Zeolite was first discovered in basalt by the Swedish mineralogy, Cronsted, in 1956. The zeolite was named after boiling when it was heated to melting. Zeolite is a framework-like aluminosilicate mineral formed by volcanic lava. At present, there are more than 50 kinds of zeolites known, and the natural zeolites used in aquaculture are mainly clinoptilolite and mordenite. It contains all the major elements and most trace elements required for the growth and development of livestock and aquatic animals. These elements are present in an ionic state and can be used by livestock and poultry and aquatic animals. In addition, zeolite has unique adsorption, catalytic, ion exchange, ion selectivity, acid resistance, thermal stability, multi-component, and high biological activity and toxicity. Therefore, once discovered, zeolite is widely used in various fields such as livestock and poultry feed, aquaculture, chemical industry, veterinary medicine, and feed additives. At present, the zeolites in many countries in the world have been commercialized. In the United States, Russia, Japan, and many other countries, feed additive for zeolites has an annual output of more than 10,000 tons, and is widely used in animal husbandry and aquaculture. China has now discovered more than 150 zeolite mines distributed in 21 provinces. The application of zeolite in our country has only just begun. Therefore, there are many technical issues that need further development and research. one. Zeolite mechanism of action and performance Zeolite has a unique mineral structure, its structure is three-dimensional silicon tetrahedron and three-dimensional aluminum oxide tetrahedron, these tetrahedrons arranged according to a certain rule has a certain shape of the crystal skeleton. The mineral framework of the zeolite is open, with a large number of uniform channels and cavities (3 to 11 Å). Metal cations and water molecules are adsorbed in these holes and channels, and the binding force between these cations and water molecules and the anion skeleton is weak. This particular structure of zeolite determines its unique properties. The volume of pores and channels inside the zeolite crystals accounts for more than half of the total crystal volume. There are many zeolite waters in the pores and channels, which can be lost by heating the water. Dehydration of the zeolite, the formation of a large surface area of ​​the hole, a gram of zeolite holes and channels within the surface area of ​​up to 500 to 1000 square meters. This porous structure determines that it has a strong adsorption. It can adsorb a large number of polar molecules (such as ammonia, carbon dioxide, hydrogen sulfide, etc.), harmful microorganisms (such as Escherichia coli, Shigella and Salmonella, etc.) and toxic gases (such as ammonia and hydrogen sulfide) produced during animal digestion. Such as) can be adsorbed at any time, adsorbed harmful substances will be excreted, thereby reducing the harmful effects of harmful substances on the intestine. This is very beneficial to maintaining the intestinal health of livestock and poultry, fish and shrimp, and improving the intestinal digestion and absorption functions. The cations in the zeolite pores and channels also have strong selective ion exchange performance. Heavy metal ions and cyanide harmful to animals can be removed. The beneficial metal ions are released. This provides conditions for the animals to fully ingest mineral nutrients. The ion exchange performance of the zeolite in the animal's intestine is slow, and the release of beneficial mineral ions is more conducive to animal absorption. Because zeolite can also extend the time for food to pass through the digestive tract, the utilization of feed can be improved, the health of the body can be improved, the disease can be reduced, and the growth of the animal can be facilitated. Because the zeolite skeleton is composed of silicon, aluminum, oxygen and other elements, there are many metal cations such as nickel, manganese, titanium, molybdenum, and selenium in the holes and channels under the action of the electric field. These metal cations are digested by the intestines. Enzyme activation material. The reactant molecules diffuse into the interior of the zeolite and are activated by the catalysis of metal cations. The reaction product is released again by diffusion. Participate in digestive activities. The catalytic properties of zeolites greatly increase the activity of digestive enzymes in animals. In addition, zeolites also stimulate the use of the animal's digestive tract, so that the animal's intestinal mucosa thickness, intestinal glands developed, intestinal villi increased, and arranged dense, regular, and promote secretion of digestive juice. Therefore, after feeding the animal zeolite, it can promote the digestion and absorption of nutrients by the animal and improve feed utilization. two. Zeolite Application in Aquaculture 1. Zeolite used as a feed additive Adding 5.0% (150 mesh) clinoptilolite powder to grass feed for grass can increase the survival rate of grass carp by 14.0%, increase the