Effects of dietary phospholipids on growth performance, antioxidant capacity, and lipid metabolism of juvenile Chinese sturgeon (Acipenser sinensis), a critically endangered sturgeon in the Yangtze River

This study aimed to investigate the effects of dietary phospholipids (PLs) on growth performance, antioxidant capacity, and lipid metabolism of juvenile Chinese sturgeon (Acipenser sinensis). Juvenile sturgeon, with an initial body weight of 12.27±0.03 g, were fed five diets containing graded levels of PLs (1.26 %, 3.29 %, 4.34 %, 5.93 %, and 7.02 %) in triplicate for 56 days. All experimental diets were formulated to be isonitrogenous (55 %) and isolipidic (10 %). Results indicated that specific growth rate increased from 2.21 to 2.89 with elevated levels of dietary PLs. The optimum PLs level for juvenile Chinese sturgeon was estimated to be 5.93 % of diet according to the broken-line regression analysis of the specific growth rate against dietary PLs levels. Diets containing higher levels of PLs (5.93 % and 7.02 % of diet) significantly reduced the lipid content of whole body and liver by around 30 % in juvenile sturgeon compared to the control group (P <0.05). The proportions of specific fatty acids present in the liver lipid were linearly correlated with their percentages in dietary lipid (P <0.05), whereas muscle fatty acid composition remained unaffected across different treatments (P >0.05). EPA and DHA were preferentially accumulated into the muscle tissue. Activities of digestive enzymes and antioxidant enzymes were linearly increased with incremental dietary PLs levels (P <0.001). Inclusion of PLs in diet significantly enhanced the expression of antioxidant genes with the transcription of GSH-Px in the liver of fish fed 7.02 % PLs of diet being approximately 8-fold greater than in those fish fed diet without PL addition (P <0.001). Dietary PLs significantly induced the gene expression related to lipid catabolism, and suppressed the transcription of genes involved in lipogenesis (P <0.001). Based on growth performance, antioxidant capacity, and liver biochemical parameters, inclusion of 5.93 % PLs (soy lecithin preparation) in the diets is recommend for juvenile Chinese sturgeon.