An activator for improving nitrogen conversion efficiency in dairy cow feed, its preparation method and application.

Abstract

This application relates to an activator, preparation method, and application in the field of dairy farming technology for improving nitrogen conversion efficiency in dairy cow feed. The activator, a zinc / iron nanomaterial, can efficiently regulate key binding sites of amino acid transporters and small peptide transporters after entering mammary gland cells, thereby effectively improving the amino acid transport efficiency and expression level of amino acid transporters in dairy cow mammary gland cells. Feeding dairy cows with this zinc / iron nanomaterial can effectively improve nitrogen absorption efficiency and increase milk protein content and milk yield without affecting feed intake. The activator provided in this application is a pioneering targeted formulation for regulating the expression activity of cellular amino acid transporters. By optimizing the parameters in the activator preparation process, the resulting zinc / iron nanomaterial can better improve the nitrogen conversion efficiency of dairy cow feed. Furthermore, the activator is both green and low-cost, with broad application prospects.

Description

Technical Field

[0001] This application relates to the field of dairy farming technology, and in particular to an activator, preparation method and application for improving nitrogen conversion efficiency in dairy cattle feed. Background Technology

[0002] In dairy farming, improving nitrogen conversion efficiency (NCE) is crucial for reducing feed costs, minimizing pollution emissions, and alleviating competition for food between humans and livestock. Currently, NCE is primarily improved through supplementation with key amino acids (methionine / lysine), increasing the energy content of dairy cow diets (promoting the conversion of crude protein into amino acids and peptides), and enhancing protein quality (optimizing amino acid and peptide varieties). These methods mainly achieve their goals by maintaining rumen microbial activity or balancing the amino acid balance entering the bloodstream. However, these methods significantly increase feed costs and fail to fundamentally solve the industry's challenge of cost reduction and efficiency improvement.

[0003] The essence of improving nitrogen conversion efficiency in dairy cows lies in the efficient absorption of substances such as amino acids and small peptides by digestive tract cells and mammary gland cells. Improving nitrogen utilization efficiency in dairy cows involves three levels: 1) increasing the supply of total amino acids / small peptides; 2) optimizing the ratio of total amino acids to small peptides; and 3) improving the absorption efficiency of amino acids / small peptides by dairy cow cells. Currently, most research focuses on 1) and 2), while research on regulating the absorption efficiency of amino acids / small peptides by dairy cow cells is relatively limited. Although some previous studies have revealed that hormones, small peptides, and amino acids themselves can regulate the expression levels of amino acid transporters in the mammary glands of dairy cows, ultimately optimizing amino acid absorption efficiency, these substances are expensive, making it uneconomical from the perspective of improving amino acid absorption efficiency. Therefore, developing a class of effective and low-cost amino acid transporter activators to improve the utilization efficiency of dietary protein in dairy cows, thereby achieving the goal of cost reduction and efficiency improvement in dairy farming, is of great significance.

[0004] Zinc and iron are essential trace elements for all organisms. They are components of many key enzymes in the body and can affect the biological activity of more than 300 enzymes, such as SOD enzymes, GSH-PX enzymes, alkaline phospholipases, carboxypeptidases, DNA polymerases, RNA polymerases, lactate dehydrogenases, and proteolytic enzymes. Meanwhile, nano-sized zinc and iron have been shown to play important roles in various biological functions (antioxidant, antitumor, and anti-aging). Studies have found that zinc amino acid chelates can effectively promote zinc absorption in animals. However, whether the modification of nano-trace elements, as a type of protein transporter, can improve the activity of amino acid transporters in dairy cows, thereby increasing the absorption rate of amino acids in the basal diet, remains to be studied. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides an activator for improving nitrogen conversion efficiency in dairy cow feed. This activator is a zinc / iron nanomaterial that can effectively improve the utilization efficiency of amino acids (nitrogen) in feed by dairy cows at a lower cost, thereby achieving cost reduction and efficiency improvement in dairy farming.

