Urea compound feed additive and preparation method thereof

Abstract

The invention discloses a urea compound feed additive and a preparation method thereof, and belongs to the field of feed additives, and the urea compound feed additive is prepared from the following raw materials in percentage by weight: 68.8-73% of urea, 19.4-21% of pretreated bentonite, 3-4% of rice hull powder, 2.5-3% of a pregelatinized starch compound, 2-3% of glycerin monostearate and 0.1-0.2% of a stabilizer magnesium oxide; and the urea compound feed additive is obtained through a spray drying granulation process. Wherein the components have a synergistic effect, slow release of urea in rumen of ruminants is realized through a slow release technology, ammonia poisoning caused by too fast release of urea is avoided, and the slow-release nitrogen source can replace part of protein feed in daily ration of ruminants.

Description

Technical Field

[0001] The invention belongs to the field of feed additives, and particularly relates to a urea compound feed additive and a preparation method thereof. Background Art

[0002] Protein is a key nutrient for healthy animal growth and is indispensable in animal husbandry. In recent years, my country's ruminant farming industry has grown rapidly, and demand for protein feed has continued to rise. However, domestic protein feed resources are scarce, and production relies heavily on imports. According to statistics, my country's soybean imports exceeded 100 million tons in 2020. The resulting high feed costs have severely constrained the sustainable development of the livestock industry.

[0003] Urea, as an important form of non-protein nitrogen (NPN), has gained widespread application in agriculture and animal husbandry due to its extremely high nitrogen content (approximately 46%). Its core value lies in its ability to effectively increase the apparent crude protein content of feed, significantly reducing reliance on expensive traditional protein feeds (such as soybean meal), and thus lowering breeding costs. However, direct feeding of urea to ruminants presents significant safety risks. Urea is rapidly hydrolyzed by urease in the rumen, producing large amounts of ammonia in a short period of time. This can not only lead to acute ammonia poisoning, which is life-threatening to animals, but also disrupt the normal microbial balance and protein metabolism efficiency in the rumen, affecting animal performance (such as weight gain and milk production) and feed conversion rate. To overcome the drawbacks of direct urea feeding, a spray drying granulation process, through physical encapsulation and rapid dehydration, has elevated urea's nitrogen utilization efficiency and safety to new levels, enabling precise control of urea release rate. Therefore, slowing the release rate of urea in the rumen of ruminants has become an urgent issue. Summary of the Invention

[0004] In order to solve the problems of ammonia poisoning caused by urea in the rumen of ruminants in the current technology, improve the utilization efficiency of nitrogen sources, and reduce protein feed waste, the present invention provides a feed additive for reducing nitrogen excretion of ruminants and a preparation method thereof.

[0005] The present invention provides a urea compound feed additive and a preparation method thereof, comprising the following steps:

[0006] Step 1: Prepare the following raw materials in percentage by weight: 68.8-73% urea, 19.4-21% pretreated bentonite, 3-4% rice husk powder, 2.5-3% pregelatinized starch complex, 2-3% glyceryl monostearate, and 0.1-0.2% stabilizer magnesium oxide;

[0007] The second step is to put urea into a jacketed heating tank, pass the urea through a 6-20 mesh screen, control the jacket temperature to 130-140°C, and maintain the jacket time at 20-40 minutes to obtain melted urea; add the melted urea to the jacketed hot tank, control the jacket temperature to 110-120°C, then add pretreated bentonite and stir, start the shear pump motor and the homogenizing pump motor, stir for 20-30 minutes, finally add glyceryl monostearate, stabilizer magnesium oxide and rice husk powder and mix for 5-10 minutes, cool to 45-50°C, and finally add pregelatinized starch complex and mix for 10-20 minutes to obtain a homogeneous mixed fluid material;

[0008] The third step is to send the obtained composite premixed feed additive to a centrifugal spray tower with an inlet air temperature of 35-40°C, pass through a high-speed rotating centrifugal atomizing disk, sieve through a vibrating sieve with a mesh size of 20-60, and package to obtain a urea composite feed additive.

