Sheep feed capable of reducing urinary stone deposition and improving mutton quality and flavor and preparation method thereof

Abstract

The invention belongs to the field of animal feeds, and particularly relates to a sheep feed capable of reducing urinary stone deposition and improving mutton quality and flavor and a preparation method of the sheep feed. Corn starch-chitosan-ammonium chloride compound polysaccharide gel particle powder is compounded with whole corn, crushed corn, soybean meal, corn dry vinasse, corn germ meal, soybean hulls, calcium carbonate, sodium chloride, calcium hydrophosphate and a fattening sheep premix, the carboxyl substitution degree of oxidized corn starch is controlled to be 0.10-0.50 mmol / g, the deacetylation degree of chitosan is controlled to be 75-95%, and the molecular weight is controlled to be 50-500 kDa; controllable slow release of ammonium chloride, synergistic improvement of particle strength and moisture absorption resistance, continuous and stable acidification of urine and improvement of mutton flavor are realized; the problems of particle strength reduction and salt precipitation pulverization caused by quick release of ammonium chloride in traditional acidified feed granulation, storage and transportation, particle instability and uneven loading in high-shear spray drying, difficulty in consideration of urine acidification effectiveness and palatability and the like are solved, and the method has application value in the fields of sheep feeding nutrition regulation and meat quality improvement.

Description

Technical Field

[0001] This invention relates to the field of animal feed, specifically to a sheep feed that reduces urinary stone deposition and enhances the flavor of mutton, and a method for preparing the same. Background Technology

[0002] In modern large-scale sheep farming, feed nutrition regulation technology has a decisive impact on sheep health and mutton quality. Fattening sheep often face two core problems: urinary stone deposition and insufficient mutton flavor and quality. The former seriously affects sheep growth performance and welfare, while the latter directly restricts product market competitiveness. Urinary stone formation is closely related to urine pH. When urine pH is high, the solubility of phosphates and carbonates in urine is significantly reduced, making them more likely to precipitate in the urinary system and form stones, leading to difficulty urinating or even urinary system obstruction. Therefore, regulating urine pH through feed composition and maintaining it within a suitable range is an effective strategy to prevent urinary stone deposition. Simultaneously, mutton flavor and quality are affected by feed composition, nutritional balance, and metabolic products. High-quality protein sources, appropriate energy structure, and a scientifically balanced micronutrient ratio can significantly improve muscle amino acid composition, fatty acid profile, and the content of flavor precursors, thereby enhancing the tenderness, juiciness, and characteristic flavor of mutton. Meeting these performance requirements is of great significance for improving breeding efficiency, ensuring animal health, and increasing product added value. It is a key scientific issue that urgently needs to be addressed in the field of ruminant nutrition regulation.

[0003] To address the needs of urinary stone prevention and mutton quality improvement, existing technologies primarily employ the addition of acidifiers to feed to lower urine pH. Ammonium chloride is widely used due to its excellent acidification effect and cost advantage. However, free ammonium chloride is prone to rapid release under the high temperature and pressure conditions during feed pelleting and conditioning, leading to osmotic pressure imbalance and loose structure within the pellets. This results in a significant decrease in pellet strength after pelleting, making them prone to breakage and pulverization during storage and transportation. For example, Chinese patent CN114009606A discloses an energy additive for ruminant feed and its preparation method, but it suffers from the problem of ammonium chloride rapidly migrating to the pellet surface and precipitating crystals during pelleting, causing surface pulverization, moisture absorption, and clumping. Furthermore, the release rate of ammonium chloride is difficult to precisely control, and its excessively rapid release in the rumen environment causes local acidification stimulation, affecting feed intake and palatability. For example, Chinese patent CN110419633B discloses a slow-release feed-grade ammonium chloride and its preparation method. However, its coating material is prone to cracking and detachment during high-shear dispersion and spray drying, resulting in insufficient particle structure stability, uneven ammonium chloride load distribution, and difficulty in precisely designing the mass transfer resistance of the coating layer, thus restricting the predictability and controllability of ammonium chloride release kinetics. The above-mentioned technical solutions still have significant shortcomings in resolving the contradiction between particle strength and controllable ammonium chloride release, the synergistic control of particle structure stability and load uniformity during the process, and the balance between the effectiveness of urine acidification and palatability, thus limiting the widespread application of acidified functional feeds in sheep farming. Summary of the Invention

[0004] The purpose of this invention is to provide a sheep feed that reduces urinary stone deposition and improves the flavor of mutton, as well as its preparation method. This invention addresses the current challenges in acidified feeds, such as the mass transfer contradiction between particle strength / resistance to moisture absorption and clumping and the controllable release of ammonium chloride during pelleting, conditioning, and storage; the process coupling conflict between particle structure stability and ammonium chloride loading uniformity / predictable release caused by high shear dispersion and spray drying; and the difficulty in simultaneously achieving effective urine acidification, palatability, irritation control, and salt precipitation and pulverization on the particle surface.

