An antibiotic-free feed additive, its preparation method and application

Abstract

This invention discloses an antibiotic-free feed additive, its preparation method, and its application, belonging to the field of feed additive technology. The additive comprises a core-shell copper-carbon composite material, zinc-calcium composite particles with interlayer confined structures, iron salts, plant polyphenols, and polysaccharides. Specifically, nano-copper or cuprous oxide particles are formed through in-situ reduction of copper salts in biomass precursors, forming a preferentially distributed carbon shell layer on their surface; zinc oxide nanoparticles are generated in-situ through adsorption of zinc salts in the interlayer structure of oyster shells and heat treatment. Polysaccharides form a coating layer on the surface of the composite material, enabling the components to form a stable composite structure. This invention achieves stable dispersion and release control of active components through structural regulation, showing promising application prospects. This antibiotic-free feed additive has a stable structure and good component dispersibility, and can be used to prepare aquatic feed, livestock and poultry feed, or pet food.

Description

Technical Field

[0001] This invention belongs to the technical field of feed additives and bio-based functional materials, specifically relating to an antibiotic-free feed additive, and more particularly to a multi-component composite antibiotic-free feed additive constructed based on a biomass carbon-supported core-shell copper-carbon composite material, oyster shell-derived zinc-calcium composite particles, and a polysaccharide coating system, as well as its preparation method and application. Background Technology

[0002] With the continuous expansion of livestock, poultry and aquaculture scale, the risks of bacterial resistance, drug residues and environmental problems caused by the long-term use of antibiotic feed additives are becoming increasingly prominent. Developing green, safe and stable antibiotic-free feed additives has become an important development direction in the feed industry.

[0003] Currently, antibiotic-free feed additives mainly include probiotics, antimicrobial peptides, organic acids, plant extracts, and minerals such as zinc and copper. While these technologies can, to some extent, replace antibiotics in inhibiting bacteria, promoting growth, or regulating gut health, they still have some shortcomings: for example, probiotics and antimicrobial peptides are sensitive to processing and storage conditions and lack stability; plant extracts, although possessing natural antibacterial activity, are highly volatile and have a short duration of action; inorganic antimicrobial components such as zinc and copper, while exhibiting good growth-promoting and antimicrobial effects, often suffer from low utilization rates, difficulty in controlling release rates, and the potential for excessively high local concentrations and significant environmental emissions in practical applications. Furthermore, compound systems of multiple active components often employ simple physical mixing methods, which can easily lead to uneven dispersion, poor structural stability, and insufficient synergistic effects.

[0004] In recent years, the technology of using porous carriers to load active metal components to improve their dispersibility and stability has gradually attracted attention. Biomass carbon materials, with their large specific surface area and good loading capacity, can serve as carriers for active metal components. US patent US8828485B2 discloses a copper-carbon composite system in which copper particles or cuprous oxide are loaded onto the surface of carbon materials, exhibiting good antibacterial effects. However, directly loading nano-copper or cuprous oxide onto the surface of a carbon carrier leads to the easy deactivation of exposed nano-copper, and the rapid release of copper ions poses a toxicity risk. Oyster shell-derived calcium carbonate possesses a naturally porous structure and good biocompatibility, making it suitable as a loading matrix for zinc-based components. Natural polysaccharides can further encapsulate the composite system, thereby enhancing its stability. Therefore, current technologies still lack a core-shell copper-carbon composite material that encapsulates nano-copper materials within a carbon shell and distributes them uniformly on biomass carbon. Furthermore, there is a lack of technology utilizing the interlayer structure of oyster shells to confine the growth of zinc oxide into zinc-calcium composite particles, and further combining this with plant polyphenols, iron salts, and polysaccharides to form a composite antibiotic-free feed additive system, thereby improving the stability and dispersibility of inorganic antibacterial components and enhancing the synergistic effect among multiple components. Therefore, there is an urgent need to provide an antibiotic-free feed additive with a controllable structure, stable components, and combining the characteristics of a copper-carbon composite structure, a zinc-calcium confinement structure, and polysaccharide encapsulation, to improve the shortcomings of existing antibiotic-free feed additives in terms of stability, composite structure construction, and synergistic effects.

[0005] Furthermore, while nano-copper exhibits good antibacterial activity, its small particle size and high surface energy make it prone to aggregation during preparation and use, affecting its dispersibility and stability. Unprotected nano-copper is also susceptible to rapid release or loss during application, hindering its stable function. Forming a carbon coating on the outer layer of nano-copper or cuprous oxide particles and loading them with a biomass carbon carrier can help improve the problems of nano-copper aggregation, insufficient stability, and difficulty in controlling release behavior. Similarly, confining zinc oxide nanoparticles within the interlayer pores of an oyster shell-derived calcium carbonate matrix can also improve the dispersibility and structural stability of the zinc-based active components.

