A strontium-containing calcium sulfate composite feed additive and a preparation method thereof

Abstract

The application discloses a kind of strontium-containing calcium sulfate composite feed additive and preparation method thereof in the field of feed additive, and the preparation raw materials of the composite feed additive include the following components by weight: strontium calcium sulfate 5-10 parts, carboxymethyl chitosan 1-2 parts, hyaluronic acid 0.1-0.2 parts.The application prepares strontium calcium sulfate by hydrothermal method, using strontium chloride and calcium chloride as raw materials, activates strontium calcium sulfate using N-acetyl cysteine, coats carboxymethyl chitosan and hyaluronic acid on the surface of strontium calcium sulfate, improves the slow-release performance of strontium calcium sulfate, so as to slow down the burst release of strontium element and calcium element in feed, and avoid the toxic reaction caused by excessive release of strontium element and calcium element to the body.

Description

Technical Field

[0001] This invention belongs to the field of feed additive technology, specifically referring to a strontium-calcium sulfate compound feed additive and its preparation method. Background Technology

[0002] Calcium sulfate, commonly known as gypsum, usually exists in the form of calcium sulfate dihydrate. It is used as an additive in animal feed and aquaculture, serving as a binder, anti-caking agent, stabilizer, and emulsifier for ruminants, poultry, and aquatic animals. It is officially listed in the Ministry of Agriculture and Rural Affairs' "List of Feed Additive Varieties (2023)," and is widely used, especially in pet food. After digestion and decomposition by animals, calcium sulfate provides calcium and sulfur. Calcium is one of the essential mineral macroelements for animals. While calcium sulfate has low solubility in the gastrointestinal tract, it dissolves slowly, providing free calcium ions. Once completely dissolved, the calcium ion aqueous solution is the main component, causing less irritation to the gastrointestinal environment and promoting full nutrient absorption. This substance provides sulfur, which is beneficial for the synthesis of cystine, cysteine, and methionine in animals. It is also a component of heparin, taurine, and bile, playing an important role in the body's detoxification process. Strontium is chemically reactive, readily reacting with oxygen and water. In nature, it mainly exists as strontium sulfate and strontium carbonate, while in animals, it mainly exists as strontium ions. Strontium promotes bone health, increases bone density, promotes bone formation and resorption, regulates reproductive health, and improves fertilization success rate and live birth rate. Strontium also enhances immunity. In animal feed, strontium often exists as strontium perchlorate and strontium chloride, but its bioavailability is low, and excessive addition of strontium can easily cause poisoning. Summary of the Invention

[0003] To address the above issues and overcome the shortcomings of existing technologies, this invention provides a strontium-containing calcium sulfate compound feed additive and its preparation method. This invention prepares strontium-containing calcium sulfate using a hydrothermal method with strontium chloride and calcium chloride as raw materials. N-acetylcysteine ​​is used to activate the strontium-containing calcium sulfate, and carboxymethyl chitosan and hyaluronic acid are coated onto its surface to improve the slow-release performance of the strontium-containing calcium sulfate. This slows down the sudden release of strontium and calcium from the feed, avoiding excessive release of strontium and calcium that could cause poisoning in the body.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention proposes a compound feed additive containing strontium calcium sulfate, wherein the raw materials for preparing the compound feed additive include the following components in parts by weight: 5-10 parts of strontium calcium sulfate, 1-2 parts of carboxymethyl chitosan, and 0.1-0.2 parts of hyaluronic acid;

[0005] Preferably, the method for preparing the strontium calcium sulfate specifically includes the following steps:

[0006] S1. Dissolve strontium chloride and calcium chloride in deionized water, mix well, add sodium sulfate, stir at 200-220 rpm for 30-40 min, adjust pH to 4-5, and obtain strontium calcium sulfate precursor solution;

[0007] Preferably, in step S1, the raw materials for preparing the strontium calcium sulfate precursor solution are the following components in parts by weight: 0.15-0.6 parts of strontium chloride, 0.9-1 parts of calcium chloride, and 1.4-1.8 parts of sodium sulfate;

[0008] S2. Raise the temperature of the strontium calcium sulfate precursor solution prepared in step S1 to 110-120℃ and perform hydrothermal reaction for 2-2.5 hours. After the temperature of the reaction system drops to 100℃, filter the solution, wash the precipitate with boiling water and anhydrous ethanol, dry it in an oven to obtain strontium calcium sulfate, grind it, and pass it through a 300-mesh sieve for later use.