[0006] Therefore, the first aspect of this application provides an activator for improving the nitrogen conversion efficiency of dairy cow feed, wherein the activator is a zinc / iron nanomaterial.

[0007] This application utilizes molecular docking technology to identify key binding sites that can efficiently regulate amino acid transporters and small peptide transporters. Using nano-trace element modification technology, an activator—zinc / iron nanomaterials—was obtained that can improve nitrogen conversion efficiency in dairy cow feed. These zinc / iron nanomaterials effectively enhance the transport efficiency of amino acids in dairy cow mammary cells and the expression level of amino acid transporters in these cells. Feeding dairy cows with these zinc / iron nanomaterials can effectively improve nitrogen absorption efficiency (i.e., amino acid absorption efficiency) without affecting feed intake, ultimately increasing nitrogen conversion efficiency, milk protein content, and milk yield. Therefore, this activator provides a cost-effective and efficient solution for improving nitrogen conversion efficiency in dairy cows.

[0008] In some embodiments, the average particle size of the zinc / iron nanomaterial is 10–20 nm.

[0009] In some specific embodiments, the average particle size of the zinc / iron nanomaterial is 10 nm, 12 nm, 15 nm, 18 nm, or 20 nm. In some preferred embodiments, the average particle size of the zinc / iron nanomaterial is 15 nm.

[0010] By controlling the average particle size of zinc / iron nanomaterials within the aforementioned range, this application enables zinc / iron nanomaterials to enter cells and exert their role and effect in regulating the cell's amino acid transport capacity.

[0011] A second aspect of this application provides a method for preparing an activator as described in the first invention of this application, the method comprising the following steps:

[0012] S1, mix hydrochloric acid solution with anhydrous ethanol to prepare an ethanol solution containing hydrochloric acid;

[0013] S2, zinc propionate and ferric propionate are mixed with N,N-dimethylacetamide to prepare a metal mixture;

[0014] S3, the ethanol solution containing hydrochloric acid and the metal mixture are mixed and stirred to obtain a reaction mixture;

[0015] S4, the reaction mixture is mixed with hydrogen peroxide solution and stirred again. After the reaction is completed, the prepared solution is collected, the supernatant in the prepared solution is removed, and the collected precipitate is washed and dried to obtain the activator.

[0016] The method described in this application utilizes a combination of hydrochloric acid, anhydrous ethanol, DMF (N,N-dimethylacetamide), and hydrogen peroxide, with zinc propionate and ferric propionate as raw materials, to ultimately prepare an activator that enhances the amino acid transport efficiency of dairy cow mammary gland cells. This activator can then be used to effectively improve the nitrogen conversion efficiency of dairy cow feed, thereby increasing milk protein content and milk yield. Furthermore, the materials used in the preparation process described in this application are all permitted for use in feed, thus retaining functionality while also being environmentally friendly.

[0017] In some embodiments, in step S1, the concentration of hydrochloric acid in the hydrochloric acid-containing ethanol solution is 0.1 to 1.0 mol / L.

[0018] In some preferred embodiments, the concentration of hydrochloric acid in the hydrochloric acid-containing ethanol solution is 0.4 mol / L.

[0019] In this application, the ethanol solution containing hydrochloric acid is mixed with the metal mixture to wash away organic reagents such as DMF in the metal mixture, which is beneficial for the formation of zinc / iron nanomaterials by zinc propionate and iron propionate under the reaction conditions.

[0020] In some embodiments, in step S2, the mass ratio of zinc propionate to ferric propionate is (2-5):1, and the sum of the concentrations of zinc propionate and ferric propionate in the metal mixture is 50-150 mg / mL.

[0021] In some specific embodiments, the mass ratio of zinc propionate to ferric propionate can be 2:1, 3:1, 4:1 or 5:1, etc.; in some preferred embodiments, the mass ratio of zinc propionate to ferric propionate is 3:1.

[0022] In some more preferred embodiments, the mass ratio of zinc propionate to ferric propionate is 3:1, and the sum of the concentrations of zinc propionate and ferric propionate in the metal mixture is 100 mg / mL.

