Effect of ensiling duration on the fate of deoxynivalenol, zearalenone and their derivatives in maize silage

Farm management practices and season dependent factors affect the microbial community and chemical profile of corn and grass-legume silages of farms in Ontario, Québec, and Northern New York

The effects of farm management practices and seasonal variation on the microbial community and chemical composition of corn and grass-legume silage are largely understudied due to the advantages of controlled mini-silo experiments. This study aims to investigate the effects that some key farm factors (use of an inoculant, farm region, and bunker or tower silo) and seasonal variations have on corn and grass-legume silage from farms across Ontario, Quebec, and New York. The silage was either treated with a commercial inoculant (Lallemand Biotal Buchneri 500® or Chr Hansen SiloSolve FC®) or left untreated. The bacterial communities of silage were compared to those of raw bulk tank milk from the same farm to determine if they were similarly affected by management practices or seasonal variations. Family level analysis of the 16S rRNA V3-V4 gene amplicon bacterial community, the ITS1 amplicon fungal community, NMR water soluble metabolome, and mycotoxin LC-MS were performed on silage over a two-year period. Chemical compounds associated with the use of inoculants in corn and grass-legume silage were higher in inoculated corn (acetate, propane-1,2-diol, γ-aminobutyrate; p < 0.001) and grass-legume (propionate; p = 0.011). However, there was no significant difference in the relative abundance (RA) of Lactobacillaceae in either silage type. Leuconostocaceae was higher in non-inoculated corn (p < 0.001) and grass-legume (p < 0.001) silage than in inoculated silage. Tower silos had higher RA of Leuconostocaceae (p < 0.001) and higher pH (p < 0.001) in corn and grass-legume silage. The one farm that used liquid manure with no other fertilizer type had higher RA of Clostridiaceae (p = 0.045) and other rumen/fecal (p < 0.006) bacteria in grass-legume silage than all other farms. Seasonal variation affected most of the key silage microbial families, however the trends were rarely visible across both years. Few trends in microbial variation could be observed in both silage and bulk tank milk: two farms had higher Moraxellaceae (p < 0.001) in milk and either corn or grass-legume silage. In farms using an inoculant, lower Staphylococcaceae was observed in the raw bulk tank milk.

Detoxifying mycotoxins and antifungal properties of two rumen-derived Enterococcus species in artificially contaminated corn silages

BACKGROUND

Mycotoxins contamination in food and feed has emerged as an issue of serious concern because they pose serious health risks to both humans and livestock. The study aimed to evaluate the effects of two rumen-derived Enterococcus spp. on fermentation and hygienic quality of artificially contaminated corn silages. The toxigenic fungal-infested (FI) and non-fungal infested (NFI) corn was harvested at 1/2 milk line stage and ensiled without additives (CON) or with Enterococcus faecalis (E) or Enterococcus faecium (M).

RESULTS

The pH of FI silages was higher than that of NFI silages, the pH in NFI-M was lower than in NFI-CON. Inoculating E. faecium markedly increased lactic acid concentration compared to CON and E silages. Both E. faecium and E. faecalis decreased the deoxynivalenol (DON) and zearalenone (ZEN) concentrations compared with the CON for FI silages, while E. faecium was more effective in eliminating aflatoxin B₁ (AFB₁ ). The FI silage had higher bacterial and fungal Shannon indexes than NFI silages. The relative abundance (RA) of Aspergillus and Fusarium marked a decline from day 5 to day 90. Inoculating E. faecium and E. faecalis reduced the RA of Penicillium compared to CON. In vitro mycotoxins removal assay indicated that E. faecium was more effective in AFB₁ detoxification while having lower detoxifying ZEN capacity than E. faecalis.

CONCLUSION

Inoculating rumen-derived Enterococcus spp. isolates alleviated the negative effects of fungal infestation on the fermentation and hygienic quality of corn silages by changing the microbial communities and detoxifying mycotoxins. © 2023 Society of Chemical Industry.