[0005] This invention employs a synergistic design that utilizes oxidized corn starch and chitosan to form a three-dimensional cross-linked gel network through electrostatic interactions and calcium ion bridging, thereby loading ammonium chloride. The carboxyl groups introduced by the oxidized corn starch and the amino groups of chitosan form multi-point electrostatic adsorption under specific pH conditions, while Ca... 2+Coordination with carboxyl groups constructs a stable "egg-box" structure. These two mechanisms synergistically enhance the mechanical strength and pore structure stability of the gel network, allowing ammonium chloride to uniformly penetrate and stably fix within the gel framework. During high-shear dispersion and spray drying, the high elastic modulus and deformation resistance of the cross-linked gel network effectively resist mechanical and thermal stress damage, avoiding problems such as coating layer rupture and non-uniform distribution of ammonium chloride. Under the high-temperature and high-pressure environment of granulation and conditioning, the dense structure of the gel network significantly slows down the diffusion and migration rate of ammonium chloride, preventing its rapid release and surface precipitation. During rumen digestion, the gel network gradually dissociates under the action of microbial enzymes and machinery, achieving a sustained release of ammonium chloride. This ensures a continuous and stable urine acidification effect while avoiding localized high-concentration stimulation, achieving a good synergistic effect.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A sheep feed that reduces urinary stone deposition and enhances the flavor of mutton, comprising the following components by dry matter weight: The corn comprises 45-65 wt%, including whole corn kernels and crushed corn, wherein the median volumetric particle size (D50) of the crushed corn is 0.5-1.0 mm, and the median volumetric particle size (D50) is measured by a laser particle size analyzer. Soybean meal 10-18 wt%; 3-12 wt% dried corn distillers grains; Corn germ meal 6-15 wt%; Soybean hulls 3-8 wt%; Calcium carbonate fine powder 1.5–3.0 wt%; Sodium chloride 0.3–1.0 wt%; 0.5–2.0 wt% of calcium hydrogen phosphate dihydrate; Compound premixed feed for fattening sheep: 0.5–2.0 wt%; Corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles, 0.6–5.0 wt%; The corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder meets the following conditions: The oxidized corn starch includes oxidized corn starch with a carboxyl substitution degree of 0.10 to 0.50 mmol / g; Includes chitosan, wherein the degree of deacetylation of the chitosan is 75-95% and the number-average molecular weight is 50-500 kDa; It includes ammonium chloride, wherein the mass fraction of ammonium chloride in the dry basis of the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder is 10-40 wt%; The median particle size of the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder is 0.5–5.0 μm.

[0007] Furthermore, the total mass fraction of ammonium chloride in the feed composition is 0.4 to 0.9 wt%, wherein the ammonium chloride present in the form of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder accounts for 60 to 75 wt% of the total ammonium chloride.

[0008] It should be noted that the present invention does not exclude the presence of a small amount of ammonium chloride in a free state (e.g., derived from the compound premixed feed for fattening sheep), which is used to provide initial acidification in the early stages of feeding; however, by encapsulating 60-75 wt% of ammonium chloride in the form of compound polysaccharide gel microparticles for slow release, the risk of rapid migration / salt precipitation during the granulation and conditioning process can be significantly reduced, and the stimulation of local high concentrations in the rumen can be avoided, thereby achieving a continuous and stable urine acidification effect.

