Occurrence and stability of masked fumonisins in corn silage samples

Review: Strategies and technologies in preventing regulated and emerging mycotoxin co-contamination in forage for safeguarding ruminant health

Ruminants are often considered less susceptible to mycotoxins than monogastrics, owing to rumen microflora converting mycotoxins to less toxic compounds or several compounds present in the rumen-reticulum compartment, being able to bind the mycotoxin "mother" molecule that make them unavailable for absorption process in the gastro-intestinal tract of host animals. However, if ruminants consume feed contaminated by mycotoxins for long periods, their growth, development, and fertility can be compromised. Among regulated mycotoxins, the most studied and known for their effects are aflatoxins (AFs) AFB1, AFB2, AFG1 and AFG2, as well as the AFM1 for its high importance in dairy sector, deoxynivalenol (DON) and its metabolites 3/15 acetyl-DON and 3-glucoside DON, T-2 and HT-2 toxins, zearalenone, fumonisins, in particular that belong to the B class, and ochratoxin A. Furthermore, because of the emergence of multiple emerging mycotoxins that are detectable in feed utilised in ruminant diets, such as ensiled forage, there is now a growing focus on investigating these compounds by the scientific community to deepen their toxicity for animal health. Despite the enhancement of research, it is remarkable that there is a paucity of in vivo trials, as well as limited studies on nutrient digestibility and the impact of these molecules on rumen and intestinal functions or milk yield and quality. In this review, recent findings regarding the occurrence of regulated and emerging mycotoxins in forage and their possible adverse effects on dairy cattle are described, with special emphasis on animal performance and on rumen functionality.

Development of a sensitive simultaneous analytical method for 26 targeted mycotoxins in coix seed and Monte Carlo simulation-based exposure risk assessment for local population

Coix seed, a versatile agricultural product, is known for its nutritional and functional components. However, the common contamination with mycotoxins represents a potential risk for human health. A sensitive analytical method was developed and validated to simultaneously determine 26 mycotoxins, including regulated and emerging, using stable-isotope-dilution-assay and LC-MS/MS. The study found co-contamination in 100% of samples from Southeast China, with 8-15 different mycotoxins for each and a total of 20 for all. Probabilistic risk assessments indicated long-term health concerns, with Aflatoxin B1, ochratoxin A, and zearalenone being priority for risk control. Overall, this study appears to be the first to develop a rapid and robust analytical method of 26 mycotoxins and to conduct Monte Carlo simulation-based chronic risk assessments for 12 individual mycotoxins detected in coix seed, which would be of significance for risk communication as well as for regulatory authority in devising effective strategies to minimize exposure health risk.

Occurrence, transformation, and toxicity of fumonisins and their covert products during food processing

Fumonisins comprise structurally related metabolites mainly produced by Fusarium verticillioides and Fusarium proliferatum. Contamination with fumonisins causes incalculable damage to the economy and poses a great risk to animal and human health. Fumonisins and their covert products are found in cereals and cereal products. Food processing significantly affects the degradation of toxins and the formation of covert toxins. However, studies on fumonisins and their covert mycotoxins remain inadequate. This review aims to summarize changes in fumonisins and the generation of covert fumonisins during processing. It also investigates the toxicity and determination methods of fumonisins and covert fumonisins, and elucidates the factors affecting fumonisins and their covert forms during processing. In addition to the metabolic production by plants and fungi, covert fumonisins are mainly produced by covalent or noncovalent binding, complexation, or physical entrapment of fumonisins with other substances. The toxicity of covert fumonisins is similar to that of free fumonisins and is a non-negligible hazard. Covert fumonisins are commonly found in food matrices, and methods to analyze them have yet to be improved. Food processing significantly affects the conversion of fumonisins to their covert toxins.

