Effects of replacing soybean oil with black soldier fly larvae oil in layer diets on egg production performance, egg quality, plasma biochemistry, intestinal morphology, and microbiota composition

Soybean oil is a conventional dietary lipid source in poultry production; however, sustainability concerns and rising costs have driven interest in insect-derived alternatives. Black soldier fly larvae oil (BSFO), rich in medium-chain fatty acids, represents a promising sustainable substitute, yet its effects on laying hens remain poorly characterized. This study evaluated the effects of partially replacing soybean oil with BSFO at 0%, 20% and 40% inclusion levels on egg production performance, egg quality, blood biochemistry, intestinal morphology and cecal microbiota in forty-two 57-week-old Lohmann Brown laying hens over 8 weeks. BSFO substitution did not affect body weight, egg production rate, egg weight or feed conversion ratio, confirming its viability as an alternative lipid source. However, eggshell strength declined with increasing BSFO levels, likely due to elevated saturated fatty acid content reducing calcium bioavailability. BSFO upregulated pro-inflammatory genes (IL-1β, IL-6, TLR4) while enhancing OCLN expression, suggesting intestinal barrier reinforcement. Microbiota analysis revealed β-diversity shifts and enrichment of short-chain fatty acid-producing taxa, including Phascolarctobacterium and Synergistes. In conclusion, partial soybean oil replacement with BSFO maintained laying performance and modulated intestinal immunity and microbiota composition, though excessive inclusion may impair eggshell strength.