Evaluation of Mulberry Silkworm, Bombyx mori, Pupae as a Sustainable Replacement for Fishmeal in the Gilthead Seabream (Sparus aurata) Diets

This study looks into the impact of partial substitution of the dietary fishmeal (FM) with silkworm (Bombyx mori) pupae meal (SP) at 30, 50, and 70% replacement levels, in the juvenile gilthead seabream, Sparus aurata diets.  Triplicate groups comprising 30 fish (IW=14.50 ± 0.50g) were fed for 58 days on one of four isoprotenic (46%) and isoenergetic (21 MJ/ Kg) diets (SP0, SP30, SP50, or SP70). The amino acid profiling of FM and SP confirmed the presence of all essential amino acids in the pupae, with a high degree of similarity observed between the two protein sources, suggesting functional equivalence for dietary protein replacement. The body weight and specific growth rate of fish, at the end of the experiment, of SP50 and SP70 groups were higher than in SP0 and SP30 fish groups (P< 0.05). The fish biochemical composition analysis indicated insignificant variations among all experimental groups. The hematological parameters illustrated that by increasing SP levels in fish diets, hemoglobin, hematocrit, and the red blood cells count recorded values were significantly increased relative to the SP0 group, and SP70 group showed the highest values. Furthermore, the white blood cell count was gradually and significantly increased with increasing the SP substitution level in fish diets. The percentage of neutrophils and lymphocytes was also the highest in SP70 group indicating an enhancement in fish immunity. From the result of our investigation, we can conclude that SP can be a promising alternative for replacement of FM in the gilthead seabream feed up to 70%, and furthermore, reducing fish oil (FO) by 28% with maintaining fish growth, health, and immunity, improving sustainability, and lowering feed costs. Further investigation is advised to look at the long-term effects of this substitution on fish performance.