Effect of Bacillus Additives on Fermentation Quality and Bacterial Community during the Ensiling Process of Whole-Plant Corn Silage

The aim of this study was to evaluate the effects of a complex Bacillus subtilis additive on the fermentation quality and bacterial community during the ensiling process of whole-plant corn silage (WPCS). The pH values of WPCS treated with the B. subtilis inoculant decreased faster than those of the control without inoculant, and significantly higher contents of lactic acid (LA) and acetic acid (AA) were observed. After 45 days of ensiling, the LA contents reached 7.95% (w/w). In the treatment group, the neutral detergent fibre (NDF) and acid detergent fibre (ADF) contents decreased significantly compared to the control, and the degradation rates of the NDF and ADF were 26.52% and 27.34% after 45 days, respectively. The deoxynivalenol (DON) content in the treatment group decreased to 205.67 μg/kg, which was significantly lower than the content of 382.51 μg/kg in the control group. The results indicated the positive effect of the B. subtilis inoculant in improving WPCS fermentation, especially in terms of degrading linocellulose and removing DON. The analysis of the bacterial community indicated that the B. subtilis inoculant resulted in an increased abundance of Lactobacillus, which contributed to the enhancement of LA production. The increased abundance of Bacillus possibly played a role in the degradation of NDF and ADF and the reduction in DON. Therefore, the complex B. subtilis additive could be used for the production of high-quality WPCS.

Factors during Production of Cereal-Derived Feed That Influence Mycotoxin Contents

Mycotoxins are naturally present in cereal-based feed materials; however, due to adverse effects on animal health, their presence in derived animal feed should be minimized. A systematic literature search was conducted to obtain an overview of all factors from harvest onwards influencing the presence and concentration of mycotoxins in cereal-based feeds. The feed production processes covered included the harvest time, post-harvest practices (drying, cleaning, storage), and processing (milling, mixing with mycotoxin binders, extrusion cooking, ensiling). Delayed harvest supports the production of multiple mycotoxins. The way feed materials are dried after harvest influences the concentration of mycotoxins therein. Applying fungicides on the feed materials after harvest as well as cleaning and sorting can lower the concentration of mycotoxins. During milling, mycotoxins might be redistributed in cereal feed materials and fractions thereof. It is important to know which parts of the cereals are used for feed production and whether or not mycotoxins predominantly accumulate in these fractions. For feed production, mostly the milling fractions with outer parts of cereals, such as bran and shorts, are used, in which mycotoxins concentrate during processing. Wet-milling of grains can lower the mycotoxin content in these parts of the grain. However, this is typically accompanied by translocation of mycotoxins to the liquid fractions, which might be added to by-products used as feed. Mycotoxin binders can be added during mixing of feed materials. Although binders do not remove mycotoxins from the feed, the mycotoxins become less bioavailable to the animal and, in the case of food-producing animals, to the consumer, lowering the adverse effects of mycotoxins. The effect of extruding cereal feed materials is dependent on several factors, but in principle, mycotoxin contents are decreased after extrusion cooking. The results on ensiling are not uniform; however, most of the data show that mycotoxin production is supported during ensiling when oxygen can enter this process. Overall, the results of the literature review suggest that factors preventing mycotoxin production have greater impact than factors lowering the mycotoxin contents already present in feed materials.

Fungal species and mycotoxins in mouldy spots of grass and maize silages in Austria

Fungi and mycotoxins in silage can have detrimental consequences for both cattle and human health. This pilot study identified, via the routinary direct plating method, the dominant cultivable fungi in mouldy grass silages (GS) (n = 19) and maize silages (MS) (n = 28) from Austria. The profiles of regulated, modified, and emerging mycotoxins together with other fungal metabolites were analysed via LC-(ESI)MS/MS. Penicillium roqueforti, Saccharomyces spp., Geotrichum candidum, Aspergillus fumigatus and Monascus ruber were the most frequent fungal organisms identified. Other species including Mucor circinelloides, Fusarium spp. and Paecilomyces niveus were detected at lower frequencies. The presence of complex mixtures of toxic and potentially toxic compounds was evidenced by high levels and occurrences (≥ 50%) of Penicillium-produced compounds such as mycophenolic acid (MPA), roquefortines (ROCs), andrastins (ANDs) and marcfortine A. Mouldy silages contained toxins commonly produced by genus Fusarium (e.g. zearalenone (ZEN) and trichothecenes), Alternaria (like tenuazonic acid (TeA) and alternariol (AHO)) and Aspergillus (such as sterigmatocystin (STC)). Compared to those in GS, mouldy spots in MS presented significantly higher fungal counts and more diverse toxin profiles, in addition to superior levels of Fusarium spp., Penicillium spp. and total fungal metabolites. Generally, no correlation between mould counts and corresponding metabolites was detected, except for the counts of P. roqueforti, which were positively correlated with Penicillium spp. metabolites in mouldy MS. This study represents a first assessment of the fungal diversity in mouldy silage in Austria and highlights its potential role as a substantial contributor to contamination with complex mycotoxin mixtures in cattle diets.

