In vitro assessment of protein digestibility and mineral solubility of black soldier fly larvae meals for monogastric animals

Animal farming is a fast-growing sector which demands a large supply of feed materials and the search for novel feed ingredients with a smaller impact on the global environment has been intensified. However, before the inclusion of these feed ingredients in animal feed, a preliminary assessment of the quality and performance is needed. This evaluation is usually done by in vivo feeding trials, but in vitro digestion methods have been successfully used for gathering information regarding the nutritional value of the different feed components. Therefore, in this work, an in vitro digestion method was developed using black soldier fly (BSF) larvae meals. The method included seven experimental variables, namely: pH in stomach, pH in intestine, reaction time in stomach, reaction time in intestine, enzyme concentration in stomach, enzyme concentration in intestine and temperature. The experimental variables were screened by means of a fractional factorial design (27-2) that allowed to select the concentration of enzyme in the intestine and temperature (at 7 U and 37 degrees C, respectively) as the most influential factors on amino acid and mineral solubility in BSF larvae meal. Performing the in vitro digestibility at 37 degrees C with pH of the stomach and intestine at 2 and 9, reaction time in the stomach and intestine at 1 hour and 4 hours and concentration of enzyme in the stomach and intestine at 1 U and 7 U resulted in the highest overall nutrient solubility. This optimised in vitro digestion methodology was used to assess the nutritional stability of three batches of BSF meals delivered by the same producer. The in vitro digestion method was able to reveal differences between the three batches of BSF meals.