Slow-release type rare earth pyridine nitrogen oxide compound and application thereof in preparation of aquatic feed

Abstract

The invention discloses a slow-release type rare earth pyridine nitrogen oxide compound and application thereof in preparation of aquatic feed. The slow-release type rare earth pyridine nitrogen oxide compound is prepared from 2-mercaptopyridine sodium nitrogen oxide, praseodymium chloride hexahydrate and water through heating reaction, washing and drying, or 2-mercaptopyridine sodium nitrogen oxide, 2-hydroxypyridine nitrogen oxide, praseodymium chloride hexahydrate and water are subjected to heating reaction, washing and drying to prepare the praseodymium chloride hexahydrate. The use frequency of antibiotics can be effectively reduced, the problem of drug residues is avoided, water pollution and generation of drug-resistant strains are reduced, and the policy requirements of antibiotic-free aquaculture are met. Meanwhile, the eel feed additive has excellent biological safety and environmental friendliness, is suitable for being widely popularized in the eel breeding industry, and assists the industry to develop towards the green, healthy and sustainable direction.

Description

Technical Field

[0001] The present invention belongs to the technical field of rare earth material applications, and particularly relates to a sustained-release rare earth pyridine nitroxide complex and its use in the preparation of aquatic feeds. Background Art

[0002] Rare earth elements are a collective term for 17 elements including lanthanide elements, as well as yttrium and scandium. Due to their unique chemical properties and biological activities, they have been widely studied and applied in multiple fields. As an important strategic resource in China, rare earth elements are rich in reserves. In recent years, their potential utilization value in agriculture and aquaculture has attracted increasing attention. Among these elements, cerium accounts for 48%, lanthanum accounts for 25%, neodymium accounts for 16%, samarium accounts for 2%, praseodymium accounts for 5%, and the remaining 12 elements only account for 4%. China has abundant rare earth resources, with industrial reserves exceeding 36 million tons, accounting for approximately 80% of the global total reserves.

[0003] In recent years, rare earth elements have been introduced into the fields of animal husbandry and aquaculture for research due to their ability to promote animal growth and enhance immunity. Relevant research shows that rare earths, as feed additives, can not only improve feed utilization rate but also improve the health status of animals, making rare earth additives one of the research hotspots in animal husbandry and aquaculture. Rare earth feed additives are divided into two categories: inorganic rare earths and organic rare earths. The main products of inorganic rare earths include rare earth nitrate, rare earth sulfate, rare earth carbonate, and rare earth chloride, while the main products of organic rare earths include rare earth with vitamin C, rare earth with citric acid, rare earth with amino acids, and rare earth with chitin, etc.

[0004] Rare earth elements are considered to be able to activate multiple metabolic pathways, enhance the activity of key enzymes in animals, and thus promote nutrient absorption and improve growth performance. By regulating the activities of various enzymes in the body, rare earths not only help improve the weight gain effect of animals but may also play an important role in stabilizing the antioxidant system.

[0005] During the process of aquaculture, the outbreak of bacterial diseases poses a serious threat to the health of fish and aquaculture benefits. In particular, Escherichia coli infection often causes diseases such as fish enteritis and septicemia, resulting in slow growth and increased mortality, bringing huge economic losses to the aquaculture industry. Currently, the prevention and control mainly rely on antibiotics, but long-term use is likely to lead to the generation of drug-resistant strains and drug residue problems, seriously affecting the safety of aquatic products.

[0006] Although the prior art has provided different improvement solutions for eels and aquaculture, there is currently a lack of research on special rare earth organic complex additives for the prevention and treatment of Escherichia coli infection. In particular, rare earth complexes based on pyridine N-oxide have not been reported. Therefore, the development of a new type of rare earth pyridine N-oxide complex feed additive can not only play the role of promoting growth and enhancing immunity of rare earth elements, but also effectively inhibit Escherichia coli infection in eels, ensuring the quality of aquatic products and aquaculture benefits. However, the stability and sustained release of rare earth pyridine N-oxide complexes in the aquaculture environment are still the key technical bottlenecks restricting their application. Summary of the Invention

[0007] The object of the present invention is to overcome the defects of the prior art and provide a sustained-release rare earth pyridine N-oxide complex.