[0009] Furthermore, the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder is prepared through the following steps: A1. An aqueous solution of ammonium chloride is added to the corn starch-chitosan crosslinked gel, wherein the mass fraction of the aqueous solution of ammonium chloride is 10-30 wt%. The mixture is stirred to allow the ammonium chloride to uniformly penetrate into the gel network, and the amount added is controlled so that the mass fraction of ammonium chloride in the dry basis of the resulting corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder is 10-40 wt%. A2. The crosslinked gel loaded with ammonium chloride is subjected to high-shear dispersion or ultrasonic dispersion, wherein the high-shear dispersion is performed at a rotation speed of 10,000 to 20,000 r / min and a dispersion time of 5 to 20 min, and the ultrasonic dispersion is performed at an ultrasonic power of 200 to 600 W and an ultrasonic time of 5 to 20 min, so that the median particle size of the resulting primary gel particles is 100 to 500 nm. A3. The obtained dispersion is spray-dried (spray drying method is two-fluid spraying or centrifugal spraying; inlet air temperature is 140-190℃, outlet air temperature is 70-95℃; solid content of dispersion is 5-20wt%; feed rate is 3-15mL / min; when using two-fluid spraying, atomizing gas pressure is 0.15-0.40MPa; when using centrifugal spraying, atomizing disc speed is 8000-20000r / min; powder collection is done using a cyclone separator) to obtain corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder with a median volumetric particle size of 0.5-5.0μm; the moisture content of the microparticle powder is not higher than 10wt%.

[0010] Furthermore, the corn starch-chitosan crosslinked gel is prepared through the following steps: B1. Dissolve chitosan in an aqueous solution of glacial acetic acid with a volume fraction of 1-5 vol% to obtain a chitosan solution with a chitosan mass fraction of 1.0-2.0 wt%, wherein the degree of deacetylation of the chitosan is 75-95% and the number average molecular weight is 50-500 kDa; B2. Disperse oxidized corn starch in deionized water to obtain an oxidized corn starch dispersion with a mass fraction of 5-20 wt%, and adjust the pH value of the dispersion to 6.0-7.0; B3. Mix the oxidized corn starch dispersion and the chitosan solution at a mass ratio of 1.0–5.0:0.1–0.5, stir at 20–40°C, and slowly add an aqueous solution of calcium chloride dihydrate with a concentration of 0.1–1.0 mol / L over a period of 5–30 min. Maintain the system temperature at 20–40°C and the pH at 6.0–7.0 during the addition process to ensure the Ca concentration in the system is within acceptable limits. 2+ The molar ratio of oxidized corn starch to carboxyl groups is 0.1–1.0:1. Stirring is continued for 0.5–2.0 h to allow oxidized corn starch and chitosan to form a three-dimensional cross-linked gel through electrostatic interaction and calcium ion bridging.

[0011] Furthermore, the oxidized corn starch is prepared through the following steps: C1. Prepare a corn starch aqueous suspension with a mass fraction of 20-40 wt%, add a sodium hypochlorite solution with a mass fraction of 5-15 wt% dropwise at 35-45℃, adjust the pH of the system to 8.0-9.0 with 0.5-2.0 mol / L sodium hydroxide solution, and react for 0.5-2.0 h; C2. Stop adding sodium hypochlorite when the degree of carboxyl substitution of the corn starch, as determined by acid-base titration, reaches 0.10–0.50 mmol / g, and adjust the pH of the system to 6.0–7.0 with 0.5–2.0 mol / L hydrochloric acid; C3. Wash and dry at 40–60 °C to obtain oxidized corn starch with a carboxyl substitution degree of 0.10–0.50 mmol / g.

[0012] Furthermore, the compound premixed feed for fattening sheep, based on 100 parts of the premixed feed, includes the following components, by weight: Vitamin A 8-15 parts; Vitamin D3 1.5–3.0 servings; Vitamin E 15-30 servings; Nicotinamide 0.1-0.2 parts; 8-10 parts of rumen-protected choline; Copper sulfate 0.15–0.25 parts; Ferrous sulfate 1.5–2.0 parts; 2.5–3.5 parts manganese sulfate; Zinc sulfate 2.5–3.5 parts; Calcium iodate 0.03–0.06 parts; Sodium selenite 0.015–0.03 parts; 0-10 parts of ammonium chloride; 3-5 parts of urease inhibitor; Antioxidant 1.5–2.5 parts; 1.5–2.5 parts of compound probiotics; 8-10 parts of compound enzyme preparation; The rice husk powder is used as a supplement to make up 100 parts of the compound premixed feed for fattening sheep; The compound probiotics include at least one microbial strain, which is selected from Saccharomyces cerevisiae, Bacillus subtilis, Aspergillus niger and Aspergillus oryzae.