[0009] Preferably, the method for preparing pretreated bentonite comprises the following steps:

[0010] The bentonite and 3-5% sodium carbonate solution are stirred in a water bath at a temperature of 45-50° C. for 2-3 hours, centrifuged at a speed of 40-80 r / min, washed with deionized water, dried, crushed and passed through a 200-mesh sieve to obtain pretreated bentonite.

[0011] Preferably, the usage ratio of bentonite and sodium carbonate solution with a mass fraction of 3-5% is 1 kg:4-6 L.

[0012] Preferably, the pregelatinized starch composite is prepared by the following steps:

[0013] S1, pregelatinized starch complex is composed of the following raw materials in parts by weight: 70 parts of pregelatinized starch, 20-30 parts of activated montmorillonite, 4-6 parts of pretreated nano zinc oxide, 3-4 parts of copper glycinate powder and 30 parts of sucrose microspheres;

[0014] S2, drying the montmorillonite at 100-110° C. for 2-3 hours, then soaking it in a 4-6% citric acid solution for 1-2 hours, adjusting the pH value to neutral, crushing it, and passing it through a 200-mesh sieve to obtain activated montmorillonite;

[0015] S3, subjecting the nano-zinc oxide and anhydrous ethanol to ultrasonic treatment at room temperature at an ultrasonic frequency of 35-45 kHz for 30-50 min to obtain pretreated nano-zinc oxide;

[0016] S4. Add pregelatinized starch and activated montmorillonite into a mixer at a speed of 450-650 r / min, mix at room temperature for 8-12 min, then add pretreated nano zinc oxide and copper glycinate powder, mix at room temperature for 20-40 min, and then grind in a zirconia ball mill with a ball-to-material ratio of 5:1, ball mill at 250-350 r / min for 30-50 min, and pass through an 80-mesh sieve to obtain a pregelatinized starch complex.

[0017] Preferably, the usage ratio of montmorillonite and 4-6% citric acid solution is 1 g:4-6 mL, and the usage ratio of nano zinc oxide and anhydrous ethanol is 1 g:20-30 mL.

[0018] Preferably, the method for preparing sucrose microspheres comprises the following steps:

[0019] Step 1: Mix sucrose powder and an 8-12% hydroxypropyl methylcellulose aqueous solution, control the inlet air temperature to 45-55° C., and the atomization pressure to 0.2-0.3 MPa to obtain a microsphere matrix;

[0020] Step 2: Mix the red clover extract, L-glutamic acid and 25-35% ethanol solution, perform wet granulation at room temperature, control the stirring speed of the paddle to 100-250 r / min, the cutter speed to 1000-1600 r / min, pass through a 60-80 mesh sieve, and dry to obtain a product;

[0021] Step 3: After spraying the product onto the microsphere matrix, spray an 8-12% hydroxypropyl methylcellulose aqueous solution, solidify at room temperature for 5-10 minutes, and finally dry in hot air at 55-60°C to obtain sucrose microspheres with a particle size of 80-100 μm.

[0022] Preferably, in the preparation method of sucrose microspheres, the ratio of sucrose powder to 8-12% hydroxypropyl methylcellulose aqueous solution is 1.5-3 g:1 mL, the ratio of red clover extract, L-glutamic acid and 25-35% ethanol solution is 1 g:1.5-3 g:20-50 mL, and the ratio of product, microsphere matrix and 8-12% hydroxypropyl methylcellulose aqueous solution is 1 g:15-20 g:1-1.4 mL.

[0023] Preferably, the high-speed rotating centrifugal atomizing disk in step three rotates at a speed of 6000-12000 r / min.

[0024] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0025] 1. The urea compound feed additive of the present invention comprises the following raw materials, calculated in percentage by weight: 68.8-73% urea, 19.4-21% pretreated bentonite, 3-4% rice husk powder, 2.5-3% pregelatinized starch complex, 2-3% glyceryl monostearate, and 0.1-0.2% stabilizer magnesium oxide. The various components act synergistically to achieve slow release of urea in the rumen of ruminants through a slow-release technology, thereby avoiding ammonia poisoning caused by excessively rapid urea release. Furthermore, the slow-release nitrogen source of the present invention can replace part of the protein feed in the ruminant diet.

