Special compound feed for Ningxia Tan sheep and preparation method thereof

Abstract

The application discloses a special compound feed for Ningxia Tan sheep and a preparation method thereof, and relates to the technical field of ruminant feed, which comprises a basic daily ration and a gate-controlled trace element component; the gate-controlled trace element component accounts for 0.7-2.0 percent of the mass of the special compound feed for Ningxia Tan sheep; trace element metal ions are combined with coordination sites on polysaccharide ligands in a three-dimensional cross-linked gate-controlled network formation process, and are distributed in the three-dimensional cross-linked gate-controlled network in a coordination combined state; the three-dimensional cross-linked gate-controlled network maintains a borate ester bond connection state under the condition of pH 6.2-6.8, and the borate ester bond is dissociated under the condition of pH 2.5-4.0. In the application, a boron source cross-linking agent is added to a coordination precursor, and the pH of a system is adjusted to construct a three-dimensional cross-linked gate-controlled network, so that the release of trace elements is controlled under neutral conditions, and the trace elements are quickly released under acidic conditions, and directional matching of release rhythm and an absorption window is realized.

Description

Technical Field

[0001] This invention relates to the field of ruminant feed technology, and in particular to a compound feed specifically for Ningxia Tan sheep and its preparation method. Background Technology

[0002] Precision nutrition technology for ruminants continues to evolve toward the design and regulation of micronutrient morphology. Common pathways include inorganic salt supplementation, organic chelate ligand complexation, coating and microencapsulation, sustained-release granulation, and network immobilization of polysaccharide carriers. By altering the ion coordination environment and diffusion boundaries, the stability of the formulation, the uniformity of mixing, and the release kinetics can be synergistically optimized.

[0003] Existing delivery strategies often suffer from a critical problem of insufficient temporal and spatial matching in the pH gradient environment of the gastrointestinal tract of ruminants. Specifically, it is difficult to maintain a low release level for a long time under near-neutral conditions, while it is difficult to trigger effective release quickly under acidic conditions. This leads to a misalignment between the trace element release curve and the absorption window, which in turn affects the stability of the coordination state and the predictability of utilization efficiency. Summary of the Invention

[0004] In view of this, this application provides a special compound feed for Ningxia Tan sheep and its preparation method.

[0005] According to one aspect of this disclosure, a special compound feed for Ningxia Tan sheep is provided, comprising a basal diet and a gated trace element component; the gated trace element component accounts for 0.7% to 2.0% by mass percentage of the special compound feed for Ningxia Tan sheep; the gated trace element component comprises a polysaccharide ligand containing an ortho-diol site, a boron source crosslinking agent, and at least one trace element metal ion; the molecular chains of the polysaccharide ligand are interconnected through dynamic covalent bonds of boron esters formed between the ortho-diol sites and the boron source under the action of the boron source crosslinking agent, forming a three-dimensional crosslinked gated network; the trace element metal ion coordinates with the coordination sites on the polysaccharide ligand during the formation of the three-dimensional crosslinked gated network and is distributed in the three-dimensional crosslinked gated network in a coordinated state; the three-dimensional crosslinked gated network maintains the boron ester bond connection state under pH 6.2 to 6.8 conditions, and the boron ester bonds dissociate under pH 2.5 to 4.0 conditions.

[0006] According to another aspect of this disclosure, a method for preparing a special compound feed for Ningxia Tan sheep is provided, comprising: Step 1, preparing an aqueous system of polysaccharide ligands containing vicinal diol sites; Step 2, adding a trace element metal ion donor to the aqueous system of polysaccharide ligands, so that the trace element metal ions and the coordination sites of the polysaccharide ligands form a coordination precursor; Step 3, adding a boron-based crosslinking agent to the coordination precursor and adjusting the pH of the system to 6.0-7.2, so that the polysaccharide ligand molecular chains form dynamic covalent bonds of borate esters and construct a three-dimensional crosslinked gated network; during the construction of the three-dimensional crosslinked gated network, the trace element metal ions coordinate with the coordination sites of the polysaccharide ligands and are distributed in the three-dimensional crosslinked gated network to obtain a gated network system; Step 4, shaping and drying the gated network system to obtain gated trace element particles; Step 5, mixing the gated trace element particles with a basal diet at a mass percentage of 0.7%-2.0% to obtain a special compound feed for Ningxia Tan sheep.

