Impact of live black soldier fly larvae supplementation on laying hen performance, stress levels and excreta microbiota.

As the global demand for poultry products, particularly eggs, continues to rise, identifying environmentally sustainable alternative protein sources is crucial and insect-based feeds, such as black soldier fly larvae (BSFL) represent a promising solution. This study investigated the effects of BSFL supplementation as environmental enrichment for laying hens, assessing its impact on bird performance, integument status, excreta corticosterone metabolites (ECMs) and microbiota composition. A total of 108 Lohman Brown hens were housed in 27 cages (nine replicates per treatment, four birds per pen) and monitored between 16 and 34 weeks of age. The hens were assigned to three dietary treatments: a control group fed a commercial diet, and two experimental groups supplemented with 15 % or 30 % of live BSFL, as fed basis on the expected daily feed intake (DFI). Larvae consumption time, hens' performance and integument scores were recorded at regular intervals. Excreta samples were collected for ECMs analysis and microbiota profiling. Hens adapted progressively to BSFL consumption, as feeding time significantly decreased over the trial, with a significant interaction between BSFL supplementation and hen age. BSFL supplementation had no adverse effect on laying performance or integument scores of the hens. ECM concentrations were influenced by both diet and age with the BSFL-fed groups showing lower corticosterone levels than the control; particularly towards the end of the experiment. While BSFL supplementation did not significantly modify the dominant microbiota taxa, it led to structural shifts in the bacterial community, possibly influenced by age and/or the environmental factors. Supplementing the diet of laying hens with live BSFL did not negatively influence productivity or plumage quality. While BSFL supplementation had a minimal impact on the overall microbiota diversity in the excreta, it influenced specific microbial taxa and appeared to reduce the stress level in the hens. These findings highlight the potential of BSFL as a functional feed ingredient that could enhance poultry welfare without impairing production performance.