[0013] Furthermore, the mass ratio of total calcium to total phosphorus in the feed composition is 2.0 to 2.5:1, the calcium carbonate powder is fine stone powder with a particle size of 100% passing through an 80-mesh standard sieve, and the calcium content is not less than 36 wt%.

[0014] Furthermore, the corn meets the second-grade corn standard and has the following quality indicators: test weight not less than 685g / L, impurity mass fraction not more than 2wt%, imperfect kernel mass fraction not more than 5wt%, fatty acid value calculated as potassium hydroxide not more than 60mg / 100g, and bright color, no moldy odor, and hygiene indicators meet the requirements of GB13078.

[0015] As a concept of this invention, the design of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles is mainly used to enhance the structural stability of feed pellets and the controllable slow-release performance of ammonium chloride. The degree of carboxyl substitution of oxidized corn starch is controlled within the range of 0.10–0.50 mmol / g, ensuring sufficient carboxyl density to form strong electrostatic adsorption with chitosan amino groups, while avoiding excessively high substitution levels that would lead to increased rigidity of starch segments and increased gel brittleness. This ensures the gel network maintains suitable elasticity and toughness during high-shear dispersion and spray drying. The degree of deacetylation of chitosan is set within the range of 75–95%. Within this range, the amino group density is moderate, allowing for sufficient binding with carboxyl groups to form multi-point crosslinks while retaining some acetyl groups to maintain segment flexibility and biocompatibility. The number-average molecular weight is controlled within the range of 50–500 kDa. The lower molecular weight ensures good solubility of chitosan in acidic solutions and uniform diffusion during gelation, while the longer chain segments in the higher molecular weight range strengthen the mechanical strength of the gel network through molecular chain entanglement. The mass fraction of ammonium chloride in the dry basis of the composite polysaccharide gel microparticle powder was set at 10–40 wt%. Below 10 wt%, the loading was insufficient to achieve effective urine acidification, while above 40 wt%, it exceeded the loading capacity of the gel network, leading to supersaturation precipitation of ammonium chloride in the gel pores and uncontrollable fluctuations in the release rate. The median particle size of the composite polysaccharide gel microparticle powder was controlled within the range of 0.5–5.0 μm. This particle size range ensures uniform dispersion of the microparticles in the feed pellet matrix, avoiding agglomeration and sedimentation due to excessively large particle size and excessively large specific surface area, increased hygroscopicity, and rapid release of ammonium chloride due to excessively small particle size. Through the synergistic crosslinking of oxidized corn starch and chitosan, a three-dimensional gel framework with high stability, high loading capacity, and controllable mass transfer characteristics was constructed. This framework maintained structural integrity under high temperature and high pressure conditions during granulation and conditioning, and gradually released ammonium chloride in the rumen environment through microbial enzymatic hydrolysis and mechanical chewing. This achieved synergistic optimization of particle strength, ammonium chloride loading uniformity, and sustained-release performance, significantly superior to single polysaccharide gel systems.

[0016] This invention also discloses a method for preparing sheep feed that reduces urinary stone deposition and enhances the flavor of mutton, comprising the following steps: S1. Prepare oxidized corn starch to obtain oxidized corn starch with a carboxyl substitution degree of 0.10-0.50 mmol / g; S2. Preparation of corn starch-chitosan crosslinked gel; S3. Preparation of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles; S4. Mix crushed corn, soybean meal, corn distillers grains, corn germ meal, soybean hulls, fine calcium carbonate powder, calcium hydrogen phosphate dihydrate, sodium chloride, and fattening sheep compound premixed feed with the corn starch-chitosan-ammonium chloride compound polysaccharide gel microparticle powder to obtain basic concentrate; S5. Conditioning and granulation of the base concentrate: Steam conditioning or steam-water combined conditioning is used to condition the material temperature to 70-90℃, the conditioning time to 30-120s, and the moisture content of the material to 14-18wt%; then ring die granulation is used, with a ring die aperture of 4-6mm; after granulation, the material is cooled countercurrently until the particle temperature is no higher than the ambient temperature +5℃, and the moisture content of the finished particles is no higher than 12wt%, to obtain granulated concentrate; S6. The pelleted concentrate and whole corn are mixed at a ratio of 0.5 to 2.0:1 to obtain the feed composition.

[0017] Furthermore, 30-40 wt% of the corn is pulverized before step S4, and the pulverization effect is such that when tested with a 14-mesh feed analysis standard sieve, the mass fraction of the material passing through the sieve is not less than 80 wt%, and the remaining 60-70 wt% of the corn is added in whole grain form in step S6; the coefficient of variation of the mass fraction of the mixing uniformity of the basic concentrate is not higher than 5%.