[0007] The beneficial effects of this invention are as follows: By adding a boron-based crosslinking agent to the coordination precursor and adjusting the pH of the system to 6.0–7.2, dynamic covalent bonds of borate esters are formed between the polysaccharide ligand molecular chains containing vicinal diol sites, and a three-dimensional crosslinked gated network is constructed. At the same time, trace element metal ions coordinate with the coordination sites during the network construction process and are distributed in the network in a coordinated state, forming a gated carrier that can switch between connection and dissociation states with pH. The three-dimensional crosslinked gated network maintains the borate ester bond connection under pH 6.2–6.8 conditions, which helps to constrain the cumulative release of trace elements to no more than 20% in 8 hours, and triggers the dissociation of borate ester bonds under pH 2.5–4.0 conditions, so that the cumulative release reaches no less than 60% in 2 hours, achieving directional matching between the release rhythm and the acidic absorption window. Attached Figure Description

[0008] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1 This is a schematic diagram of a three-dimensional cross-linked gated network structure.

[0010] Figure 2 This is a schematic diagram of the pH-responsive release mechanism. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0012] This invention aims to construct a compound feed specifically for Ningxia Tan sheep. In this embodiment, the compound feed for Ningxia Tan sheep comprises: a basal diet and gated trace element components; the gated trace element components account for 0.7% to 2.0% by mass of the compound feed for Ningxia Tan sheep; the gated trace element components include polysaccharide ligands containing vicinal diol sites, a boron-based crosslinking agent, and at least one trace element metal ion; the molecular chains of the polysaccharide ligands are interconnected through dynamic covalent bonds formed between the vicinal diol sites and the boron source under the action of the boron-based crosslinking agent, forming a three-dimensional crosslinked gated network; the trace element metal ions coordinate with the coordination sites on the polysaccharide ligands during the formation of the three-dimensional crosslinked gated network and are distributed in a coordinated state within the three-dimensional crosslinked gated network; the three-dimensional crosslinked gated network maintains the boron ester bond connection state under pH 6.2 to 6.8 conditions, and the boron ester bonds dissociate under pH 2.5 to 4.0 conditions.

[0013] In some embodiments of this application, the gated trace element components, based on 100 parts by mass, include 60-85 parts by mass of polysaccharide ligands containing vicinal diol sites, 2-12 parts by mass of boron-based crosslinking agent, 3-15 parts by mass of trace element metal ion donor, and 5-25 parts by mass of granulation framework or molding aid.

[0014] In some embodiments of this application, the molar ratio of boron in the boron-based crosslinking agent to the molar ratio of vicinal diol in the polysaccharide ligand is 0.15:1 to 0.85:1.

[0015] In some embodiments of this application, the molar ratio of the trace element metal ions to the coordination sites in the polysaccharide ligands is 0.02:1 to 0.30:1.

[0016] In some embodiments of this application, the trace element metal ions at least include Zn. 2+ and further contains Fe 2 + Fe 3+ Mn 2+ and Cu 2+ One or more of them.

[0017] In some embodiments of this application, the gated trace element component further comprises a competitive ion shielding ligand, wherein the competitive ion shielding ligand accounts for 0.5 to 6 parts by mass of the gated trace element component; The competitive ion-shielding ligand contains components that can interact with Ca. 2+ and Mg 2+ Coordinating groups that undergo coordination bonding.

[0018] In some embodiments of this application, the number-average molecular weight of the polysaccharide ligand containing the vicinal diol site is 5 × 10⁻⁶. 3 ~5×10 5 Da, and the molar fraction of the vicinal diol structural unit of the polysaccharide ligand is 20–65 mol.