[0008] Another object of the present invention is to provide the use of the above-mentioned sustained-release rare earth pyridine N-oxide complex as an aquaculture feed additive.

[0009] The technical solution of the present invention is as follows:

[0010] A sustained-release rare earth pyridine N-oxide complex is prepared by heating reaction, washing and drying with sodium 2-mercaptopyridine N-oxide, praseodymium chloride hexahydrate and water, or is prepared by heating reaction, washing and drying with sodium 2-mercaptopyridine N-oxide, 2-hydroxypyridine N-oxide, praseodymium chloride hexahydrate and water.

[0011] In a preferred embodiment of the present invention, the mass ratio of sodium 2-mercaptopyridine N-oxide, praseodymium chloride hexahydrate and water is 0.7 - 0.8:0.4 - 0.6:40, or the mass ratio of sodium 2-mercaptopyridine N-oxide, 2-hydroxypyridine N-oxide, praseodymium chloride hexahydrate and water is 0.4 - 0.5:0.1 - 0.2:0.5 - 0.6:20.

[0012] In a preferred embodiment of the present invention, its preparation method includes the following steps:

[0013] (1) Dissolve sodium 2-mercaptopyridine N-oxide in part of the water, heat to 75 - 85 °C under stirring at 250 - 350 rpm to form a first solution;

[0014] (2) Dissolve praseodymium chloride hexahydrate in the remaining water to form a second solution;

[0015] (3) Mix the first solution and the second solution, continue stirring and reacting at 250 - 350 rpm for 7 - 9 h, maintain the reaction temperature at 75 - 85 °C, and then naturally cool to room temperature;

[0016] (4) Wash the material obtained in step (3) with deionized water and then dry it at 75 - 85 °C to obtain the product.

[0017] In a preferred embodiment of the present invention, its preparation method comprises the following steps:

[0018] (1) Dissolve sodium 2 - mercaptopyridine N - oxide, 2 - hydroxypyridine N - oxide and praseodymium chloride hexahydrate in water, heat to 75 - 85 °C under stirring at 250 - 350 rpm, and then naturally cool to room temperature;

[0019] (2) Wash the material obtained in step (1) with deionized water and then dry it at 75 - 85 °C to obtain the product.

[0020] Use of the above - mentioned sustained - release rare - earth pyridine N - oxide complex in the preparation of aquatic feed.

[0021] In a preferred embodiment of the present invention, the addition amount of the sustained - release rare - earth pyridine N - oxide complex is 1 - 2 wt%.

[0022] More preferably, the aquatic feed further comprises fish meal, starch, skimmed milk powder, dried pig lung, fish viscera powder, high - gluten wheat flour and shrimp powder.

[0023] An aquatic feed comprising the above - mentioned sustained - release rare - earth pyridine N - oxide complex.

[0024] In a preferred embodiment of the present invention, the addition amount of the sustained - release rare - earth pyridine N - oxide complex is 1 - 2 wt%.

[0025] More preferably, it further comprises fish meal, starch, skimmed milk powder, dried pig lung, fish viscera powder, high - gluten wheat flour and shrimp powder.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1. Through the synergistic antibacterial effect of the rare - earth element praseodymium and pyridine N - oxide, the present invention can continuously release and stably exert its efficacy in the eel intestine. This not only effectively inhibits the growth of Escherichia coli, reduces the proportion of harmful bacteria, but also helps maintain the balance of the intestinal microecology, thereby reducing the risk of diseases caused by dysbacteriosis. Compared with traditional antibacterial methods, the present invention significantly prolongs the action time of the effective antibacterial components, reduces the loss of active substances in the water body, and improves the persistence and stability of the antibacterial effect, providing continuous protection for the healthy cultivation of eels.

[0028] 2. The sustained - release rare - earth pyridine N - oxide complex used in the present invention has the advantages of rich sources, simple preparation, safety and non - toxicity, etc. The formed particle system has good structural stability and sustained - release performance, and can maintain high activity during feed processing, storage and the aquatic - farming environment.