[0018] As another aspect of this invention, the step-by-step preparation process is designed to enhance the precise control of the carboxyl substitution degree of oxidized corn starch and the structural uniformity of the corn starch-chitosan crosslinked gel network. During the preparation of oxidized corn starch, by controlling the slow dropping rate of sodium hypochlorite at 35–45°C and monitoring the carboxyl substitution degree in real time to the range of 0.10–0.50 mmol / g, excessive degradation of starch chains and uneven carboxyl distribution caused by high temperature or rapid oxidation are avoided, ensuring the uniform introduction of carboxyl groups on the surface and inside of starch granules. In the crosslinked gel formation stage, by pre-adjusting the pH of the oxidized corn starch dispersion to 6.0–7.0, the carboxyl groups are partially deprotonated and become negatively charged. When mixed with the chitosan solution, the positive charge of the amino groups and the negative charge of the carboxyl groups form preliminary electrostatic adsorption under mild conditions of 20–40°C. Subsequently, an aqueous solution of calcium chloride dihydrate is slowly added, and Ca... 2+The ammonium chloride is gradually infiltrated into the gel system and forms coordination crosslinks with carboxyl groups. This stepwise construction of a dual crosslinking mechanism avoids excessive local crosslinking and structural inhomogeneity under rapid mixing or high-temperature conditions, ensuring the controllability of the gel network pore structure and the uniformity of subsequent ammonium chloride loading. High-shear dispersion or ultrasonic dispersion steps disperse the ammonium chloride-loaded crosslinked gel to a median particle size of 100–500 nm in the primary gel particles. This size ensures rapid drying and structural solidification of the particles during subsequent spray drying, avoiding internal stress accumulation and cracking of large-scale gel particles during drying. The 0.5–5.0 μm particles obtained by spray drying exhibit good flowability and dispersibility, and are thoroughly and uniformly mixed with other components during the basic concentrate mixing stage. The coefficient of variation of mixing uniformity is controlled to be no higher than 5%, ensuring the consistency of ammonium chloride distribution in each feed pellet. Through the post-mixing design of pelleted concentrate and whole corn kernels, the slow degradation of whole corn kernels in the rumen provides a continuous energy supply. This, combined with the slow-release ammonium chloride from the composite polysaccharide gel microparticle powder, achieves a dynamic balance between energy release and urine acidification, significantly superior to traditional single-mixing processes.

[0019] The synergistic mechanism between oxidized corn starch and chitosan in this invention is manifested at two levels: structural complementarity and functional synergy. Oxidized corn starch focuses on providing carboxyl active sites and a gelling framework for the starch matrix. Its carboxyl groups not only form electrostatic adsorption with the amino groups of chitosan, but also interact with Ca... 2+ The coordination of the molecule constructs an "egg-box" structure, significantly enhancing the mechanical strength and deformation resistance of the gel network. Chitosan focuses on providing cationic amino groups and biodegradable properties; its long-chain molecules enhance gel toughness through molecular chain entanglement, while the degree of protonation of the amino groups allows for adjustable gel crosslinking density as pH changes. Regarding improving particle strength and moisture resistance, the starch segments of oxidized corn starch partially gelatinize during high-temperature conditioning to form a continuous phase, filling particle pores and enhancing the compactness of the particle matrix. The chitosan molecular chains form a thin film layer on the particle surface, reducing the surface adsorption and diffusion rate of water molecules. The synergistic effect of these two components increases particle hardness and significantly reduces moisture absorption. In improving the uniformity of ammonium chloride loading and its sustained-release performance, the carboxyl groups of oxidized corn starch form ionic bonds with the ammonium ions of ammonium chloride, enhancing the fixation strength of ammonium chloride in the gel network. The protonation degree of chitosan amino groups changes with the pH of the system, thus affecting the charge density and pore structure of the composite gel network, and consequently regulating the diffusion and release kinetics of ammonium chloride in the network. Together, they construct a dual barrier of "physical encapsulation + chemical adsorption," achieving the slow and sustained release of ammonium chloride. The core of the synergistic effect of oxidized corn starch and chitosan lies in the electrostatic adsorption of carboxyl and amino groups, which provides rapid gelation capability, Ca... 2+The bridging enhances network stability, starch gelatinization and chitosan film formation synergistically improve particle physical properties, and the dual adsorption mechanism precisely regulates ammonium chloride release, achieving a triple synergistic optimization of structural stability, loading capacity and sustained-release performance. A single component can hardly achieve this comprehensive effect.