[0019] This application also provides a method for preparing a special compound feed for Ningxia Tan sheep, including, Step 1: Prepare an aqueous system of polysaccharide ligands containing vicinal diol sites; Step 2: Add trace element metal ion donors to the polysaccharide ligand aqueous system to form coordination precursors between the trace element metal ions and the coordination sites of the polysaccharide ligands. Step 3: Add boron-based crosslinking agent to the coordination precursor and adjust the pH of the system to 6.0–7.2 to form dynamic covalent bonds of borate esters between polysaccharide ligand molecular chains and construct a three-dimensional crosslinked gated network. During the construction of the three-dimensional crosslinked gated network, trace element metal ions coordinate with the coordination sites of polysaccharide ligands and are distributed in the three-dimensional crosslinked gated network to obtain the gated network system. Step 4: The gated network system is shaped and dried to obtain gated trace element particles; Step 5: Mix the gated trace element granules with the basal diet at a mass percentage of 0.7% to 2.0% to obtain the special compound feed for Ningxia Tan sheep.

[0020] Preferably, the polysaccharide ligand containing the vicinal diol site is a natural polysaccharide or a modified polysaccharide having vicinal diol structural units; the boron-based crosslinking agent is water-soluble boric acid or borate.

[0021] Example 1: In the finished compound feed for Ningxia Tan sheep, the gated trace element components account for 1.2% of the finished product weight, and the basal diet accounts for 98.8%; the basal diet consists of 36% corn, 18% alfalfa hay meal, 12% wheat bran, 18% soybean meal, and 14.8% conventional feed additives.

[0022] The gated trace element component, based on 100 parts by mass, comprises 72 parts of a polysaccharide ligand containing vicinal diol sites, 6 parts of a boron-based crosslinking agent, 8 parts of a trace element metal ion donor, and 14 parts of a granulation framework or molding aid. The polysaccharide ligand is a modified natural polysaccharide with a number-average molecular weight of 1.2 × 10⁵ Da and a vicinal diol structural unit molar fraction of 45 mol%. The trace element metal ion donor contains at least Zn. 2+ and further includes Mn 2+ .

[0023] In preparation, polysaccharide ligands are added to an aqueous system for full swelling. Trace element metal ion donors are then added to the polysaccharide ligand aqueous system to form coordination precursors. Subsequently, a boron source crosslinking agent is added, and the pH of the system is adjusted to 6.4–6.8. This allows the polysaccharide ligand molecular chains to form dynamic covalent bonds with the boron source through vicinal diol sites, constructing a three-dimensional crosslinked gated network. Simultaneously, trace element metal ions coordinate with the coordination sites of the polysaccharide ligands during network construction and are distributed in a coordinated state within the three-dimensional crosslinked gated network. A granulation framework or molding aid is then added for molding and drying to obtain gated trace element particles. Finally, the gated trace element particles are mixed evenly with the basal diet at a mass percentage of 1.2% to obtain a compound feed specifically for Ningxia Tan sheep. The molar ratio of boron to vicinal diol in the polysaccharide ligand is 0.49:1, and the molar ratio of trace element metal ions to coordination sites of the polysaccharide ligand is 0.11:1.

[0024] During the preparation process, polysaccharide ligands containing vicinal diol sites are interconnected via dynamic covalent bonds of boron esters under the action of a boron-based crosslinking agent. Simultaneously, while constructing a three-dimensional crosslinked gated network, trace element metal ions are distributed in a coordinated state within the network structure, forming pH-responsive gated trace element particles. A schematic diagram of the structure is shown below. Figure 1 As shown.

[0025] Example 2: In the finished compound feed for Ningxia Tan sheep, the gated trace element component accounts for 1.0% of the finished product mass, and 99.0% of the basal diet. The gated trace element component, per 100 parts by mass, includes 78 parts of polysaccharide ligand, 5 parts of boron-based crosslinking agent, 7 parts of trace element metal ion donor, and 10 parts of granulation framework or molding aid, wherein the trace element metal ion donor contains at least Zn. 2+ And further includes Cu 2+In the preparation process, a polysaccharide ligand aqueous system was first prepared, and trace element metal ion donors were added to form coordination precursors. Then, a boron source crosslinking agent was added, and the pH of the system was adjusted to 6.2-6.6 to construct a three-dimensional crosslinked gated network. After molding and drying, gated trace element particles were obtained, and they were mixed evenly with the basal diet at a mass percentage of 1.0% to obtain a compound feed. The molar ratio of boron to vicinal diol was 0.33:1, and the molar ratio of trace element metal ions to coordination sites was 0.09:1.

