Effects of several commercial or pure lactic acid bacteria inoculants on fermentation and mycotoxin levels in high-moisture corn silage

Effects of 3 commercial lactic acid bacteria (LAB) inoculants and 6 single strains of LAB on fermentation and levels of aflatoxins and other mycotoxins in high-moisture corn (HMC) silage were examined. Corn plants were inoculated with Aspergillus flavus at silk emergence and wet corn kernels were harvested at black layer stage (dry matter [DM]: 704 ± 5.0 g/kg). Samples were ground and ensiled directly (control group, CTR) or after treatment with one of the 9 LAB inoculants. The commercial inoculants contained Lentilactobacillus (Lent.) buchneri LB1819 and Lactococcus lactis O224 (SiloSolve FC; Chr. Hansen A/S, Hørsholm, Denmark), applied at a final dose of 250,000 CFU/g or 1,250,000 CFU/g (SiloSolve FC₁ₓ and SiloSolve FC₅ₓ, respectively); and Lent. buchneri and Lactiplantibacillus (Lac.) plantarum (Pioneer brand 11B91, Pioneer Hi-Bred International, Des Moines, USA) applied at a final dose of 250,000 CFU/g. One pure strain of Levilactobacillus (Lev.) brevis DSMZ 20054, two pure strains of Lac. plantarum (LP ATCC 8014 and LP PB) and three of Lacticaseibacillus (La.) rhamnosus (LR ATCC 7469, LR LR7 and LR RI) were also applied at a final expected dose of 250,000 CFU/g. Wet corn kernels were ensiled in 20 L mini-silos, compacted to a density of 389 kg DM/m³, and stored at room temperature. Conditions before ensiling were pH 5.87 ± 0.169, and (log₁₀ CFU/g) of 7.68 ± 0.473 for LAB, 5.71 ± 0.121 for molds and 6.81 ± 0.341 for yeasts. The mini-silos were opened after 30 or 120 days. From day 30–120 days, levels of acetic acid, propionic acid and 1,2 propanediol increased (P < 0.05) in the SiloSolve FC₁ₓ, SiloSolveFC₅ₓ and Pioneer 11B91, and in LR LR7 groups. During this time, butyric acid level increased 5-fold in CTR; by two to three-fold in pure strains groups; and only slightly in the three commercial inoculants and the LR LR7 (P < 0.05). Aerobic stability increased (P < 0.05) with storage time from 32 to 97 h, and the commercial inoculants and LR LR7 groups had longer stability than CTR (P < 0.05). The storage time and the inoculants did not affect aflatoxin levels. No zearalenone or tenuazonic acid were detected in the mini-silos, even if they contaminated the corn plants. Results indicate that different silage inoculants affected fermentation of HMC and its contamination by mycotoxins, although no inoculant had an effect on levels of aflatoxins.