[0026] 2. The pretreated bentonite in the present invention is evenly dispersed in the molten urea to form a physical barrier, effectively blocking the rapid contact and decomposition of urea by rumen urease, absorbing water and swelling in the rumen environment to form a gel network structure, further delaying the release of urea; the layered structure of montmorillonite can adsorb urea molecules and delay diffusion; the Zn in the pretreated nano zinc oxide 2+ It specifically binds to the sulfhydryl group (-SH) in the active center of urease, inhibiting urease activity; glycine, as a small molecule nitrogen carrier, is directly taken up by rumen microorganisms, Cu 2+ Activate microbial glutamine synthetase, accelerate the conversion of ammonia into glutamate, and improve the efficiency of converting ammonia nitrogen into bacterial protein.

[0027] 3. In the present invention, sucrose molecules are rich in hydroxyl groups and are combined with ether bonds and residual hydroxyl groups in the aqueous solution of hydropropyl methylcellulose through multiple hydrogen bonds to form a three-dimensional cross-linked network. The red clover extract contains natural polyphenols that directly bind to the active site of urease and inhibit urease activity. L-glutamic acid forms a hydrogen bond network with the hydroxyl groups of hydropropyl methylcellulose through the amino group, thereby enhancing the bonding strength between the coating layer and the sucrose matrix. L-glutamic acid forms intermolecular hydrogen bonds with isoflavones in the red clover extract through the carboxyl group, thereby inhibiting the oxidative degradation of isoflavones in the red clover extract.

[0028] Example 1: This example discloses a method for preparing sucrose microspheres, comprising the following steps:

[0029] Step 1: Mix 1.5 kg of sucrose powder and 1 L of 8% hydroxypropyl methylcellulose aqueous solution, control the inlet air temperature to 45°C, the atomization pressure to 0.2 MPa, and the particle size to 60 μm to obtain a microsphere matrix;

[0030] Step 2: 2 kg of red clover extract, 3 kg of L-glutamic acid and 40 L of 25% ethanol solution were mixed and wet granulated at 25° C., the stirring speed was controlled at 100 r / min and the cutting speed was controlled at 1000 r / min, the mixture was passed through a 60-mesh sieve, and dried to obtain a product;

[0031] Step 3: After spraying 1 kg of the product onto 15 kg of microsphere substrate, 1 L of 8% hydroxypropyl methylcellulose aqueous solution was sprayed in, solidified at 25°C for 5 min, and finally dried in hot air at 55°C to obtain sucrose microspheres with a particle size of 80 μm.

[0032] This embodiment discloses a method for preparing a pregelatinized starch composite, comprising the following steps:

[0033] S1. Dry 2 kg of montmorillonite at 100°C for 2 h, then soak it in 8 L of 4% citric acid solution for 1 h, adjust the pH to 7, crush it, and pass it through a 200-mesh sieve to obtain activated montmorillonite;

[0034] S2, ultrasonically treating 2 kg of nano-zinc oxide and 40 L of anhydrous ethanol at 25° C. with an ultrasonic frequency of 35 kHz for 30 min to obtain pretreated nano-zinc oxide;

[0035] S3. Add 7 kg of pregelatinized starch and 2 kg of activated montmorillonite into a mixer at a speed of 450 r / min and mix at 25 ° C for 8 min. Then add 0.4 kg of pretreated nano zinc oxide and 0.3 kg of glycinate copper powder and mix at 25 ° C for 20 min. Grind in a zirconia ball mill with a ball-to-material ratio of 5:1, ball mill at 250 r / min for 30 min, and pass through an 80-mesh sieve to obtain a pregelatinized starch complex.

[0036] This embodiment discloses a method for preparing pretreated bentonite, comprising the following steps:

[0037] 1 kg of bentonite and 4 L of 3% sodium carbonate solution were stirred in a water bath at 55° C. for 2 h, centrifuged at 40 r / min, washed with deionized water, dried, crushed and passed through a 200-mesh sieve to obtain pretreated bentonite.