[0006] Therefore, there is an urgent need to provide an antibiotic-free feed additive that includes a core-shell copper-carbon composite material supported on biomass carbon, zinc-calcium composite particles with interlayer confined structure, plant polyphenolic compounds, iron salt trace elements, and polysaccharides, in order to improve the shortcomings of existing antibiotic-free feed additives in terms of the dispersibility of active components, structural stability, and multi-component compounding. Summary of the Invention

[0007] The purpose of this invention is to provide a structurally stable, uniformly dispersed, and synergistically antibacterial antibiotic-free feed additive, as well as its preparation method and application.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] An antibiotic-free feed additive, comprising the following components: copper-carbon composite material, zinc-calcium composite granules, iron salt, plant polyphenols, and polysaccharides;

[0010] Wherein: the copper-carbon composite material includes a biomass carbon carrier and core-shell structured copper-carbon nanoparticles dispersed and loaded on its surface; the core-shell structured copper-carbon nanoparticles include nano-copper or cuprous oxide particles and a carbon shell layer covering their surface.

[0011] The zinc-calcium composite particles comprise a calcium carbonate matrix derived from oyster shells and zinc oxide nanoparticles distributed within its interlayer pores.

[0012] The polysaccharides are distributed on the surface of the copper-carbon composite material and the zinc-calcium composite particles, forming a continuous or semi-continuous coating layer.

[0013] An antibiotic-free feed additive, comprising the following components by weight:

[0014] 30-50 parts of copper-carbon composite material;

[0015] 20-40 parts of zinc-calcium compound granules;

[0016] 5-10 parts iron salt;

[0017] 25-40 parts of plant polyphenols;

[0018] 10-15 parts of polysaccharides.

[0019] In the above-mentioned antibiotic-free feed additives, preferably, the particle size of the copper nanoparticles or cuprous oxide nanoparticles in the core-shell structured copper-carbon nanoparticles is 10-100 nm; the carbon layer thickness is 2-10 nm; the loading amount of the core-shell structured copper-carbon nanoparticles on the biomass carbon carrier is 0.01-0.10 g / g; the particle size of the zinc oxide nanoparticles is 2-20 nm; and the interlayer pore size of the calcium carbonate matrix derived from oyster shells is 1-10 μm.

[0020] Preferably, the carbon shell only coats the surface of the nano-copper or cuprous oxide particles and is not distributed on the surface of the biomass carbon carrier;

[0021] Preferably, the zinc oxide nanoparticles are distributed within the interlayer pores of the calcium carbonate matrix derived from oyster shells, and are dispersed due to the pore structure.

[0022] Preferably, the core-shell structured copper-carbon nanoparticles of the present invention are not obtained by simple coating, but by the synergistic construction of in-situ reduction of copper ions and secondary deposition of carbon source, so that the carbon shell is selectively formed on the surface of the nano-copper, thereby achieving structural regulation of copper ion release.

[0023] Preferably, the plant polyphenolic compound is selected from one or more of guaiacol, cinnamylphenol, vanillin, eugenol, p-hydroxyphenol, tea polyphenols, tannic acid, proanthocyanidins and catechins;

[0024] Preferably, the polysaccharide is selected from one or more of carrageenan, sodium alginate, chitosan, pectin or gum arabic;

[0025] Preferably, the iron salt is selected from one or more of ferrous sulfate, ferric citrate, or amino acid iron.

[0026] The preparation method of the above-mentioned antibiotic-free feed additive includes the following steps:

[0027] (1) Preparation of copper-carbon composite material: After copper ions are adsorbed onto biomass powder, they are pre-oxidized and carbonized in situ to reduce the biomass carbon to form nano-copper or cuprous oxide nanoparticles; the biomass carbon loaded with nano-copper or cuprous oxide nanoparticles is then soaked in an organic carbon source solution and carbonized again to obtain a copper-carbon composite material including biomass carbon carrier and core-shell structured copper-carbon nanoparticles dispersed on its surface.

[0028] (2) Preparation of zinc-calcium composite particles: Zinc ions are adsorbed in the interlayer pore structure of calcium carbonate matrix derived from oyster shells. After calcination, the zinc salt is converted in situ in the interlayer pores to form zinc oxide nanoparticles, thus obtaining zinc-calcium composite particles with interlayer confined structure.

[0029] (3) Disperse the copper-carbon composite material, zinc-calcium composite particles, iron salts, plant polyphenols and polysaccharides in the aqueous phase:

[0030] (4) Stirring at a certain temperature for a certain number of hours allows the polysaccharide to form a coating structure:

[0031] (5) Antibiotic-free feed additives are obtained by spray drying or freeze drying.

[0032] The preparation of copper-carbon composite material in step (1) above includes the following steps:

[0033] 1) The biomass powder is soaked in a copper salt solution and adsorbed at 50-80℃ for 4-8 hours to obtain the biomass precursor;

[0034] 2) The biomass precursor is pre-oxidized in air at 250-300°C for 1-3 hours;

[0035] 3) Carbonize at 500~700℃ for 2~4 hours under nitrogen protection to obtain biomass carbon loaded with nano-copper or cuprous oxide;

[0036] 4) The obtained material is immersed in an organic carbon source solution, dried, and then carbonized at 500-700℃ under nitrogen protection, so that the carbon source is preferentially deposited on the surface of nano-copper or cuprous oxide particles and forms a carbon shell layer.

