Lecithin as a rich energy source with nutritional performance
Lecithin may be produced from egg yolk, but more commonly used in aquafeed are soya and rape seed lecithin. It is well known that the phospholipids (PL) present in lecithin act as an emulsifier of lipids in the animal stomach and gut, but especially the nutritional benefits of lecithin is why fish nutritionists like to include it in fish and shrimp diets. Lecithin is widely used in feed for larval and juvenile stages of various species of fish and crustaceans, because those developing fish have a limited ability to the novo phospholipid synthesis. Phosphatidylcholine (PC) is the most abundant PL in fish tissues (Bell and Dick, 1991) and is among many others an important catabolic energy source for egg and larval embryogenesis (Finn et al., 1996) and important for intestinal lipid absorption (Fontagne et al., 1998). In literature many examples may be found of the benefits of PL on survival, growth, resistance to stress tests, prevention of malformations, essential lipid composition of the fish. Seemingly phosphatidylcholine (PC) is more effective for growth improvement while phosphatidylinositol (PI) and phosphatidylethanolamine (PE) are more important for survival and preventing deformities in the developing fish and are a structural component of practically all cell membranes (Kagan et al., 1984). This article will highlight some of the other reasons and benefits to include lecithin in aquafeed for all life stages.
PL may improve the performance of the diet by improving the water stability of food particles, or by their action as antioxidant or feed attractant. An interesting example of a practical application of lecithin was already published in 1997 (Castell in Coutteau et al.). They hypothesize that dietary supplementation of soybean lecithin prevents molt death in lobsters, by reducing the leaching of water soluble nutrients, in particular manganese and B vitamins. Various forms and concentrations of dietary choline were not as effective as PC in reducing molt death syndrome in juvenile lobsters (Conklin in Coutteau et al, 1997). Soy lecithin may increase the physical water stability of aquafeed pellets and thereby reduce the loss of water soluble nutrients (Nutrient Requirements of Fish and Shrimp, 2011).
Lipid transport and retention
PL are required in shrimp feed for the efficient transport of dietary fatty acids and lipids from the gut epithelium into the haemolymph, and the mobility of lipids between the various tissues and organs. Dietary PL also improves the mobilization of cholesterol, which is essential in the molting process of crustaceans (Coutteau et al.,1997). PL also reduce the accumulation of lipid droplets in the intestine, due to its essential role in the transportation of Triacylglycerol (TAG) from the intestinal mucosa via the haemolymph into the serum of shrimp as chylomicron and other lipoprotein (Sargent et al., 2002). Diets with additional PL have higher levels of plasma lipoproteins and epithelial enzymes (Azarm et al., 2013).
The inclusion of PL in the diet affects lipid deposition, resulting in increased lipid retention and levels in the animal. A higher proportion of EPA and DHA was observed in juvenile P. japonicas due to the addition of 3% of soybean lecithin in the diet (Coutteau et al., 1997).
Phosphorous and choline
Phosphorous is a nutritionally important mineral due to its requirement for growth, bone mineralization, reproduction, nucleic acid synthesis and energy metabolism. Choline is an essential nutrient for fish and shrimp (and other animals), and thus needs to be provided by the feed (Tocher et al., 2008).
Effect on enzymes
PL shows a beneficial effect on brush border (or microvilli) and pancreatic enzymes in rainbow trout. Soybean lecithin induced a significantly higher activity of amylase, lipase, phospholipase A2 and secretion of cholecystokinin (CCK). CCK stimulates the pancreatic enzymes secretion and bile release (Azarm et al., 2013). Hamza et al. (2008) describes an increase of the brush border enzymes activity like aminopeptidase N and alkaline phosphatase (AN and AP) associated with dietary phospholipid level in pikeperch larvae. This higher AP activity suggest a better development and intestinal maturation process. Increase in dietary lecithin in microdiets for seabream larvae significantly improved digestive enzymes activities next to better enterocyte maturation, utilization and deposition of dietary essential fatty acids and larval growth, as a consequence of a better digestion, absorption, transport and deposition of dietary nutrients (Saleh, 2013).
Marvesa developed a liquid lecithin blend, named Lecifeed®Aqua R100. Native liquid lecithin has a very high viscosity and is therefore not so easy to handle in a feed plant. In Lecifeed®Aqua R100, oil and fatty acids have been added to lecithin which makes its application much easier. This Lecifeed®Aqua R100 is based upon rape lecithin. It is a NON-GMO blend. Beside this rape base blend, there are also mixtures of Lecifeed® Aqua based upon soybean lecithin.
What makes Lecifeed® Aqua R100 stand out from other lecithin products? There are many dry lecithin products on the market, those are mainly used for the juvenile and larvae stages. A liquid product is often cheaper than a dry product. With the usage of Lecifeed® Aqua you have the possibility to increase the inclusion levels of lecithin, and that is interesting because of the nutritional mechanisms and benefits described in this article. Because of the stickiness of lecithin, blended with fish oil it may be applied as coating for the pellets contributing to a better pellet quality. Lecifeed® Aqua is suitable for larvae, juvenile, and grower diets for many species of fish and crustaceans.