Dietary inclusion of black soldier fly larvae as a partial protein source: effects on growth performance, carcass...

1. Black soldier fly larvae (BSF) can convert kitchen waste (KW) into usable organic resources. This study evaluated the effects of BSF derived from kitchen waste on the growth performance, carcass traits, meat quality and caecal microbiota in broilers.2. A total of 180 broilers were randomly assigned to three groups: a control group (CON), LBF or HBF group (containing 3% and 6% of BSF respectively). Performance was measured as feed intake (FI), Average daily weight gain (ADG), allowing feed conversion ratios (FCR) to be calculated. Carcass and muscle yields and characteristics were recorded. Caecal samples were taken for analysis of populations.3. The results showed that the 3% BSF group had better performance, including significant reductions in FI and abdominal fat and increased breast meat yield and muscle fibre diameter (p < 0.05). The mRNA levels of myostatin (MSTN), muscle RING finger protein 1 (MuRF1) and muscle atrophy F-box (MAFbx) were significantly downregulated (p < 0.05). The LBF group showed significantly elevated levels of specific fatty acids in breast meat, such as lauric acid and myristoleic acid (p < 0.05). However, replacing soybean meal with BSF in diet reduced meat quality and increased cooking loss and toughness (p < 0.05).4. The 16S rRNA microbiome sequencing showed that the LBF birds had significant increases in beneficial bacteria, including Butyricicoccus pullicaecorum and Akkermansia muciniphila and reduced Alistipes finegoldii abundance (p < 0.05). Spearman correlation analysis showed that Butyricicoccus pullicaecorum was positively associated with breast meat yield, muscle fibre size and cooking loss and negatively associated with the expression of MSTN, MuRF1 and MAFbx. Alistipes finegoldii showed opposite correlated trends to these indicators.5. In conclusion, dietary inclusion of BSF can regulate gut microbial composition and the expression of genes related to muscle development, thereby improving meat production, but affecting meat quality. Additionally, BSF alter the fatty acid profile of breast meat.