Exploration on the Enhancement of Detoxification Ability of Zearalenone and Its Degradation Products of Aspergillus niger FS10 under Directional Stress of Zearalenone

Zearalenone (ZEN) is one of the most common mycotoxin contaminants in food. For food safety, an efficient and environmental-friendly approach to ZEN degradation is significant. In this study, an Aspergillus niger strain, FS10, was stimulated with 1.0 μg/mL ZEN for 24 h, repeating 5 times to obtain a stressed strain, Zearalenone-Stressed-FS10 (ZEN-S-FS10), with high degradation efficiency. The results show that the degradation rate of ZEN-S-FS10 to ZEN can be stabilized above 95%. Through metabolomics analysis of the metabolome difference of FS10 before and after ZEN stimulation, it was found that the change of metabolic profile may be the main reason for the increase in the degradation rate of ZEN. The optimization results of degradation conditions of ZEN-S-FS10 show that the degradation efficiency is the highest with a concentration of 10⁴ CFU/mL and a period of 28 h. Finally, we analyzed the degradation products by UPLC-q-TOF, which shows that ZEN was degraded into two low-toxicity products: C₁₈H₂₂O₈S (Zearalenone 4-sulfate) and C₁₈H₂₂O₅ ((E)-Zearalenone). This provides a wide range of possibilities for the industrial application of this strain.

Effect of Lactic Acid Bacteria on the Fermentation Quality and Mycotoxins Concentrations of Corn Silage Infested with Mycotoxigenic Fungi

This study was conducted to evaluate the effect of lactic acid bacteria (LAB) on fermentation quality, mycotoxin concentrations, and microbial communities of whole-crop corn silages infested with mycotoxigenic fungi. Cultured spores (10⁶ cfu/mL) of mycotoxigenic Aspergillus flavus and Fusarium graminearum were sprayed (5 mL) on corn forage on 27 July and 10 August 2018. On 21 August 2018, sprayed (FI; 3 plots) and unsprayed (NFI; 3 plots) corn forage were harvested at the 1/2 kernel milk line stage, followed by chopping and ensiling without inoculants (CON), or with Lactobacillus buchneri (LB, 1 × 10⁶ cfu/g FW), Lactobacillus plantarum (LT, 1 × 10⁶ cfu/g FW), or L. buchneri + L. plantarum (BT: both L. buchneri and L. plantarum applied at 0.5 × 10⁶ cfu/g FW). After 90 d of ensiling, FI silages had a higher (p < 0.05) pH value and higher acetic acid (ACA), ethanol, and ammonia nitrogen (ammonia N) concentrations, but lower (p < 0.05) lactic acid (LA) concentrations than NFI silage. The inoculants decreased pH and increased LA concentration and LA/ACA compared with CON. The aflatoxin B₁ (AFB₁) was only detected in FI fresh corn and silages; ensiling decreased (p < 0.05) AFB₁ concentration compared with fresh corn, and LB and BT decreased AFB₁ concentration compared with CON. The zearalenone (ZEN), deoxynivalenol (DON), and fumonisin B₁ (FB₁) concentrations were similar (p < 0.05) for NFI silages, while ZEN concentration in BT was the lowest (p < 0.05) among all FI silages; DON and FB₁ concentrations in LB, LT, and BT silages were significantly lower (p < 0.05) than those of CON in FI silages. The fungal infestation increased the bacterial and fungal diversity of silages compared with NFI silages. The FI silages had a higher relative abundance (RA) of Lactobacillus, Weissella, Wickerhamomyces, Pichia, and Epicoccum than the corresponding NFI silages. The RA of Aspergillus and Fusarium markedly decreased after 90 d of ensiling, and the inoculation expanded this trend irrespective of fungal infestation. The Penicillium in FI silages survived after 90 d of ensiling, while the inoculants decreased the RA of Penicillium. Inoculants mitigate the adverse effects of fungal infestation on corn silage quality by changing the bacterial and fungal communities.

Evaluation of Inner Exposure of Horses to Zearalenone (ZEN), Deoxynivalenol (DON) and Their Metabolites in Relation to Colic and Health-Related Clinical-Chemical Traits

Mycotoxin contaminated feed has been associated with colic of horses caused by intestinal disorders. Whether such disease conditions alter the intestinal toxin metabolism and transfer across a compromised mucosal barrier is unknown. A screening approach was used to relate blood residue levels of DON, ZEN and their metabolites to the status of the horses (sick vs. healthy). A total of 55 clinically healthy horses from 6 different farms with varying feeding background served as control for sick horses (N = 102) hospitalized due to colic. ZEN, alpha-zearalenol (ZEL), beta-ZEL and DON were detectable in peripheral blood as indicators for the inner exposure with significant farm effects for alpha- and beta-ZEL. However, the levels in sick horses were similar to all farms. Moreover, the proportion of beta-ZEL of all detected ZEN metabolites as an indicator for the degree of metabolism of ZEN was not different for sick horses but differed amongst the control farms. Although the incidence of DON in blood was generally low and not significantly different amongst healthy and sick horses, the positive samples were nearly exclusively found in sick horses suggesting either a higher toxin transfer, an association of DON with the development of colic or a different feeding background.

