Effects of black soldier fly larvae replacing soybean meal on growth, blood traits, carcass characteristics, and jejunal microbiota in ducks

Abstract This study evaluated the effects of replacing soybean meal with defatted black soldier fly ( Hermetia illucens ) larvae (BSFL) meal in the diets of Cherry Valley ducks. A 21-day feeding trial was conducted using 200 1-day-old Cherry Valley ducks (half male, half female). Ducks were randomly assigned to four dietary treatments with five replicates per treatment and 10 ducks per replicate. Ducks were fed a corn-soybean meal-based control diet or isocaloric and isonitrogenous diets in which 3%, 6%, or 9% of soybean meal was replaced with defatted BSFL meal. Average daily feed intake (ADFI) and average daily gain (ADG) decreased linearly with increasing dietary BSFL levels ( ). However, live body weight, ADG, ADFI, and breast and thigh muscle weights were comparable between the 3% BSFL group and the control ( ). Increasing BSFL levels resulted in linear decreases in neutrophil count, monocyte percentage, red blood cell count, haemoglobin concentration, and serum lactate dehydrogenase activity, whereas lymphocyte percentage, total white blood cell count, and serum superoxide dismutase activity increased linearly ( ). Jejunal microbiota analysis further showed a significantly higher relative abundance of Lactobacillus in the 9% BSFL group ( ). Overall, dietary inclusion of 6-9% BSFL meal negatively affected growth performance, whereas 3% BSFL inclusion maintained growth performance while modulating immune function and antioxidant status. These findings suggest that defatted BSFL meal can be recommended at a 3% inclusion level as a partial replacement for soybean meal in diets of 1-21-day-old Cherry Valley ducks.