[0037] The biomass powder is one or more of wood powder, bamboo powder, cellulose, lignin, and seaweed powder; the copper salt is selected from one or more of copper sulfate, copper nitrate, and copper chloride; and the organic carbon source is selected from one or more of glucose, sucrose, starch, and dextrin.

[0038] The preparation of zinc-calcium composite particles in step (2) above includes the following steps:

[0039] 1) The oyster shells are cleaned, dried and crushed to obtain oyster shell powder;

[0040] 2) The oyster shell powder is soaked in a zinc salt solution, so that zinc ions are adsorbed into its interlayer pore structure;

[0041] 3) After drying, calcination is carried out at 500~700℃ for 2~6 hours to convert zinc salt into zinc oxide nanoparticles in situ within the interlayer channels, thereby obtaining zinc-calcium composite particles with interlayer confined structure.

[0042] The above describes the application of antibiotic-free feed additives in aquatic feed, livestock and poultry feed, or pet food.

[0043] The core-shell structured copper-carbon composite material of this invention improves the dispersibility and stability of copper active components through the composite structure design of "copper core-carbon shell-biomass carbon carrier" and helps to reduce the excessively rapid release of copper components.

[0044] The antibiotic-free feed additive of the present invention can be mixed with the base feed to replace antifungal agents and antibiotics to prevent feed from becoming moldy and to inhibit the growth of harmful microorganisms in the animal's intestines. The base feed is aquatic feed, livestock and poultry feed or pet feed, and the addition amount is preferably 0.2% to 2% of the total feed mass.

[0045] The principle of this invention:

[0046] This invention constructs a multi-level structure of "copper core-carbon shell-biomass carbon carrier" and further constructs a multi-level composite system of "copper-carbon core-shell structure-zinc-calcium confined structure-polysaccharide coating layer" to achieve the synergistic effect of each functional component. Among them: (1) In the copper-carbon composite material, nano-copper or cuprous oxide serves as the antibacterial active center, and the carbon shell layer forms a protective layer and regulates its release behavior, while biomass carbon serves as a carrier to improve its dispersibility; (2) In the zinc-calcium composite particles, zinc oxide nanoparticles are generated in situ and distributed in a confined manner in the pores between the oyster shell layers, which helps to inhibit particle aggregation and improve stability; (3) Polysaccharides form a coating layer on the surface of the composite system, which helps to improve the stability of the system and achieve a sustained-release effect. Through the above structural design, the inorganic antibacterial components and the organic active components form a synergistic system, thereby improving the overall antibacterial effect and the stability of use.

[0047] Compared with the prior art, the present invention has at least the following beneficial effects:

[0048] (1) After adsorbing copper ions, the dispersibility of nano-copper or cuprous oxide nanoparticles on the surface of biomass carbon carrier is improved and agglomeration is reduced by pre-oxidation fixation and carbonization in situ reduction.

[0049] (2) During the secondary heat treatment, the organic carbon source preferentially grows on the surface of the copper nanoparticles or cuprous oxide particles and forms a carbon shell, reducing the exposed area of ​​the copper nanoparticles or cuprous oxide particles and reducing the risk of rapid release of copper ions.

[0050] (3) The distribution of zinc oxide nanoparticles in oyster shell matrix is ​​achieved through interlayer confinement structure, which helps to improve its dispersion uniformity and structural stability and inhibit the aggregation of zinc oxide nanoparticles.

[0051] (4) The stability of the composite structure is improved by coating the composite system with polysaccharides;

[0052] (5) The environmentally friendly raw materials used in this invention are relatively simple to prepare. The prepared products can replace antibiotics in feed, avoiding the risk of antibiotic residues in food and livestock farming, and have good application prospects. Attached Figure Description

[0053] Figure 1 Transmission electron microscopy (TEM) image of the core-shell structured copper-carbon nanoparticles prepared in Example 1.

[0054] Figure 2 Transmission electron microscopy (TEM) image of the core-shell copper-carbon nanoparticles loaded on biomass carbon prepared in Example 1.

[0055] Figure 3 Scanning electron microscope image of oyster shell powder loaded with zinc oxide prepared in Example 1.

[0056] Figure 4 The image shows the XRD pattern of the zinc oxide-loaded oyster shell powder prepared in Example 1. Detailed Implementation

[0057] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0058] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0059] Example 1

[0060] (1) Preparation of copper-carbon composite materials

[0061] Poplar wood powder (particle size 100–200 μm) was added to a 0.1 mol / L copper sulfate solution at a liquid-to-solid ratio of 10:1. The mixture was magnetically stirred at 60 °C for 6 h to allow copper ions to fully penetrate the porous structure of the wood fibers. After filtration, the mixture was dried at 80 °C for 12 h to obtain a copper-loaded biomass precursor. This precursor was placed in a tube furnace and pre-oxidized at 280 °C for 2 h in air to induce preliminary pyrolysis of the biomass and fix the copper ion distribution. Subsequently, nitrogen gas (flow rate 100 mL / min) was switched to carbonization at 600 °C for 3 h, causing in-situ reduction of copper ions to form nano-copper or cuprous oxide particles, which were then uniformly loaded onto the surface of the biomass carbon carrier to obtain a primary copper-carbon composite material.