[0026] Example 3: In the finished compound feed for Ningxia Tan sheep, the gated trace element component accounts for 1.5% of the finished product mass, and 98.5% of the basal diet. The gated trace element component, per 100 parts by mass, includes 70 parts of polysaccharide ligand, 8 parts of boron-based crosslinking agent, 10 parts of trace element metal ion donor, and 12 parts of granulation framework or molding aid. The trace element metal ion donor contains at least Zn. 2+ And further includes Fe 2+ During preparation, after forming coordination precursors for polysaccharide ligands and trace element metal ions, a boron-based crosslinking agent was added and the pH of the system was adjusted to 6.6–7.0 to construct a three-dimensional crosslinked gated network of dynamic covalent bonds in boron esters. Subsequently, the mixture was shaped, dried, and mixed with a basal diet to obtain a compound feed. The molar ratio of boron to vicinal diol was 0.66:1, and the molar ratio of trace element metal ions to coordination sites was 0.12:1.

[0027] Example 4: In the finished compound feed for Ningxia Tan sheep, the gated trace element component accounts for 0.8% of the finished product mass, and 99.2% of the basal diet. The gated trace element component, per 100 parts by mass, includes 82 parts of polysaccharide ligand, 4 parts of boron-based crosslinking agent, 6 parts of trace element metal ion donor, and 8 parts of granulation framework or molding aid. The trace element metal ion donor contains at least Zn. 2+ And further includes Fe 3+ During preparation, the pH of the coordination precursor system was adjusted to 6.3–6.7 to form a stable three-dimensional cross-linked gated network. After molding and drying, it was mixed evenly with the basal diet at a mass percentage of 0.8%. The molar ratio of boron to vicinal diol was 0.28:1, and the molar ratio of trace element metal ions to coordination sites was 0.07:1.

[0028] Example 5: In the finished compound feed for Ningxia Tan sheep, the gated trace element component accounts for 2.0% of the finished product mass, and 98.0% of the basal diet. The gated trace element component, per 100 parts by mass, includes 65 parts of polysaccharide ligand, 9 parts of boron-based crosslinking agent, 12 parts of trace element metal ion donor, and 14 parts of granulation framework or molding aid, wherein the trace element metal ion donor contains at least Zn. 2+ And further includes Mn 2+ and Cu2+ During preparation, a three-dimensional cross-linked gated network with a high degree of cross-linking was constructed under pH conditions of 6.5–6.8. After molding and drying, the network was mixed with a basic diet to obtain a compound feed. The molar ratio of boron to vicinal diol was 0.80:1, and the molar ratio of trace element metal ions to coordination sites was 0.15:1.

[0029] Example 6: In the finished compound feed for Ningxia Tan sheep, the gated trace element component accounts for 1.8% of the finished product mass, and 98.2% of the basal diet. The gated trace element component, per 100 parts by mass, includes 74 parts of polysaccharide ligand, 7 parts of boron-based crosslinking agent, 9 parts of trace element metal ion donor, and 10 parts of granulation framework or molding aid, wherein the trace element metal ion donor contains at least Zn. 2+ And further includes Fe 2+ and Mn 2+ During preparation, the pH of the system was adjusted to 6.0–6.4 to form a three-dimensional cross-linked gated network with good reversibility. After molding and drying, the compound feed was mixed with the basal diet to obtain the compound feed. The molar ratio of boron to vicinal diol was 0.53:1, and the molar ratio of trace element metal ions to coordination sites was 0.11:1.

[0030] Example 7: In the finished compound feed for Ningxia Tan sheep, the gated trace element component accounts for 1.1% of the finished product mass, and 98.9% of the basal diet. The gated trace element component, per 100 parts by mass, includes 80 parts of polysaccharide ligand, 3 parts of boron-based crosslinking agent, 5 parts of trace element metal ion donor, and 12 parts of granulation framework or molding aid, wherein the trace element metal ion donor contains at least Zn. 2+ And further includes Cu 2+ During preparation, a three-dimensional cross-linked gated network was constructed under pH conditions of 6.4–6.8. After molding and drying, the network was mixed with a basal diet to obtain a compound feed. The molar ratio of boron to vicinal diol was 0.21:1, and the molar ratio of trace element metal ions to coordination sites was 0.06:1.