Effects of Fumonisin B and Hydrolyzed Fumonisin B on Growth and Intestinal Microbiota in Broilers

Fumonisins are mainly produced by Fusarium verticillioides and proliferatum, which causes a variety of toxicities in humans and animals, including fumonisin Bs (FBs) as the main form. After they are metabolized by plants or microorganisms, modified fumonisins are difficult to detect by conventional methods, which result in an underestimation of their contamination level. Fumonisins widely contaminate maize and maize products, especially in broiler feed. As an economically important food, broilers are often adversely affected by mycotoxins, leading to food safety hazards and high economic losses. However, there are few studies regarding the adverse effects of FBs on broiler growth and health, especially modified FBs. Our data shows that after exposure to FBs or hydrolyzed fumonisin Bs (HFBs), the body weight and tissue weight of broilers decreased significantly, especially the testes. Moreover, they significantly affect the intestinal microbiota and the relative abundance of bacteria from phylum-to-species levels, with the differentially affected bacteria mainly belonging to Firmicutes and Proteobacteria. Our findings suggest that both the parent and hydrolyzed FBs could induce growth retardation, tissue damage and the imbalance of intestinal microbiota in broilers. This indicated that the harmful effects of HFBs cannot be ignored during food safety risk assessment.

Ensiling process and pomegranate peel extract as a natural additive in potential prevention of fungal and mycotoxin contamination in silage

A study was conducted on six animal feed centers in Israel where fungal and mycotoxin presence was examined in maize and wheat silages. Fumonisin mycotoxins FB₁ and FB₂ were present in every maize silage sample analyzed. Interestingly, no correlation was found between the occurrence of specific mycotoxins and the presence of the fungal species that might produce them in maize and wheat silages. We further investigated the effect of pomegranate peel extract (PPE) on Fusarium infection and fumonisin biosynthesis in laboratory-prepared maize silage. PPE had an inhibitory effect on FB₁ and FB₂ biosynthesis by Fusarium proliferatum, which resulted in up to 90 % reduction of fumonisin production in silage samples compared to untreated controls. This finding was supported by qRT-PCR analysis, showing downregulation of key genes involved in the fumonisin-biosynthesis pathway under PPE treatment. Our results present promising new options for the use of natural compounds that may help reduce fungal and mycotoxin contamination in agricultural foodstuff, and potentially replace traditionally used synthetic chemicals.

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The mycotoxins fumonisin B₁ and B₂ were detected in all analyzed maize silage samples.

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No correlation was found between mycotoxins and their fungal sources in silages.

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Treatment with PPE demonstrated strong anti-mycotoxigenic activity in silages samples.

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.

Sphinganine-Analog Mycotoxins (SAMs): Chemical Structures, Bioactivities, and Genetic Controls

Sphinganine-analog mycotoxins (SAMs) including fumonisins and A. alternata f. sp. Lycopersici (AAL) toxins are a group of related mycotoxins produced by plant pathogenic fungi in the Fusarium genus and in Alternaria alternata f. sp. Lycopersici, respectively. SAMs have shown diverse cytotoxicity and phytotoxicity, causing adverse impacts on plants, animals, and humans, and are a destructive force to crop production worldwide. This review summarizes the structural diversity of SAMs and encapsulates the relationships between their structures and biological activities. The toxicity of SAMs on plants and animals is mainly attributed to their inhibitory activity against the ceramide biosynthesis enzyme, influencing the sphingolipid metabolism and causing programmed cell death. We also reviewed the detoxification methods against SAMs and how plants develop resistance to SAMs. Genetic and evolutionary analyses revealed that the FUM (fumonisins biosynthetic) gene cluster was responsible for fumonisin biosynthesis in Fusarium spp. Sequence comparisons among species within the genus Fusarium suggested that mutations and multiple horizontal gene transfers involving the FUM gene cluster were responsible for the interspecific difference in fumonisin synthesis. We finish by describing methods for monitoring and quantifying SAMs in food and agricultural products.

Free and hidden fumonisins in Argentinean raw maize samples

The concentrations of free fumonisins (FBs) and hydrolysed fumonisins (HFBs) were determined in 72 maize samples collected in 2017 from five Argentine provinces. The methodology for HFBs analysis consisted of alkaline hydrolysis followed by high performance liquid chromatography with a fluorescence detector (HPLC-FLD). The developed analytical methodology presented percentages of recovery greater than 74%. Limits of detection were 4.5, 13.0 and 12.9 μg/kg for HFB1, HFB2 and HFB3, respectively. Presence of FBs was found in 86% of the samples. In all cases, the concentration of total HFBs (after the hydrolysis treatment) was superior to the free FBs content (HFBs to FBs median ratio of 2.5), which indicates the presence of hidden fumonisins in Argentinean maize. 8% of the traditionally analysed samples exceeded the limit established by the European Commission for FB1 + FB2. When applying alkaline hydrolysis to the samples, 24% of them exceed this limit.