[0020] Beneficial technical effects 1. Significantly enhances the structural stability and moisture resistance of feed pellets: The three-dimensional cross-linked gel network formed by oxidized corn starch and chitosan maintains structural integrity under high temperature and high pressure conditions during pelleting and conditioning. The partial gelatinization of starch segments and the entanglement of chitosan molecular chains synergistically fill the pores of the pellets and enhance the density of the matrix. At the same time, the thin film layer formed by chitosan on the surface of the pellets significantly reduces the adsorption and diffusion rate of water molecules, thereby increasing the hardness of the pellets and reducing the moisture absorption rate. This effectively solves the problems of decreased pellet strength and moisture absorption and clumping in traditional acidified feeds during storage and transportation.

[0021] 2. Achieving uniform loading and controlled sustained release of ammonium chloride: By controlling the degree of carboxyl substitution of oxidized corn starch to 0.10–0.50 mmol / g and the degree of deacetylation of chitosan to 75–95%, a dual barrier of "physical encapsulation + chemical adsorption" was constructed. Ammonium chloride was uniformly distributed in the pores of the gel network and fixed by the ionic bonds of carboxyl and amino groups, avoiding rapid migration and surface precipitation during the granulation process. It was gradually released in the rumen environment through microbial enzymatic hydrolysis and mechanical chewing, achieving a continuous and stable urine acidification effect and effectively preventing the deposition of urinary stones.

[0022] 3. Significantly improves feed palatability and sheep feeding performance: The slow-release design of the compound polysaccharide gel microparticle powder avoids the rapid release of free ammonium chloride in the rumen and local high-concentration irritation, reducing irritation to the rumen mucosa and negative impact on feed intake. At the same time, the combination design of whole corn kernels and pelleted concentrate enhances the chewability and palatability of the feed, improving the sheep's feeding enthusiasm and feed utilization rate.

[0023] 4. Enhance the flavor, quality, and nutritional value of mutton: Through the scientific formulation of high-quality protein sources (soybean meal, corn germ meal), energy raw materials (corn, corn distillers' grains), and functional additives (compound probiotics, compound enzyme preparations), the nutritional metabolism of sheep and the amino acid composition of muscles are improved, promoting the accumulation of flavor precursors and the formation of characteristic flavors, and significantly enhancing the tenderness, juiciness, and consumer acceptance of mutton.

[0024] 5. Optimize process stability and product consistency: By precisely controlling the degree of carboxyl substitution, cross-linked gel network structure and particle size distribution of oxidized corn starch through stepwise preparation process, high shear dispersion or ultrasonic dispersion combined with spray drying technology ensures the stability of particle structure and uniformity of ammonium chloride loading. The coefficient of variation of basic concentrate mixing uniformity is controlled to no more than 5%, ensuring the quality consistency and performance predictability of each batch of feed products, and reducing production fluctuations and quality risks. Attached Figure Description

[0025] Figure 1 Comparison of the volume median particle size (D50) of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles.

[0026] Figure 2 A comparison of parameters of the composite polysaccharide gel microparticle system based on the degree of carboxyl substitution of oxidized corn starch.

[0027] Figure 3 This is a comparison chart of the parameters of the chitosan deacetylation degree on the composite polysaccharide gel microparticle system.

[0028] Figure 4 This is a comparison chart of the parameters of the chitosan number-average molecular weight and the composite polysaccharide gel microparticle system.

[0029] Figure 5 This is a comparison chart of the mass fraction of ammonium chloride in the composite polysaccharide gel microparticle powder.

[0030] Figure 6 This is a comparison chart of the total mass fraction of ammonium chloride in feed compositions.

[0031] Figure 7 This is a comparison chart showing the proportion of ammonium chloride present in the form of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles.

[0032] Figure 8 This is a comparison chart of the proportions of whole corn kernels and pelleted feed.

[0033] Figure 9 The image shows the FTIR spectrum of the corn starch-chitosan-NH4Cl composite polysaccharide gel microparticle powder from Example 1.

[0034] Figure 10 The image shows the XRD pattern of the corn starch-chitosan-NH4Cl composite polysaccharide gel microparticle powder from Example 1.