[0031] Example 8: In the finished compound feed for Ningxia Tan sheep, the gated trace element component accounts for 1.6% of the finished product mass, and 98.4% of the basal diet. The gated trace element component, per 100 parts by mass, includes 76 parts of polysaccharide ligand, 9 parts of boron-based crosslinking agent, 6 parts of trace element metal ion donor, and 9 parts of granulation framework or molding aid, wherein the trace element metal ion donor contains at least Zn. 2+ And further includes Mn 2+During preparation, a fully connected three-dimensional cross-linked gated network of dynamic covalent bonds of borate ester was constructed under pH conditions of 6.6–7.2. After molding and drying, the compound feed was mixed evenly with the basal diet at a mass percentage of 1.6%. The molar ratio of boron to vicinal diol was 0.62:1, and the molar ratio of trace element metal ions to coordination sites was 0.07:1.

[0032] Comparative Example 1: In the finished compound feed for Ningxia Tan sheep, the trace element component accounts for 1.6% of the finished product mass, and the basal diet accounts for 98.4%; the composition of the basal diet is the same as in Example 1. The trace element component is a conventional inorganic salt trace element premix, containing only trace element metal ion donors in the form of inorganic salts such as zinc sulfate and manganese sulfate, as well as conventional carriers. It does not contain polysaccharide ligands with vicinal diol sites, nor does it contain boron-based crosslinking agents, and no boron ester dynamic covalent bond structure is formed during the preparation process. During preparation, the inorganic salt trace element premix is ​​directly mixed evenly with the basal diet and granulated to obtain the comparative sample.

[0033] Comparative Example 2: In the finished compound feed for Ningxia Tan sheep, the trace element component accounted for 1.6% of the finished product mass, and the basal diet accounted for 98.4%; the composition of the basal diet was the same as in Example 1. The trace element component, per 100 parts by mass, included 76 parts of polysaccharide ligands containing vicinal diol sites, 6 parts of trace element metal ion donors, and 18 parts of granulation framework or molding aids, but did not contain boron-based crosslinking agents. During preparation, the polysaccharide ligands were added to the aqueous system to swell, and then the trace element metal ion donors were added to allow the trace element metal ions to coordinate with the coordination sites of the polysaccharide ligands. However, no boron-based crosslinking agent was added during the entire process, and the pH of the system was not adjusted to 6.0–7.2 to form dynamic covalent bonds in the borate ester. The resulting system did not form a three-dimensional crosslinked gated network. Subsequently, the feed was shaped, dried, and mixed with the basal diet for granulation to obtain the comparative sample.

[0034] Comparative Example 3: In the finished compound feed for Ningxia Tan sheep, trace element components accounted for 1.6% of the finished product's mass, and the basal diet accounted for 98.4%; the composition of the basal diet was the same as in Example 1. The trace element components were coated trace element particles, and the trace element metal ion donors included at least Zn. 2+ The outer layer of the micronutrient particles is physically coated with lipid or waxy materials to achieve sustained release, but it does not contain polysaccharide ligands with vicinal diol sites or boron-derived crosslinking agents, and the coating structure does not have boron ester dynamic covalent bonds. During preparation, the coated micronutrient particles are directly mixed with a basal diet and granulated to obtain comparative samples.

[0035] The following three tests were conducted on the products of Examples 1-8 and the samples of Comparative Examples 1-3: First, the cumulative release rate of trace elements in 8 hours was determined under pH 6.5 conditions; second, the cumulative release rate of trace elements in 2 hours was determined under pH 3.0 conditions; and third, the apparent bioavailability of trace elements was determined using an in vitro ruminant digestion model.

[0036] Under different pH conditions, the dynamic covalent bond state of borate esters in gated trace element particles changes, thereby regulating the release behavior of trace element metal ions. The network structure remains stable under neutral conditions, but dissociates and promotes release under acidic conditions. A planar schematic diagram of its pH-responsive release mechanism is shown below. Figure 2 As shown.

