Damage to corn ears, the most edible part, represents a significant danger and stress factor to the entire plant. Damage increases available moisture and facilitates the accumulation of fungi that can produce various mycotoxins. High concentrations of mycotoxins are often associated with damaged kernels. Several studies have investigated the impact of such damaging agents on the production of mycotoxins in silage.
The analysis of this harvest’s corn silage samples from Central Europe shows a remarkable outcome in terms of mycotoxin contamination (Figure 1). Deoxynivalenol (DON), nivalenol (NIV) and zearalenone (ZEN) were detected in all 20 analyzed samples with average concentrations of 2930 ppb DON, 128 ppb NIV and 958 ppb ZEN.
Figure 1: Mycotoxin occurrence in Central European corn silage
The masked forms of DON and ZEN, DON-3-glucoside and zearalenone-sulfate, also show a high prevalence at 95% with average levels that represent 5% of the average concentration of DON and 30% of the average level of ZEN respectively. These masked mycotoxins can be transformed to their toxic parental form in the intestine of animals leading to an increase in toxic bioavailability.
On average, 37 metabolites were found in corn silage samples. Type B trichothecenes (representing the sum of DON, DON-3-glucoside, 15-acetyldeoxynivalenol, 3-acetyldeoxynivalenol and NIV) and ZEN-metabolites were detected in all corn silage samples with average concentrations of 3474 ppb and 1227 ppb, respectively. Additionally, 80% of all samples were contaminated with fumonisins.
Cut ‘em before analyzing…
In a study by Teller et al (2012) the effects of plant damage on mycotoxin contamination were investigated. To mimic plant damage, the ears of corn were cut with a knife on different days before harvesting, exposing damaged kernels to the environment. The corn plants were harvested and silages were treated with chemical and microbial additives to measure their influence on mycotoxin production and other parameters compared to undamaged plants.
Effects of microbial additives
In a first experiment, ears were cut 7 days before harvest and plants were ensiled with and without the inoculants (INOC) Lactobacillus buchneri 40788 (400,000 cfu/g of fresh forage) and Pediococcus pentosaceus (100,000 cfu/g). Results showed that:
- After ensiling, corn silage from damaged plants had lower starch yet higher concentrations of deoxynivalenol and fumonisins (Figure 2) no matter if treated with the inoculant.
- Microbial inoculation resulted in fewer total yeast count and lower zearalenone concentrations compared to non-inoculated silage.
Figure 2: Fumonisin contamination in silage of undamaged plants (light orange) and damaged plants (dark orange) with and without inoculant (INOC).
Effects of chemical additives
In a second experiment, ears were cut 27 days before harvest and plants were ensiled with or without 0.1% potassium sorbate (PS). Results showed that:
- Ears damaged 27 days before harvest showed increase in deoxynivalenol and fumonisin (Figure 3) levels accompanied by a decrease in starch content.
- Addition of potassium sorbate had no significant effect on mycotoxin concentrations in the resulting silage, though the number of yeast cells and molds were reduced.
Figure 3: Fumonisin contamination in silage of undamaged plants (light orange) and damaged plants (dark orange) with and without potassium sorbate (PS).
These studies demonstrate that physical damage to ears of corn prior to harvest resulted in higher production of mycotoxins in the field. Mycotoxin production can occur during the aerobic phase of ensiling or during storage. Hence, producers should closely monitor corn silage for mycotoxins prior to feeding, especially if signs of physical plant damage (e.g., hail, bird, or insect damage) prior to harvest are present.