[0062] The obtained primary copper-carbon composite material was immersed in a 1 wt% glucose solution for 12 h (liquid-solid ratio 10:1), dried, and then carbonized at 600 °C for 2 h under a nitrogen atmosphere. This allowed the carbon source to preferentially deposit on the surface of nano-copper or cuprous oxide particles and form a carbon shell, thus obtaining a core-shell structured copper-carbon composite material.

[0063] (2) Preparation of zinc-calcium composite particles

[0064] After removing impurities and cleaning, the oyster shells were dried at 105℃ for 12 hours and then pulverized to a particle size of 5-20 μm. The resulting oyster shell powder was added to a 0.2 mol / L zinc sulfate solution with a liquid-to-solid ratio of 10:1 and soaked at room temperature for 8 hours, allowing zinc ions to diffuse into the interlayer pore structure of the oyster shell and be adsorbed.

[0065] After filtration, the mixture was dried at 80℃ for 12 h, and then calcined at 600℃ for 4 h in a muffle furnace to convert zinc salt into zinc oxide nanoparticles in situ within the interlayer pores of the oyster shell, thus obtaining interlayer confined structure zinc-calcium composite particles.

[0066] (3) Preparation of antibiotic-free feed additives

[0067] Weigh out 40 g of copper-carbon composite material, 30 g of zinc-calcium composite granules, 30 g of plant polyphenols (15 g tea polyphenols + 15 g eugenol), 8 g of ferrous sulfate, and 12 g of carrageenan. Add the above components to deionized water (solid-liquid ratio 1:8) and stir at 90℃ for 3 h to fully dissolve the carrageenan and form a coating network structure on the surface of each particle. Spray dry the powder (inlet air temperature 160℃, outlet air temperature 80℃) to obtain the antibiotic-free feed additive.

[0068] (4) Preparation of shrimp aquaculture feed

[0069] The above-mentioned antibiotic-free feed additives were added to the basic feed at 0.5 wt% to prepare shrimp aquaculture feed.

[0070] Basic feed composition: 25kg fish meal, 20kg soybean meal, 15kg wheat flour, 8kg corn gluten meal, 6kg wheat bran, 3kg fish oil, 1kg soybean lecithin, 1.2kg calcium dihydrogen phosphate, 0.5kg compound vitamins, and 0.3kg compound minerals.

[0071] Experimental group: The antibiotic-free feed additive of this embodiment was added at 0.5% of the total feed, for a total of approximately 0.4 kg;

[0072] Control group (antibiotic group): Florfenicol 50mg / kg feed was added, for a total of about 4g.

[0073] Figure 1 Transmission electron microscopy (TEM) image of the core-shell structured copper-carbon nanoparticles prepared in Example 1. Figure 1 As can be seen, the copper nanoparticles or cuprous oxide particles in the copper-carbon composite material obtained in Example 1 exhibit a relatively clear core-shell structure, with the dark inner region representing the copper core and the lighter outer coating layer representing the carbon shell. This result indicates that a continuous carbon layer can be formed on the surface of copper-based nanoparticles through a secondary carbon source immersion and heat treatment process, thereby obtaining a core-shell structured copper-carbon composite material. This structure helps improve the dispersibility of the copper nanoparticles, reduces direct contact between particles, decreases the tendency to agglomerate, and contributes to improving the structural stability of the copper active component.

[0074] Figure 2 The image shows a transmission electron microscope (TEM) image of the copper-carbon composite material prepared in Example 1.

[0075] Figure 3 Scanning electron microscope (SEM) image of the zinc oxide-loaded oyster shell powder prepared in Example 1. Figure 3As can be seen, the oyster shell-based composite particles obtained in Example 1 retain the original layered stacking and porous surface characteristics of oyster shells, with relatively uniformly distributed nanoparticles observed on their surface and in the interlayer pore areas. Combined with the preparation process of the example, it can be known that these nanoparticles are zinc oxide particles generated in situ and loaded into the interlayer structure of oyster shells. The above results indicate that the calcium carbonate matrix derived from oyster shells can serve as a natural interlayer confinement template, enabling zinc oxide nanoparticles to form a relatively uniform distribution within their interlayer pores, thereby helping to improve the aggregation phenomenon of nano-zinc oxide and enhance the structural stability of the composite particles.