[0037] Table 1. Comparison of three test results between Examples 1-8 and Comparative Examples 1-3

[0038] Table 2. Dosage and internal composition of gated trace elements in Examples 1-8

[0039] As shown in Table 1, the cumulative release rate of trace elements in Examples 1-8 under pH 6.5 conditions within 8 hours was no higher than 20%, and the overall distribution was concentrated in the range of 14.6% to 19.7%, with a relatively slow release rate. This indicates that the gated trace element components can maintain the dynamic covalent bond connection state of borate esters under near-neutral conditions, forming a stable constraint on trace element metal ions. In contrast, the trace elements in Comparative Example 1 existed directly in the form of inorganic salts, with a cumulative release rate of nearly 60% within 8 hours. Although Comparative Examples 2 and 3 had a certain slow-release effect, they still showed a significantly higher release level than the Examples under neutral conditions. This indicates that without the three-dimensional cross-linked gated network formed by boron source cross-linking, it is difficult to effectively inhibit the release behavior of trace elements.

[0040] Further analysis of the cumulative release rate data at pH 3.0 for 2 hours in Table 1 shows that Examples 1-8 all exhibited a cumulative release rate of no less than 60% in an acidic environment, with some examples reaching over 70%. This indicates that after the dynamic covalent bonds of the borate ester dissociate under decreasing pH conditions, the gated network can quickly release the binding of trace element metal ions, achieving directional release. In contrast, Comparative Example 1 showed a release rate of less than 40% under the same conditions. Although Comparative Examples 2 and 3 showed some improvement, their overall release levels were still significantly lower than those of the Examples. This suggests that relying solely on physical coating or simple coordination binding is insufficient to form a clear and controllable release triggering behavior in an acidic environment.

[0041] A comprehensive analysis of the low release characteristics under neutral conditions and the high release characteristics under acidic conditions in Table 1 reveals that Examples 1-8 exhibit a clear difference in release behavior between pH 6.5 and pH 3.0, demonstrating the selective response of gated trace element components to changes in environmental pH. This release window allows trace elements to remain in a controlled state during non-absorption-dominant phases and to be released in concentrated form during acidic phases that favor absorption, thus helping to reduce ineffective losses and improve utilization efficiency. In contrast, the comparative samples, lacking a dynamically reversible cross-linked gated structure, show lower differentiation in release behavior with pH changes.

[0042] The results of the in vitro ruminant digestion model test show that the apparent bioavailability of Examples 1-8 is generally in the range of 65.7%-71.8%, which is significantly higher than that of Comparative Examples 1-3 (48.6%-58.3%). This indicates that coordinating and immobilizing trace element metal ions through a three-dimensional cross-linked gating network and achieving pH-responsive release helps to increase the proportion of trace elements entering the absorbable state under simulated digestion conditions. The trend of changes in apparent bioavailability is consistent with the behavioral characteristics of controlled release under neutral conditions and enhanced release under acidic conditions.

[0043] As shown in Table 2, the content and internal composition of gated trace element components indicate that by controlling the content of gated trace element components within the range of 0.8% to 2.0%, the release behavior and apparent bioavailability can be synergistically improved without significantly increasing the amount added, by adjusting the ratio of polysaccharide ligands, boron source crosslinking agents, trace element metal ion donors, and granulation frameworks or molding aids. The functional effects exhibited by gated trace element components are correlated with the internal structure construction method and the setting of crosslinking and coordination parameters.

[0044] The above description is only a specific embodiment of this disclosure, but the protection scope of this disclosure is not limited thereto. The protection scope of this disclosure should be determined by the protection scope of the claims.

