There should be no doubt that there are probably mycotoxins in your silage, especially when Danish studies show that up to 61% of all Danish maize silage contains at least one type of mycotoxin.
But you can always ask yourself the question “how big is the problem really?” or “are mycotoxins a big enough problem for my production results that I should treat for it?” A better question to ask yourself would be “What do I risk by ensuring that the mycotoxins do not cause problems in my silage?”
You protect your business and your animals daily against various health. For example, you use teat dip after milking to prevent your cows from getting mastitis and have probably chosen a specific bedding for the stalls to avoid the same problem. Maybe you also treat the animals against getting hoof problems by letting them go through a hoof bath regularly. The point is that you are doing something proactive to ensure many parts of your business against potential problems with bacteria, viruses, and other potential risks. And yet many farmers are still reluctant to be proactive against what constitutes an equally large, if not larger, threat to their production results – mycotoxins
Signs of mycotoxin poisoning are often diffuse
Mycotoxin poisoning caused by moulds can affect animal health and productivity. A chronic exposure to toxins, even at low levels, can cause a range of unspecified symptoms, making it difficult to diagnose mycotoxin intoxication. The picture is also muddled by the fact that other diseases cause similar symptoms. Symptoms include loss of appetite, poor performance, food rejection, diarrhea, increased cell counts and signs of foetal, kidney, liver, or lung damage. It can also manifest itself as a weakened immune system, increased infections, or metabolic and hormonal imbalances.
Today, there is talk of a mycotoxin syndrome, that is non-specific and comprises an impairment of rumen and liver function as well as immunosuppressive effects (Santos & Fink-Gremmels 2014). Suspicion is therefore often only directed at mycotoxins when symptoms cannot be explained by other diagnoses. However, given the general prevalence of molds and the derived mycotoxins, it would probably make more sense to rule out mycotoxins as a cause of disease earlier in the diagnostic course.
Difficult to measure mycotoxins
Mycotoxins are produced in silage from the moulds that are formed in the crop, either out in the field before harvest, or during storage in the silo. There is a multitude of different moulds that can affect the animal, but most often Fusarium spp., Alternaria spp. and Aspergillus spp. are formed in the field. Whilst Penicillum spp., Aspergillus fumigatus and others grow during storage.
In Northern Europe, we have developed a large data base on the presence of the fungal toxins, especially in maize silage. The problem is that there are quite large differences in findings from study to study. There are several factors that make it difficult to get a true picture of the problem. The differences in study design that affect results include, when were the samples taken, where in the silo where they taken, and how were they analysed? For example, if you hit a spot of a mould – a hot spot – when you take the sample, you get falsely elevated levels of mycotoxins and a sample that is unrepresentative of the whole silo. Analytical methods will also affect the result; if you are screening for many different toxins will typically require a higher tolerance for recovery, than if you are on the trail of a single toxin that you want to be sure not to miss. Therefore, results in scientific literature of a fairly common toxin DON which comes from Fusarium spp. can range from 15% to 100% in detection in maize silage (Gallo et al. 2015)
Probable extent of the problem in Danish silage
The latest comprehensive study in the field in Denmark found that one or more mycotoxins are present in 61% of maize silage in Denmark (Storm et al. 2014). The same authors also found that in at least one-third, more than one mycotoxin is present. In a separate study from 2010, Storm et al. that the level of mould is highest 5-7 months after ensiling.
Many farmers assess the level of their mycotoxin problem by seeing if they have visible hot-spots of mould in the silage and simply discard the feed around the hot-spot. However, studies show that when analysing for mould, individual species occur in all samples and yet hot-spots were only visible in half of the cases (Storm et al. 2010). This means that you can have a significant contamination of the silage without any visible cues of contamination.
How to find out if you have a mycotoxin problem
This brings us back to the original question; are mycotoxins a big enough problem for my production result that I should treat for it?
In response, we can say that the likelihood of you having mycotoxins in the silage is high. In addition, there is evidence that it is not a high level of contamination with one or two mycotoxins that causes the biggest problem, but that a continuous low level contamination from several mycotoxins has a more insidious and greater impact on production results.
The complexity of obtaining a representative sample from which to diagnose the presence and level of mycotoxins, as well as interpreting the significance of those result for your herd probably makes it easier to make an exclusion diagnosis. This means that, due to overall high prevalence of fungi in silages, it is highly probable that you have toxins in your feed. By treating your silage for a period to see if the symptoms diminish or production outcome improves incurs a low financial risk whilst giving a high value in diagnosing an actual mycotoxin problem.
In our next article you will be able to read more about the impact mycotoxins have on your production results and the economics of doing something about them.