Growth performance, proximate composition and fatty acid profile of black soldier fly larvae reared on two grape pomace varieties

•We evaluated two grape pomace varieties as rearing media for black soldier fly larvae.•The growth rate was higher when the larvae were reared on Becuet than Moscato pomace.•The larvae fed on Moscato contained higher total lipids than the larvae fed on Becuet.•Both grape pomaces and black soldier fly larvae contained conjugated linoleic acids.•Grape pomace can be used to enrich larvae with potential health-promoting fatty acids. The black soldier fly (Hermetia illucens) is attracting increasing interest for its ability to convert low-value substrates into highly nutritious feed. This study aimed at evaluating grape pomace from two varieties (Becuet – B; Moscato – M) as rearing substrates for black soldier fly larvae (BSFL), focusing on the related effects on larval growth performance, proximate composition, and fatty acid profile. A total of six replicates per treatment, and 1 000 BSFL per replica, were used. Larval development was assessed by larvae weight, which was recorded eight times during the trial: the day after the beginning of the trial, and then on days 5, 8, 13, 15, 20, 22, and 27 (day in which the 30% of BSFL reached the prepupal stage). Production and waste reduction efficiency parameters, namely the growth rate, substrate reduction and substrate reduction index, were calculated. The two grape pomace varieties were analysed for their proximate composition and fatty acid profile; the same analyses were conducted on BSFL (30 larvae per replica) that were collected at the end of the trial (day 27). The growth rate of BSFL showed a higher value when the larvae were reared on B substrate (4.4 and 3.2 mg/day for B and M, respectively; P