Claims

1. A compound feed specifically for Ningxia Tan sheep, characterized in that: Including basal diet and gated trace element components; The gated trace element components account for 0.7% to 2.0% of the mass percentage of the Ningxia Tan sheep-specific compound feed; The gated trace element component comprises a polysaccharide ligand containing a diol site, a boron-based crosslinking agent, and at least one trace element metal ion. The molecular chains of the polysaccharide ligands are interconnected through dynamic covalent bonds of boron esters formed between the ortho-diol sites and the boron source under the action of the boron source crosslinking agent, forming a three-dimensional crosslinked gated network. During the formation of the three-dimensional cross-linked gated network, the trace element metal ions coordinate with the coordination sites on the polysaccharide ligands and are distributed in the three-dimensional cross-linked gated network in a coordinated state. The three-dimensional cross-linked gated network maintains the borate ester bond connection state under pH 6.2–6.8 conditions, and the borate ester bond dissociates under pH 2.5–4.0 conditions.

2. The compound feed specifically for Ningxia Tan sheep as described in claim 1, characterized in that: The gated trace element components, per 100 parts by mass, consist of 60-85 parts by mass of polysaccharide ligands containing vicinal diol sites, 2-12 parts by mass of boron-based crosslinking agent, 3-15 parts by mass of trace element metal ion donor, and 5-25 parts by mass of granulation framework or molding aid.

3. The compound feed specifically for Ningxia Tan sheep as described in claim 2, characterized in that: The ratio of the molar amount of boron in the boron-based crosslinking agent to the molar amount of vicinal diol in the polysaccharide ligand is 0.15:1 to 0.85:

1.

4. The compound feed specifically for Ningxia Tan sheep as described in claim 3, characterized in that: The molar ratio of the trace element metal ions to the coordination sites in the polysaccharide ligands is 0.02:1 to 0.30:

1.

5. The compound feed specifically for Ningxia Tan sheep as described in claim 4, characterized in that: The trace element metal ions include at least Zn. 2+ and further contains Fe 2+ Fe 3+ Mn 2+ and Cu 2+ One or more of them.

6. The compound feed specifically for Ningxia Tan sheep as described in claim 5, characterized in that: The gated trace element component further comprises a competitive ion shielding ligand, wherein the competitive ion shielding ligand accounts for 0.5 to 6 parts by mass of the gated trace element component; The competitive ion-shielding ligand contains components that can interact with Ca. 2+ and Mg 2+ Coordinating groups that undergo coordination bonding.

7. The compound feed specifically for Ningxia Tan sheep as described in claim 6, characterized in that: The number-average molecular weight of the polysaccharide ligand containing the vicinal diol site is 5 × 10⁻⁶. 3 ~5×10 5 Da, and the molar fraction of the vicinal diol structural unit of the polysaccharide ligand is 20–65 mol.

8. The compound feed specifically for Ningxia Tan sheep as described in any one of claims 1 to 7, characterized in that: The cumulative release of trace element metal ions of the gated trace element component is not higher than 20% within 8 hours under pH 6.2-6.8 conditions, and not lower than 60% within 2 hours under pH 2.5-4.0 conditions.

9. A method for preparing a compound feed specifically for Ningxia Tan sheep, based on the compound feed specifically for Ningxia Tan sheep according to any one of claims 1 to 8, characterized in that: include, Step 1: Prepare an aqueous system of polysaccharide ligands containing vicinal diol sites; Step 2: Add trace element metal ion donors to the polysaccharide ligand aqueous system to form coordination precursors between the trace element metal ions and the coordination sites of the polysaccharide ligands. Step 3: Add boron-based crosslinking agent to the coordination precursor and adjust the pH of the system to 6.0–7.2 to form dynamic covalent bonds of borate esters between polysaccharide ligand molecular chains and construct a three-dimensional crosslinked gated network. During the construction of the three-dimensional crosslinked gated network, trace element metal ions coordinate with the coordination sites of polysaccharide ligands and are distributed in the three-dimensional crosslinked gated network to obtain the gated network system. Step 4: The gated network system is shaped and dried to obtain gated trace element particles; Step 5: Mix the gated trace element granules with the basal diet at a mass percentage of 0.7% to 2.0% to obtain the special compound feed for Ningxia Tan sheep.

10. The preparation method according to claim 9, characterized in that: The polysaccharide ligand containing the vicinal diol site is a natural polysaccharide or a modified polysaccharide with vicinal diol structural units; the boron-based crosslinking agent is water-soluble boric acid or borate.

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