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FEATURE

KRILL OIL

Phospholipids that make a difference to filet quality and quantity

T

he nutritional quality of larvae diets affects fishes’ fillet quality and quantity. Studies show that phospholipids increase fish larvae growth and development; so phospholipids are an essential component of the early weaning diet. During embryo and larval development, yolk sac lipids or wild prey provide young fish with ample amount of phospholipids. In fish larvae diets, the aim is to provide larvae nutrition and an effective diet that substitutes live prey as early as possible during the larval development. Scientists have studied the effectiveness of phospholipids including those derived from soybean lecithin and dietary marine phospholipids from krill. Krill phospholipids, rich on docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), have a positive effect on larvae performance and development, which makes a difference later to filet quality and quantity.

Phospholipids: a core component to larvae development

Studies have shown that dietary phospholipids improve culture performance, enhance growth and increase the survival of various freshwater and marine species including ayu (Plecoglossus altivelis), carp (Cyprinus carpio), Japanese flounder (Paralichthys olivaceous), knife jaw (Oplegnatus fasciatus) and red seabream (Pagrus major). Phospholipids also reduce incidents of skeletal deformities in larvae and early juveniles, and increases fish resistance to stress. Phospholipids are the main structural component of cell membranes, tissues and are vital organ development. They especially play a vital role in the development of organs including the digestive system. Dietary phospholipids play a contributing role to the assimilation of dietary lipids; increase the efficiency of transporting dietary fatty acids and lipid from the gut to the rest of the body. So adding phospholipids to larval diets has unique benefits to the development of larvae, juveniles and fishes later in life.

Efficient and effective krill phospholipids

Phospholipids include a large group of compounds, and the lipid

classes as well as the fatty acid content determine their effectiveness. Studies show that dietary marine phospholipids, in comparison to soybean lecithin, improve culture performance. Three recent studies indicate the different benefits of this form of phospholipid. In the first study, scientists compared the effect of krill phospholipid to soybean lecithin in micro diets for gilthead seabream larvae on molecular markers of antioxidative metabolism and bone development. The results from the studies show that marine phospholipids have a higher effectiveness in promoting survival, growth and skeletal mineralization of gilthead seabream larvae in comparison with soybean lecithin, regardless of the dietary phospholipid level (R.Saleh, M.B. Betancor, J.Roo, V. Benitez-Dorta, M. J. Zamorano, J.G. Bell and M. Izquierdo, 2014). The study was conducted as follows. Scientists fed larvae, from 16 to 44 days post hatching, three levels of phospholipids from marine phospholipid and soybean lecithin (50, 70 and 90 g kg-1). The increase of up to 70 g kg-1 marine phospholipid was enough to see and improve larval gilthead seabream performance and even the highest level of soybean lecithin (90 g kg-1) was unable to provide similar successful results. However, larvae that were fed diets without phospholipid supplements, also known as the control diet, showed a very low survival rate. This indicates that phospholipids are an essential competent of the natal diet. Despite increasing soybean lecithin up to 90 g kg-1 to improve larval survival, stress resistance, growth and skeletal development, the results showed that dietary marine phospholipid was more effective in promoting these parameters. Krill phospholipids’ higher content in PC, LPC, ARA, antioxidants factors such as carotenoids (astaxanthin) eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), promotes digestion, transport and deposition of dietary lipids, and contributes to reduce skeletal anomalies. The study also showed that krill phospholipids affect skeleton malfunction, bone mineralization, biochemical composition, oxidative status and selected genes expression. Just like the results from other studies, by increasing marine phospholipids in species such as Atlantic cod (Gadus morhua) and European sea bass (D. labrax), larvae growth increases.

24 | March | April 2016 - International Aquafeed

Mar | Apr 2016 - International Aquafeed