Black soldier fly larvae oil (BSFLO) is a co-product derived from processing Hermetia illucens into meal. It is characterized by presenting high levels of lauric acid (30-40%), a fatty acid suggested to enhance hepato-metabolic status and promote glycolytic muscle fibre formation, improving growth in mammals. The study herein presented aims to appraise the potential of this new ingredient to replace another terrestrial animal fat already in use in aquafeed formulations. A comparative approach with European seabass and gilthead seabream was established to evaluate the impact of increasing levels of BSFLO on fish growth performance, feed efficiency, and nutrient utilisation.
A commercial formulation including 6% fish oil and 5% poultry fat (PF) was used as a control diet (CTRL). Three additional experimental diets were formulated to replace 33%, 66% and 100% PF with BSFLO supplied by Entrogreen® - Ingredient Odissey S.A., resulting in the BSFLO33, BSFLO66 BSFLO100 diets, respectively. These experimental diets were tested in triplicate groups for both seabass and seabream juveniles (11-16g), at a temperature of 23oC. Fish were fed three times a day to visual satiety until the CTRL groups quadrupled their initial body weight. Subsequently, the feed efficiency, growth performance, and nutrient balance of both fish species were assessed.
In European seabass, the dietary inclusion of BSFLO to totally replace PF (BSFLO100 diet) improved feed conversion ratio (FCR), without affecting voluntary feed intake (VFI), resulting in significantly higher final body weight. In gilthead seabream, both partial (i.e., 66%) and total PF replacement by BSFLO resulted in enhanced growth performance of fish without significant alterations in both VFI and FCR. Seabass fed BSFLO66 exhibited lower whole-body (WB) energy content compared to those fed CTRL and BSFLO100 which was associated with lower energy gain and retention. Although there were no significant alterations in the somatic indexes or in WB macronutrient composition among dietary treatments, a slight decrease in lipid utilization was observed in fish fed BSFLO66, indicating changes in lipid and energy metabolism in these fish. Conversely, in seabream, although the WB nutrient composition, gain and retention were not affected by dietary inclusion of BSFLO, the total PF replacement induced alterations in somatic indexes, also suggesting potential alterations in the animals’ metabolism. The metabolic pathways affected by the dietary inclusion of BSFLO and the resulting impact on flesh fatty acid profile will be discussed in both species.
Acknowledgments
This work has been supported by InsectERA Mobilising Agenda, framed in the Portuguese Recovery and Resilience Plan (PRR), with reference: C644917393-00000032.