Full-Fat Black Soldier Fly Larvae Meal in Diets for Pacu, <i>Piaractus brachypomus</i>: Digestibility, Growth Performance, Blood Biochemistry and Gut Morphology.

Black soldier fly larvae meal has emerged as a sustainable alternative to fishmeal (FM) in aquafeeds. However, the use of full-fat black soldier fly larvae meal (FF-BSFL) may be limited by its relatively high lipid and chitin contents, which could affect nutrient digestibility and fish performance. This study determined the apparent digestibility coefficients (ADCs) of FF-BSFL and evaluated the effects of replacing 0%, 30%, 60%, and 100% of FM with FF-BSFL in diets for juvenile pacu (Piaractus brachypomus). A 60-day feeding trial was conducted using 320 juvenile pacu (initial weight: 3.0 g) to evaluate growth performance, serum biochemical parameters, and intestinal histomorphology. The results showed high ADCs for protein (88.76%), lipids (97.09%), and gross energy (85.96%) in FF-BSFL. Fish fed the diet containing 30% FM replacement exhibited growth performance comparable to the control group. However, replacement levels of 60% and 100% significantly reduced growth and feed efficiency. Furthermore, high fishmeal replacement levels decreased mucosal thickness and muscularis thickness, reduced goblet cell abundance, and increased serum triglyceride concentrations and aspartate aminotransferase (AST) activity. In conclusion, FF-BSFL was highly digestible for juvenile pacu. Replacement of up to 30% of FM maintained growth performance and intestinal integrity, whereas higher replacement levels negatively affected growth performance and intestinal health.