Effects of inclusion level of black soldier fly larvae protein or oil on broiler growth performance during heat stress

Beyond their nutritional value, insects contain bioactive compounds, including chitin, lauric acid, and antimicrobial peptides, and could potentially exert positive effects on animals consuming insect-based diets in health challenging conditions. A total of 648 Ross 308 male chicks were fed four different soybean meal-maize-wheat based diets in which soybean meal or oil was partly replaced by black soldier fly larvae (BSFL) protein or oil, respectively, in cyclic heat stress or thermoneutral (control) conditions. BSFL protein or oil was included at 5 and 10 %, and 2 and 4 %, respectively, in a 2 × 2 × 3 factorial design. The growth performance (ADFI, ADG, body weight gain : feed intake ratio (G:F), and mortality) was recorded at d 9, 21, and 34. Carcass yields were determined at 35 d of age and blood and ileal tissue samples were collected to examine heat stress-related biomarkers. The heat stress challenge was successfully implemented, demonstrated by a significant reduction in ADFI, with numerical reductions in ADG and final BW across the overall trial. The cyclic heat stress applied was mild and chronic, with mortality and removals recorded at 2 %. Broilers exposed to heat stress showed elevated levels of ileum calprotectin, while serum corticosterone levels tended to be lower compared to controls. A significant interaction was observed between heat stress, insect product, and inclusion level. In heat stress conditions, the inclusion of BSFL oil led to a numerical increase in ADFI, ADG, and BW, whereas inclusion of BSFL protein resulted in a numerical decrease in BW. BSFL protein at 5 and 10 % and BSFL oil at 2 and 4 % inclusion level did not exhibit notable growth performance benefits in Ross 308 broilers under mild cyclic heat stress conditions. The mild nature of the heat stress challenge may have limited the detection of BSFL product effects, highlighting the need for future investigations under more intense heat stress conditions.