Hermetia illucens and Tenebrio molitor as Supplements in Maize Silage for Potential Use in Waterfowl Diets: Effects on Nutritional Composition, Selected Microbial Indicators, and Selected Mycotoxins

Alternative protein sources are increasingly considered in poultry nutrition, and insect meals may represent a promising strategy for modifying the compositional profile of maize silage in the context of waterfowl feeding. This study evaluated maize silage supplemented with Hermetia illucens (BAHI) or Tenebrio molitor (BATM) meal as alternatives to urea (BAUR) as a nitrogen source, including variants with lauric acid (BALA) and with the lactic acid bacteria (LAB) inoculant alone (BA), focusing on nutritional composition, microbiological quality, and selected mycotoxins (MT). Maize forage treated with LAB was ensiled for 8 weeks in five variants, with three independent silage replicates per treatment, and the silages were analyzed for nutrients, energy value, amino acids, fatty acids, microbial and MT content. Insect meals increased crude protein compared with BA (64.94–67.32 vs. 49.73 g/kg dry matter, DM) and nearly doubled ether extract in BAHI (40.08 vs. 21.74 g/kg DM), while apparent metabolizable energy for poultry ranged from 8.55 to 9.87 MJ/kg DM (BAHI). Urea elevated crude protein content to 66.37 g/kg DM without improving the essential amino acid index. Microbial indicators did not differ among treatments. In the MT profile, lower deoxynivalenol concentrations were observed in BAUR, BAHI, and BATM, and lower fumonisin B1 concentrations were observed in BATM and BALA, while aflatoxins and ochratoxin A were not detected. Overall, the results indicate that low-level inclusion of insect meals in combination with LAB improved the compositional characteristics of maize silage, while no significant differences were detected in the monitored microbial counts and only selective changes were observed in the mycotoxin profile.