Sustainable Shrimp Feeding: Digestibility of Defatted Hermetia illucens Meal by In Vitro and In Vivo Methods

This study evaluated the digestibility of defatted black soldier fly larvae (BSFL, Hermetia illucens) meals as alternative protein sources to partially replace fish meal (FM) in blue shrimp (Penaeus stylirostris) diets. It also examined the relationship between in vivo and in vitro digestibility methods to support the development of a reliable in vitro approach. Two BSFL-based mixes were tested: one with a higher chitin content (H70), and the other with a lower chitin content and also presenting a more balanced essential amino acid profile (M70). Each replaced 60% of FM in experimental diets (H20 and M20, respectively) and were compared to a control diet containing no BSFL meal. Apparent digestibility coefficients (ADCs) were measured in vivo using chromium oxide (Cr₂O₃; 1%) as an inert marker. In vitro digestibility was assessed using the pH-stat method with shrimp hepatopancreas enzyme extracts. In vivo results showed that the M20 feed had significantly higher digestibility than the control (p <0.05), while no significant difference in protein ADC was observed among diets. In vitro results indicated that the H20 feed had lower digestibility than the control (p <0.05). The ranking of protein digestibility (Control ≥ M20 ≥ H20) was consistent between both methods. A satisfactory correlation was found between in vivo and in vitro protein digestibility (R ² = 0.691), which improved substantially after adjusting the in vitro assay temperature to match in vivo conditions (R ² = 0.864). These findings suggest that the pH-stat method is a promising tool for preliminary assessment of ingredient digestibility, more precisely protein digestibility, in shrimp diets. Moreover, industrial BSFL meal appears to be a viable protein source for replacing upto 60% of FM in shrimp feed formulations without compromising shrimp survival or digestibility.