[0029] 3. The present invention can effectively reduce the usage frequency of antibiotics, avoid the problem of drug residues, reduce water pollution and the generation of drug-resistant strains, meeting the policy requirements of antibiotic-free aquaculture. At the same time, the present invention also has excellent biosafety and environmental friendliness, is suitable for wide promotion in the eel aquaculture industry, and helps the industry develop in a green, healthy and sustainable direction. Brief Description of the Drawings

[0030] Figure 1 It is the infrared spectrum analysis diagram of Complex 1 and Complex 2 in the present invention.

[0031] Figure 2 It is one of the experimental result diagrams of Example 7 of the present invention, showing the content of Escherichia coli in the eel intestine.

[0032] Figure 3 It is the second experimental result diagram of Example 7 of the present invention, where: (a) Scanning electron microscope photograph of Escherichia coli in the eel intestine without any antibacterial feed treatment, (b) Scanning electron microscope photograph of Escherichia coli in the eel intestine after giving the basic aquatic feed prepared in Comparative Example 1, (c) Scanning electron microscope photograph of Escherichia coli in the eel intestine after giving the aquatic feed prepared in Example 5. Detailed Embodiments

[0033] The technical solution of the present invention will be further described and illustrated below through specific embodiments in conjunction with the drawings.

[0034] The sustained-release rare earth pyridine N-oxide complexes in the following examples are divided into Complex 1 and Complex 2.

[0035] The preparation method of Complex 1 includes: dissolving 0.71 g of sodium 2-mercaptopyridine N-oxide (purchased from Shanghai Bide Pharmaceutical Technology Co., Ltd.) in 20 mL of water, heating to 80 °C under stirring conditions, with a stirring speed of 300 rpm to form Solution 1; dissolving 0.50 g of praseodymium chloride hexahydrate (PrCl3·6H2O) in 20 mL of water to form Solution 2; mixing Solution 1 and Solution 2 and then continuing to stir and react, maintaining stirring at 80 °C and 300 rpm for 8 h, and then cooling for 3 h to room temperature. The obtained product is washed 3 times with 20 mL of deionized water and dried at 80 °C, with a yield of 76.95%. The infrared spectrum analysis of Complex 1 is as Figure 1As shown, the theoretical values of its elemental analysis are C, 33.525%; H, 2.608%; O, 11.920%; N, 7.823%, and the experimental values are C, 33.206%; H, 2.648%; O, 12.472%; N, 7.869%. Infrared spectrum analysis (cm-1): 3215(s), 1598(s), 1544(s), 1459(w), 1419(m), 1267(s), 1219(w), 1199(m), 1165(s), 1147(m), 1090(m), 1041(s), 958(s), 847(m), 830(m), 760(w), 709(w), 601(w), 586(m), 548(m).

[0036] The preparation method of complex 2 includes: dissolving 0.45 g of sodium 2-mercaptopyridine N-oxide (purchased from Shanghai Bide Pharmaceutical Technology Co., Ltd.) and 0.17 g of 2-hydroxypyridine N-oxide (purchased from Shanghai Bide Pharmaceutical Technology Co., Ltd.) in 20 mL of water, and mixing it with a solution formed by dissolving 0.53 g of praseodymium chloride hexahydrate (PrCl3·6H2O) in 20 mL of water. Maintain the pH value at 6.7, heat to 80 °C under stirring conditions, with a stirring speed of 300 rpm, and maintain for 8 h. Then cool down for 3 h to room temperature, wash 3 times with 20 mL of deionized water, and dry at 80 °C, with a yield of 78.03%. The infrared spectrum analysis of complex 2 is as Figure 1 shown, the theoretical values of its elemental analysis are C, 33.401%; H, 2.969%; O, 17.814%; N, 7.794%, and the experimental values are C, 33.468%; H, 2.846%; O, 18.036%; N, 7.855%. Infrared spectrum analysis (cm-1): 3109(s), 1680(s), 1621(s), 1602(s), 1529(w), 1461(w), 1420(m), 1369(s), 1274(s), 1206(w), 1155(w), 1126(s), 1093(m), 1041(s), 980(s), 931(s), 889(s), 837(w), 793(m), 761(w), 747(w), 713(w), 616(m), 599(w), 551(w). IR(cm-1): 3440(br,s), 2920(w), 1598(s), 1380(m), 1252(m), 1028(m), 790(m).