Mycotoxins in Flanders' Fields: Occurrence and Correlations with Fusarium Species in Whole-Plant Harvested Maize

Mycotoxins are well-known contaminants of several food- and feedstuffs, including silage maize for dairy cattle. Climate change and year-to-year variations in climatic conditions may cause a shift in the fungal populations infecting maize, and therefore alter the mycotoxin load. In this research, 257 maize samples were taken from fields across Flanders, Belgium, over the course of three years (2016-2018) and analyzed for 22 different mycotoxins using a multi-mycotoxin liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. DNA of Fusarium graminearum, F. culmorum and F. verticillioides was quantified using the quantitative polymerase chain reaction (qPCR). Multi-mycotoxin contamination occurred frequently, with 47% of samples containing five or more mycotoxins. Nivalenol (NIV) was the most prevalent mycotoxin, being present in 99% of the samples, followed by deoxynivalenol (DON) in 86% and zearalenone (ZEN) in 50% of the samples. Fumonisins (FUMs) were found in only 2% of the samples in the wet, cold year of 2016, but in 61% in the extremely hot and dry year of 2018. Positive correlations were found between DON and NIV and between F. graminearum and F. culmorum, among others. FUM concentrations were not correlated with any other mycotoxin, nor with any Fusarium sp., except F. verticillioides. These results show that changing weather conditions can influence fungal populations and the corresponding mycotoxin contamination of maize significantly, and that multi-mycotoxin contamination increases the risk of mycotoxicosis in dairy cattle.

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

Fusarium mycotoxins and their derivatives are frequently detected in freshly harvested forage maize. This study assessed the time course effects during ensiling of forage maize on the fate of Fusarium mycotoxins, using laboratory-scale silos and artificially contaminated raw material. A multi-mycotoxin liquid chromatography-high-resolution mass spectrometry (LC-HRMS) method was used to determine the levels of deoxynivalenol (DON), zearalenone (ZEN) and their derivatives DON-3-glucoside, 3-acetyl-DON, 15-acetyl-DON, deepoxy-DON, α-zearalenol and β-zearalenol. A significant increase of DON was observed during ensiling, whereas the levels of DON-3-glucoside and its acetylated forms proportionally decreased. In contrast, levels of ZEN, α-zearalenol and β-zearalenol were not affected by the ensiling process. Based on these findings, ensiling is not a practical method for reducing the total amount of Fusarium mycotoxins present at harvest.

Mycotoxin Occurrence in Maize Silage-A Neglected Risk for Bovine Gut Health?

Forages are important components of dairy cattle rations but might harbor a plethora of mycotoxins. Ruminants are considered to be less susceptible to the adverse health effects of mycotoxins, mainly because the ruminal microflora degrades certain mycotoxins. Yet, impairment of the ruminal degradation capacity or high ruminal stability of toxins can entail that the intestinal epithelium is exposed to significant mycotoxin amounts. The aims of our study were to assess i) the mycotoxin occurrence in maize silage and ii) the cytotoxicity of relevant mycotoxins on bovine intestinal cells. In total, 158 maize silage samples were collected from European dairy cattle farms. LC-MS/MS-based analysis of 61 mycotoxins revealed the presence of emerging mycotoxins (e.g. emodin, culmorin, enniatin B1, enniatin B, and beauvericin) in more than 70% of samples. Among the regulated mycotoxins, deoxynivalenol and zearalenone were most frequently detected (67.7%). Overall, 87% of maize silages contained more than five mycotoxins. Using an in vitro model with calf small intestinal epithelial cells B, the cytotoxicity of deoxynivalenol, nivalenol, fumonisin B1 and enniatin B was evaluated (0-200 µM). Absolute IC50 values varied in dependence of employed assay and were 1.2-3.6 µM, 0.8-1.0 µM, 8.6-18.3 µM, and 4.0-6.7 µM for deoxynivalenol, nivalenol, fumonisin B1, and enniatin B, respectively. Results highlight the potential relevance of mycotoxins for bovine gut health, a previously neglected target in ruminants.

