Results from 2020 showed that all samples tested positive for at least one mycotoxin. Deoxynivalenol was found to be positive in all 49 samples. This was similar to 2019 also, when all samples tested positive for DON. At least 12% of the samples had DON concentrations higher than 1 ppm (DON threshold limit) in 2020 whereas in 2019 about 50% of samples had DON levels higher than 1 ppm. Other mycotoxins that occurred in all samples were enniatins and beauvericin, but their concentrations were low. However, when present in high concentration, beauvericin and enniatins can negatively impact androgen receptors and can also impede muscle contraction in cattle.
The second most frequently occurring category of mycotoxins found were fumonisins—47 out of 49 samples tested positive with eight samples having levels higher than threshold (2 ppm). Fumonisin levels were as high as 10 ppm in two samples. Mycotoxins were found to co-exist in most of the silage samples. Four samples tested positive for more than 20 mycotoxins. Each sample tested positive for at least seven different mycotoxins.
Overall, since the 2020 growing season was drier and rainfall was more sporadic, mycotoxins occurred in lower concentration and frequency than the previous year. The mycotoxin co-existence was also more pronounced in 2019 than in 2020 with a maximum of 24 mycotoxins detected in a single sample. Also, the highest DON and ZON concentrations were 5.7 and 2.5 ppm in 2019, respectively, while in 2020 highest toxin concentrations were 1.4 ppm for DON and only 0.07 ppm for ZON. The only toxin that occurred in higher concentration in 2020 than in 2019 was fumonisin (highest concentration reported 10.6 ppm in 2020). This is because fumonisin accumulation occurs due to F. verticilloides infection, which is favored when the environment is warm and dry around silking.
Results from 2019 and 2020 showed that mycotoxins are present in Michigan silage and their frequency and concentration largely depend on the temperature and moisture conditions throughout the growing season and, in particular, around silking. Since there are few ways to overcome problems once mycotoxins are present in corn, prevention of mycotoxin accumulation in the field is essential. Field management strategies begin with crop rotation and hybrid selection (including insect protection traits), scouting and spraying for ear feeding insects, fungicide application and harvest timing (early harvest can help in preventing toxin accumulation later in the season). Hybrid selection and insect control help control ear rot infections and eventually mycotoxin accumulation.
Furthermore, hybrids with resistance against stalk rots can also help alleviate the accumulation of mycotoxins. Research shows a significant amount of mycotoxins are contributed by stalk rots as well. Fermentation processes in bunker silos will not break down mycotoxins from an already infected silage which makes the field management even more crucial.
We are continuing our efforts to determine the effects of management practices, insect damage and weather conditions on mycotoxin development in corn silage. Please visit our Cropping Systems Agronomy website for more details.
Farmers are invited again to submit corn silage samples for free testing of 26 different mycotoxins and quality analysis. Silage samples of approximately 1 pound should be collected from various locations in the same field and then either dried or frozen soon after collection. A data sheet along with sample collection instructions is available and can be used to record detailed field information and sent along with samples. This information must be completed before samples will be analyzed. Results will be available the following summer as individual grower reports.
Continued participation by corn silage producing farmers in this study will enable Michigan State University researchers and Extension educators to better help farmers improve control of mycotoxins and, therefore, improve cattle performance.
Source : msu.edu