[0009] This invention also provides a method for preparing a strontium-calcium sulfate-containing compound feed additive, specifically including the following steps:

[0010] ① Place calcium strontium sulfate in a beaker, add deionized water to disperse it, add N-acetylcysteine ​​and mix well. Raise the reaction temperature to 80-90℃, stir at 400-500 rpm for 4-6 hours, centrifuge at 5000 rpm for 20 minutes, collect the precipitate, disperse it in sodium hydroxide solution, keep the reaction temperature at 30-35℃, and the reaction time at 30-40 minutes. After the reaction system cools to room temperature, filter and collect the precipitate to obtain activated calcium strontium sulfate.

[0011] Preferably, in step ①, the mass ratio of calcium strontium sulfate to N-acetylcysteine ​​is 4:1-2;

[0012] Preferably, in step ①, the mass concentration of sodium hydroxide in the sodium hydroxide solution is 5-10 g / L, and the mass-to-volume ratio of calcium strontium sulfate to sodium hydroxide solution is 0.06-0.08 g / mL.

[0013] ② Place carboxymethyl chitosan in deionized water, ultrasonically disperse and mix evenly, add EDC and NHS, and stir at 450-500 rpm for 4-5 h at room temperature. Then add the activated strontium calcium sulfate prepared in step ① and continue stirring for 10-12 h. After the reaction is complete, centrifuge at 5000 rpm for 10 min, collect the precipitate, and dry it under vacuum to obtain carboxymethyl chitosan modified strontium calcium sulfate.

[0014] Preferably, in step ②, the mass ratio between EDC and carboxymethyl chitosan is 2.5-3:1, and the mass ratio between NHS and carboxymethyl chitosan is 1.5-2:1.

[0015] ③ Disperse hyaluronic acid evenly in deionized water, add carboxymethyl chitosan-modified calcium strontium sulfate prepared in step ②, add EDC and NHS, stir at 500-550 rpm for 20-24 h, centrifuge at 5000 rpm for 15 min, collect the precipitate, freeze dry to obtain modified calcium strontium sulfate powder;

[0016] Preferably, in step ③, the mass ratio of EDC to hyaluronic acid is 4-5:1, and the mass ratio of NHS to hyaluronic acid is 2.5-3:1.

[0017] ④ Mix the modified strontium calcium sulfate prepared in step ③ with deionized water and inject it into a mold with a diameter of 10 mm and a height of 3 mm. After solidification, a composite feed additive is obtained.

[0018] Preferably, in step ④, the mass-to-volume ratio of the modified strontium calcium sulfate to deionized water is 1-1.5 g / mL.

[0019] The beneficial effects achieved by this invention are as follows:

[0020] This invention provides a strontium-containing calcium sulfate compound feed additive and its preparation method. The invention uses a hydrothermal method to prepare strontium-containing calcium sulfate from strontium chloride and calcium chloride. N-acetylcysteine ​​is used to activate the strontium-containing calcium sulfate, and carboxymethyl chitosan and hyaluronic acid are coated on its surface to improve the slow-release performance of the strontium-containing calcium sulfate, thereby slowing down the burst release of strontium and calcium in the feed and avoiding the toxic reaction caused by excessive release of strontium and calcium. This invention utilizes N-acetylcysteine, through its carboxyl group, to interact with calcium and strontium ions. Electrostatic forces link N-acetylcysteine ​​to calcium strontium sulfate. A mild alkaline hydrolysis reaction deacetylates the strontium sulfate, yielding calcium strontium sulfate with amino active groups. Hydrogen bonds between the amino group and carboxymethyl chitosan coat the surface of the calcium strontium sulfate. The varying swelling properties of hyaluronic acid under different pH conditions result in different release rates of calcium and strontium ions, improving the sustained-release performance of the compound feed additive and preventing excessive absorption of these ions. Attached Figure Description

[0021] Figure 1 This is a SEM image of the compound feed additive prepared in Example 1 of the present invention;

[0022] Figure 2The feed additive Ca prepared in Examples 1-3 and Comparative Examples 1-2 2+ Release result diagram;

[0023] Figure 3 The feed additive Sr prepared in Examples 1-3 and Comparative Examples 1-2 2+ Release result diagram;

[0024] Figure 4 The Ca content of the feed additives prepared in Examples 1-3 and Comparative Examples 1-2 under different pH conditions 2+ Release result diagram.

