Nutritional and bacterial microbiota implications of partial inclusion of live Hermetia illucens larvae in “Collo Nudo Italiana” chicken diets

The increasing demand for sustainable protein sources in poultry production has intensified interest in insects as alternative feed ingredients. This study evaluated the effects of partially replacing conventional dietary protein sources with live Hermetia illucens larvae in chicken diets, focusing on nutrient intake, growth performance, health status, gut microbiota, and carcass fat fatty acid (FA) composition. Three independent feeding trials were conducted using female “Collo Nudo Italiana” chickens reared under extensive conditions. Chickens were assigned to either a control or an experimental diet administered ad libitum, and feed intake was monitored. In the experimental diet, live H. illucens larvae replaced approximately 20% of dietary protein, significantly increasing dry matter and protein intake, indicating high palatability of the larvae. However, body weight (BW) and growth performance were not significantly affected, and no adverse effects on health status or welfare indicators were observed. Caecal bacterial microbiota analysis revealed no differences in alpha diversity between groups ( p > 0.05[jls-end-space/]), whereas beta diversity showed a significant ( p < 0.05[jls-end-space/]) but moderate shift in microbial community structure. The genera Staphylococcus, Brevibacterium, and Alloprevotella were enriched in treated animals, whereas a relative abundance of Pseudoflavonifractor, Tyzzerella and Shuttleworthia was observed in the control group. Inclusion of live larvae influenced carcass fat composition, increasing medium-chain saturated FAs characteristic of H. illucens lipids and reducing polyunsaturated FAs, particularly n-3 fatty acids. These findings support the potential of live insect larvae as a sustainable feed component in circular poultry production systems, highlighting the need for optimized dietary formulations to balance nutritional outcomes.