Black soldier fly larvae oil downregulated gene expression related to fat metabolism of broilers fed low protein diet

Feeding low crude protein (LCP) diets supplemented with crystalline amino acids improves environmental and welfare parameters of broilers. However, increased body fat contents in broilers fed LCP diets have become a concern. Black soldier fly larvae oil (BSFLO), rich in lauric acid, has been reported to inhibit lipogenesis and reduce body fat. A 3 × 2 factorial experiment was conducted to evaluate the effect of BSFLO on performance, blood biochemistry, carcass quality, fat metabolism gene expression, and litter quality in broilers fed protein-reduced diets. A total of 288 broilers were divided into 6 treatments: three CP levels (200, 185, or 170 g/kg; high HCP, medium MCP, or low LCP) and two oil sources (BSFLO and Crude Palm Oil CPO), with 6 replicate pens of 8 birds each. Results showed a 15 g/kg CP reduction had no effect on body weight and feed intake (P > 0.05) but increased FCR (P = 0.001). A 30 g/kg CP significantly reduced the body weight and feed intake with inferior FCR (P < 0.05). However, negative effect of low CP diets on FCR was mitigated by BSFLO (P = 0.008). Reducing CP by 30 g/kg increased fat pads (P = 0.033), whereas BSFLO reduced fat pads (P = 0.049) at all three CP levels. Protein-reduced diets increased blood cholesterol (P = 0.002), HDL (P < 0.001), and LDL (P = 0.002). BSFLO decreased blood triglyceride (P = 0.026) and cholesterol (P < 0.001). Reducing 30 g/kg CP increased meat cooking loss (P = 0.035), while BSFLO decreased cooking loss (P < 0.001). BSFLO increased meat protein (P < 0.001) and decreased cholesterol (P = 0.003). The inclusion of BSFLO in protein-reduced diet down-regulated the gene expression of FAS, ACC, SREBP-1, and HMGR in broilers (P < 0.001). Reducing CP levels decreased litter pH (P = 0.011), nitrogen (P < 0.001), ammonia (P < 0.001) and moisture (P = 0.018). The study concludes that BSFLO reduced body fat by down-regulating the lipogenesis gene expression. In addition, BSFLO enhanced feed efficiency in broilers fed protein-reduced diet. © 2025