[0025] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the experimental materials and test strains used in the following examples were purchased from commercial channels.

[0029] Example 1

[0030] This embodiment provides a strontium-calcium sulfate-containing compound feed additive and its preparation method. The raw materials for preparing the compound feed additive include the following components in parts by weight: 5 parts strontium-calcium sulfate, 2 parts carboxymethyl chitosan, and 0.1 parts hyaluronic acid.

[0031] The preparation method of strontium calcium sulfate specifically includes the following steps:

[0032] S1. Accurately weigh 0.15g of strontium chloride and 1g of calcium tetrachloride dihydrate into a beaker, add 100mL of deionized water, mix well, then accurately weigh 1.4g of sodium sulfate and add it to the reaction system. Stir the reaction at 220rpm for 30min, then adjust the pH to 5 with 0.1mol / L hydrochloric acid solution to obtain the strontium calcium sulfate precursor solution.

[0033] S2. Raise the temperature of the strontium calcium sulfate precursor solution prepared in step S1 to 110-120℃ and perform hydrothermal reaction for 2-2.5 hours. After the temperature of the reaction system drops to 100℃, filter the solution, wash the precipitate with boiling water and anhydrous ethanol, dry it in an oven to obtain strontium calcium sulfate, grind it, and pass it through a 300-mesh sieve for later use.

[0034] This embodiment also provides a method for preparing a strontium calcium sulfate compound feed additive, which specifically includes the following steps:

[0035] ① Accurately weigh 4g of calcium strontium sulfate and place it in a beaker. Add 50mL of deionized water to the beaker and ultrasonically disperse the calcium strontium sulfate at 400W. Add 1g of N-acetylcysteine ​​and continue ultrasonic dispersion. After uniform dispersion, raise the reaction temperature to 90℃ and stir at 400rpm for 5h. After the reaction cools to room temperature, centrifuge at 5000rpm for 20min. Collect the precipitate and disperse it in 50mL of sodium hydroxide solution with a mass concentration of 5g / mL. Raise the reaction temperature to 35℃ and react for 30min. After the reaction system cools to room temperature, filter and collect the precipitate. Dry it under vacuum at 25℃ to obtain activated calcium strontium sulfate.

[0036] ② Accurately weigh 1.6g of carboxymethyl chitosan and disperse it in 100mL of deionized water. Place it under 400W power for ultrasonic dispersion. After uniform dispersion, add 4g of EDC and 2.4g of NHS. Stir at 500rpm for 5h. Add the activated strontium calcium sulfate prepared in step ① and continue stirring for 12h. After the reaction is completed, centrifuge at 5000rpm for 10min, collect the precipitate, and vacuum dry at 25℃ to obtain carboxymethyl chitosan modified strontium calcium sulfate.

[0037] ③ Accurately weigh 0.08g of hyaluronic acid and disperse it in 50mL of deionized water. After the dispersion is uniform, add the carboxymethyl chitosan-modified strontium sulfate prepared in step ② and ultrasonically disperse it uniformly under 400W. Add 0.4g of EDC and 0.2g of NHS, stir and react at 550rpm for 20h, centrifuge at 5000rpm for 15min, collect the precipitate, freeze dry and obtain modified strontium sulfate powder;

[0038] ④ Take 5g of the modified strontium calcium sulfate prepared in step ③, mix it with 5mL of deionized water to form a paste, inject it into a polytetrafluoroethylene mold with a diameter of 10mm and a height of 3mm, and after curing, obtain a composite feed additive.

[0039] Example 2

[0040] This embodiment provides a strontium-calcium sulfate-containing compound feed additive and its preparation method. The raw materials for preparing the compound feed additive include the following components in parts by weight: 8 parts strontium-calcium sulfate, 1.5 parts carboxymethyl chitosan, and 0.15 parts hyaluronic acid.

[0041] The preparation method of strontium calcium sulfate specifically includes the following steps:

[0042] S1. Accurately weigh 0.3g of strontium chloride and 0.9g of calcium tetrachloride dihydrate into a beaker, add 100mL of deionized water, mix well, then accurately weigh 1.4g of sodium sulfate and add it to the reaction system. Stir the reaction at 200rpm for 40min, then adjust the pH to 4.5 with 0.1mol / L hydrochloric acid solution to obtain the strontium calcium sulfate precursor solution.

