Black soldier fly larvae as a better lipid source than yellow mealworm or silkworm oils for juvenile mirror carp (Cyprinus carpio var. specularis)

Abstract A feeding trial was conducted to study the effects of different insect oils on growth performance, lipid metabolism, inflammation and related gene expression in juvenile mirror carp (Cyprinus carpio var. Specularis). Triplicate cages of juvenile mirror carp were fed one of four isonitrogenous and isolipidic diets, including black soldier fly oil (BSFO, 25 g kg−1), silkworm pupae oil (SWPO, 25 g kg−1), yellow mealworm oil (YMO, 25 g kg−1), and a mixture of the three insect oils, BSFO, SWPO and YMO (MIXO, 25 g kg−1) (n = 3). After 59 days, the results showed that weight gain and specific growth rate of fish fed with BSFO and MIXO diets were significantly higher than the fish fed the other two insect oil diets, while feed conversion rate in the same dietary groups was significantly lower than fish fed the SWPO and YMO diets. Intra-peritoneal fat index and adipocyte size in intra-peritoneal fat tissue decreased in the fish fed with BSFO and MIXO compared to fish fed the SWPO and YMO diets. Relative gene expression of fatty acid synthase (FAS) significantly decreased, while peroxisome proliferator-activated receptor-α (PPAR-α) significantly increased in intra-peritoneal fat tissue of fish fed with BSFO and MIXO diets compared with mirror carp fed with SWPO and YMO diets. The activity and transcription of total superoxide dismutase (SOD) significantly increased in the liver of fish fed with BSFO and MIXO than fish fed with SWPO and YMO diets. The content of hepatic maleic dialdehyde (MDA) significantly decreased, while serum globulin (GLO) significantly increased in fish fed with BSFO and MIXO than fish fed with SWPO and YMO diets. Moreover, the transcription of anti-inflammatory cytokine (IL-10) was higher in liver of fish fed with BSFO and MIXO diets. Fish fed with SWPO diet significantly up-regulated the hepatic expression of pro-inflammatory cytokine (IL-1β) and tumor necrosis-α (TNF-α) than fish fed with BSFO, YMO or MIXO diets. Overall, compared to others insect oils source (YMO and SWPO), inclusion of BSFO or the combination of the three oils (MIXO) in the diets positively influence growth performance, lipid metabolism of intra-peritoneal fat, liver antioxidant capacity and inflammatory response of juvenile mirror carp.