Meat-based diets for Hermetia illucens larvae: effects on growth and proximate composition

Edible insects are an innovative food and feed resource that is rapidly gaining interest worldwide, as they represent a valid solution to current sustainability issues and food security. Among the species used, black soldier fly (BSF, Hermetia illucens) is one of the most reared species for feed purposes, due to its ability to bio-convert a wide variety of substrates (high in proteins and lipids). Farmed insects for feed and food purposes are considered in the European Union fully-fledged farm animals (Reg. EU 1069/2009) and, as such, rearing substrates must be composed of the authorized ingredients (Reg. EU 68/2013), which does not include any feed component containing meat or fish (Reg. (EC) 999/2001). This study explored the effects of meat-based diets on growth performances and proximate composition of BSF larvae. Three rearing substrates were formulated (three replicates/diet); one made by 100% plant ingredients (C) and two containing a mixture (1:1:1) of pork, chicken and turkey meat in raw (R) and processed (P) forms (75% plant ingredients + 25% raw or processed meat). For each crate, 1000 nine-year-old larvae were employed, feed was administered once. Larvae were sieved at the appearance of the first prepupae. Better growth performances were reported in meat-fed larvae, which resulted in higher growth rates (5.42 mg/d, 5.30 mg/d, 3.86 mg/d for R, P and C larvae respectively; p value 0.013) and consequently shorter development time (20, 21 and 22 days for R, P and C larvae respectively). Likewise, FCR values (5.13, 5.36, 6.60 for R, P, and C larvae, respectively; p value 0.009) highlighted the better performances of the meat-fed larvae. Unexpectedly, larvae did not show significant differences in protein content, whereas larvae fat contents followed the diets characteristics, with higher amounts of fats on DM respectively in larvae fed R, P and C (17.24%, 14.27%, 8.72%; p value < 0.001). No changes were highlighted for DM and ashes. These results proved the suitability of meat-based substrates in BSF larvae rearing, confirming the potentiality of BSF to play a key role in a circular economy system, increasing food-chain productions and reducing waste material. The authorization of meat-based substrates for insects rearing would represent a huge step forward in terms of sustainability, giving a second life to wastes and by-products containing meat. Future studies will focus on potential risks related to the use of meat-fed larvae as feed and food.