[0023] By controlling the mass ratio of zinc propionate and iron propionate within the aforementioned range, this application helps to improve the structural stability of the prepared zinc / iron nanomaterials, thereby helping them to enhance the transport efficiency of amino acids.

[0024] In some embodiments, in step S3, the volume ratio of the hydrochloric acid-containing ethanol solution to the metal mixture is (1-4):1; the mixing of the hydrochloric acid-containing ethanol solution and the metal mixture is achieved by pumping the hydrochloric acid-containing ethanol solution into the metal mixture at a pumping rate of 50-150 mL / h.

[0025] In some embodiments, in step S3, the volume ratio of the hydrochloric acid-containing ethanol solution to the metal mixture is 2:1; the mixing of the hydrochloric acid-containing ethanol solution and the metal mixture is achieved by pumping the hydrochloric acid-containing ethanol solution into the metal mixture at a pumping rate of 100 mL / h.

[0026] This application, by controlling the volume ratio of the hydrochloric acid-containing ethanol solution to the metal mixture within the aforementioned range, can more effectively elute organic reagents such as DMF from the metal mixture and improve the performance of the resulting zinc / iron nanomaterials. Furthermore, in this application, the hydrochloric acid-containing ethanol solution needs to be slowly pumped into the metal mixture (at a pumping speed of 100 mL / h) to prevent excessively high pumping speeds from causing the zinc / iron nanomaterials (alloy material) to disintegrate or suffer structural damage.

[0027] In some embodiments, in step S4, the concentration of hydrogen peroxide in the hydrogen peroxide solution is 0.1 to 0.5 wt%, and the volume ratio of the hydrogen peroxide solution to the metal mixture is 1:(8 to 12).

[0028] In some preferred embodiments, the concentration of hydrogen peroxide in the hydrogen peroxide solution is 0.3 wt%, and the volume ratio of the hydrogen peroxide solution to the metal mixture is 1:10.

[0029] In this application, hydrogen peroxide solution is used to remove the positive and negative charges present on the surface of the zinc / iron nanomaterials generated in the reaction mixture of step S3, thereby improving the stability of the zinc / iron nanomaterials binding to the transport carrier. By controlling the concentration of hydrogen peroxide in the hydrogen peroxide solution and the amount of hydrogen peroxide solution added within the above-mentioned range, this application can achieve a better removal effect on the positive and negative charges present on the surface of the zinc / iron nanomaterials, thereby making the binding of the zinc / iron nanomaterials to the amino acid transport carrier genes more robust.

[0030] In some embodiments, in step S4, the mixing of the reaction mixture with the hydrogen peroxide solution is achieved by pumping the hydrogen peroxide solution into the reaction mixture at a pumping rate of 50–150 mL / h.

[0031] In this application, the hydrogen peroxide solution also needs to be pumped slowly (e.g., at a pumping speed of 100 mL / h) into the reaction mixture to prevent excessively high pumping speeds from causing the zinc / iron nanomaterials (alloy materials) to disintegrate or be structurally damaged.

[0032] In some embodiments, the conditions for the stirring reaction in steps S3 and S4 are each independently: temperature of 25-35°C, stirring speed of 300-800 rpm, and time of 20-30 h.

[0033] By controlling the stirring reaction conditions within the aforementioned range, this application enables the obtained zinc / iron nanomaterials to have a more stable structure, and also helps to improve the stability of the zinc / iron nanomaterials binding to the transport carrier, thereby making the zinc / iron nanomaterials more effective in improving the nitrogen conversion efficiency of dairy cow feed.

[0034] In this application, in step S4, the supernatant in the prepared solution can be removed by centrifugation at a speed of 4000–5000 rpm. The collected precipitate can be washed with deionized water 2–3 times, and the precipitate after washing can be dried in an oven at a temperature of 50–60°C for 10–15 hours.

[0035] The third aspect of this application provides the application of an activator as described in the first aspect of this application or an activator prepared by the method described in the second aspect of this application in improving the nitrogen conversion efficiency of dairy cow feed.