Multi-Mycotoxin Contamination of Maize Silages in Flanders, Belgium: Monitoring Mycotoxin Levels from Seed to Feed

Maize silage, which in Europe is the main feed for dairy cattle in winter, can be contaminated by mycotoxins. Mycotoxigenic Fusarium spp. originating from field infections may survive in badly sealed silages or re-infect at the cutting edge during feed-out. In this way, mycotoxins produced in the field may persist during the silage process. In addition, typical silage fungi such as Penicillium spp. and Aspergillus spp. survive in silage conditions and produce mycotoxins. In this research, 56 maize silages in Flanders were sampled over the course of three years (2016-2018). The concentration of 22 different mycotoxins was investigated using a multi-mycotoxin liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, and the presence of DNA of three Fusarium spp. (F. graminearum, F. culmorum and F. verticillioides) was analyzed in a selection of these samples using quantitative polymerase chain reaction (qPCR). Every maize silage contained at least two different mycotoxins. Nivalenol (NIV) and deoxynivalenol (DON) were the most prevalent (both in 97.7% of maize silages), followed by ENN B (88.7%). Concentrations often exceeded the EU recommendations for DON and zearalenone (ZEN), especially in 2017 (21.3% and 27.7% of the maize silages, respectively). No correlations were found between fungal DNA and mycotoxin concentrations. Furthermore, by ensiling maize with a known mycotoxin load in a net bag, the mycotoxin contamination could be monitored from seed to feed. Analysis of these net bag samples revealed that the average concentration of all detected mycotoxins decreased after fermentation. We hypothesize that mycotoxins are eluted, degraded, or adsorbed during fermentation, but certain badly preserved silages are prone to additional mycotoxin production during the stable phase due to oxygen ingression, leading to extremely high toxin levels.

Occurrence of Fusarium Mycotoxins and Their Modified Forms in Forage Maize Cultivars

Forage maize is often infected by mycotoxin-producing Fusarium fungi during plant growth, which represent a serious health risk to exposed animals. Deoxynivalenol (DON) and zearalenone (ZEN) are among the most important Fusarium mycotoxins, but little is known about the occurrence of their modified forms in forage maize. To assess the mycotoxin contamination in Northern Germany, 120 natural contaminated forage maize samples of four cultivars from several locations were analysed by liquid chromatography-high resolution mass spectrometry (LC-HRMS) for DON and ZEN and their modified forms deoxynivalenol-3-glucoside (DON3G), the sum of 3- and 15-acetyl-deoxynivalenol (3+15-AcDON), α- and β-zearalenol (α-ZEL, β-ZEL). DON and ZEN occurred with high incidences (100 and 96%) and a wide range of concentrations, reaching levels up to 10,972 and 3910 µg/kg, respectively. Almost half of the samples (46%) exceeded the guidance value in complementary and complete feeding stuffs for ZEN (500 µg/kg), and 9% for DON (5000 µg/kg). The DON related mycotoxins DON3G and 3+15-AcDON were also present in almost all samples (100 and 97%) with amounts of up to 3038 and 2237 µg/kg and a wide range of concentrations. For the ZEN metabolites α- and β-ZEL lower incidences were detected (59 and 32%) with concentrations of up to 423 and 203 µg/kg, respectively. Forage maize samples were contaminated with at least three co-occurring mycotoxins, whereby 95% of all samples contained four or more mycotoxins with DON, DON3G, 3+15-AcDON, and ZEN co-occurring in 93%, together with α-ZEL in 57% of all samples. Positive correlations were established between concentrations of the co-occurring mycotoxins, especially between DON and its modified forms. Averaged over all samples, ratios of DON3G/DON and 3+15-AcDON/DON were similar, 20.2 and 20.5 mol%; cultivar-specific mean ratios ranged from 14.6 to 24.3 mol% and 15.8 to 24.0 mol%, respectively. In total, 40.7 mol% of the measured DON concentration was present in the modified forms DON3G and 3+15-AcDON. The α-ZEL/ZEN ratio was 6.2 mol%, ranging from 5.2 to 8.6 mol% between cultivars. These results demonstrate that modified mycotoxins contribute substantially to the overall mycotoxin contamination in forage maize. To avoid a considerable underestimation, it is necessary to analyse modified mycotoxins in future mycotoxin monitoring programs together with their parent forms.