Phospholipids are compound lipids containing phosphoric acid that are found in plants and animals. In the past few decades, people have studied the effect of adding phospholipids to aquatic crustaceans and fish baits. The importance of phospholipids in fish and shrimp nutrition has attracted people's attention.
First, the type and structure of phospholipids Phospholipids are widely found in animals and plants. Phospholipids consist of one molecule of glycerol with two fatty acids, one phosphate and one amino alcohol residue. According to the proportion of N/P in the phospholipid molecule, it is often divided into aminophospholipids, P:N=1:1 (eg, lecithin, cephalin); diaminophospholipids, P:N=1:2 (eg, phospholipids). ); and three types of nitrogen-free phosphates. Phospholipids mainly include lecithin, cephalin, inositol phospholipids, serine phospholipids, glycolipids, sterol esters, and phosphatidic acid. Chemical components include phosphorus, nitrogen, choline, inositol, sterols, oil-bearing substances, and ash. .
Second, the function of phospholipids has a nutritional role Phospholipids constitute the essential elements of the organism, plays an important role in the biofilm cells and subcellular structures. Many important enzymes are concentrated on its surface and involved in complex biosynthesis and catabolism. Phospholipids contain phosphorus, nitrogen, choline, inositol, sterols, etc. They are important nutrients for Macrobrachium rosenbergii, crabs, lobsters, and shrimps.
2. Promote fat metabolism Lecithin participates in the process of digestion, absorption and transport of fat, forming chylomicrons and low-density lipoproteins. The liver is the main site for the synthesis of triglycerides and lipoproteins. Under normal circumstances, triglycerides are used in the form of lipoproteins and are used in extrahepatic tissues. If the liver lacks phospholipids, the synthesis or secretion of lipoproteins will be hindered, and large amounts of triglycerides in the liver will accumulate, which exceeds the storage of the liver. Fatty liver. Choline, inositol, vitamin B12, vitamin E, linoleic acid and some unknown growth factors in phospholipids can promote the digestion and absorption of fat and eliminate excess fat in the liver.
3. The immune function test showed that soybean phospholipids can increase the function of macrophages, promote the proliferation of T lymphocytes, and enhance the body's immune function, thus can improve the disease resistance and survival rate of livestock and poultry, fish and shrimp.
4. The antioxidant effect of lecithin with antioxidation has now been widely used. Experiments have shown that when the content of lecithin is more than 0.2% in oil, the antioxidant effect of rapeseed oil, sunflower oil and fish oil can be significantly improved. According to reports, artificial lecithin in the presence of copper, iron, manganese and other ions, anti-oxidation accompany oxygen.
5. Other functions Phospholipids also have a lure effect, which can improve the palatability of the diet and provide unknown growth factors. Addition of phospholipids in compound feeds can improve the physical quality of granulation, increase feed slip, reduce the wear of granulation machinery, and Reduce the loss of water-soluble nutrients in feed.
Third, the application of phospholipids in aquatic animals A large number of studies have shown that phospholipids can effectively promote the growth of aquatic animals, improve the survival rate of fish, promote crustacean oyster shell, and reduce the incidence of miscarriage of aquatic animals. Kanazawa et al. reported that the addition of egg yolk phospholipids or soy phospholipids to rotifer-type biofeeds reduced the incidence of scoliosis to 0-5% (usually as high as 18%-80%). Rumsey et al. added phospholipids as a growth promoter to rainbow trout feed and found that it was effective for fry in the open or fast growing stage. Cao Junming et al. (1997) studied grass carp showed that when a certain amount of soybean phospholipids was added to feed, the liver lipid content of grass carp was greatly reduced, and it was found that in terms of reducing liver fat, lecithin, choline, and betaine The best combination is: 4%, 0.2%, 0.4%.
Phospholipids are important lipids for crustaceans. They can emulsify lipids in foods, make them easier to digest and absorb, and promote the formation of cell membranes. The phospholipids contained in the diet help cholesterol transport in the liver, pancreas and hemolymph tissues, thereby promoting the survival and growth of juvenile shrimp. Many studies have shown that the addition of soybean phospholipids can promote the growth of grass shrimp, Japanese shrimp, and American crayfish, improve survival rate and reduce the feed coefficient.
Fourth, the optimal amount of phospholipids Add phospholipids should pay attention to the following points: the younger the more phospholipids need to be provided; the higher the fat content in the diet, the more the demand for phospholipids; the third is the body can not be synthesized ( For shrimps, phospholipids must be added to the diet.
With respect to the study of the optimal amount of phospholipids, a large number of experiments have been conducted. At present, it is widely believed that the amount of lecithin in general aquatic feeds is 1%-2%. Akiyama and Dominy recommend 2% of the "seed shrimp nutrition in the feed industry"; in the Philippines, the amount of phospholipid added in the compound feed is also 2%, and the highest amount added from the test is 8%.
Fifth, the application prospects of phospholipids China's lecithin production is a new industry for nearly a decade or so, but also the comprehensive utilization of plant oil, deep processing, precision products. At present, some grease processing plants in the grain departments of Heilongjiang, Jilin, Liaoning, Zhejiang, Tianjin and other provinces already have soy lecithin production. High-quality lecithin, our country mainly relies on imports. In recent years, the extensive application of supercritical technology has enabled China to begin production of high-quality, high-purity egg yolk lecithin (PC content above 80%). With the further development of phospholipids, phospholipids with multiple nutritional functions and physiological functions will be more widely used in aquatic animals.
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