Five pieces of common sense of feed for cultured eel

1. The main binder-- α-starch: the adhesive is the earliest additive used in eel feed. Antibiotics, wheat gluten and α-starch were added in Japan in the 1950s when raising yellow stripes with raw fish as bait. Due to the use of binders such as α-starch, not only prevent the loss of antibiotics and nutrients, reduce water pollution, but also improve the feeding rate, thus accelerating the commercialization of feed.

The main binder of eel feed is α-starch (also known as pre-gelatinized starch), which is made of cassava or potato raw flour as raw materials. after mixing with water, gelatinization, drying, crushing and cooling make it a commodity with white color, good viscoelasticity and good malleability. the palatability of potato powder is the best, and the palatability of corn meal is good but the adhesion is poor. Cassava starch is between the two but the price is low. Cassava or potato starch or both can be used according to the needs of feed. The digestibility of α-starch of eel is about 80%, and the addition amount of α-starch in eel feed is 20-23%. If more is added, it will affect its nutritional value. In addition to its good stickiness, the bonding property of α-starch is also related to its fineness and other substances in feed.

1. Freshness of fishmeal: the acid value and volatile base nitrogen of fishmeal should not be too high, the use of poor freshness of fishmeal will destroy the viscoelasticity of feed.

two。 Trace inorganic salts: the proportion should be reasonable and should not be excessive, especially the adhesion of divalent ions to α-starch.

3. Raw material crushing fineness: preferably up to 98%, can pass 80 mesh screen, so because the contact surface is large, easy to bond, after the feed is stirred, the surface gloss is good, the commodity image is good.

In addition, after buying α-starch, it should be used up within 4 months after the production date, otherwise it will be degraded, its molecular weight and adhesion will be reduced due to the influence of heat, light, air and other factors.

Second, auxiliary adhesive

1. Sodium caseinate: contains more than 88% crude protein, which can not only provide the protein source for eels, but also be a good adhesive for the production of special black and white eel feed. It can balance amino acids. It is recommended that 0.5-2% should be added in the special black and white stage.

2. Sodium alginate: also known as algin, white or light yellow, non-toxic, tasteless colloid, soluble in water into gel solution, when PH is 6-9, the stability is good. For ease of use, most of them are dried and crushed into powder. Because it contains carboxyl-COO-, on the polymer chain of poly β-D mannose and poly α-L gulose, it can form water-insoluble calcium salt with Ca+1 (calcium ion) in the base material, so its viscosity is 5 times that of flour, and it is more suitable to be used especially in waters with high salinity.

3. Wheat gluten: the starch is washed off after adding water, dried and ground, with a crude protein content of more than 72%, a fineness of more than 90% and a water absorption of about 80%. Adding 1-3% to the feed contributes to the stability of the feed in water. However, its lysine content is less, and its amino acid composition is more unbalanced than that of eel.

In addition, other commonly used adhesives are sodium polyacrylate, resin compounds and carboxymethyl cellulose. Their molecular weight is about one million, and they have carboxymethyl, carboxyl and hydroxyl groups on the molecular chain. Depending on hydrogen bonds and ionic electricity, they have strong adhesion with feed base materials. The use effect of these adhesives is related to the base material, variety and quantity, water quality, water temperature and the degree of pulling material.

III. Attractive substances

The feeding of eels living in natural waters is accomplished by the synergistic action of olfactory, visual and taste organs. in this process, eels perceive the position of food by olfactory organs to determine the position of food. when vision reaches the range of action, vision can tell whether it can eat or not, so the eel's sense of smell is very sensitive. Its sensitivity to phenylethanol is much higher than that of humans, and the sensory valve is as low as 3.5 × 10-19. Similar to a dog. Through the separation and analysis of raw materials, Carr, Mackie, Fuke and other scholars found that the food-inducing components of fish feed are mainly nitrogen-containing compounds, especially amino acids, nucleotides, quaternary amine bases and organic acids, and some short-chain fatty acids, pteridine and chlorazine derivatives also have good food-inducing effects on some fish. The feeding induction effect of non-polar α-amino acids was the best.

According to Carr1982, food attractants extracted from animal tissues have four characteristics: ① has low molecular weight, generally less than 1000 ② nitrogen-containing ③ is non-volatile, and water-soluble ④ has the characteristics of amphoteric H + and OH-. In addition, the food-inducing ingredients of eel feed also have synergistic effect, that is to say, some ingredients have low or general activity when used alone, but when two or more kinds of ingredients coexist, they show strong activity, such as a, amino acid and betaine, b, amino acid and nucleotide, c, between two kinds of amino acid.

