The yellow mealworm (Tenebrio molitor L.) in animal nutrition: Advances and prospects for sustainable livestock production

Tenebrio molitor (TM) is one of the most promising insect species proposed as an alternative to conventional food and feed in the last years. This insect is interesting for its valuable nutritional profile, lower environmental impact compared to traditional livestock and its ability to valorise organic waste. Optimising production is essential for insects farmers and several factors including environmental parameters, rearing density, nutritional strategies are involved. These aspects are essential to maximize the growth and productivity of TM. For instance, supplementing the basal diet of TM larvae with additional sources of protein, carbohydrates and lipids proved to enhance nutritional composition and growth performance of larvae. Likewise, the right combination of temperature, relative humidity, and oxygen, strongly influences development time and reproductive success. Moreover, adopting high breeding density of beetles can increase the overall productivity, although it may reduce the productivity per female. This review also examines the processing methods of TM larvae and their inclusion, in various forms, in the diets of poultry, rabbits, and aquaculture species. The incorporation at proper level of TM larvae meal showed to supports growth performance, feed efficiency and quality of the final product without compromising animal health. However, further efforts are needed to make TM meal cost-competitive with conventional feed ingredients. Finally, the review examines one of the most abundant by-products of the TM industry, the frass, highlighting its potential applications as a sustainable fertilizer, its effects on common crops, and its possible use as biochar to support more sustainable agricultural practices and environmental management strategies.