By Catharina Nieuwenhuizen MBA
Lecithin may be produced from egg yolk, but more commonly used in aquafeed are soya and rapeseed 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 the fish nutrionists like to include like to include it in fish and shrimp diets.
Lecithin is widely used in food for larval and juvenile stages of various species of fish and crustaceans; because those developing fish have a limited ability to novo phospholipid synthesis.
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Phosphatidylcholine (PC) is the most abundant PL in fish tissues and is among many others an important catabolic energy source for egg and larval embryogenesis and important for intestinal lipid absorption. 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 phosphatdycoline (PC) is more effective for growth improvement while phosphatidylinositol (PL) and phosphatidylethanolamine (PE) are more important for survival and preventing deformities in the developing fish and are a structural component of all cell membranes. This article will highlight some of the other reasons and benefits to include lecithin in aquafeed for all stages.
PL may improve the performance of the diet by improving the water stability of food particles, or by
their action as an antioxidant or feed attractant. Castell in Coutteau et al published an interesting example of a practical example of a practical application of Lecithin in 1997. They hypothesise that that dietary supplementation of soybean lecithin prevent 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 soy lecithin may increase the physical water stability of aquafeed pellets and thereby reduce the loss of water-soluble nutrients.
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Catharina Nieuwenhuizen MBA |
Liquid transport and retention.
Pl are required in shrimp feed for the efficient transport of dietary fatty acids and lipids from the gut epithelium into haemolymph, and the mobility of lipids between the various tissues and organs. Dietary PL also improves the mobilisation of cholesterol; which is essential in the molting process of crustaceans. PL also reduces the accumaltion of lipid droplets in the intestine, due to its essential role in the transportation Triacylglycerol (TAG) from the intestinal mucosa via the haemolymph into the serum of shrimp chylomicron and other lipoprotein. Diets with additional PL have higher levels of plasma lipoproteins and epithelial enzymes.
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 three percent of soybean lecithin in the diet.
Effect on Enzymes
PL shows a beneficial effect on brush border (or mycovilli) and pancreatic enzymes in rainbow trout. Soybean lecithin induced a significantly higher activity of amylase, lipase, lipase, phospholipase A2 and secretion of cholecystokinin (CCK). CCK stimulates the pancreatic enzymes secretion and bile release.
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