Effects of several lactic acid bacteria inoculants on fermentation and mycotoxins in corn silage

Abstract

Effects of commercial and pure lactic acid bacteria (LAB) inoculants on fermentation and levels of aflatoxins and other mycotoxins in corn silage that was experimentally contaminated in the field with a toxigenic strain of Aspergillus flavus (ITEM 8069) were determined. Late-season corn hybrid plants were inoculated with A. flavus at silk emergence, and fresh-chopped corn was harvested at the ⅔ milk line stage (dry matter [DM]: 428 ± 6.5 g/kg) and ensiled directly (control, CTR) or after treatment with 9 LAB inoculants. Commercial inoculants contained Lactobacillus (L.) buchneri LB1819 and Lactococcus lactis O224 or Enterococcus faecium, Lactobacillus plantarum, Lactococcus lactis SR3.54 (respectively SiloSolve FC or SiloSolve MC, Chr. Hansen A/S, Hørsholm, Denmark), L. buchneri and L. plantarum (Pioneer brand 11C33, Pioneer Hi-Bred International, Des Moines, USA). One pure strain of L. brevis DSMZ 20054, two pure strains of L. plantarum (LP ATCC 8014 and LP PB) and three of L. rhamnosus (LR ATCC 7469, LR LR7 and LR RI) were also used. Each silage received an inoculant at final expected dose of approximately 250,000 CFU/g of freshly chopped forage, and was ensiled in 20 L mini-silos, compacted to density of 160 kg dry-mass/m3, stored at room temperature, and opened after 30 or 120 days. The commercial and pure inoculants had few effects on fermentation relative to CTR. Ensiling time and LAB treatment had no effect on silage pH. However SiloSolve FC silage had lower ethanol levels than CTR group, while 1,2 propanediol level doubled as ensiling time increased and the high values were with SiloSolve FC and Pioneer CFT. Aerobic stability increased with ensiling time, with the longest stability in SiloSolve FC and L. rhamnosus ATCC 7469 silage. Lowest aflatoxin B1 (AFB1) concentrations were in the L. rhamnosus LR7 and L. plantarum ATCC 8014 silages (about 8–10 μg/kg DM) and the highest concentration was in L. brevis DSMZ 20054 silage (34.2 μg/kg DM). Concluding, future investigations should be carried out to examine the relationship between LAB and mycotoxinegic fungi during ensiling.