[0037] Example 1

[0038] Weigh each component according to the following mass percentages: fish meal 41.25%, starch 12.87%, skimmed milk powder 3.53%, dried pig lungs 9.41%, dried fish viscera powder 2.53%, high-gluten wheat flour 5.88%, shrimp powder 23.53%, complex 1 1.00%. Add the above raw materials to the mixing equipment in sequence, stir for 30 minutes to make them evenly mixed. Then send them to an extruder and granulate at 120 °C and 8 MPa pressure. After granulation is completed, cool to room temperature and dry at 60 °C until the moisture content ≤ 10%, thus obtaining an aquatic feed containing 1% complex 1.

[0039] Example 2

[0040] Weigh each component according to the following mass percentages: fish meal 41.25%, starch 11.87%, skimmed milk powder 3.53%, dried pig lungs 9.41%, dried fish viscera powder 2.53%, high-gluten wheat flour 5.88%, shrimp powder 23.53%, complex 1 2.00%. Use the same technological steps as in Example 1 for mixing, granulating, cooling and drying treatments, thus obtaining an aquatic feed containing 2% complex 1.

[0041] Example 3

[0042] Weigh each component according to the following mass percentages: fish meal 41.25%, starch 10.87%, skimmed milk powder 3.53%, dried pig lungs 9.41%, dried fish viscera powder 2.53%, high-gluten wheat flour 5.88%, shrimp powder 23.53%, complex 1 3.00%. Use the same technological steps as in Example 1 for mixing, granulating, cooling and drying treatments, thus obtaining an aquatic feed containing 3% complex 1.

[0043] Example 4

[0044] Weigh each component according to the following mass percentages: fish meal 41.25%, starch 12.87%, skimmed milk powder 3.53%, dried pig lungs 9.41%, dried fish viscera powder 2.53%, high-gluten wheat flour 5.88%, shrimp powder 23.53%, complex 2 1.00%. Add the above raw materials to the mixing equipment in sequence, stir for 30 minutes to make them evenly mixed. Then send them to an extruder and granulate at 120 °C and 8 MPa pressure. After granulation is completed, cool to room temperature and dry at 60 °C until the moisture content ≤ 10%, thus obtaining an aquatic feed containing 1% complex 2.

[0045] Example 5

[0046] Weigh each component according to the following mass percentages: fish meal 41.25%, starch 11.87%, skimmed milk powder 3.53%, dried pig lungs 9.41%, dried fish viscera powder 2.53%, high-gluten wheat flour 5.88%, shrimp powder 23.53%, complex 2 2.00%. Carry out mixing, granulation, cooling and drying treatments using the same technological steps as in Example 4 to obtain the aquatic feed containing 2% of complex 2.

[0047] Example 6

[0048] Weigh each component according to the following mass percentages: fish meal 41.25%, starch 10.87%, skimmed milk powder 3.53%, dried pig lungs 9.41%, dried fish viscera powder 2.53%, high-gluten wheat flour 5.88%, shrimp powder 23.53%, complex 2 3.00%. Carry out mixing, granulation, cooling and drying treatments using the same technological steps as in Example 4 to obtain the aquatic feed containing 3% of complex 2.

[0049] Comparative Example 1 (control group)

[0050] Weigh each component according to the following mass percentages: fish meal 41.25%, starch 12.87%, skimmed milk powder 3.53%, dried pig lungs 9.41%, dried fish viscera powder 2.53%, high-gluten wheat flour 5.88%, shrimp powder 23.53%, vitamin C 1%. Add the above raw materials into the mixing equipment in sequence and stir for 30 min to make them fully and evenly mixed. Feed the mixture into the extruder and carry out extrusion granulation under the conditions of 120 °C and 8 MPa pressure. After granulation is completed, cool it to room temperature and dry it at 60 °C until the moisture content ≤ 10% to obtain the basic aquatic feed, and the control group is used for subsequent feeding experiment comparison.