[0076] Figure 4 XRD pattern of oyster shell powder loaded with zinc oxide prepared in Example 1. Figure 4 As can be seen, in addition to the characteristic diffraction peaks of the calcium carbonate matrix derived from oyster shells, characteristic diffraction peaks of zinc oxide also appeared in the sample, indicating that the zinc salt was successfully converted into zinc oxide and loaded into the oyster shell matrix after calcination. This result is consistent with the observation results of scanning electron microscopy, demonstrating that the immersion adsorption-calcination conversion method used in this invention can achieve in-situ construction of zinc oxide in the interlayer structure of oyster shells, thereby obtaining zinc-calcium composite particles with interlayer confined structure.

[0077] Example 2

[0078] (1) Preparation of copper-carbon composite materials

[0079] Bamboo powder (particle size 80-150 μm) was added to a 0.15 mol / L copper sulfate solution at a liquid-to-solid ratio of 10:1. The mixture was magnetically stirred at 70℃ for 5 h to adsorb copper ions into the porous structure of the biomass. After filtration, the mixture was dried at 90℃ for 10 h to obtain a copper-loaded biomass precursor.

[0080] The precursor was placed in a tube furnace and pre-oxidized at 300°C for 1.5 h in an air atmosphere to allow the biomass to undergo preliminary pyrolysis and fix the distribution of copper ions. Then, the atmosphere was switched to nitrogen (flow rate 100 mL / min) and carbonized at 650°C for 2.5 h to reduce copper ions in situ to generate nano-copper or cuprous oxide particles, which were then loaded onto the surface of the biomass carbon carrier to obtain a primary copper-carbon composite material.

[0081] The obtained primary copper-carbon composite material was immersed in a 2 wt% glucose solution for 10 h (liquid-solid ratio 10:1), dried, and then carbonized again at 650 °C for 2 h under a nitrogen atmosphere. This allowed the carbon source to preferentially deposit on the surface of the nano-copper or cuprous oxide particles and form a thicker carbon shell, thus obtaining a core-shell structured copper-carbon composite material.

[0082] (2) Preparation of zinc-calcium composite particles

[0083] After removing impurities and cleaning, the oyster shells were dried at 105℃ for 12 hours and then crushed to a particle size of 10-30 μm. The resulting oyster shell powder was added to a 0.3 mol / L zinc sulfate solution with a liquid-to-solid ratio of 10:1 and allowed to stand and soak at room temperature for 10 hours, allowing zinc ions to diffuse into the interlayer pores of the oyster shell and be adsorbed.

[0084] After filtration, the mixture was dried at 80℃ for 12 h, and then calcined in a muffle furnace at 650℃ for 3 h to allow the zinc salt to be converted into zinc oxide nanoparticles in situ within the interlayer pores of the oyster shell, thus obtaining interlayer confined structure zinc-calcium composite particles.

[0085] (3) Preparation of antibiotic-free feed additives

[0086] Weigh out by weight:

[0087] 45 g copper-carbon composite material

[0088] Zinc-calcium compound granules 25 g

[0089] Plant polyphenols (20 g tea polyphenols + 10 g tannins) 30 g

[0090] 6 g ferrous sulfate

[0091] Sodium alginate 14 g

[0092] The above components were added to deionized water (solid-liquid ratio 1:8) and stirred at 85°C for 2.5 h to fully dissolve sodium alginate and form a coating structure on the surface of each particle. Spray drying (inlet air temperature 160°C, outlet air temperature 80°C) was used to obtain powder, which is the antibiotic-free feed additive.

[0093] (4) Preparation of livestock and poultry feed

[0094] The above antibiotic-free feed additives were added to the basal feed at 1.0 wt% for use in broiler feed.

[0095] Basic feed composition: 55 kg corn, 25 kg soybean meal, 5 kg fish meal, 5 kg wheat bran, 2 kg vegetable oil, 1.5 kg limestone powder, 1.0 kg dicalcium phosphate, 0.5 kg compound vitamins, and 0.5 kg compound minerals.

[0096] Experimental group: Added 1.0 wt% of the antibiotic-free feed additive from this embodiment;

[0097] Control group (antibiotic group): chlortetracycline antibiotic was added at a dose of 75 mg / kg.

[0098] Example 3

[0099] (1) Preparation of copper-carbon composite materials

[0100] Corn straw powder (particle size 100-250 μm) was added to a 0.08 mol / L copper sulfate solution at a liquid-to-solid ratio of 10:1. The mixture was stirred and adsorbed at 50℃ for 8 h to allow copper ions to fully enter the porous structure of the biomass and undergo complexation adsorption. After filtration, the mixture was dried at 80℃ for 12 h to obtain a biomass precursor loaded with copper ions.

[0101] The precursor was placed in a tube furnace and pre-oxidized at 270°C for 2 h in an air atmosphere to allow the biomass to undergo preliminary pyrolysis and fix the distribution of copper ions. Then, the atmosphere was switched to nitrogen (flow rate 100 mL / min) and carbonized at 550°C for 3 h to reduce copper ions in situ to generate nano-copper or cuprous oxide particles, which were then loaded onto the surface of the biomass carbon carrier to obtain a primary copper-carbon composite material.

