BACKGROUND: The poultry industry is increasingly looking for sustainable feed ingredients which support animal productivity. Insects, such as the larvae of Hermetia illucens, represent a promising alternative protein source that has a positive effect on gut health. AIM: The aim of this study is to evaluate the effects of a partial replacement of soybean meal with H. illucens larvae meal on the caecal microbiota of laying hens. METHODOLOGY: A total of 162 hens were divided equally into three treatment groups: a control group (C) with a diet containing corn-soybean meal and two treatment groups (HI25, HI50) in which 25% and 50% of the soybean meal protein was replaced by H. illucens larvae meal protein. At 40 weeks of age, 30 animals (10 per group) were slaughtered and the bacterial community of the caecal content was analysed by high-throughput sequencing using the V4-V5 region of the 16S rRNA gene. The DNA was extracted using the PowerSoil DNA Kit, the library preparation was performed using the NEBNext Fast DNA Library Prep Set kit and sequencing was performed using the Ion Torrent PGM. The bacterial diversity was assessed by alpha and beta diversity indices, and the differential abundance of taxa was determined using LEfSe analysis. RESULTS: Firmicutes and Bacteroidetes were the dominant phylum in all groups. Alpha diversity indices showed no significant differences between diets, however, beta diversity measures showed statistical dissimilarities between the three studied groups. Several beneficial genera, including Alistipes, Christensenellaceae R-7 group, Parabacteroides, Butyricimonas and Parasutterella, were enriched in the HI50 group, while Lactobacillus, Bifidobacterium, Blautia and the opportunistic pathogen Enterococcus were reduced. CONCLUSION: The consumption of H. illucens larvae meal showed beneficial effect on the microbiota of the caecum of laying hens, with 50% replacement showing the strongest positive effects, suggesting that this is the most effective amount under the given conditions. Further research should explore microbial functions and long-term impacts, and validate the optimal levels of insect meal inclusion.

Department of Veterinary Medicine and Animal Production University of Napoli Federico 2 Napoli Italy

Department of Veterinary Medicine and Animal Sciences University of Milan Via dell'Università Lodi Italy

Department of Veterinary Medicine University of Sassari Sassari Italy

Laboratory of Anaerobic Microbiology Institute of Animal Physiology and Genetics Czech Academy of Science Prague Czech Republic

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