Effects of insect-derived protein form and replacement level on growth performance and skeletal traits in broiler...

This study evaluated black soldier fly (Hermetia illucens) products as alternatives to soybean meal protein in broiler pheasants, focusing on growth performance and skeletal traits in both sexes. Birds were assigned to five dietary treatments: a soybean meal control and diets in which 50% or 100% of soybean protein was replaced with either insect meal or dried larvae. Growth performance was recorded, and bone quality was assessed using densitometry, mechanical testing, and geometrical analysis of the femur and tibia. In males, insect-based diets increased body weight and thigh muscle mass, whereas females showed only minor or non-significant changes in performance traits. Skeletal responses were sex- and bone-specific. In males, higher replacement levels were associated with improved bone mineralization and enhanced structural mechanical properties, particularly in the tibia. In contrast, females exhibited more pronounced changes in apparent material properties of bone tissue, with relatively minor effects on bone geometry and whole-bone strength. Differences between insect meal and dried larvae were evident in several skeletal parameters, particularly in tibial apparent material properties, indicating that the physical form of the insect-derived ingredient influenced bone tissue behavior rather than gross bone size alone. Overall, skeletal responses reflected combined effects of dietary composition and growth-related mechanical loading. These findings indicate that skeletal responses reflect adaptive adjustments of bone to combined nutritional and mechanical stimuli, rather than uniform changes in bone mass or size.