Fermentation Characteristics of Lactobacillus Plantarum and Pediococcus Species Isolated from Sweet Sorghum Silage and Their Application as Silage Inoculants

This study aims to evaluate the fermentation characteristics of Lactobacillus plantarum and Pediococcus spp isolated from sweet sorghum silage to enhance the fermentation quality of Napier grass and sweet sorghum silage. Based on molecular 16S ribosomal ribonucleic identification the isolated strains were phylogenetically related to Lactobacillus plantarum (HY1), Pediococcus acidilactici (HY2) and Pediococcus claussenii (HY3). Strains HY1, HY2 and HY3 and commercial bacteria Lactobacillus plantarum, Ecosyl; (MTD\1( were ensiled with sweet sorghum and Napier grass and the non-inoculated grasses, have been arranged in a completely randomized experimental design in a 5 (inoculants) × 3 (ensiling periods). In both grasses, the fermentation characteristics chemical composition and microbial population were assessed at 5–30 and 90 days of ensiling. The results showed that the effect of addition inoculants significantly reduced (p < 0.05) the pH, ammonia-N, acetic acid and undesirable microbial population and increased (p < 0.05) lactic acid and lactic acid bacteria counting when compared to the control. The effect of ensiling days on silage quality through the increasing lactic acid, acetic acid, ammonia-N, propionic acid and butyric acid whereas decreasing pH and water-soluble carbohydrates and microbial counts. In both sweet sorghum and Napier silage treated with isolated strains showed the best results in silage quality. The HY3 belongs to Pediococcus claussenii was not extensively studied in silage but it has shown good fermentation quality which strongly recommended to apply as probiotic.

Development of antibodies for N-(1-deoxy-D-fructos-1-yl) fumonisin B1 and cross-reaction with modified fumonisins

Fumonisins are a group of mycotoxins that are routinely found worldwide in commodities such as maize. The group, which has many members, is generally characterised by the presence of one or more tricarballylic acid groups esterified to a long carbon backbone. The diversity of this group of toxins is further augmented by their ability to interact with matrix components non-covalently and to form covalent products with matrix constituents, such as carbohydrates and proteins. Covalent modifications to the toxins make it more difficult to assess the total amounts that may be present in a commodity. We developed monoclonal antibodies (Mabs) against a known product of the reaction of fumonisin B1 (FB1) with glucose: N-(1-deoxy-D-fructos-1-yl) fumonisin B1 (NDFrc-FB1). Similar reactions were used to produce fructosyl-analogs of fumonisins B2 and B3, as well as galactose, maltose, and rhamnose analogs of FB1. These analogs were tested in a competitive indirect ELISA for cross-reactivity towards one of the developed antibodies (Mab 213221). All of the carbohydrate analogs cross-reacted with the Mab, at levels ranging from 75% (the FB3 analog derived from D-glucose) to 181% (the FB1 analog derived from maltose). These results suggested the assay was capable of binding to a wide variety of fumonisin-carbohydrate derivatives. The same antibody was incorporated into an immunoaffinity column that was used to isolate modified fumonisins from a sample of naturally contaminated maize. These results demonstrate the potential to isolate and detect modified fumonisins and will facilitate efforts to determine the frequency of the occurrence of these compounds in maize.

Evaluation of gaseous allyl isothiocyanate against the growth of mycotoxigenic fungi and mycotoxin production in corn stored for 6 months

BACKGROUND

Brazil produces approximately 63 million tons of corn kernels annually, which is commonly contaminated with fungi and mycotoxins. The objective of this study was to evaluate the efficacy of gaseous allyl isothiocyanate (AITC) to inhibit the growth of Aspergillus parasiticus and Fusarium verticillioides, and mycotoxin production (aflatoxins B₁ , B₂ , G₁ and G₂ , fumonisins B₁ and B₂ ) in corn during 180 days of storage.

RESULTS

AITC at 50 µL L^-1 resulted in a significant reduction of the fungal population (P < 0.05) after 180 days, decreasing 3.17 log(CFU g^-1 ) and 3.9 log(CFU g^-1 ) of A. parasiticus and F. verticillioides respectively in comparison with the control. In addition, 10 and 50 µL L^-1 treatments prevented the production of fumonisin B₁ for the whole period. Aflatoxins were not detected in either control or treated groups. Residual levels of AITC in corn treated with 10 µL L^-1 and 50 µL L^-1 were detected up to 14 days and 30 days respectively.

