Suitability of <i>Hermetia illucens</i> meal in post-weaning piglet diets under commercial conditions: growth performance, nutrient digestibility, health status and gut health

This study evaluated the effects of dietary Hermetia illucens (HI) meal on growth performance, nutrient digestibility, general health status and gut health of post-weaning piglets reared under commercial conditions. A total of 336, 28–days-old mixed-sex weaned piglets were randomly allotted to 4 dietary treatments (control [C] and 3, 6 and 9% HI meal inclusion [HI3, HI6 and HI9], with 4 replicate boxes/treatment, 21 animals/box and 3 feeding phases) and slaughtered after 63 days of trial (4 animals/box, 16 piglets/diet). In the whole trial, the average daily gain and feed conversion ratio showed a linear response to dietary HI meal inclusion (p < 0.05). The nutrient digestibility also displayed a linear and/or quadratic response to dietary HI meal inclusion during phases I and II, while the opposite trend was highlighted during phase III (p < 0.05). Increased blood antioxidant response was also identified for HI6- and HI9-fed animals (p < 0.01). Dietary HI meal inclusion did not influence gut histomorphology or organ histopathological findings, as well as caecal microbiota alpha and beta diversity. However, selected amplicon sequence variants were associated with specific dietary treatments (p < 0.05), such as Dorea, Faecalitalea, Bacteroides, Anaerostipes and Oscillospiraceae (HI3), Phascolarctobacterium, Rhodospirillales and Odoribacter (HI9), Lachnospiraceae, Oscillospiraceae, Anaerovoracaceae, Faecalibacterium, Lachnospira, Alistipes, Lachnoclostridium and Acinetobacter (HI3 and HI6), and Enterobacter, Roseburia, Ruminococcaceae, Lachnospiraceae and Bifidobacterium (HI-based diets). In conclusion, including up to 9% of HI meal enhanced growth performance and antioxidant response, and partially improved nutrient digestibility and caecal microbiota of the weaned piglets, without impairing their gut morphology and overall health status.