[0038] The present invention provides a method for preparing a urea compound feed additive, comprising the following steps:

[0039] The first step is to put 34.4 kg of urea into a jacketed heating tank, pass the urea through a 6-mesh sieve, control the jacket temperature to 130°C, and maintain the jacket time for 20 minutes to obtain melted urea; add the melted urea to the jacketed hot tank, control the jacket temperature to 110°C, then add 9.7 kg of pretreated bentonite and stir, start the shear pump motor and the homogenizing pump motor, and stir for 20 minutes. Finally, add 1 kg of glyceryl monostearate, 0.05 kg of stabilizer magnesium oxide and rice husk powder and mix them for 5 minutes, cool to 45°C, and finally add pregelatinized starch complex and mix for 10 minutes to obtain a homogeneous mixed fluid material;

[0040] The second step is to send the obtained composite premixed feed additive to a centrifugal spray tower with an inlet air temperature of 35°C, pass through a high-speed rotating centrifugal atomizing disk at a speed of 6000r / min, sieve through a vibrating sieve with 20 meshes, and package to obtain a urea composite feed additive.

[0041] Example 2: This example discloses a method for preparing sucrose microspheres, comprising the following steps:

[0042] Step 1: Mix 3 kg of sucrose powder and 1 L of a 12% hydroxypropyl methylcellulose aqueous solution, control the inlet air temperature to 55°C, the atomization pressure to 0.3 MPa, and the particle size to 80 μm to obtain a microsphere matrix;

[0043] Step 2: 2 kg of red clover extract, 6 kg of L-glutamic acid and 100 L of 35% ethanol solution were mixed and wet granulated at 25° C., the stirring speed was controlled at 250 r / min and the cutting speed was controlled at 1600 r / min, the mixture was passed through an 80-mesh sieve and dried to obtain a product;

[0044] Step 3: After spraying 1 kg of the product onto 20 kg of microsphere substrate, 1.4 L of 12% hydroxypropyl methylcellulose aqueous solution was sprayed in, solidified at 25°C for 10 min, and finally dried in hot air at 60°C to obtain sucrose microspheres with a particle size of 100 μm.

[0045] This embodiment discloses a method for preparing a pregelatinized starch composite, comprising the following steps:

[0046] S1. Dry 2 kg of montmorillonite at 110°C for 3 h, then soak it in 12 L of 6% citric acid solution for 2 h, adjust the pH to 7, crush it, and pass it through a 200 mesh sieve to obtain activated montmorillonite;

[0047] S2, ultrasonically treating 2 kg of nano-zinc oxide and 60 L of anhydrous ethanol at 25° C. with an ultrasonic frequency of 45 kHz for 50 min to obtain pretreated nano-zinc oxide;

[0048] S3. Add 7 kg of pregelatinized starch and 3 kg of activated montmorillonite into a mixer at a speed of 650 r / min and mix at 25 ° C for 12 min. Then add 0.6 kg of pretreated nano zinc oxide and 0.4 kg of glycinate copper powder and mix at 25 ° C for 40 min. Grind in a zirconia ball mill with a ball-to-material ratio of 5:1, ball mill at 350 r / min for 50 min, and pass through an 80-mesh sieve to obtain a pregelatinized starch complex.

[0049] This embodiment discloses a method for preparing pretreated bentonite, comprising the following steps:

[0050] 1 kg of bentonite and 6 L of 5% sodium carbonate solution were stirred in a water bath at 65° C. for 3 h, centrifuged at 80 r / min, washed with deionized water, dried, crushed and passed through a 200-mesh sieve to obtain pretreated bentonite.

