Effects of dietary vitamin C, thyme essential oil, and quercetin on the immunological and antioxidant status of common carp (Cyprinus carpio)

Nowadays, natural bioactive substances are a used in aquaculture feeds to improve fish welfare and therefore increase the quality and sustainability of fish production. The present study was conducted to compare the effects of dietary vitamin C (VC), thyme essential oil (TE), and quercetin (QR) levels on the hematology, and antioxidant and immune parameters of common carp, Cyprinus carpio. Four hundred twenty fish (20.46 ± 0.07 g) were distributed randomly into seven experimental groups (assayed in triplicates). The experimental diets were formulated as follows: CON (0, control); VCL (500 mg VC/kg); VCH (1000 mg VC/kg); TEL (10 g TE/kg); TEH (20 g TE/kg); QRL (200 mg QR/kg); and QRH (800 mg QR/kg). At the end of the 60-day feeding trial, an increase in white blood cells (WBC) was recorded in the treatment groups compared to that of the control (P