Sustainable Shrimp Feeding: Digestibility of Defatted <i>Hermetia illucens</i> Meal by In Vitro and In Vivo Methods.

Abstract

This study evaluated the digestibility of defatted black soldier fly larvae (BSFL, <i>Hermetia illucens</i>) meals as alternative protein sources to partially replace fish meal (FM) in blue shrimp (<i>Penaeus stylirostris</i>) 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 (<i>p</i> <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 (<i>p</i> <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 (<i>R</i> ² = 0.691), which improved substantially after adjusting the in vitro assay temperature to match in vivo conditions (<i>R</i> 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.