[0051] The present invention provides a method for preparing a urea compound feed additive, comprising the following steps:

[0052] The first step is to put 36.5 kg of urea into a jacketed heating tank, pass the urea through a 10-mesh sieve, control the jacket temperature to 140 ° C, and maintain the jacket time for 40 minutes to obtain melted urea; add the melted urea to the jacketed hot tank, control the jacket temperature to 120 ° C, then add 10.5 kg of pretreated bentonite and stir, start the shear pump motor and the homogenizing pump motor, and stir for 30 minutes. Finally, add 1 kg of glyceryl monostearate, 0.1 kg of stabilizer magnesium oxide and rice husk powder and mix them for 10 minutes, cool to 50 ° C, and finally add pregelatinized starch complex and mix for 20 minutes to obtain a homogeneous mixed fluid material;

[0053] The second step is to send the obtained composite premixed feed additive to a centrifugal spray tower with an inlet air temperature of 40°C, pass through a high-speed rotating centrifugal atomizing disk at a speed of 12000r / min, sieve through a vibrating sieve with 60 mesh, and package to obtain a urea composite feed additive.

[0054] Example 3: This example discloses a method for preparing sucrose microspheres, comprising the following steps:

[0055] Step 1: Mix 2 kg of sucrose powder and 1 L of a 10% hydroxypropyl methylcellulose aqueous solution, control the inlet air temperature to 50°C, the atomization pressure to 0.25 MPa, and the particle size to 70 μm to obtain a microsphere matrix;

[0056] Step 2: 2 kg of red clover extract, 4 kg of L-glutamic acid and 60 L of 30% ethanol solution were mixed and wet granulated at 25° C. The stirring speed was controlled at 200 r / min and the cutting speed was controlled at 1200 r / min. The mixture was passed through a 70-mesh sieve and dried to obtain a product;

[0057] Step 3: After spraying 1 kg of the product onto 18 kg of microsphere substrate, 1.2 L of a 10% hydroxypropyl methylcellulose aqueous solution was sprayed in, solidified at 25°C for 8 minutes, and finally dried in hot air at 58°C to obtain sucrose microspheres with a particle size of 90 μm.

[0058] This embodiment discloses a method for preparing a pregelatinized starch composite, comprising the following steps:

[0059] S1. Dry 2 kg of montmorillonite at 105°C for 2.5 h, then soak it in 10 L of 5% citric acid solution for 1.5 h, adjust the pH to 7, crush it, and pass it through a 200 mesh sieve to obtain activated montmorillonite;

[0060] S2, ultrasonically treating 2 kg of nano-zinc oxide and 50 L of anhydrous ethanol at 25° C. with an ultrasonic frequency of 40 kHz for 40 min to obtain pretreated nano-zinc oxide;

[0061] S3. Add 7 kg of pregelatinized starch and 2.5 kg of activated montmorillonite into a mixer at a speed of 500 r / min and mix at 25 ° C for 10 min. Then add 0.5 kg of pretreated nano zinc oxide and 0.35 kg of glycinate copper powder and mix at 25 ° C for 30 min. Grind in a zirconia ball mill with a ball-to-material ratio of 5:1, ball mill at 300 r / min for 40 min, and pass through an 80-mesh sieve to obtain a pregelatinized starch complex.

[0062] This embodiment discloses a method for preparing pretreated bentonite, comprising the following steps:

[0063] 1 kg of bentonite and 5 L of 4% sodium carbonate solution were stirred in a water bath at 60° C. for 2.5 h, centrifuged at 60 r / min, washed with deionized water, dried, crushed and passed through a 200-mesh sieve to obtain pretreated bentonite.

[0064] The present invention provides a method for preparing a urea compound feed additive, comprising the following steps:

[0065] The first step is to put 35.6 kg of urea into a jacketed heating tank, pass the urea through an 8-mesh sieve, control the jacket temperature to 134 ° C, and maintain the jacket time for 30 minutes to obtain melted urea; add the melted urea to the jacketed hot tank, control the jacket temperature to 118 ° C, then add 10.2 kg of pretreated bentonite and stir, start the shear pump motor and the homogenizing pump motor, and stir for 25 minutes. Finally, add 1 kg of glyceryl monostearate, 0.08 kg of stabilizer magnesium oxide and rice husk powder and mix them for 8 minutes, cool to 48 ° C, and finally add pregelatinized starch complex and mix for 15 minutes to obtain a homogeneous mixed fluid material;

[0066] The second step is to send the obtained composite premixed feed additive to a centrifugal spray tower with an inlet air temperature of 38° C., pass through a high-speed rotating centrifugal atomizing disk at a speed of 8000 r / min, sieve through a 40-mesh oscillating sieve, and package to obtain a urea composite feed additive.

