Evaluating the In Vitro Digestibility of Black Soldier Fly (Hermetia illucens L.) Larvae as Potential Feed Ingredient in Dairy Cattle Silage‐Based Diets: A Focus on Proteins

: Dietary protein has a substantial economic impact on cattle feed, and it is also a critical component for animal growth and productivity. Several environmental issues related to soybeans have led to an increased interest in novel protein sources, such as insects. However, research on the inclusion of insects in bovine diets is limited, also due to the current European legislation on the topic. For this reason, this study aimed at investigating the use of black soldier fly (BSF) larvae as a soybean replacer in dairy cattle diet. Three iso-nitrogenous and iso-energetic diets for lactating dairy cattle were formulated, including (i) soybean, (ii) a commercial protein-rich feedstuff and (iii) BSF larvae as a main protein source. After an in vitro bovine digestion, dry matter digestibility (DMD) and crude protein digestibility (CPD), were determined. Additionally, for the first time to our knowledge, individual amino acids and chitin digestibility, degree of hydrolysis (DH%), molecular weight distribution of proteins via SDS-PAGE gel electrophoresis and HR-MS analysis of peptides released after digestion were also assessed. The results showed that the formulated diets did not differ in terms of DMD, CPD, amino acid solubilization and DH%, highlighting the potential of replacing soybean meal with insects without negatively affecting these parameters. In addition, 50% of chitin was solubilized at the end of the intestinal phase, both in individually digested BSF larvae and in the diet formulated with BSF larvae, meaning that chitinolytic microorganisms were present in the rumen and that chitin represents a potential source of carbon and nitrogen for ruminants.