Alternative animal protein sources for aquaculture: a preliminary study on nutritional traits of Mediterranean brocade (Spodoptera littoralis, Boisduval) larvae

In formulating diets for farmed aquatic species, the main ingredi- ent used is fish meal (FM). Due to the growth that aquaculture is experiencing throughout the world, the increasing demand of feeds is resulting in a FM price increase that represents an eco- nomic limit for fish farming. The need to seek protein sources alternative to FM is a matter of great interest. Among others, the use of insect larvae as feed for fish represents an interesting alter- native. The aim of this study was to evaluate the nutritional traits of mediterranean brocade larvae (Spodoptera littoralis Bois.) in view of their possible use as feedstuffs for rainbow trout. A sample of mediterranean brocade larvae (MBL) (VI instar) and one of pupae (MBP) were assayed for fat (EE), ash (ASH) and crude pro- tein (CP) contents by conventional methods. Amino-acidic profile was obtained by HPLC on sample hydrolysates. Relative digestibil- ity of protein (RDP) was estimated by the Lazo (1988) method. Data, expressed on DM basis, were compared with those of a com- mercial feed (CF). The fat content of MBL was lower than that recorded for CF (9.4% vs 13.6%) while MBP showed a very high value (30.3% DM). Ashes in MBL (7.7%) and MBP (6.7%) were lower than in the CF (10.9%). The CP content of MBL (44.3%) was slightly higher than the CF (40.0%) but lower than in MBP (59.1%). The RDP of MBL and MBP were about a half of the value observed in CF (27.2%). Both MBL and MBP showed a lower per- centage of essential amino acids (AA) (35.8%, 36.8%) compared to CF (39.4%) even if the AA profiles were in line with the require- ments found in literature for rainbow trout. In conclusion, these preliminary results suggest that preimaginal stages of S. littoralis may be of interest in fish feeding, though more exhaustive studies have to be performed to fully assess their use as alternative for fish meal.