CONCLUSION

Prophylactic treatment with AITC reduced the fungal population and inhibited fumonisin B₁ production in stored corn, exhibiting great potential to be applied in corn silos to prevent fungi contamination and minimize mycotoxin levels. © 2018 Society of Chemical Industry.

Silage review: Mycotoxins in silage: Occurrence, effects, prevention, and mitigation

Ensiled forage, particularly corn silage, is an important component of dairy cow diets worldwide. Forages can be contaminated with several mycotoxins in the field pre-harvest, during storage, or after ensiling during feed-out. Exposure to dietary mycotoxins adversely affects the performance and health of livestock and can compromise human health. Several studies and surveys indicate that ruminants are often exposed to mycotoxins such as aflatoxins, trichothecenes, ochratoxin A, fumonisins, zearalenone, and many other fungal secondary metabolites, via the silage they ingest. Problems associated with mycotoxins in silage can be minimized by preventing fungal growth before and after ensiling. Proper silage management is essential to reduce mycotoxin contamination of dairy cow feeds, and certain mold-inhibiting chemical additives or microbial inoculants can also reduce the contamination levels. Several sequestering agents also can be added to diets to reduce mycotoxin levels, but their efficacy varies with the type and level of mycotoxin contamination. This article gives an overview of the types, prevalence, and levels of mycotoxin contamination in ensiled forages in different countries, and describes their adverse effects on health of ruminants, and effective prevention and mitigation strategies for dairy cow diets. Future research priorities discussed include research efforts to develop silage additives or rumen microbial innocula that degrade mycotoxins.

Risks for animal health related to the presence of fumonisins, their modified forms and hidden forms in feed

Fumonisins, mycotoxins primarily produced by Fusarium verticillioides and Fusarium proliferatum, occur predominantly in cereal grains, especially in maize. The European Commission asked EFSA for a scientific opinion on the risk to animal health related to fumonisins and their modified and hidden forms in feed. Fumonisin B1 (FB 1), FB 2 and FB 3 are the most common forms of fumonisins in feedstuffs and thus were included in the assessment. FB 1, FB 2 and FB 3 have the same mode of action and were considered as having similar toxicological profile and potencies. For fumonisins, the EFSA Panel on Contaminants in the Food Chain (CONTAM) identified no-observed-adverse-effect levels (NOAELs) for cattle, pig, poultry (chicken, ducks and turkeys), horse, and lowest-observed-adverse-effect levels (LOAELs) for fish (extrapolated from carp) and rabbits. No reference points could be identified for sheep, goats, dogs, cats and mink. The dietary exposure was estimated on 18,140 feed samples on FB 1-3 representing most of the feed commodities with potential presence of fumonisins. Samples were collected between 2003 and 2016 from 19 different European countries, but most of them from four Member States. To take into account the possible occurrence of hidden forms, an additional factor of 1.6, derived from the literature, was applied to the occurrence data. Modified forms of fumonisins, for which no data were identified concerning both the occurrence and the toxicity, were not included in the assessment. Based on mean exposure estimates, the risk of adverse health effects of feeds containing FB 1-3 was considered very low for ruminants, low for poultry, horse, rabbits, fish and of potential concern for pigs. The same conclusions apply to the sum of FB 1-3 and their hidden forms, except for pigs for which the risk of adverse health effect was considered of concern.

Modified mycotoxins: An updated review on their formation, detection, occurrence, and toxic effects

Modified mycotoxins are metabolites that normally remain undetected during the testing for parent mycotoxin. These modified forms of mycotoxins can be produced by fungi or generated as part of the defense mechanism of the infected plant. In some cases, they are formed during food processing. The various processing steps greatly affect mycotoxin levels present in the final product (free and modified), although the results are still controversial regarding the increase or reduction of these levels, being strongly related to the type of process and the composition of the food in question. Evidence exists that some modified mycotoxins can be converted into the parent mycotoxin during digestion in humans and animals, potentially leading to adverse health effects. Some of these formed compounds can be even more toxic, in case they have higher bioaccessibility and bioavailability than the parent mycotoxin. The modified mycotoxins can occur simultaneously with the free mycotoxin, and, in some cases, the concentration of modified mycotoxins may exceed the level of free mycotoxin in processed foods. Even though toxicological data are scarce, the possibility of modified mycotoxin conversion to its free form may result in a potential risk to human and animal health. This review aims to update information on the formation, detection, occurrence, and toxic effects caused by modified mycotoxin.