[0043] S2. Raise the temperature of the strontium calcium sulfate precursor solution prepared in step S1 to 110-120℃ and perform hydrothermal reaction for 2-2.5 hours. After the temperature of the reaction system drops to 100℃, filter the solution, wash the precipitate with boiling water and anhydrous ethanol, dry it in an oven to obtain strontium calcium sulfate, grind it, and pass it through a 300-mesh sieve for later use.

[0044] This embodiment also provides a method for preparing a strontium-calcium sulfate-containing compound feed additive, which specifically includes the following steps:

[0045] ① Accurately weigh 4g of calcium strontium sulfate and place it in a beaker. Add 50mL of deionized water to the beaker and ultrasonically disperse the calcium strontium sulfate at 400W. Add 2g of N-acetylcysteine ​​and continue ultrasonic dispersion. After uniform dispersion, raise the reaction temperature to 80℃ and stir at 500rpm for 4h. After the reaction cools to room temperature, centrifuge at 5000rpm for 20min. Collect the precipitate and disperse it in 70mL of sodium hydroxide solution with a mass concentration of 7.5g / mL. Raise the reaction temperature to 30℃ and react for 30min. After the reaction system cools to room temperature, filter, collect the precipitate, and vacuum dry it at 25℃ to obtain activated calcium strontium sulfate.

[0046] ② Accurately weigh 0.75g of carboxymethyl chitosan and disperse it in 100mL of deionized water. Place it under 400W power for ultrasonic dispersion. After uniform dispersion, add 2.25g of EDC and 1.5g of NHS. Stir at 500rpm for 4h. Add the activated strontium calcium sulfate prepared in step ① and continue stirring for 10h. After the reaction is completed, centrifuge at 5000rpm for 10min, collect the precipitate, and vacuum dry at 25℃ to obtain carboxymethyl chitosan modified strontium calcium sulfate.

[0047] ③ Accurately weigh 0.075g of hyaluronic acid and disperse it in 50mL of deionized water. After the dispersion is uniform, add the carboxymethyl chitosan-modified strontium calcium sulfate prepared in step ② and ultrasonically disperse it uniformly under 400W. Add 0.3g of EDC and 0.2g of NHS, stir and react at 500rpm for 24h, centrifuge at 5000rpm for 15min, collect the precipitate, freeze dry and obtain modified strontium calcium sulfate powder;

[0048] ④ Take 5g of the modified strontium calcium sulfate prepared in step ③, mix it with 7.5mL of deionized water to form a paste, pour it into a polytetrafluoroethylene mold with a diameter of 10mm and a height of 3mm, and after curing, obtain a composite feed additive.

[0049] Example 3

[0050] This embodiment provides a strontium-calcium sulfate-containing compound feed additive and its preparation method. The raw materials for preparing the compound feed additive include the following components in parts by weight: 10 parts strontium-calcium sulfate, 1 part carboxymethyl chitosan, and 0.2 parts hyaluronic acid.

[0051] The preparation method of strontium calcium sulfate specifically includes the following steps:

[0052] S1. Accurately weigh 0.47 g of strontium chloride and 0.8 g of calcium tetrachloride dihydrate into a beaker, add 100 mL of deionized water, mix well, then accurately weigh 1.4 g of sodium sulfate and add it to the reaction system. Stir the reaction at 220 rpm for 30 min, then adjust the pH to 4 with 0.1 mol / L hydrochloric acid solution to obtain the strontium calcium sulfate precursor solution.

[0053] S2. Raise the temperature of the strontium calcium sulfate precursor solution prepared in step S1 to 110-120℃ and perform hydrothermal reaction for 2-2.5 hours. After the temperature of the reaction system drops to 100℃, filter the solution, wash the precipitate with boiling water and anhydrous ethanol, dry it in an oven to obtain strontium calcium sulfate, grind it, and pass it through a 300-mesh sieve for later use.

[0054] This embodiment also provides a method for preparing a strontium-calcium sulfate-containing compound feed additive, which specifically includes the following steps:

[0055] ① Accurately weigh 4g of calcium strontium sulfate and place it in a beaker. Add 50mL of deionized water to the beaker and ultrasonically disperse the calcium strontium sulfate at 400W. Add 1.5g of N-acetylcysteine ​​and continue ultrasonic dispersion. After uniform dispersion, raise the reaction temperature to 85℃ and stir at 450rpm for 6h. After the reaction cools to room temperature, centrifuge at 5000rpm for 20min. Collect the precipitate and disperse it in 60mL of sodium hydroxide solution with a mass concentration of 10g / mL. Raise the reaction temperature to 30℃ and react for 40min. After the reaction system cools to room temperature, filter, collect the precipitate, and vacuum dry at 25℃ to obtain activated calcium strontium sulfate.