In factory production, it is generally possible to choose liver powder, milk powder or fresh milk essence, betaine, earthworm powder and amino acid protein sources as attractive substances.

IV. Digestive substances

The digestion of feed by eel is mainly carried out in the intestine. the intestinal tract of eel is shorter, and the ratio of length to body length is 0.52-0.82, but the pepsin activity of eel is stronger, which is 4 times higher than that of rainbow trout, and its amylase activity is weaker. Eel generally completes the process of digestion and absorption of feed for 6 hours. Generally speaking, in the production of feed, beer yeast, molasses yeast, single-cell cell protein and live bacterial preparations with digestion and bowel function are also added.

1. Beer yeast: composed of yeast cells in the wort culture of the beer industry and the residue of the culture medium, the crude protein is generally 40-50%, containing a large number of B vitamins and unknown growth factors. In eel feed, 2-3% can be added.

2. Molasses yeast: it is rich in B vitamins, which is prepared by low temperature spray drying, which can promote the appetite of eel and has a good seductive effect. The various nutrients contained in it are well preserved and have strong fragrance.

3. Single-celled cell protein: it is prepared by bacteria after refining and drying in the process of beet molasses fermentation. it has yeast-like sweet taste and good taste, and contains bacterial protein, minerals, vitamins and unknown growth factors that are easy to be absorbed by eels. The content of crude protein is more than 65% and the crude fat is less than 4.5%. It is recommended to add 1-2% in the feed.

4. Living bacteria preparation: it is composed of Lactobacillus, Streptococcus faecalis, Micrococcus Lactococcus and other nutritional substrates, containing more than 120 million effective living bacteria per gram, which can assist digestion and intestine. the so-called intestinal function is that after the speed of small intestinal peristalsis becomes slow, nutrients can be fully absorbed, which accelerates the peristalsis of large intestine and shortens the time of excreta in animals. In the intestinal tract, these beneficial bacteria can compete with harmful bacteria for living space and nutrients, and can combine favorable bacteria in the intestine to resist or even kill bad bacteria, especially Micrococcus lactis (Pediococcusacidilatici), which is 10 times more effective than general lactic acid bacteria in inhibiting the growth of miscellaneous bacteria. In addition, it contains a large number of B vitamins, which can produce high dose of lactic acid in the body, inhibit the growth of miscellaneous bacteria, stimulate the secretion of digestive enzymes, and increase the utilization rate of protein.

5. substances that protect the liver and strengthen the gallbladder

The liver is an important gland in the eel. It can secrete bile and store it in the gallbladder. In addition to helping to digest fat, it can also store excess glucose in the body in the form of glycogen and synthesize vitamin An in the liver. It can also relieve the poison caused by the abuse of antibiotics and pesticides. It can be said that the liver is the "chemical factory" of the eel. In order to strengthen the normal absorption function of eel and eliminate the adverse effects caused by eel living in high density environment for a long time, water quality deterioration and drug abuse, it is necessary to add some traditional Chinese medicine, bile acid and other liver-protecting and gallbladder-protecting substances to eel feed.

1. Bupleurum: bitter, slightly cold, with surface and interior functions, containing saponins, volatile fatty acids and other substances, with anti-virus, protozoa and other functions, but also anti-liver damage and other functions.

2. Radix Isatidis: bitter and cold, the main ingredient is indigo, with the function of clearing away heat and detoxification. Proprietary Chinese medicine is generally sold on the market by adding 10-15 grams per kilogram of feed.

3. Bile acid: it can promote the digestion and absorption of fat and fat-soluble vitamins and cholesterol. for the rancidity substances produced by eating aquatic feed with high oil content, it has the effect of detoxification and strengthening the liver, generally adding 100 grams per ton of feed.

4. Promoting bile secretion and other liver-protecting and bile-tonifying agents can strengthen liver function, promote bile secretion, increase bile alcohol excretion, reduce fat deposition in liver, promote physiological metabolism of carbohydrates and sugars, and regulate endocrine system. These substances (including fatty acids, fermentation concentrate and dehydrocholicacid, etc.) can eliminate toxins in the blood of eel liver by hydrolysis, oxidation and acetylation, regenerate damaged hepatocytes and enhance the secretory function of hepatocytes.