[0067] Comparative Example 1: This comparative example discloses a method for preparing a urea compound feed additive, comprising the following steps:

[0068] The first step is to put 35.6 kg of urea into a jacketed heating tank, pass the urea through an 8-mesh sieve, control the jacket temperature to 134 ° C, and maintain the jacket time for 30 minutes to obtain melted urea; add the melted urea to the jacketed hot tank, control the jacket temperature to 118 ° C, then add 10.2 kg of pretreated bentonite and stir, start the shear pump motor and the homogenizing pump motor, and stir for 25 minutes. Finally, add 1 kg of glyceryl monostearate, 0.08 kg of stabilizer magnesium oxide and rice husk powder and mix them for 8 minutes, cool to 48 ° C, and finally add pregelatinized starch and mix for 15 minutes to obtain a homogeneous mixed fluid material;

[0069] The second step is to send the obtained composite premixed feed additive to a centrifugal spray tower with an inlet air temperature of 38° C., pass through a high-speed rotating centrifugal atomizing disk at a speed of 8000 r / min, sieve through a 40-mesh oscillating sieve, and package to obtain a urea composite feed additive.

[0070] Comparative Example 2

[0071] Compared with Comparative Example 1, the pregelatinized starch in Comparative Example 1 was replaced with rice husk powder, and the remaining raw materials and preparation process were the same as those in Comparative Example 1.

[0072] The urea compound feed additives obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were placed at 25° C. for 12 days, and their film adhesion was preliminarily evaluated by sensory evaluation. The results are shown in Table 1:

[0073] Table 1

[0074] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Phenomenon Complete coating Complete coating Complete coating Complete coating Partial detachment of the coating

[0075] It can be seen from Table 1 that, compared with Comparative Example 1, the coating films of the urea compound feed additives obtained in Examples 1-3 and Comparative Example 1 have better adhesion.

[0076] The sustained-release rates of Examples 1-3, Comparative Examples 1-2, and urea granules were compared using an in vitro simulated rumen environment experiment and a fistula cow experiment.

[0077] Accurately measure 700 mL of pure water in the dissolution tank of the dissolution apparatus, set the temperature to 35°C and the speed to 80 r / min to simulate the rumen environment; then weigh 5.00 g of each of Examples 1-3 and Comparative Examples 1-2 in the dissolution tank, and take 10 mL of samples after 2, 4, 8, and 12 hours, respectively. The nitrogen content in the samples was determined using a Kjeldahl nitrogen analyzer. The sustained release rate is calculated based on (a1-a2) / a1×100%. The results are shown in Table 2:

[0078] Table 2

[0079]

[0080] As can be seen from Table 2, compared with Comparative Examples 1-2, the sustained release rates of the compound feed additives obtained in Examples 1-3 were all lower than 15% after 2 hours, lower than 30% after 4 hours, lower than 65% after 8 hours, and lower than 80% after 12 hours. The sustained release rate of the feed additives with pregelatinized starch complexes was even slower.

[0081] Chinese Holstein cows equipped with permanent rumen cannulas were selected. 300-mesh nylon cloth was used to make 8 cm × 16 cm nylon bags. Before use, the bags were allowed to equilibrate in the rumen for 24 hours, then removed, cleaned, and oven-dried at 65°C to constant weight. The weight was recorded. 5 g of each urea granule from Examples 1-3 and Comparative Examples 1-2 was placed at the bottom of a nylon bag of known mass, and the nitrogen content, A1, was measured. Six urea granules containing Examples 1-3 and Comparative Examples 1-2 were fixed to each plastic hose, for a total of seven. These were then introduced into the rumen plenum chyme 2 hours after the morning feeding. The plastic hoses were secured to the cannula cover with nylon thread. The bags were removed after 2, 4, 8, and 12 hours, respectively, and rinsed with deionized water until the water was clear. The rinsed nylon bags were then oven-dried at 65°C to constant weight. The nitrogen content, A2, was measured. The sustained-release rate was calculated as (A1-A2) / A1 × 100%. The results are shown in Table 3.