[0056] ② Accurately weigh 0.4g of carboxymethyl chitosan and disperse it in 100mL of deionized water. Place it under 400W power for ultrasonic dispersion. After uniform dispersion, add 1g of EDC and 0.6g of NHS. Stir at 450rpm for 5h. Add the activated strontium calcium sulfate prepared in step ① and continue stirring for 12h. After the reaction is completed, centrifuge at 5000rpm for 10min, collect the precipitate, and vacuum dry at 25℃ to obtain carboxymethyl chitosan modified strontium calcium sulfate.

[0057] ③ Accurately weigh 0.08g of hyaluronic acid and disperse it in 50mL of deionized water. After the dispersion is uniform, add the carboxymethyl chitosan-modified strontium calcium sulfate prepared in step ② and ultrasonically disperse it uniformly under 400W. Add 0.32g of EDC and 0.24g of NHS, stir and react at 550rpm for 20h, centrifuge at 5000rpm for 15min, collect the precipitate, freeze dry and obtain modified strontium calcium sulfate powder;

[0058] ④ Take 5g of the modified strontium calcium sulfate prepared in step ③, mix it with 6mL of deionized water to form a paste, inject it into a polytetrafluoroethylene mold with a diameter of 10mm and a height of 3mm, and after curing, obtain a composite feed additive.

[0059] Comparative Example 1

[0060] This comparative example provides a feed additive and its preparation method. The only difference between this example and Example 1 is that the compound feed additive does not include hyaluronic acid, and its components and component content are the same as in Example 1.

[0061] Comparative Example 2

[0062] This comparative example provides a feed additive and its preparation method. The difference between this example and Example 1 is that the preparation method of the compound feed additive does not include step ①, and strontium calcium sulfate is used instead of activated strontium calcium sulfate in step ②.

[0063] Experimental Example 1

[0064] This experiment observes and analyzes the microstructure of the composite feed additive prepared in Example 1. The sample surface is subjected to brittle fracture with liquid nitrogen, and after thorough drying, the sample surface is sputtered with gold. Finally, the surface morphology of the sample is observed using a JSM-6510 scanning electron microscope.

[0065] Figure 1 The image shows an SEM image of the composite feed additive prepared in Example 1 of the present invention. As shown in the figure, the particles of the composite feed additive have a rough surface, are ellipsoidal in shape, and have an average particle size of 80-90 nm.

[0066] Experiment Example 2

[0067] This experiment tested the in vitro release performance of the feed additives prepared in Examples 1-3 and Comparative Examples 1-2. The feed additives prepared in Examples 1-3 and Comparative Examples 1-2 were dispersed in simulated body fluid at a concentration of 10 mg / mL and shaken at 37°C and 150 rpm. Samples of the simulated body fluid were taken at different time points, and the Ca2+ content was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). 2+ and Sr 2+ The concentration;

[0068] Figure 2 The feed additive Ca prepared in Examples 1-3 and Comparative Examples 1-2 2+ The release result diagram, Figure 3 The feed additive Sr prepared in Examples 1-3 and Comparative Examples 1-2 2+ The release results are shown in the figure. The feed additives prepared in Examples 1-3 can continuously release calcium ions and strontium ions within 7 days. The feed additive prepared in Comparative Example 1 can also continuously release calcium ions and strontium ions within 7 days, but the release amount is significantly lower than that in Examples 1-3. The feed additive prepared in Comparative Example 2 reaches equilibrium at 4 days. In the following 3 days, the release amount of calcium ions and strontium ions is significantly reduced. This shows that the feed additives prepared in this invention can slowly release calcium ions and strontium ions in the body environment.

[0069] Figure 4 The Ca content of the feed additives prepared in Examples 1-3 and Comparative Examples 1-2 under different pH conditions 2+ The release results diagram shows the calcium ion release concentration of the feed additives prepared in Examples 1-3 and Comparative Examples 1-2 after 7 days at pH=5.0 and pH=7.4. It can be seen that, under pH=5 conditions, the calcium ion release concentration of the feed additives prepared in Examples 1-3 is significantly lower. 2+ The release concentration was significantly higher than at pH=7.4, compared to the Ca concentration of the feed additive and calcium strontium sulfate described in Comparative Example 1 under different pH conditions. 2+The release concentrations were the same, with the feed additive described in Comparative Example 2 showing a 7.4-fold higher release concentration at pH=5.0.