[0051] Example 7

[0052] Select healthy and disease-free Japanese eels (Anguilla japonica) as the experimental subjects, with a body weight of about 250 - 300 g. Before the experiment starts, conduct an adaptive feeding for all eels for 7 days and stop feeding 24 h before the experiment starts. The experiment is set up with a control group and experimental groups with different addition amounts. The number of eels in each group is 30 tails, and they are placed in a circulating water aquaculture system with the same specifications for feeding. The feeding water temperature is controlled at 26 - 30 °C, the dissolved oxygen is maintained at 6.0 - 7.0 mg / L, the pH value is maintained within the range of 7.2 - 7.8, the salinity is maintained at 2‰ - 5‰, and the light cycle is set as 12 h light / 12 h dark.

[0053] During the feeding process, the control group was fed the basic aquatic feed prepared in Comparative Example 1, and the experimental groups were fed different proportions of feed supplemented with Complex 1 or Complex 2 in the above-mentioned examples (the addition amounts were 1%, 2%, and 3% respectively). Feed was given once in the morning and once in the evening at regular times every day, and the daily feed amount was controlled at 3%-5% of the eel body weight. The feeding period was 14 days. During the experiment, the feeding behavior, swimming state, and death situation of the eels were observed every day, and the breeding water was replaced regularly to keep the water quality indicators stable.

[0054] After the feeding period ended, intestinal samples of all experimental group eels were taken for detection under aseptic operation. The intestinal contents were collected, the content of Escherichia coli in the intestine was determined by the plate counting method, and the proportion of Escherichia coli was determined by the analysis of the flora ratio. The results are shown in Table 1 and Figures 2 to 3 as follows.

[0055] Table 1 Comparison of Escherichia coli content in the control group and the examples in the experiment

[0056]

[0057] Example 8

[0058] Take appropriate amounts of the aquatic feeds of Examples 1 to 6, and place them in 1 mL of eel intestinal fluid (28 °C, pH 6.8 phosphate buffer solution) respectively. After 0, 3, 6, 9, 12, and 24 h, take out the microparticles, collect the filtrate through a 0.45 μm filter membrane, and use a high-performance liquid chromatograph (HPLC) to measure the release concentration of the sustained-release rare earth pyridine nitroxide complex in the filtrate, and analyze the sustained-release effect under different coating ratios and concentrations to evaluate the sustained-release performance of the aquatic feed.

[0059] Table 2 Coating rates of the control group and Examples 1-6

[0060]

[0061] According to the experimental data, different types of slow-release rare earth pyridine nitroxide complexes and their addition amounts have a significant impact on the coating rate of aquatic feed. The control group had the highest coating rate of 72.2% under the condition of no complex, but lacked antibacterial active substances and could not achieve the actual antibacterial effect. Under the condition of adding Complex 1, as the addition amount increased from 1% to 3%, the coating rate showed a trend of first increasing and then decreasing, which were 48.3%, 62.8% and 54.1% respectively. Among them, the coating rate was the highest at the addition amount of 2%, indicating that appropriately increasing the content of Complex 1 was beneficial to form a more stable coating structure, but too high an addition amount might damage the coating integrity and lead to a decrease in the coating rate. Under the condition of Complex 2, the coating rate showed a similar pattern. When the addition amounts were 1%, 2% and 3% respectively, the coating rates were 64.6%, 50.2% and 59.5%. Among them, the coating rate was the highest at the addition amount of 1%, indicating that Complex 2 was more conducive to maintaining the stability of the coating system at a lower addition amount. Therefore, Complex 2 achieved a better coating effect (64.6%) at the addition amount of 1% (Example 4), with stable structure and good slow-release performance, which was an ideal slow-release condition in this experiment. Considering the balance between the coating rate and the antibacterial effect, both Complex 1 at the addition amount of 2% (Example 2) and Complex 2 at the addition amount of 1% (Example 4) had good application potential and were suitable for popularization and use.