[0082] Table 3

[0083]

[0084] As can be seen from Table 3, compared with Comparative Examples 1-2, the sustained release rates of the compound feed additives obtained in Examples 1-3 were all lower than 15% after 2 hours, lower than 30% after 4 hours, lower than 65% after 8 hours, and lower than 80% after 12 hours. The sustained release rate of the feed additive with the pregelatinized starch complex was even slower.

[0085] In order to verify the effect of the slow-release nitrogen source of the present invention on the blood biochemical indicators of beef cattle, 6-month-old, healthy Simmental growing bulls of similar weight were selected and randomly divided into a control group and an Example 3 group. Example 1 group: 0.9% of the compound feed additive obtained in Example 3 was added to the diet. The control group was fed a basal diet, and the Example 3 group was fed urea granules. Other aspects were the same as those of Example 1 group; the remaining groups were fed with 0.9% of the compound feed additive. The experimental period was fed at 7 am and 6 pm every day, and the daily feed intake of each cow was recorded. The pre-feeding period was 15 days and the formal feeding period was 80 days.

[0086] Blood biochemical index detection: Before the morning feeding on the last day of the experimental feeding, blood was collected from the jugular vein of the experimental cows using a vacuum blood collection tube. 20mL of blood was collected from each cow, and after standing for 30 minutes, the blood was centrifuged at 3500r / min for 10 minutes. The supernatant after centrifugation was aspirated and divided into 1.5mL EP tubes and stored at -20℃ for testing. The total protein (TP), urea nitrogen (BUN), blood ammonia (AN) content in the serum and the activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) were measured. All indicators were measured by colorimetry using a fully automatic biochemical analyzer. The test results of each blood biochemical index are shown in Table 4:

[0087] Table 4

[0088]

[0089] As shown in Table 4, there were no significant differences in TP, BUN, ALT, and AST levels between the Example 1 and 2 groups and the control group (P>0.05), indicating that feeding the coated slow-release nitrogen source to cattle did not affect urea conversion, protein metabolism, and kidney function in beef cattle; the TP, BUN, and AST levels in the urea group were significantly lower than those in the control group (P<0.05), indicating that directly feeding urea would reduce the TP, BUN, and AST levels in the blood, partially affect protein metabolism in beef cattle, and affect their development; the AN content in the urea group and the Example 1 and 2 groups was slightly higher than that in the control group, and the AN content in the Example 1 and 2 groups was lower than that in the urea group (P>0.05); the ALP content in the Example 1 and 2 groups was slightly higher than that in the control group, while that in the urea group was lower than that in the control group (P>0.05).

[0090] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0091] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a urea compound feed additive, characterized in that: The following steps are involved: Step 1: Prepare the following raw materials in percentage by weight: 68.8-73% urea, 19.4-21% pretreated bentonite, 3-4% rice husk powder, 2.5-3% pregelatinized starch complex, 2-3% glyceryl monostearate, and 0.1-0.2% stabilizer magnesium oxide; The second step is to put urea into a jacketed heating tank, pass the urea through a 6-20 mesh sieve, control the jacket temperature to 130-140°C, and maintain the jacket time at 20-40 minutes to obtain melted urea; add the melted urea to the jacketed hot tank, control the jacket temperature to 110-120°C, then add pretreated bentonite and stir, start the shear pump motor and the homogenizing pump motor, stir for 20-30 minutes, finally add glyceryl monostearate, stabilizer magnesium oxide and rice husk powder and mix for 5-10 minutes, cool to 45-50°C, and finally add pregelatinized starch complex and mix for 10-20 minutes to obtain a homogeneous mixed fluid material; The third step is to send the obtained homogeneous mixed fluid material to a centrifugal spray tower with an inlet air temperature of 35-40°C, pass through a high-speed rotating centrifugal atomizing disk, sieve through an oscillating sieve with 20-60 mesh, and package to obtain a urea compound feed additive.