Yeast and bacteria from ensiled high moisture maize grains as potential mitigation agents of fumonisin B1

BACKGROUND

Fumonisin B₁ (FB₁ ) is a mycotoxin produced by several Fusarium species and is a very common contaminant of maize-based food and feed throughout the world. The selection and use of FB₁ -degrading microorganisms appears as a promising alternative to cope with the problem of toxicity towards humans and livestock. High moisture maize grain silage, which is based on natural maize fermentation, could be an interesting reservoir of such microorganisms.

RESULTS

Using an in vitro simulated silage model with FB₁ naturally contaminated grains, we demonstrated a significant raw decrease in FB₁ during ensiling process ascribed to biodegradation mechanisms. A panel of 98 bacteria and yeasts were isolated from this matrix and selected for their ability to use FB₁ as the sole source of C and N. For nine of them, the ability to degrade FB₁ in vitro was evidenced. Notably, two bacteria identified as Lactobacillus sp. were highlighted for their efficient FB₁ -degrading capacity and production of hydrolysed FB₁ as intermediate degradation metabolite.

CONCLUSION

Fermentation of high moisture maize grain contaminated with FB₁ leads to a significant reduction of the toxin and allows the isolation of FB₁ -degrading microorganisms that could further be used as FB₁ decontaminating agents. © 2016 Society of Chemical Industry.

Fumonisins and their modified forms, a matter of concern in future scenario?

Masked mycotoxins are found in grains and derived foods as a result of plant phase II metabolism. Recently, masked mycotoxins senso strictu, together with other covalently or non-covalently conjugated forms, even formed upon processing, have been classified as modified mycotoxins. In this context, the issue of modified fumonisins is of great interest, on account of the wide range of factors affecting their formation and accumulation in maize pre- and postharvest. Fumonisins, indeed, may undergo modification in plants, along the growing season, but also during storage and drying of maize kernels, and upon processing. All these modifications strongly affect the analytical outcome, thus making more difficult the assessment of maize compliance. Since the ratio between free and modified fumonisins is affected by maize composition and environmental factors, a deeper knowledge on the phenomena driving the production and accumulation of free and modified forms in plants may support the selection of resistant hybrids. This review provides a critical picture of the state of the art on this topic, mainly focusing on those events occurring in field, identified as crucial in determining amount and partitioning of contamination. Nevertheless, knowledge on modified fumonisins is still in its dawn, on account of the wide range of factors involved. Anyway, reported results, taking altogether, clearly indicate that modified fumonisins should be included in the monitoring plans to have an overview of the possible contribution to human exposure. Furthermore, next efforts should focus on the events occurring in field and on the cross-talk between the plant and the fungus, to support the identification of resistant hybrids and to provide data for predictive models, the most suitable tool to forecast what is going to happens in the future changing climate.

Evolution of fungal population and mycotoxins in sorghum silage

Silage, one of the most important feed sources for cattle, is vulnerable to contamination by spoilage moulds and mycotoxins because ensilage materials are excellent substrates for fungal growth. The aim of this study was to identify the mycobiota of sorghum silages, to determine the presence of aflatoxins and fumonisins, and to correlate these results with physical parameters of the silage. A total of 275 samples of sorghum were collected from dairy farms in the south-west region of Uruguay were silage practices are developed. The presence of fungi was observed in all of the sorghum samples with values varying from 0.2 × 10⁴ to 4085 × 10⁴ UFC g^-1. Significant difference were detected in the total number of fungi during the storage period; at six months there is a high risk of fungal spoilage. The most frequent genera isolated from sorghum samples were Penicillium (70%), Aspergillus (65%), Absidia (40%), Fusarium (35%), Paecilomyces (35%) and Alternaria, Cladosporium, Gliocadium and Mucor (30%). The toxigenic species most frequently found were Penicillium citrinum, Aspergillus flavus and Fusarium nygamai. Only two samples were contaminated by AFB1 with levels of 1 and 14 µg kg^-1. Fumonisin was detected in 40% of freshly harvest samples with levels ranged from 533 µg kg^-1 to 933 µg kg^-1. The use of silo bags seems to be an effective tool to store sorghum. However, the presence of toxigenic fungi show that regular screening for mycotoxins levels in silages must be performed to avoid the exposure of animals to contaminated feed and the introduction of these compounds into the food chain.