Mycotoxin Occurrence and Microbiological Quality of Maize Silage Supplemented with Insect Meals for Potential Use in Waterfowl Nutrition

Whole crop maize silage may represent a complementary feed material in waterfowl nutrition, but its hygienic quality and mycotoxin profile remain important safety considerations. This study evaluated the microbiological quality, occurrence, and concentrations of selected mycotoxins in non-inoculated whole crop maize silage under five treatments: untreated control (CON), urea-supplemented silage (UR), silage supplemented with full fat Hermetia illucens meal (HI), silage supplemented with full fat Tenebrio molitor meal (TM), and lauric acid-supplemented silage (LA). All the variants were prepared from freshly harvested chopped maize forage and ensiled for 8 weeks in three independent replicates per treatment. The silages were analyzed for microbiological indicators and for the occurrence of fumonisin B1 (FB1), fumonisin B2 (FB2), total aflatoxins (ΣAFs), ochratoxin A (OTA), zearalenone (ZEA), T2 toxin (T2), HT2 toxin (HT2) and deoxynivalenol (DON). The initial occurrence of the selected mycotoxins in the raw materials was also assessed. In the silages, FB1 and FB2 were detected only in CON and UR, whereas both the fumonisins remained below the limit of detection in HI, TM and LA. DON was detected in all the treatments; HI, TM and CON did not differ significantly and showed the highest concentrations, whereas LA and UR were significantly lower and also differed from each other, with the lowest concentration observed in UR. HT2 was detected in CON and in one TM sample, while T2, ΣAFs, OTA and ZEA remained below the limit of detection in all the silage treatments. No significant differences were observed among the treatments in total viable count, lactic acid bacteria, coliform bacteria or microscopic filamentous fungi, and all the monitored microbiological indicators remained at low levels. Overall, the tested additives did not produce a uniform reduction across the monitored mycotoxin profile. A lower fumonisin occurrence was observed in HI, TM and LA, which should be interpreted with caution given the limited replication, whereas DON remained present in all the treatments.