[0102] The obtained primary copper-carbon composite material was immersed in a 1.5 wt% starch solution (liquid-solid ratio 10:1) for 12 h, dried, and then carbonized again at 550 °C for 2 h under a nitrogen atmosphere. This process preferentially deposited the carbon source on the surface of the nano-copper or cuprous oxide particles, forming a carbon shell layer, thus obtaining a core-shell structured copper-carbon composite material.

[0103] (2) Preparation of zinc-calcium composite particles

[0104] Oyster shells were cleaned, dried (105℃, 12 h) and pulverized to a particle size of 5-15 μm. The resulting oyster shell powder was added to a 0.25 mol / L zinc nitrate solution with a liquid-to-solid ratio of 10:1 and soaked at room temperature for 6 h to allow zinc ions to diffuse into the interlayer pore structure of the oyster shell and be adsorbed.

[0105] The mixture was filtered and dried at 80℃ for 12 h, and then calcined at 600℃ for 5 h in a muffle furnace to convert zinc salt into zinc oxide nanoparticles in situ within the interlayer pores of the oyster shell, thus obtaining interlayer confined structure zinc-calcium composite particles.

[0106] (3) Preparation of antibiotic-free feed additives

[0107] Weigh out by weight:

[0108] 35 kg of copper-carbon composite material

[0109] 35 kg of zinc-calcium compound granules

[0110] Plant polyphenols (10 kg proanthocyanidins + 20 kg catechins) 30 kg

[0111] 7 kg of amino acid chelated iron

[0112] 13 kg of chitosan

[0113] The above components were added to deionized water (solid-liquid ratio 1:8) and stirred at 95°C for 4 h to allow the chitosan to fully dissolve and form a coating layer on the surface of each particle.

[0114] Subsequently, freeze-drying (pre-freezing at -50℃ for 12 h, followed by vacuum sublimation for 48 h) was performed to obtain porous powder, which is the antibiotic-free feed additive.

[0115] (4) Preparation of pet food

[0116] The above antibiotic-free feed additives were added to the pet dog food at a rate of 0.8 wt%.

[0117] Basic feed composition: 30 kg chicken meal, 20 kg corn, 15 kg rice, 10 kg soybean meal, 5 kg animal fat, 2 kg vitamin and mineral premix, etc.

[0118] Experimental group: 0.8 wt% of the antibiotic-free feed additive from this embodiment was added.

[0119] Control group (blank group): No antibiotics or antibiotic additives were added.

[0120] Comparative Example 1: Core-shell-less copper-carbon system

[0121] (1) Preparation of copper-carbon composite materials

[0122] Poplar wood powder (particle size 100-200 μm) was added to a 0.1 mol / L copper sulfate solution at a liquid-to-solid ratio of 10:1. The mixture was magnetically stirred at 60℃ for 6 h to adsorb copper ions into the biomass structure. The mixture was then filtered and dried at 80℃ for 12 h to obtain a copper-loaded biomass precursor.

[0123] The precursor was placed in a tube furnace and pre-oxidized at 280°C for 2 h in an air atmosphere; then carbonized at 600°C for 3 h in a nitrogen atmosphere to obtain biomass carbon material loaded with nano-copper or cuprous oxide.

[0124] (2) Preparation of zinc-calcium composite particles

[0125] Same as Example 1.

[0126] (3) Preparation of antibiotic-free feed additives

[0127] Prepared according to the formula and process in Example 1.

[0128] (4) Application

[0129] Add it to shrimp feed according to the method in Example 1.

[0130] Comparative Example 2: ZnO system without interlayer confinement structure

[0131] (1) Preparation of copper-carbon composite materials

[0132] Same as Example 1.

[0133] (2) Preparation of zinc-calcium composite particles (without interlayer confinement)

[0134] The oyster shells were cleaned, dried, and crushed to a particle size of 5–20 μm;

[0135] Commercial nano zinc oxide (particle size 10-50 nm) was directly mechanically mixed with oyster shell powder at a mass ratio of 1:4 and mechanically stirred at room temperature for 2 h to obtain a ZnO / oyster shell mixture.

[0136] (3) Preparation of antibiotic-free feed additives

[0137] The preparation was carried out according to the formulation ratio and process conditions of Example 1.

[0138] (4) Application

[0139] Add it to shrimp feed according to the method in Example 1.

[0140] Table 1 shows the inhibition rates of different samples prepared in the examples against the two bacteria.

[0141]

[0142] Table 2. Duration of antimicrobial activity against E. coli in the samples corresponding to the examples.

[0143]

[0144] Table 3 Cu content of different samples prepared in the examples in deionized water at pH 6 2+ Cumulative release (unit: mg / L)

[0145]

[0146] Table 4. Mold and oxidative stability of the blank group, antibiotic group, and Example 1 (antibiotic-free group) after 30 days of storage.

