Phospholipids improve the performance, physiological, antioxidative responses and, lpl and igf1 gene expressions in juvenile stellate sturgeon (Acipenser stellatus)

Abstract

The effects of dietary phospholipids (PL) on the performance of juvenile stellate sturgeon (Acipenser stellatus) was evaluated in terms of growth and feed efficiency parameters, muscle and liver fatty acid profiles, activity of digestive and antioxidative stress enzymes, and expression of lipoprotein lipase (lpl) and insulin-like growth factor (igf1). For this purpose, seven isoproteic (44% crude protein) and isolipidic (17% crude fat) diets containing graded levels of soybean lecithin (0, 1, 2, 4, 6, 8 and 10%) were prepared, resulting in 0.3, 0.9, 1.6, 2.7, 3.9, 5.3 and 5.4% of dietary PLs, respectively. At the end of the nutritional study (75 days), we found that there was a positive quadratic polynomial response between growth performance parameters and dietary PLs; somatic growth increased with increasing dietary PL levels up to 3.9% when growth parameters remained stable. Dietary PLs reduced the accumulation of fat stores in the liver and up-regulated the expression of the lipoprotein lipase gene, confirming the important role of this enzyme in incorporating plasma lipids into tissues, whereas the activities of CAT and SOD showed a positive linear increase with dietary PL levels. Increasing dietary PLs from 0.9 to 3.9% promoted the activity of gastric (pepsin) and pancreatic (trypsin, chymotrypsin, bile salt-activated lipase and α-amylase) enzymes, whereas higher inclusion levels of PLs did not provide any advantage in terms of A. stellatus digestive capacities. The analysis of fatty acid profiles in diets and selected tissues (liver and muscle) showed the capacity of A. stellatus juveniles to desaturate and elongate linoleic (C18:2n–6) and alpha-linolenic (C18:3n–3) acids to arachidonic (C20:4n-6), eicosapentaenoic (C20:5n-3) and docosahexaenoic (C22:6n-3) acids. Based on the results of growth performance, feed efficiency and physiological parameters, the inclusion of 3.9% of PLs in compound diets for juvenile stellate sturgeon are recommended.