toxin risk will actually look like in feed.
Myth #2: Quick tests make mycotoxin risk management easy
The Facts: Quick tests are designed for single ingredients, not the finished diet. Due to all of the steps in between the ingredient test and formulating the diet, we cannot use quick tests for measuring the risk in a finished diet. While we can get the same answer with a quick test as we do with the lab test, if we want to test for a range of toxins, we will have to purchase multiple quick tests. The cost of an individual test is low compared to the lab cost, however, when running quick tests, a reader is required. The price of a reader can ranges $3,000-4,000, so this extra expense can often be limiting for some operations. The final and most important limitation for quick tests in dairy operations is that there is no quick test for forages. Since forage makes up a large portion of the dry matter in a diet, this creates a large variable we are unable to manage with quick tests.
Myth #3: “Incidents” effectively predicts mycotoxin risk levels
The Facts: Mycotoxin tests have gotten increasingly more sensitive, such that you can measure mycotoxins at levels that are not biologically important. This means that in most cases you can measure toxins at levels that do not harm the animal, however, these test results could be defined as a “positive” result for mycotoxin contamination. When suppliers share information about “incidents” without sharing information on the level as it relates to creating problems for the animal, it can be misleading as to what the actual levels being shared are, and it doesn’t necessarily help us understand the actual risk. In order to avoid misunderstanding, ask your supplier the distribution of mycotoxin levels (range, mean, and variation) and how they relate to the threshold at which the animal will be negatively impacted.
Myth #4: All toxins are created equal
While the six most common mycotoxins tend to come from three primary mold families, mycotoxins are extremely different and there is much variation on how they impact the animal. The different molecular structures and modes of action create these vast differences. For example, zearalenone looks like estrogen to the body, which leads to disruption of the reproductive system function and development. DON/vomitoxin appears to rapidly absorb and go to the brain, resulting in reductions in feed intake in a very short amount of time. Aflatoxin can be acute but is also a carcinogen with a cumulative effect that can damage the liver, leading to issues with metabolizing nutrients. Ochratoxin targets the kidneys and create issues with detoxifying the body. T-2 has a severe effect on the mucosa of the gastrointestinal tract and can cause lesions, leading to feed intake drastically dropping. The action effects of different toxins can also be significant, ranging from a few ppb (such as aflatoxin) to several ppm (as seen with fumonisin). Additionally, different species react different to toxins, with dairy cattle being most susceptible to aflatoxin, DON/vomitoxin, and zearalenone.
Myth #5: Toxins are destroyed in the rumen
The Facts: Mycotoxins can be modified in the rumen, but not necessarily destroyed. In fact, some toxins have metabolites that are even more toxic than toxin itself. For example, roughly 90% of zearalenone is converted to alpha-zearalenol (a-Z-enol), which is four times more estrogenic than zearalenone itself. Additionally, a low percentage of zearalenone converts to beta-zearalenol (b- Z-enol) which binds less readily to estrogen receptors but is toxic to endometrial cells in the uterus. Another example of modification of mycotoxins in the rumen is aflatoxin, which is only slightly degraded by rumen microflora and is efficiently absorbed from the cow’s gut. Roughly 1% of aflatoxin is converted to aflatoxicol, which actually has toxicity similar to the parent aflatoxin compound.
Myth #6 Using certain products can eliminate mycotoxin risk
The Facts: Regardless of what advertisements tell you, some things are too good to be true. The best defense for mycotoxin risk management is a good offense. By being proactive in your management approach, you can help minimize impacts to herd health and productivity. So, what does this proactive approach look like? We like to break it out into three easy steps: monitor, manage, mitigate. That means making sure you are doing everything possible to monitor mycotoxin risk in your area and in your feedstuffs. Manage the toxins when they are present by properly screening and drying feedstuffs, store moldy grain separately, and consider feeding suspect grain before the temperature of the stored grain begins to rise. Finally, mitigate the risk when mycotoxin exposure is unavoidable by utilizing your nutritional resources. Ensuring your animals are receiving a safe, balanced diet is important to their health and productivity.
The Bottom Line
Mycotoxins can be a complex topic but educating yourself on the facts will help you improve risk management. Utilize your resources and don’t be afraid to ask questions to your nutritionist or veterinarian.