relative growth rate by 10.8%, decrease the feed coefficient by 0.28, and increase the intestinal protease activity of grass carp. 27.0%, while hepatopancreas protease activity was not affected. There were no adverse effects on blood biochemical indicators such as BUN, GBT, creatinine (CR), cholesterol (CH) and total triglyceride (TG), and grass carp quality (Chen Jianming 1992). The test was to add 5.0% zeolite powder or 2.5% zeolite powder + 2.5% superphosphate (fertilizer) to grass carp fingerlings and adult fish feed. Results The addition of 5.0% zeolite powder group showed that the growth, plumpness, back muscle composition, hemoglobin, and feed digestibility of grass carp were better than those of the control group with zeolite powder added and 2.5% of zeolite and superphosphate added respectively. . The addition of zeolite powder has obvious growth-promoting effect, and it also changes the shape of grass carp into a high-quality alfalfa. The experiment also pointed out that the amount of zeolite powder added has an impact on blood parameters such as hemoglobin (HB), urea nitrogen (BUN), blood glucose (BG), hematocrit (%), and serum calcium (Ca2-) total cholesterol (TC). Triglycerides (TG) and other indicators have no significant effect. (Lu Qinglu 1992) The tests were carried out in aquariums and ponds. The aquarium was 904560 cm in size. There were altogether six tests. The size of the test carp was 11 to 16 grams, and 230 grams of fish were given per carton. The clinoptilolite was tested ( 180 mesh) The inorganic salt in the feed of the control group was replaced by 2%, and the other conditions were the same as those of the control group. The bait rate is 7% and it is fed four times a day. The test pool area is 7.37 mu, the water depth is 1 meter, and 6500 fish are put in the mu. The feed is the same as the aquarium. The experimental aquarium was 40 days and the pond was 50 days. The average weight gain of the experimental group was 10.52% higher than that of the control group, and the feed coefficient was 38.26% lower than that of the control group. (Chen Duo-xu 1991) 2. Zeolite is used as a water quality improver. The use of zeolite powder (200 mesh) 50 kg per mu water depth can remove 95% of the ammonia nitrogen in the water, purify the water quality, and relieve the water transfer phenomenon (Li Songxun 1993). When the total amount of ammonia nitrogen in the shrimp pond exceeds the allowable content, it reaches 1.2 mg/L, and after treatment with zeolite 16 mg/L, the ammonia nitrogen content in the pool water can be reduced to a safe concentration. (Sun Guoping (1997), when using zeolite as a water quality improver, the general amount of seawater is 80 pmm, and the freshwater amount is 15 pmm. (Hu Wenping, 1998) 3. Zeolite used as an additive carrier Zeolite is used as a carrier for additive premixes and The various basic conditions of the diluent, the zeolite has a neutral pH of 7 to 7.5, and only 3.4 to 3.9% when it contains water, and it is not easily wetted and mixed with inorganic salts containing crystal water to absorb moisture therein, and the feed is reinforced. The fluidity, rough surface and porous structure of zeolite, make it have a strong carrying capacity, not only can make the material evenly adsorbed on the surface, but also can be adsorbed into holes and channels, and improve the availability of materials. It can greatly improve the uniformity of mixing and at the same time, it can extend the release time of trace components more favorably for animal absorption.Furthermore, zeolite can be processed according to requirements, generally can choose from 30 to 200 meshes. The specification of the diluent provides great convenience.The zeolite is resistant to acids and has a bulk density of 1.2-1.4 kg/litre. It contains no grease, crude fibers and no static electricity. The carrier and the diluent should have the conditions, so it should be further researched and developed.III. Matters needing attention when using zeolites 1. The zeolite powder should be selected according to the application, such as for feeding fish, shrimp, bullfrog, etc. The specification is from 150 mesh to 200 mesh, and if it is used for water quality improvement, the specification of 180 mesh to 200 mesh should be used.There are many specifications of zeolite powder, different specifications for different animals and different uses, and special zeolites for ducks and pigs should not be used in water production. Powder, chicken and duck zeolite powder specifications are 40 to 80 mesh. Pigs are 80 to 120 mesh coarse. 2. Good quality zeolite powder, natural zeolite content should reach more than 50%. Zeolite powder available on the market A lot of zeolite content is only 10~30%.Using this kind of zeolite as feed additive is not only useless, and if it is mixed with lime, feldspar, etc. will also play a back role.3 The ammonia absorption value is an important quality index of zeolite powder. The ammonia absorption value of the qualified zeolite powder is generally greater than 100 mg equivalent/100 g.
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