Agricultural By-Products and Black Soldier Fly Larvae Meal as Alternatives to Soybean Meal in Commercial Broiler Diets: Effects on Meat Quality, Fecal Microbiota, and Environmental Impact.

Abstract

The present study aimed to evaluate the effect of partially replacing soybean meal with agricultural by-products with or without supplementation of dried black soldier fly larvae (BSFL) meal on meat quality, intestinal microbiota of commercial broiler chickens, and environmental sustainability. A total of 252 day-old Cobb 500 chicks were divided into three dietary treatments, including a corn-soybean-based Control diet and two alternative diets. Alternative diets were a diet in which soybean meal was replaced partly (SPR) by sunflower meal, brewers dried grain, and wheat middlings, and a diet in which BSFL meal was added (5%) to the SPR diet. At 39 days of age, the feces of chickens from each dietary treatment were sampled for fecal microbiota analysis. Birds were slaughtered at day 40 to assess breast meat quality. A life cycle assessment (LCA) was conducted to estimate the environmental impacts of each diet. The SPR and SPR+BSFL diets significantly (p = 0.003) reduced breast meat pH₂₄ without affecting lightness and yellowness values. While cooking losses were similar in the breast meat of chickens fed the Control and SPR diets, adding BSFL meal to the SPR diet reduced cooking losses (p < 0.001). The SPR+BSFL diet increased total saturated fatty acids (SFA), while the SPR diet elevated polyunsaturated fatty acid (PUFA) content, particularly linoleic acid (p < 0.001). Microbiota analysis revealed a higher abundance of Firmicutes, particularly Lactobacillus and Bacillus, in broilers fed the SPR+BSFL diet, while Clostridiaceae was more prevalent in the SPR group compared to the Control (p < 0.01). These changes in microbiota were likely attributed to the increased fiber content of the diets. Environmental impact analysis showed that both SPR and SPR+BSFL diets reduced global warming potential, damage to ecosystems, human health burden, and resource use compared to the Control diet (p < 0.001). The two alternative diets performed similarly in most environmental indicators. The results suggested that agricultural by-products with or without BSFL meal supplementation could be used to partially replace soybean meal in the diets of commercial broiler chickens and would beneficially modulate gut microbiota and reduce the environmental footprint of broiler production.