Replacing maize partially or totally with sorghum alters mycotoxin profile in their silages in microsilos

Heat- and drought-tolerant sorghum is an attractive alternative to maize, yet its silage mycotoxin trade-offs remain unclear. We compared maize (Zea mays L.), sorghum (Sorghum bicolor (L.) Moench; cultivars Goliath and Sucrosorgo 506) and 1:1 maize-sorghum silages after 60 d ensiling (microsilo scale), with or without a commercial multi-strain lactic acid bacteria (LAB) inoculant. All silages fermented well (pH 4.06 - 4.21; lactic acid 18.1 - 27.9 g/kg dry matter). Maize silage showed the highest Fusarium toxins-deoxynivalenol (DON) 499 - 516 and nivalenol (NIV) 173 - 216 μg/kg dry matter. In sorghum-only silages, DON was below quantification limits, and NIV was not detected. This benefit came with a new hazard: in silages of maize and sorghum mixture (0.51 - 3.72 μg/kg dry matter) and was absent from maize-only silage. Maize and sorghum mixing reduced DON (80.4 - 180 μg/kg dry matter) while keeping OTA low (0.54 - 1.82 μg/kg dry matter). LAB inoculation sharply suppressed yeasts and ethanol in maize silage (4.7 × 10⁷ → 1.4 × 10⁵ CFU/g; 8.26 → 5.03 g/kg dry matter) but showed substrate-dependent effects in sorghum-based silages and did not reliably reduce mycotoxins. Sorghum substitution by maize therefore shifts, rather than removes, hygienic risk - from Fusarium toxins toward OTA-associated storage mould contamination-underscoring the need for stringent anaerobiosis and OTA monitoring when diversifying forages under warm growing conditions.