[0035] Figure 11 This is a comparison graph of the in vitro cumulative release rate of ammonium chloride from sheep feed in Example 1 over time. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0037] Example 1

[0038] This embodiment provides a sheep feed that reduces urinary stone deposition and enhances the flavor of mutton. Based on the dry matter weight of the feed, it includes the following components: 57.1725 wt% corn, of which 19.8 wt% is crushed corn and 37.3725 wt% is whole corn. The median volumetric particle size D50 of the crushed corn in this embodiment is 0.75 mm. The median volumetric particle size D50 of this embodiment was measured by a laser particle size analyzer. Soybean meal 13.86wt%; Corn distillers grains 7.425 wt%; Corn germ meal 9.9 wt%; Soybean hulls 4.95 wt%; Calcium carbonate fine powder 2.178 wt%; Sodium chloride 0.594 wt%; 1.188 wt% of calcium hydrogen phosphate dihydrate; Compound premixed feed for fattening sheep: 0.495 wt%; Free ammonium chloride 0.2275 wt%; 1.584 wt% of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder.

[0039] In this embodiment, the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder meets the following conditions: Including oxidized corn starch, the degree of carboxyl substitution of the oxidized corn starch in this embodiment is 0.30 mmol / g; Including chitosan, the degree of deacetylation of the chitosan in this embodiment is 85%, and the number-average molecular weight is 275 kDa; Including ammonium chloride, the mass fraction of ammonium chloride in the dry basis of the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder in this embodiment is 25 wt%. The median particle size of the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder in this embodiment is 2.5 μm.

[0040] In this embodiment, the total mass fraction of ammonium chloride in the feed composition is 0.6375 wt%, of which ammonium chloride present in the form of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles accounts for 62.1 wt% of the total ammonium chloride.

[0041] The corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder of this embodiment is prepared by the following steps: A1. Add a 20 wt% ammonium chloride aqueous solution to the corn starch-chitosan crosslinked gel of this embodiment, stir to allow the ammonium chloride to uniformly penetrate into the gel network, and control the amount added so that the mass fraction of ammonium chloride in the dry basis of the resulting corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder is 25 wt%; A2. The crosslinked gel of this embodiment loaded with ammonium chloride was subjected to high-shear dispersion at a speed of 15000 r / min for 12 min, resulting in a median particle size of 300 nm for the primary gel particles. A3. The obtained dispersion was subjected to two-fluid spray drying, with the inlet air temperature set at 170℃ and the outlet air temperature at 85℃; the solid content of the dispersion was 12wt%; the feed rate was 8mL / min; the atomizing gas pressure was 0.25MPa; the powder was collected using a cyclone separator to obtain corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles with a median particle size of 2.5μm; the moisture content of the microparticles was 8wt%.

[0042] The corn starch-chitosan crosslinked gel in this embodiment was prepared through the following steps: B1. Chitosan was dissolved in a 3 vol% aqueous solution of glacial acetic acid to obtain a chitosan solution with a chitosan mass fraction of 1.5 wt%. In this embodiment, the degree of deacetylation of the chitosan was 85%, and the number average molecular weight was 275 kDa. B2. Oxidized corn starch was dispersed in deionized water to obtain an oxidized corn starch dispersion with a mass fraction of 12 wt%, and the pH value of the dispersion in this embodiment was adjusted to 6.5; B3. The oxidized corn starch dispersion and the chitosan solution of this embodiment were mixed at a mass ratio of 3.0:0.3. The mixture was stirred at 30°C, and a calcium chloride dihydrate aqueous solution with a concentration of 0.50 mol / L was slowly added over a dropping time of 15 min. During the dropping process, the system temperature was maintained at 30°C and the system pH was maintained at 6.5, so that the Ca in the system... 2+ The molar ratio of oxidized corn starch to carboxyl groups was 0.5:1. Stirring was continued for 1.2 h to allow oxidized corn starch and chitosan to form a three-dimensional cross-linked gel through electrostatic interaction and calcium ion bridging.