[0062] The type and addition amount of the complex have a significant impact on the coating rate of aquatic feed. Among them, Complex 2 showed the best performance at the addition amount of 1% (Example 4), with both a high coating rate and good slow-release performance, and was suitable for the development of the antibacterial system of aquatic feed. At the same time, reasonably controlling the addition amount of the complex can effectively optimize the coating effect, avoid the rupture of the coating film or the reduction of stability caused by too high loading, and provide technical support for achieving continuous antibacterial and immune enhancement in the eel intestine.

[0063] The above is only the preferred embodiment of the present invention, and thus the scope of implementation of the present invention cannot be limited thereby. That is, equivalent changes and modifications made according to the scope of the present invention patent and the content of the specification should still fall within the scope covered by the present invention.

Claims

1. A sustained-release rare earth pyridine nitroxide complex, characterized in that: It is prepared by heating and reacting sodium 2-mercaptopyridine N-oxide, praseodymium chloride hexahydrate and water, followed by washing and drying, or by heating and reacting sodium 2-mercaptopyridine N-oxide, 2-hydroxypyridine N-oxide, praseodymium chloride hexahydrate and water, followed by washing and drying.

2. The sustained-release rare earth pyridine nitroxide complex according to claim 1, characterized in that: The mass ratio of the sodium 2-mercaptopyridine N-oxide, praseodymium chloride hexahydrate and water is 0.7 - 0.8:0.4 - 0.6:40, or the mass ratio of the sodium 2-mercaptopyridine N-oxide, 2-hydroxypyridine N-oxide, praseodymium chloride hexahydrate and water is 0.4 - 0.5:0.1 - 0.2:0.5 - 0.6:

20.

3. The sustained-release rare earth pyridine nitroxide complex according to claim 1 or 2, characterized in that: Its preparation method comprises the following steps: (1) Dissolve sodium 2-mercaptopyridine N-oxide in part of the water, and heat it to 75 - 85 °C under stirring at 250 - 350 rpm to form a first solution; (2) Dissolve praseodymium chloride hexahydrate in the remaining water to form a second solution; (3) After mixing the first solution and the second solution, continue stirring and reacting at 250 - 350 rpm for 7 - 9 h, maintain the reaction temperature at 75 - 85 °C, and then naturally cool to room temperature; (4) Wash the material obtained in step (3) with deionized water and then dry it at 75 - 85 °C to obtain the product.

4. The sustained-release rare earth pyridine nitroxide complex according to claim 1 or 2, wherein: Its preparation method comprises the following steps: (1) Dissolve sodium 2-mercaptopyridine N-oxide, 2-hydroxypyridine N-oxide and praseodymium chloride hexahydrate in water, heat it to 75 - 85 °C under stirring at 250 - 350 rpm, and then naturally cool to room temperature; (2) Wash the material obtained in step (1) with deionized water and then dry it at 75 - 85 °C to obtain the product.

5. Use of the sustained-release rare earth pyridine N-oxide complex according to any one of claims 1 to 4 in the preparation of aquatic feeds.

6. The use according to claim 5, characterized in that: The addition amount of the sustained-release rare earth pyridine N-oxide complex is 1 - 2 wt%.

7. The use according to claim 6, wherein: The aquatic feed further comprises fish meal, starch, skimmed milk powder, dried pig lungs, fish offal powder, high-gluten wheat flour and shrimp powder.

8. An aquatic feed, characterized in that: It has the sustained-release rare earth pyridine N-oxide complex according to any one of claims 1 to 4.

9. The aquatic feed according to claim 8, wherein: The addition amount of the sustained-release rare earth pyridine N-oxide complex is 1 - 2 wt%.

10. The aquatic feed according to claim 9, characterized in that: It further comprises fish meal, starch, skimmed milk powder, dried pig lungs, fish offal powder, high-gluten wheat flour and shrimp powder.

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