Insect rearing: agri-food, welfare and feed sustainability - BEFWelSust

The future growth of the global population underlines an urgent need to enhance the agri-food sector. Food production faces significant challenges, in particular food waste and management, which hold negative impacts on social, economic, and environmental dimensions. To address these issues, innovative methods for reusing and valorising biomasses are required. The feed industry represents another concern, due to its dependence on soybean meal, which is characterised by a high environmental footprint and contributing to greenhouse gas emissions, deforestation, and biodiversity loss. In this context, insects offer a remarkable solution within a circular and innovative framework, as certain species can grow on organic material, thereby reducing waste and producing proteins and fats suitable for animal feed. Black soldier fly (BSF, Hermetia illucens L.) is gaining increasing attention due to its potential to bridge the gap between food and feed sectors. The BSF rearing industry is expanding rapidly, which requires further knowledge of the key factors that characterise insect rearing, such as diet and welfare. The aim of the thesis project is to introduce and develop a sustainable insect-to-feed chain based on circular economy principles. The thesis adopts a multidisciplinary approach, integrating the food, feed, and insect sectors. It explores innovative methods to valorise agricultural by-products through insect farming, with a particular focus on improving the environmental sustainability of the agri-food system. This includes evaluating the use of organic waste, such as fruits, vegetables, and agro-industrial by-products from the Italian food sector, as rearing substrates for BSF larvae. Considering this potential application, factors that influence the willingness of potential upstream symbiosis partners to adopt insect biorefinery were studied. Focusing on the features of black soldier fly’s biology, the influence of the dietary substrate on the final larval body composition, especially in terms of fatty acids was investigated. Answering to the urgent need of welfare assessment in insect rearing, the project examines the application of the Brambell’s "five freedoms" framework to BSF larvae welfare for optimising rearing conditions by evaluating dietary source, feeding rates and rearing densities. With an even more innovative approach on insect’s welfare, different processing conditions were compared in terms of stress factors for the larvae, by studying the Volatile Organic Components (VOCs) emitted. Moreover, insects represent a relevant feed resource for the future. For this reason, the thesis focuses on the practical use of BSF larvae in animal feed. It investigates the effects of live BSF larvae supplementation in poultry diets, assessing its potential to improve animal performance, welfare and feed efficiency. The main findings of this thesis reveal the potential of valorising organic wastes and agro-industrial by-products as substrates for BSF, creating a system of locally-based insects rearing. By utilising ingredients available near the production plant, agri-food residual biomasses can be combined to formulate diets for the insects. This approach highlights the possibility of creating a sustainable network of actors within the agri-food industries, offering benefits to all stakeholders involved in this innovative activity. Additionally, favorable government policies, along with public and private investment in promoting insect rearing, were identified as key factors in increasing its attractiveness to investors, consumers, and other stakeholders. Interestingly, emerged that the substrate and in particular different vegetable by-products can influence larval fatty acids’ composition, underling how the dietary enrichment with omega-3 and omega-6 can rise the larvae’s saturated fatty acids concentration. Moreover, lauric and myristic acids were directly synthetized by the larvae, creating lipids component with positive effect on animal nutrition. Focusing on BSF welfare, the study identified optimal rearing conditions and dietary regimes that not only improve the growth and performances of the larvae but also ensure their ethical treatment. Specifically, an omnivorous diet composed by vegetable and meat by-products optimised larvae growth performance without causing difficulties in movement within the substrate, due to a balanced in oil and fiber content. Moreover, omnivorous diet with a medium feeding rate (90 mg feed per larvae/day) and low densities (5 larvae/cm2) optimise rearing efficiency. The VOCs analysis by purging the larvae on dark and light environment confirmed, as indicated in literature, that light represent a stress factor for the insects. In fact, after GC-MS analysis and data elaboration compounds potentially related to a stress expression were detected. This is an extremely innovative approach for BSF, more research is needed to validate and compare our data. Studying BSF as sustainable feed ingredient, the evaluation of laying hen age and the inclusion of live BSF larvae at 15% and 30% of daily feed intake (DFI) in their diets revealed that supplementing up to 30% of DFI with live BSF larvae does not negatively affect egg physical or chemical quality, as well as fatty acids composition. Similarly, the productive performance of the animals was not negatively influenced, while insects’ reduced the level of excreta corticosterone, indicating less stress level in insects’ supplemented animals. The BSF-fed hens had no significant impact on the dominant microbiota genera, despite this, bacterial community showed a different structure, possibly influenced by age and/or the environment. This research helps to fill a gap in the literature, underlying the possibility of shift the poultry sector toward an efficient and sustainable protein source. In conclusion, this thesis underscores the significant potential of insects in enhancing the sustainability of the agri-food sector. Insects rearing act both as a tool for agri-food by-products valorisation and as innovative feed source, anyway their utilisation require further investigation to address literature gaps and open a new field of research. In this sense, this thesis research focused from one side on insects’ welfare evaluation, improving industrial rearing, and at the same time on creating an innovative and more sustainable feed sector, focusing on poultry sector.