[0036] The activator-zinc / iron nanomaterials provided in this application can efficiently regulate the key binding sites of amino acid transporters and small peptide transporters after entering mammary cells, thereby effectively improving the transport efficiency of amino acids in dairy cow mammary cells and the expression level of amino acid transporters in dairy cow mammary cells. Therefore, it can be well applied to improve the nitrogen conversion efficiency of dairy cow feed, and will provide a cost-saving and efficiency-enhancing solution for improving the nitrogen conversion efficiency of dairy cows.

[0037] In some embodiments, the application is achieved by feeding dairy cows the activator at a dosage of 1.0–2.0 g / day.

[0038] By consuming the above-mentioned amount of activator, dairy cows can effectively improve their nitrogen absorption efficiency (i.e., amino acid absorption efficiency) without affecting their feed intake, ultimately increasing their nitrogen conversion efficiency to 33.2%, and also improving milk protein content and milk yield.

[0039] The beneficial technical effects of this application are as follows: The activator-zinc / iron nanomaterials provided in this application can efficiently regulate the key binding sites of amino acid transporters and small peptide transporters after entering mammary gland cells, thereby effectively improving the transport efficiency of amino acids and the expression level of amino acid transporters in mammary gland cells. By feeding dairy cows with this zinc / iron nanomaterial, the nitrogen absorption efficiency of dairy cows can be effectively improved without affecting their feed intake, increasing the nitrogen conversion efficiency to 33.2%, and improving the milk protein content and milk yield. Simultaneously, by optimizing the parameters in the activator preparation process, this application can make the structure of the prepared zinc / iron nanomaterials more stable, and also help improve the stability of the binding process of zinc / iron nanomaterials to transporters, thus making the zinc / iron nanomaterials more effective in improving the nitrogen conversion efficiency of dairy cow feed. Furthermore, the materials used in the preparation process described in this application are all permitted for use in feed and are inexpensive, therefore, while retaining functionality, they are also green and low-cost, with broad application prospects. Attached Figure Description

[0040] Figure 1 To test the amino acid transporters (CAT1, CAT2, rBAT, b0, ...) in mammary cells of experimental group well 1, insulin well, and control well in Example 1. + AT, 4F2hc and y + The relative expression levels of LAT1 are shown in the figure. Detailed Implementation

[0041] To make this application easier to understand, the following detailed description will be provided with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of application of this application. Unless otherwise specified, the raw materials or components used in this application can be obtained commercially or by conventional methods.

[0042] Example 1: Preparation of zinc / iron nanomaterials as activators to improve nitrogen conversion efficiency in dairy cow feed

[0043] (1) Dissolve 20wt% hydrochloric acid aqueous solution in anhydrous ethanol to prepare an ethanol solution with a hydrochloric acid concentration of 0.4mol / L;

[0044] (2) Take 0.3g of zinc propionate and 0.1g of ferric propionate, dissolve them in 40mL of DMF to prepare a metal mixture; the mass ratio of zinc propionate to ferric propionate in the metal mixture is 3:1, and the sum of the concentrations of zinc propionate and ferric propionate is 100mg / mL.

[0045] (3) Add 80 mL of the 0.4 mol / L hydrochloric acid ethanol solution prepared in step (1) dropwise to the metal mixture prepared in step (2) using a micro-injection pump (the volume ratio of the 0.4 mol / L hydrochloric acid ethanol solution to the metal mixture is 2:1). The injection rate is 100 mL / h, and the mixture is continuously stirred with a magnetic stirrer at a speed of 500 rpm for 24 h. The reaction temperature is 30 °C to obtain the reaction mixture.

[0046] (4) 4 mL of 0.3 wt% hydrogen peroxide solution was added dropwise to the reaction mixture obtained in step (3) using a micro-injection pump (the volume ratio of hydrogen peroxide solution to metal mixture was 1:10). The injection rate was 100 mL / h. At the same time, the mixture was continuously stirred with a magnetic stirrer at a speed of 500 rpm for 24 h. The reaction temperature was 30 °C. After the reaction was completed, the prepared solution was collected. After centrifugation (at a speed of 5000 rpm), the supernatant was discarded. Deionized water was added to the obtained precipitate and ultrasonically dispersed. The precipitate was then centrifuged again for washing. The washing was repeated 3 times and the supernatant was discarded. The washed precipitate was dried in an oven at 60 °C for 12 h to obtain zinc / iron nanomaterials with an average particle size of 15 nm.