[0147]

[0148] Control group: basal feed; Antibiotic group: florfenicol; Example 1: Antibiotic-free group

[0149] As shown in Table 1, Examples 1, 2, and 3 all exhibited high antibacterial rates against *Escherichia coli* and *Staphylococcus aureus*, with Example 1 showing the best antibacterial effect, achieving inhibition rates of 96.8 ± 1.2% against *Escherichia coli* and 97.5 ± 1.0% against *Staphylococcus aureus*. In contrast, Comparative Examples 1 and 2 showed significantly lower inhibition rates, with Comparative Example 2 showing the lowest, at only 84.3 ± 2.4% against *Escherichia coli* and 86.5 ± 2.1% against *Staphylococcus aureus*. These results indicate that the composite structure system constructed in this invention helps improve the overall antibacterial performance of the material. The superior performance of the example samples compared to the comparative examples demonstrates that the introduction of the core-shell copper-carbon composite material and the interlayer confined zinc-calcium composite particles plays a positive role in enhancing the antibacterial effect of the composite system. In particular, Example 1, with its more rational structural construction and proportioning of each component, exhibited superior broad-spectrum antibacterial ability.

[0150] As shown in Table 2, Examples 1, 2, and 3 maintained high antibacterial levels from 12 to 72 hours. Example 1 maintained an antibacterial rate of 93.9% at 72 hours, Example 2 at 94.1%, and Example 3 at 93.0%. However, the sustained antibacterial performance of Comparative Examples 1 and 2 decreased significantly, especially Comparative Example 1 at 72.4% and Comparative Example 2 at 74.8% at 72 hours. These results indicate that the composite system constructed in this invention not only possesses good initial antibacterial ability but also good sustained antibacterial performance. Table 4 shows that this sustained antibacterial characteristic is related to the controlled release behavior of the copper active component and the stable distribution of zinc oxide in the interlayer structure of the oyster shell. Comparative Example 1, lacking a carbon shell structure, experienced faster release of the copper component, leading to a more significant decrease in antibacterial ability in the later stages. Example 2, with its relatively thick carbon shell, exhibited a more pronounced slow-release effect, thus maintaining a high antibacterial rate even after 72 hours.

[0151] As can be seen from Table 3, the Cu in Examples 1, 2 and 3 2+ The cumulative release was generally lower than that of Comparative Example 1, with Comparative Example 1 showing lower Cu release at 6 h, 12 h, 24 h, 48 h, and 72 h. 2+ The cumulative release amounts reached 0.95, 1.68, 2.74, 3.61, and 4.08 mg / L, respectively, which were the highest among all groups. In contrast, the Cu releases at each time point in Example 2 were significantly lower. 2+ The lowest release levels were observed in Examples 1, 2, and 3, at 0.31, 0.60, 1.02, 1.68, and 2.18 mg / L, respectively, indicating the most significant sustained-release effect. The release levels of Examples 1 and 3 were between those of Examples 2 and Comparative Example 1. These results demonstrate that the carbon shell in the core-shell structure has a significant regulatory effect on the copper active component, effectively reducing Cu... 2+The rapid release of copper components was observed. In particular, Example 2, with its thicker carbon shell providing stronger protection for the copper core, exhibited a more pronounced slow-release characteristic. Conversely, in Comparative Example 1, the lack of a carbon shell allowed the copper component to be released more easily into the medium, resulting in the fastest release rate. These results further demonstrate that constructing a core-shell structured copper-carbon composite material helps improve the release behavior of the active copper component and the stability of the system.

[0152] As shown in Table 4, after 30 days of storage, the total mold count, acid value, and peroxide value of the antibiotic-free group in Example 1 were all lower than those of the blank group and the antibiotic group. Specifically, the total mold count in the Example 1 group was 3.22 ± 0.10 log CFU·g. -1 The value was significantly lower than that of the control group (4.21 ± 0.14 log CFU·g). -1 The antibiotic group had 3.76 ± 0.12 log CFU·g -1 The acid value and peroxide value were 4.01 ± 0.16 mg KOH·g, respectively. -1 and 6.84 ± 0.28 meq·kg -1 The results also indicate that the levels of these additives were lower than those of the other two groups. This demonstrates that the antibiotic-free feed additive described in this invention exhibits good anti-mold and antioxidant stabilizing effects during feed storage. On one hand, the inorganic active components such as copper and zinc in the composite system, along with plant polyphenols, can jointly inhibit mold growth; on the other hand, polyphenols themselves possess certain antioxidant properties, which can, to some extent, slow down the lipid oxidation process in feed. Compared to the antibiotic group, the group in Example 1 performed better in inhibiting mold and improving feed oxidative stability, indicating that the antibiotic-free feed additive described in this invention has the potential to replace traditional antibiotics or anti-mold components.

[0153] This invention is not limited to the specific embodiments described above. Any reasonable modifications and improvements made based on the core technical solution of this invention, including but not limited to the following aspects, should be considered to fall within the protection scope of this invention. All technical solutions implemented under the guidance of the technical concept of this invention through equivalent substitution or adaptive modification are within the protection scope of this invention.

