Evaluating sustainable ingredients including black soldier fly larvae (Hermetia illucens) in laying hens through performance, physiology and nutrient metabolism

To increase the sustainability of laying hen diets in subtropical rural conditions, corn and soybean meal were partially substituted with locally produced ingredients, topped or not with black soldier fly ( Hermetia illucens , BSF) larvae, simulating rural practices. To understand the underlying metabolic causes of potentially altered performance, blood biochemical parameters, including acylcarnitines, were evaluated. From 30 to 40 weeks of age, 150 Lohman White laying hens were allocated to three diets: standard corn–soybean meal diet (CONTROL), an alternative diet with triticale, faba beans and rapeseed meal (ALTER), and an ALTER diet supplemented with 5% BSF-dried larvae (ALTER + BSF). Laying performance, organ traits, selected carnitine esters and serum biochemical parameters were assessed. The CONTROL and ALTER diets resulted in comparable laying performance, whereas ALTER + BSF decreased the laying rate by 2% ( p < 0.001 ) and increased egg weight by 2 grams ( p < 0.001 ). Multivariate analysis revealed coordinated remodeling of the global acylcarnitine profile (p =  0.002 , R ²  = 0.74), which was associated with BSF supplementation and driven by free carnitine (C0), ϐ-oxidation (3-hydroxybutyrylcarnitine, C4-OH) and amino acid degradation (propionylcarnitine, C3) markers. The ALTER diet increased alanine aminotransferase (ALT) levels, which were normalized by BSF feeding ( p = 0.01 ). No differences were observed in organ weights. In conclusion, the substitution of alternative ingredients for soybean and corn effectively maintained laying performance. The BSF larvae acted as a functional nutrient, favoring egg weight and stimulating fat oxidation. These findings support the use of alternative ingredients for sustainable poultry production in subtropical rural areas.