[0047] Example 2: Preparation of zinc / iron nanomaterials as activators to improve nitrogen conversion efficiency in dairy cow feed. The preparation process is basically the same as in Example 1, except that step (2) is: take 0.32g of zinc propionate and 0.08g of iron propionate, dissolve them in 40mL of DMF to prepare a metal mixture; the mass ratio of zinc propionate to iron propionate in the metal mixture is 4:1, and the sum of the concentrations of zinc propionate and iron propionate is 100mg / mL.

[0048] Example 3: Preparation of zinc / iron nanomaterials as activators to improve nitrogen conversion efficiency in dairy cow feed. The preparation process is basically the same as in Example 1, except that step (2) is: take 2.0g of zinc propionate and 2.0g of iron propionate, dissolve them in 40mL of DMF to prepare a metal mixture; the mass ratio of zinc propionate to iron propionate in the metal mixture is 1:1, and the sum of the concentrations of zinc propionate and iron propionate is 100mg / mL.

[0049] Example 4: Preparation of zinc / iron nanomaterials as activators to improve nitrogen conversion efficiency in dairy cow feed. The preparation process is basically the same as in Example 1, except that in step (1), the amount of anhydrous ethanol added to the 20wt% hydrochloric acid aqueous solution is adjusted to obtain an ethanol solution with a hydrochloric acid concentration of 0.2mol / L.

[0050] Example 5: Preparation of Zinc / Iron Nanomaterials as an Activator to Improve Nitrogen Conversion Efficiency in Dairy Cow Feed. The preparation process is basically the same as in Example 1, except that 4 mL of 0.1 wt% hydrogen peroxide solution is added dropwise to the reaction mixture obtained in step (3) using a micro-injection pump.

[0051] Comparative Example 1: Preparation of Zinc / Iron Nanomaterials as Activators to Improve Nitrogen Conversion Efficiency in Dairy Cow Feed

[0052] (1) Dissolve 20wt% hydrochloric acid aqueous solution in anhydrous ethanol to prepare an ethanol solution with a hydrochloric acid concentration of 0.4mol / L;

[0053] (2) Take 0.3g of zinc propionate and 0.1g of ferric propionate, dissolve them in 40mL of DMF to prepare a metal mixture; the mass ratio of zinc propionate to ferric propionate in the metal mixture is 3:1, and the sum of the concentrations of zinc propionate and ferric propionate is 100mg / mL.

[0054] (3) 80 mL of the 0.4 mol / L hydrochloric acid ethanol solution prepared in step (1) was uniformly added dropwise to the metal mixture prepared in step (2) using a micro-injection pump (the volume ratio of the 0.4 mol / L hydrochloric acid ethanol solution to the metal mixture was 2:1). The injection rate was 100 mL / h, and the mixture was continuously stirred with a magnetic stirrer at a speed of 500 rpm for 24 h. The reaction temperature was 30 °C, and the reaction mixture was obtained. The reaction mixture was centrifuged (at a speed of 5000 rpm) and the supernatant was discarded. Deionized water was added to the obtained precipitate and ultrasonically dispersed. The mixture was then centrifuged again for washing. The washing was repeated 3 times and the supernatant was discarded. The washed precipitate was dried in an oven at 60 °C for 12 h to obtain zinc / iron nanomaterials with an average particle size of 15 nm.

[0055] Test Example 1: Determining the effect of zinc-iron nanomaterial addition on the expression level and amino acid transport efficiency of amino acid transporters in bovine mammary epithelial cells.

