Dietary oxidized fish oil negatively affected the feed utilization, health status and fillet quality of juvenile Amur sturgeon, A. schrenckii

Abstract

This study was carried out to explore the effects of dietary oxidized fish oil on growth, feed utilization, health status and fillet quality of juvenile Amur sturgeon (A. schrenckii) (initial mean body weight = 70.0 ± 0.02 g). An 8-week experiment with diets containing 6% fresh fish oil (FFO) or 6% oxidized fish oil (OFO) was conducted. The peroxide values (POV) of fresh and oxidized fish oil were 9.14 and 384.73 meq/kg, respectively. The results indicated that compared to the FFO group, dietary OFO had no significant influence on growth (P > 0.05), but increased feeding rate (FR) and decreased productive protein value (PPV) significantly (P < 0.05). The fish in the OFO group had lower serum high-density lipoprotein cholesterol (HDL-C), albumin (ALB), and the ratio of ALB to globulin (GLOB), and higher serum malonaldehyde (MDA) and superoxide anion free radical (O2−) than those in the FFO group (P < 0.05). OFO induced inflammatory cell infiltration in the liver, and the expressions of hepatic inflammatory cytokines were significantly up regulated in the fish fed with OFO (P < 0.05). The fish in the OFO group showed abnormal yellow skin, and the yellowness value of the dorsal muscle was significantly elevated in comparison with the FFO group (P < 0.05). The contents of muscle protein, lipid, and glycogen were significantly declined by dietary OFO (P < 0.05). Dietary OFO affected the muscle essential amino acid (EAA) composition remarkably, among which the proportions of Ile and Met were reduced while Leu was promoted significantly (P < 0.05). The fish fed with OFO had significantly higher n-6 polyunsaturated fatty acids (PUFA) proportion and n-6 PUFA/n-3 PUFA ratio (P < 0.05) than the fish fed with FFO, but there were no changes in the proportion of saturated (SFA), monounsaturated fatty acid (MUFA) and n-3 PUFA (P > 0.05). The total free amino acid (FAA) was enhanced significantly by dietary OFO, but the delicious amino acid (DAA) proportion was decreased in the muscle of the fish fed with OFO (P < 0.05). In summary, dietary OFO had no significant influence on growth, but decreased feed utilization of Amur sturgeon. Dietary OFO impaired the health status of Amur sturgeon by inducing oxidative stress, lowering serum HDL-C, ALB and causing liver damage. Dietary OFO adversely affected the fillet quality of Amur sturgeon by altering body color, muscle proximate composition, glycogen content, EAA, fatty acid and FAA profiles.