2. The method for preparing a urea compound feed additive according to claim 1, wherein The method for preparing pretreated bentonite comprises the following steps: The bentonite and 3-5% sodium carbonate solution are stirred in a water bath at a temperature of 45-50° C. for 2-3 hours, centrifuged at a speed of 40-80 r / min, washed with deionized water, dried, crushed and passed through a 200-mesh sieve to obtain pretreated bentonite.

3. The method for preparing a urea compound feed additive according to claim 2, wherein: The usage ratio of bentonite and sodium carbonate solution with a mass fraction of 3-5% is 1kg:4-6L.

4. The method for preparing a urea compound feed additive according to claim 1, wherein The pregelatinized starch compound is prepared by the following steps: S1, the pregelatinized starch complex is composed of the following raw materials in parts by weight: 70 parts of pregelatinized starch, 20-30 parts of activated montmorillonite, 4-6 parts of pretreated nano zinc oxide, 3-4 parts of copper glycinate powder and 30 parts of sucrose microspheres; S2, drying the montmorillonite at 100-110° C. for 2-3 hours, then soaking it in a 4-6% citric acid solution for 1-2 hours, adjusting the pH value to neutral, crushing it, and passing it through a 200-mesh sieve to obtain activated montmorillonite; S3, subjecting the nano-zinc oxide and anhydrous ethanol to ultrasonic treatment at room temperature at an ultrasonic frequency of 35-45 kHz for 30-50 min to obtain pretreated nano-zinc oxide; S4. Add pregelatinized starch and activated montmorillonite into a mixer at a speed of 450-650 r / min, mix at room temperature for 8-12 min, then add pretreated nano zinc oxide and copper glycinate powder, mix at room temperature for 20-40 min, and then grind in a zirconia ball mill with a ball-to-material ratio of 5:1, ball mill at 250-350 r / min for 30-50 min, and pass through an 80-mesh sieve to obtain a pregelatinized starch complex.

5. The method for preparing a urea compound feed additive according to claim 4, wherein: The usage ratio of montmorillonite and 4-6% citric acid solution is 1g:4-6mL, and the usage ratio of nano zinc oxide and anhydrous ethanol is 1g:20-30mL.

6. The method for preparing a urea compound feed additive according to claim 4, wherein: The preparation method of sucrose microspheres comprises the following steps: Step 1: Mix sucrose powder and an 8-12% hydroxypropyl methylcellulose aqueous solution, control the inlet air temperature to 45-55° C., and the atomization pressure to 0.2-0.3 MPa to obtain a microsphere matrix; Step 2: Mix the red clover extract, L-glutamic acid and 25-35% ethanol solution, perform wet granulation at room temperature, control the stirring speed of the paddle to 100-250 r / min, the cutter speed to 1000-1600 r / min, pass through a 60-80 mesh sieve, and dry to obtain a product; Step 3: After spraying the product onto the microsphere matrix, spray an 8-12% hydroxypropyl methylcellulose aqueous solution, solidify at room temperature for 5-10 minutes, and finally dry in hot air at 55-60°C to obtain sucrose microspheres with a particle size of 80-100 μm.

7. The method for preparing a urea compound feed additive according to claim 4, wherein: In the preparation method of sucrose microspheres, the dosage ratio of sucrose powder and 8-12% hydroxypropyl methylcellulose aqueous solution is 1.5-3g:1mL, the dosage ratio of red clover extract, L-glutamic acid and 25-35% ethanol solution is 1g:1.5-3g:20-50mL, and the dosage ratio of the product, microsphere matrix and 8-12% hydroxypropyl methylcellulose aqueous solution is 1g:15-20g:1-1.4mL.

8. The method for preparing a urea compound feed additive according to claim 1, wherein: In step 3, the high-speed rotating centrifugal atomizing disk rotates at a speed of 6000-12000 r / min.

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