[0056] 1. Cultivars were seeded into 12-well plates, with 8 wells per well, and the seeding density per well was 1.2 × 10⁶ cells. 6 indivual;

[0057] 2. Add 9 essential amino acids (lysine, tryptophan, phenylalanine, methionine, threonine, isoleucine, leucine, valine, and histidine), each at a concentration of 0.26 mmol / L, and pretreat for 24 h.

[0058] 3. Add 1 mL of different test solutions; the control wells were added with basal culture medium, the insulin wells were added with basal culture medium + 0.1 g / L insulin, the experimental group well 1 was added with basal culture medium + 0.05 g / L of zinc / iron nanomaterials prepared in Example 1, the experimental group well 2 was added with basal culture medium + 0.05 g / L of zinc / iron nanomaterials prepared in Example 2, the experimental group well 3 was added with basal culture medium + 0.05 g / L of zinc / iron nanomaterials prepared in Example 3, the experimental group well 4 was added with basal culture medium + 0.05 g / L of zinc / iron nanomaterials prepared in Example 4, the experimental group well 5 was added with basal culture medium + 0.05 g / L of zinc / iron nanomaterials prepared in Example 5, and the experimental group well 6 was added with basal culture medium + 0.05 g / L of zinc / iron nanomaterials prepared in Comparative Example 1.

[0059] 4. Incubate in an incubator for 48 hours;

[0060] 5. Remove the culture medium and determine the residual amount of each amino acid in the solution. The results are shown in Table 1.

[0061] Table 1: Residual amino acid concentrations in the culture medium of each well (mmol / L)

[0062]

[0063]

[0064] Table 1 shows that, in the experimental wells with added zinc / iron nanomaterials, except for valine, the transport efficiency of mammary cells for the remaining amino acids (lysine, tryptophan, phenylalanine, methionine, threonine, isoleucine, leucine, and histidine) was higher than that of the insulin wells and the control wells. Among these, well 1 of the experimental group showed the highest transport efficiency for the remaining amino acids (lysine, tryptophan, phenylalanine, methionine, threonine, isoleucine, leucine, and histidine), significantly better than the insulin wells and the control wells, suggesting that zinc / iron nanomaterials can effectively improve amino acid transport efficiency. The results from wells 1 and 6 of the experimental group show that the addition of hydrogen peroxide solution significantly improved the amino acid transport efficiency of zinc / iron nanomaterials. This is because hydrogen peroxide can remove the positive and negative charges on the surface of the generated zinc / iron nanomaterials, improving the stability of the binding process between the zinc / iron nanomaterials and the transport carrier, thereby increasing the amino acid transport efficiency.

[0065] 6. Collect the remaining cells from the control wells, insulin wells, and experimental group well 1, wash with PBS, obtain the cells, and perform qPCR assays to determine the amino acid transport vectors (CAT1, CAT2, rBAT, b0, ...). + AT, 4F2hc and y + The expression level of LAT1 was measured, and the results were as follows: Figure 1 As shown. From Figure 1It can be seen that when the zinc / iron nanomaterials prepared in Example 1 are added, the expression levels of amino acid transporters detected in mammary cells are significantly higher than those in insulin wells and control wells, suggesting that adding zinc / iron nanomaterials can significantly increase the expression levels of amino acid transporters in bovine mammary cells.

[0066] Test Example 2: Testing the effect of zinc / iron nanomaterials on nitrogen conversion efficiency in dairy cow feed

[0067] ① Select 30 lactating dairy cows with the same milk production, lactation days, and parity, and divide them into 3 groups of 10 cows each for the experiment.

[0068] ② Three groups of dairy cows were fed a basal diet with 0, 1.0 and 2.0 g of the zinc / iron nanomaterials prepared in Example 1 added to their daily feed, respectively, for an experimental period of 8 weeks.

[0069] ③The lactation performance, feed intake, milk composition and nitrogen conversion efficiency of dairy cows in different groups were measured after an 8-week experimental period. The results are shown in Table 2.

