Utilising brewer’s spent grain as a cost-effective feed formula for sustainable house cricket (Acheta domesticus) rearing

Abstract This study investigates the potential of brewer’s spent grain (BSG) as a cost-effective alternative to soybean meal in the diets of house crickets ( Acheta domesticus ) to enhance sustainable cricket rearing. BSG, a by-product of the brewing industry, was chosen due to its local availability and high protein content (38%). Here, the impacts of varying levels of BSG substitution (0%, 10%, 20% and 30%) on the growth performance, nutrient utilisation, chemical composition, and volatile compound profiles of crickets over a 45-day period was assessed. Crickets were reared under controlled conditions and divided into five groups, each receiving one of the experimental diets. Growth performance parameters, including body weight, average daily gain, and feed conversion ratio, were measured. Chemical analysis of the crickets and their diets was conducted, focusing on protein efficiency ratio, apparent dry matter digestibility (ADMD), and nitrogen retention. Volatile compounds were identified using gas chromatography-mass spectrometry. Crickets fed BSG diets exhibited higher protein deposition and lower fat content compared to those on a commercial diet, suggesting BSG’s potential to improve protein quality while reducing fat accumulation. ADMD was also higher in BSG-fed crickets, likely due to the prebiotic effects of components such as β-glucans and arabinoxylans. Additionally, the inclusion of BSG up to 30% in cricket diets reduced production costs by up to 29% compared to a commercial diet. Volatile compound analysis revealed that crickets fed BSG diets produced different odour profiles, with 2-heptanone, a compound with a fruity aroma, detected only in BSG-fed crickets. These findings suggest that BSG is a viable and sustainable ingredient for cricket feed, offering both economic and nutritional benefits while also influencing the sensory characteristics of crickets. Further research is recommended to optimise BSG inclusion levels and explore its broader applications in insect and animal farming.