Feeding live or processed black soldier fly larvae to slow-growing broilers impacts their behaviour differently

In response to increasing public concerns and retailer demands, the broiler production industry and legislative authorities are looking for measures to improve broiler welfare. Black soldier fly (BSF) larvae could be used in broiler diets as these insects contain bioactive compounds that may improve broiler health. The underlying pathways of these bioactive compounds to support broiler health are not fully understood yet. However, experimental evidence indicates that BSF larvae as part of laying hen diets can lead to improved disease resistance and immune response in those chickens, based on improved blood biochemical profiles. Moreover, BSF larvae may trigger natural behaviour through visual cues, potentially stimulating natural foraging behaviour and pecking towards larvae. BSF larvae products (live and processed), varying in physical and nutritional properties, may affect broiler health and welfare differently based on product choice and inclusion level (low and high). The purpose of this study was to investigate whether BSF larvae products as part of slow-growing broiler (Hubbard JA757) diets or rations can contribute to better health and welfare. Therefore, the following BSF larvae products were tested at two inclusion levels: live larvae (L), a combination of BSF larvae meal and fat (MO) mimicking the nutritional composition of the live larvae, and BSF larvae meal (M) and fat (O) separately. Each treatment group was replicated 8 times with 24 broilers per replicate. The experimental diets were provided to the 1-day-old chickens until 51 days of age. The health of the broilers was quantified based on blood biochemical parameters and weight and length of intestinal organs, while the welfare of the broilers was quantified based on physical welfare scores, behavioural observations, and activity tracking. Feeding live BSF larvae to broilers affected their behaviour, leading to broilers showing more eating, locomotion, and active behaviour, while showing less resting and foraging behaviour compared to broilers receiving only compound feed with or without processed BSF larvae products. Biochemical blood parameters and dimensions of intestinal organs did not differ between the control group and treatment groups containing BSF larvae products. Based on our results, the insect product form, feeding live larvae rather than processed larvae, seems to stimulate eating and active behaviour in broilers, while inclusion level seems to play a less important role. We therefore recommend to use low quantities of live BSF larvae in broiler diets to improve activity in modern broiler production systems.