[0070] Table 2: Effects of zinc / iron nanomaterials on nitrogen conversion efficiency in dairy cow feed

[0071]

[0072] As shown in Table 2, adding zinc / iron nanomaterials to the diet can effectively improve the absorption efficiency of nitrogen (i.e., the absorption efficiency of amino acids) in dairy cows without affecting their feed intake, thereby increasing the nitrogen conversion efficiency and improving the milk protein content and milk yield.

[0073] It should be noted that the embodiments described above are only for explaining this application and do not constitute any limitation on this application. This application has been described with reference to typical embodiments, but it should be understood that the terms used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to this application within the scope of the claims, and revisions can be made to the invention without departing from the scope and spirit of this application. Although the application described herein relates to specific methods, materials, and embodiments, it does not mean that this application is limited to the specific examples disclosed herein; on the contrary, this application can be extended to all other methods and applications with the same function.

Claims

1. An activator for improving nitrogen conversion efficiency in dairy cow feed, characterized in that, The activator is a zinc / iron nanomaterial; The preparation method of the activator includes the following steps: S1, mix hydrochloric acid solution with anhydrous ethanol to prepare an ethanol solution containing hydrochloric acid; S2, zinc propionate and ferric propionate are mixed with N,N-dimethylacetamide to prepare a metal mixture; S3, the ethanol solution containing hydrochloric acid and the metal mixture are mixed and stirred to obtain a reaction mixture; S4, the reaction mixture is mixed with hydrogen peroxide solution and stirred again. After the reaction is completed, the prepared solution is collected, the supernatant in the prepared solution is removed, and the collected precipitate is washed and dried to obtain the activator.

2. The activator according to claim 1, characterized in that, The average particle size of the zinc / iron nanomaterial is 10~20nm.

3. A method for preparing the activator as described in claim 1 or 2, characterized in that, The method includes the following steps: S1, mix hydrochloric acid solution with anhydrous ethanol to prepare an ethanol solution containing hydrochloric acid; S2, zinc propionate and ferric propionate are mixed with N,N-dimethylacetamide to prepare a metal mixture; S3, the ethanol solution containing hydrochloric acid and the metal mixture are mixed and stirred to obtain a reaction mixture; S4, the reaction mixture is mixed with hydrogen peroxide solution and stirred again. After the reaction is completed, the prepared solution is collected, the supernatant in the prepared solution is removed, and the collected precipitate is washed and dried to obtain the activator.

4. The method according to claim 3, characterized in that, In step S1, the concentration of hydrochloric acid in the ethanol solution containing hydrochloric acid is 0.1~1.0 mol / L; in step S2, the mass ratio of zinc propionate to ferric propionate is (2~5):1, and the sum of the concentrations of zinc propionate and ferric propionate in the metal mixture is 50~150 mg / mL.

5. The method according to claim 3 or 4, characterized in that, In step S3, the volume ratio of the hydrochloric acid-containing ethanol solution to the metal mixture is (1~4):1; the mixing of the hydrochloric acid-containing ethanol solution and the metal mixture is achieved by pumping the hydrochloric acid-containing ethanol solution into the metal mixture at a pumping speed of 50~150mL / h.

6. The method according to claim 3 or 4, characterized in that, In step S4, the concentration of hydrogen peroxide in the hydrogen peroxide solution is 0.1~0.5wt%, and the volume ratio of the hydrogen peroxide solution to the metal mixture is 1:(8~12).

7. The method according to claim 3 or 4, characterized in that, In step S4, the reaction mixture and the hydrogen peroxide solution are mixed by pumping the hydrogen peroxide solution into the reaction mixture at a pumping rate of 50~150mL / h.

8. The method according to claim 3 or 4, characterized in that, In steps S3 and S4, the conditions for the stirring reaction are each independent: temperature is 25~35℃, stirring speed is 300~800rpm, and time is 20~30h.

9. The application of an activator as described in claim 1 or 2, or an activator prepared by the method of any one of claims 3-8, in improving the nitrogen conversion efficiency of dairy cow feed.

10. The application according to claim 9, characterized in that, The application is achieved by feeding dairy cows the activator, and the dosage of the activator is 1.0~2.0g / day.

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