Claims

1. An antibiotic-free feed additive, characterized in that, It includes the following components: copper-carbon composite material, zinc-calcium composite particles, iron salt, plant polyphenols and polysaccharides; The copper-carbon composite material includes a biomass carbon carrier and core-shell copper-carbon nanoparticles dispersed and loaded on its surface; the core-shell copper-carbon nanoparticles include copper nanoparticles or cuprous oxide nanoparticles and a carbon shell layer covering their surface; the zinc-calcium composite particles include a calcium carbonate matrix derived from oyster shells and zinc oxide nanoparticles distributed in the interlayer pores; the polysaccharide is distributed on the surface of the copper-carbon composite material and the zinc-calcium composite particles, forming a continuous or semi-continuous coating layer.

2. The antibiotic-free feed additive according to claim 1, characterized in that, The components, by mass, include: 30-50 parts copper-carbon composite material; 20-40 parts zinc-calcium composite particles; 5-10 parts iron salt; 25-40 parts plant polyphenols; and 10-15 parts polysaccharides.

3. The antibiotic-free feed additive according to claim 1, characterized in that: The diameter of the copper nanoparticles or cuprous oxide nanoparticles is 10–100 nm, the thickness of the carbon shell layer is 2–10 nm, the loading amount of the core-shell structured copper-carbon nanoparticles on the biomass carbon support is 0.01–0.10 g / g, the particle size of the zinc oxide nanoparticles is 2–20 nm, and the interlayer pore size of the calcium carbonate matrix derived from oyster shells is 1–10 μm.

4. The antibiotic-free feed additive according to claim 1, characterized in that: The plant polyphenols are selected from one or more of guaiacol, cinnamylphenol, vanillin, eugenol, p-hydroxyphenol, tea polyphenols, tannic acid, proanthocyanidins and catechins; the polysaccharides are selected from one or more of carrageenan, sodium alginate, chitosan, pectin and gum arabic; the iron salts are selected from one or more of ferrous sulfate, ferric citrate and amino acid iron.

5. A method for preparing the antibiotic-free feed additive according to claim 1, characterized in that, Includes the following steps: (1) Preparation of copper-carbon composite material: After copper ions are adsorbed onto biomass powder, they are pre-oxidized and carbonized to reduce copper ions in situ to form biomass carbon loaded with nano-copper or cuprous oxide nanoparticles; the biomass carbon loaded with nano-copper or cuprous oxide nanoparticles is then soaked in an organic carbon source solution and carbonized again to obtain a copper-carbon composite material including biomass carbon carrier and core-shell structured copper-carbon nanoparticles dispersed on its surface. (2) Preparation of zinc-calcium composite particles: Zinc ions are adsorbed in the interlayer pore structure of calcium carbonate matrix derived from oyster shells. After calcination, the zinc salt is converted in situ in the interlayer pores to form zinc oxide nanoparticles, thus obtaining zinc-calcium composite particles with interlayer confined structure. (3) Disperse copper-carbon composite material, zinc-calcium composite particles, iron salt, plant polyphenols and polysaccharides in an aqueous phase; (4) Stir at 80-95℃ for 2-4 hours to allow the polysaccharide to form a coating structure; (5) Antibiotic-free feed additives are obtained by spray drying or freeze drying.

6. The preparation method according to claim 5, characterized in that, The copper-carbon composite material is prepared by the following steps: (1) The biomass powder is soaked in a copper salt solution and adsorbed at 50-80℃ for 4-8 hours to obtain the biomass precursor; (2) The biomass precursor is pre-oxidized in air at 250-300°C for 1-3 hours; (3) Carbonize at 500~700℃ for 2~4 hours under nitrogen protection to obtain biomass carbon loaded with nano-copper or cuprous oxide nanoparticles; (4) The obtained material is immersed in an organic carbon source solution, dried, and then carbonized at 500-700°C under nitrogen protection to deposit the carbon source on the surface of nano-copper or cuprous oxide nanoparticles and form a carbon shell.

7. The preparation method according to claim 5, characterized in that: The biomass powder is one or more of wood powder, bamboo powder, cellulose, lignin, and seaweed powder; the copper salt is selected from one or more of copper sulfate, copper nitrate, and copper chloride; and the organic carbon source is selected from one or more of glucose, sucrose, starch, and dextrin.

8. The preparation method according to claim 5, characterized in that, The zinc-calcium composite particles are prepared through the following steps: (1) The oyster shells are cleaned, dried and crushed to obtain oyster shell powder; (2) The oyster shell powder is soaked in a zinc salt solution so that zinc ions are adsorbed into its interlayer pore structure; (3) After drying, calcination is carried out at 500~700℃ for 2~6 hours to convert zinc salt into zinc oxide nanoparticles in situ within the interlayer channels, thereby obtaining zinc-calcium composite particles with interlayer confined structure.

9. The application of the antibiotic-free feed additive according to any one of claims 1 to 4, characterized in that: The feed is aquatic feed, livestock and poultry feed, or pet feed.

Images