EFFECTS OF DIETARY LIPID LEVELS ON GROWTH PERFORMANCE, FEED DIGESTIBILITY, ANTIOXIDANT STATUS AND FILLET FATTY ACID COMPOSITIONS OF JUVENILE HYBRID STURGEON

To investigate the effects of dietary different lipid levels on the growth performance, feed digestibility, antioxidant status, and fillet fatty acid compositions of juvenile hybrid sturgeon (Acipenser baerii Brandt ♀ × A. schrenckii Brandt ♂), four isonitrogenous (42% crude protein) experimental diets were formulated with various lipid levels at 5% (D05), 10% (D10), 15% (D15) and 20% (D20), respectively. Hybrid sturgeon with an initial body weight of (152.83±0.67) g were randomly divided into 4 groups with 3 replicates in each group and 25 fish per replicate for a 12-week trial. The results showed that dietary different lipid levels had significant effect on the growth performance of juvenile hybrid sturgeon. Among them, final body weight (FBW), weight gain rate (WGR) and specific growth rate (SGR) in D15 group were significantly higher than those in D05, D10 and D20 groups (P<0.05). Feed efficiency (FE) in D15 group was significantly higher than that in D05 and D10 groups (P<0.05). With the enhanced dietary lipid level, viscerasomatic index (VSI), hepatosomatic index (HSI) and crude fat in fillet and liver increased significantly (P<0.05). Dietary different lipid levels had no significant effects on the apparent digestibility of dry matter (ADC_d) and protein (ADC_p) (P>0.05). The apparent digestibility of fat (ADC_f) in D10, D15 and D20 groups was significantly higher than that in the D05 group (P<0.05). The highest apparent digestibility of energy (ADC_e) was in D15 group, which was significantly higher than that in D05 and D10 groups (P<0.05). When the dietary lipid level increased from 5% to 20%, the activities of total antioxidant capacity (T-AOC), superoxide dismutase (SOD) and myeloperoxidase (MPO) were boosted (P<0.05) while glutathione peroxidase (GSH-Px) activity reduced significantly (P<0.05) in serum of juvenile hybrid sturgeon. The activities of the four liver function indicators, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and lactic dehydrogenase (LDH), also showed an increasing trend (P<0.05). There was a significant positive linear correlation between the content of fillet fatty acids and the fatty acid content in the diets (R²>0.90, P<0.05). These results revealed that the optimal lipid level in the diet of juvenile hybrid sturgeon was 15%, and P/E was 23.54 mg/kJ.