Increase in aflatoxins due to Aspergillus section Flavi multiplication during the aerobic deterioration of corn silage treated with different bacteria inocula

Abstract

The growth of Aspergillus flavus and the production of aflatoxins (AF) during the aerobic deterioration of corn silage represent a problem for animal and human health. This experiment was conducted to evaluate whether the presence of A. flavus and AF production originate from the field or additional AF are produced during the fermentation phase or during aerobic deterioration of corn silage. The trial was carried out in northern Italy on corn at a dry matter (DM) level of 34%. The fresh herbage was either not treated (C) or treated with a Lactobacillus buchneri (LB) NCIMB 40788 [(at 3 × 10 5 cfu/g of fresh matter (FM)], Lactobacillus hilgardii (LH) CNCM I-4785 (at 3 × 10 5 cfu/g of FM), or their combination (LB+LH; at 1.5 × 10 5 cfu/g of FM of each strain) ensiled in 20-L silos and opened after 250 d of ensiling. After silo opening, the aerobic stability was evaluated and samples were taken after 7 and 14 d of air exposure. The pre-ensiled material, the silages at silo opening, and the aerobically exposed silages were analyzed for DM content, fermentative profiles, microbial count, nutritive characteristics, DM losses, and AFB 1 , AFB 2 , AFG 1 , and AFG 2 contents. Furthermore, a subsample of colonies with macromorphological features of Aspergillus section Flavi was selected for AF gene pattern characterization and in vitro AF production. The presence of A. flavus was below the detection limit (<1.00 log 10 cfu/g) in the fresh forage before ensiling, whereas it was found in 1 out of 16 silage samples at silo opening at a level of 1.24 log 10 cfu/g. The AF were found in both the fresh forage and at opening in all the samples, with a predominance of AFB 2 (mean value of 1.71 μg/kg of DM). The inocu-lation of lactic acid bacteria determined a reduction in the lactic-to-acetic ratio compared with the control. A larger amount of acetic acid resulted in a lower yeast count and higher aerobic stability in the treated silages than in the control ones. At the beginning of aerobic deterioration, the yeasts increased to over 5 log 10 cfu/g, whereas the molds were close to the value observed at silo opening. When the inhibiting conditions were depleted (pH and temperature higher than 5 and 35°C, respectively), both the total molds and A. flavus reached higher values than 8.00 and 4.00 log 10 cfu/g, respectively, thus determining the ex novo production of AFB 1 during aerobic deterioration, regardless of treatments. The analysis of gene pattern showed that 64% of the selected colonies of A. flavus showed the presence of all 4 AF gene patterns, and 43% of the selected colonies were able to produce AF in vitro. During air exposure, after 1,000°C·h have been cumulated, starch content decreased (below 10% DM) and concentration of neutral detergent fiber, acid detergent fiber, hemicelluloses, crude protein, and ash increased. The inoculation with LB and LB+LH increased the aerobic stability of the silages and delayed the onset of aerobic microbial degradation, which in turn indirectly reduced the risk of A. flavus outgrowth and A...

Aspergillus fumigatus population dynamics and sensitivity to demethylation inhibitor fungicides in whole‐crop corn, high moisture corn and wet grain corn silages

“…Thus, in this study, the highest number of contaminated samples by A. fumigatus was found after 60 days of silage conservation, indicating that the fungus was able to survive 60 days under anaerobic conditions. Whereas, after longer conservation period (160 days of anaerobic condition), the number of samples containing A. fumigatus was low, as reported previously by Ferrero et al . The occurrence of A. fumigatus in corn silages at opening was previously described by Dolci et al .…”

Adverse Effects, Transformation and Channeling of Aflatoxins Into Food Raw Materials in Livestock

“…Leuconostoc, and Pediococcus (P. pentosaceus) genera can inhibit or can even prevent completely the growths of various mycotoxigenic molds and their mycotoxin productions as well (Dalié et al, 2010;Cavallarin et al, 2011;Queiroz et al, 2012;Dogi et al, 2013;Ahlberg et al, 2015;Ma et al, 2017;Gallo et al, 2018;Zielińska and Fabiszewska, 2018;Ferrero et al, 2019). It is noteworthy that there is a wide spectrum of environmental factors which influence the antifungal activity of LAB, including the type of the matrix and culture medium, the availability of nutritional compounds, the incubation time and temperature (Dalié et al, 2010;Ahlberg et al, 2015;Leyva Salas et al, 2017).…”

“…The interaction of L. buchneri, L. reuteri, L. plantarum, and L. fermentum strains reduced the AFB 1 level, improved the stability and, furthermore, the microbiological and chemical purity of maize silage (Zielińska and Fabiszewska, 2018). In a most recent study by Ferrero et al (2019), the authors examined the effect of L. buchneri, Lactobacillus hilgardii, and their combination on A. flavus contaminants and their aflatoxin production in maize silage. The results showed that the inoculation of corn silage with L. buchneri and L. hilgardii increased the aerobic stability and delayed the beginning of aerobic microbial degradation of maize silage, and indirectly reduced the risk of A. flavus emergence and aflatoxin B 1 level after silage opening.…”

Effect of Supplemental Kluyveromyces marxianus and Pichia kudriavzevii on Aflatoxin M1 Excretion in Milk of Lactating Dairy Cows

“…have been reported to inhibit growth of aflatoxin-producing Aspergillus spp. [15][16][17][18][19][20]. Yeast has also been used in some research to help animal performance and ruminal metabolism and to detoxify mycotoxins in feed [16,21].…”