[0070] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

[0071] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A compound feed additive containing strontium calcium sulfate, characterized in that: The raw materials for preparing the compound feed additive include the following components in parts by weight: 5-10 parts of calcium strontium sulfate, 1-2 parts of carboxymethyl chitosan, and 0.1-0.2 parts of hyaluronic acid; The preparation method of the aforementioned strontium-containing calcium sulfate compound feed additive specifically includes the following steps: ① Place calcium strontium sulfate in a beaker, add deionized water to disperse it, add N-acetylcysteine ​​and mix well. Raise the reaction temperature to 80-90℃, stir at 400-500 rpm for 4-6 hours, centrifuge at 5000 rpm for 20 minutes, collect the precipitate, disperse it in sodium hydroxide solution, keep the reaction temperature at 30-35℃, and the reaction time at 30-40 minutes. After the reaction system cools to room temperature, filter and collect the precipitate to obtain activated calcium strontium sulfate. ② Place carboxymethyl chitosan in deionized water, ultrasonically disperse and mix evenly, add EDC and NHS, and stir at 450-500 rpm for 4-5 h at room temperature. Then add the activated strontium calcium sulfate prepared in step ① and continue stirring for 10-12 h. After the reaction is complete, centrifuge at 5000 rpm for 10 min, collect the precipitate, and dry it under vacuum to obtain carboxymethyl chitosan modified strontium calcium sulfate. ③ Disperse hyaluronic acid evenly in deionized water, add carboxymethyl chitosan-modified calcium strontium sulfate prepared in step ②, add EDC and NHS, stir at 500-550 rpm for 20-24 h, centrifuge at 5000 rpm for 15 min, collect the precipitate, freeze dry to obtain modified calcium strontium sulfate powder; ④ Mix the modified strontium calcium sulfate prepared in step ③ with deionized water and inject it into a mold with a diameter of 10 mm and a height of 3 mm. After solidification, a composite feed additive is obtained.

2. The strontium-containing calcium sulfate compound feed additive according to claim 1, characterized in that: The preparation method of the strontium calcium sulfate specifically includes the following steps: S1. Dissolve strontium chloride and calcium chloride in deionized water, mix well, add sodium sulfate, stir at 200-220 rpm for 30-40 min, adjust pH to 4-5, and obtain strontium calcium sulfate precursor solution; S2. Raise the temperature of the strontium calcium sulfate precursor solution prepared in step S1 to 110-120℃ and perform hydrothermal reaction for 2-2.5 hours. After the temperature of the reaction system drops to 100℃, filter the solution, wash the precipitate with boiling water and anhydrous ethanol, dry it in an oven to obtain strontium calcium sulfate, grind it, and pass it through a 300-mesh sieve for later use.

3. The strontium-containing calcium sulfate compound feed additive according to claim 2, characterized in that: In step S1, the raw materials for preparing the strontium calcium sulfate precursor solution are the following components in parts by weight: 0.15-0.6 parts of strontium chloride, 0.9-1 parts of calcium chloride, and 1.4-1.8 parts of sodium sulfate.

4. The strontium-containing calcium sulfate compound feed additive according to claim 1, characterized in that: In step ①, the mass ratio of calcium strontium sulfate to N-acetylcysteine ​​is 4:1-2; the mass concentration of sodium hydroxide in the sodium hydroxide solution is 5-10 g / L, and the mass-volume ratio of calcium strontium sulfate to sodium hydroxide solution is 0.06-0.08 g / mL.

5. The strontium-containing calcium sulfate compound feed additive according to claim 4, characterized in that: In step ②, the mass ratio between EDC and carboxymethyl chitosan is 2.5-3:1, and the mass ratio between NHS and carboxymethyl chitosan is 1.5-2:

1.

6. The strontium-containing calcium sulfate compound feed additive according to claim 5, characterized in that: In step ③, the mass ratio of EDC to hyaluronic acid is 4-5:1, and the mass ratio of NHS to hyaluronic acid is 2.5-3:

1.

7. The strontium-containing calcium sulfate compound feed additive according to claim 6, characterized in that: In step ④, the mass-to-volume ratio of the modified strontium calcium sulfate to deionized water is 1-1.5 g / mL.

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