[0043] The oxidized corn starch in this embodiment is prepared through the following steps: C1. Prepare a 30 wt% corn starch aqueous suspension, add a 10 wt% sodium hypochlorite solution dropwise at 40°C, adjust the pH of the system to 8.5 with a 0.5 mol / L sodium hydroxide solution, and react for 1.2 h; C2. When the degree of carboxyl substitution of the corn starch in this embodiment, as determined by acid-base titration, reaches 0.30 mmol / g, the addition of sodium hypochlorite is stopped, and the pH of the system is adjusted to 6.5 with 0.5 mol / L hydrochloric acid; C3. Wash and dry at 50°C to obtain oxidized corn starch with a carboxyl substitution degree of 0.30 mmol / g.

[0044] The compound premixed feed for fattening sheep in this embodiment, based on 100 parts of the premixed feed, includes the following components, by weight: Vitamin A 10 servings; Vitamin D3 2.0 servings; Vitamin E 20 servings; Nicotinamide 0.18 parts; 9.5 parts of rumen-protected choline; 0.2 parts copper sulfate; 1.75 parts ferrous sulfate; 3.2 parts manganese sulfate; 3.3 parts zinc sulfate; 0.045 parts of calcium iodate; Sodium selenite 0.0225 parts; 2.0 parts ammonium chloride; 4.5 parts of urease inhibitor; Antioxidant 2.2 parts; 2.3 portions of compound probiotics; 10 portions of compound enzyme preparation; Rice husk powder is used to supplement the total amount of the fattening sheep compound premixed feed to 100 parts; The compound probiotics in this embodiment include Saccharomyces cerevisiae and Bacillus subtilis.

[0045] In this embodiment, the mass ratio of total calcium to total phosphorus in the feed composition is 2.1:1. The calcium carbonate powder in this embodiment is fine stone powder with a particle size of 100% passing through an 80-mesh standard sieve and a calcium content of 37wt%.

[0046] The corn in this embodiment meets the second-grade corn standard and has the following quality indicators: bulk density of 695 g / L, impurity mass fraction of 1.5 wt%, imperfect kernel mass fraction of 4 wt%, fatty acid value calculated as potassium hydroxide of 50 mg / 100 g, and bright color, no moldy odor, and hygiene indicators meet the requirements of GB13078.

[0047] This embodiment describes a method for preparing sheep feed that reduces urinary stone deposition and enhances the flavor of mutton, comprising the following steps: S1. Prepare oxidized corn starch to obtain oxidized corn starch with a carboxyl substitution degree of 0.30 mmol / g; S2. Preparation of corn starch-chitosan crosslinked gel; S3. Preparation of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles; S4. The pulverized corn, soybean meal, corn distillers grains, corn germ meal, soybean hulls, calcium carbonate powder, calcium hydrogen phosphate dihydrate, sodium chloride, free ammonium chloride, and fattening sheep compound premixed feed are mixed with the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder of this embodiment to obtain the basic concentrate; S5. Conditioning and granulation of the base concentrate in this embodiment: Steam conditioning is used to bring the temperature of the conditioned material to 82°C for 60 seconds, resulting in a moisture content of 16 wt%; then ring die granulation is performed with a die diameter of 4 mm; after granulation, the material is countercurrently cooled to a particle temperature of 25°C, and the moisture content of the finished particles is brought to 11.5 wt%, yielding granulated concentrate; S6. The pelleted concentrate and whole corn kernels of this embodiment are mixed at a ratio of 1.67:1 to obtain the feed composition of this embodiment.

[0048] In this embodiment, 34.6 wt% of the corn was pulverized before step S4. The pulverization effect was such that when tested with a 14-mesh feed analysis standard sieve, the mass fraction of the material passing through the sieve was 85 wt%. The remaining 65.4 wt% of the corn was added in whole kernel form in step S6. The coefficient of variation of the mass fraction of the mixing uniformity of the basic concentrate in this embodiment was 4.2%.

[0049] Features of this embodiment: This embodiment uses moderate parameter configurations. The corn content of 57.4 wt% is at a moderate level. The amount of compound polysaccharide gel microparticle powder is 1.6 wt%. The degree of carboxyl substitution of oxidized corn starch is 0.30 mmol / g, the degree of deacetylation of chitosan is 85%, and the molecular weight is 275 kDa, all of which are moderate values. The median particle size of the powder is 2.5 μm. The mass fraction of ammonium chloride in the powder is 25 wt%, and the total amount of ammonium chloride is 0.6375 wt%. The formula has good stability and strong process repeatability, making it suitable for large-scale production applications. This embodiment is suitable for the daily feeding of fattening sheep during the growing season. It can effectively prevent urinary stones while ensuring nutritional balance and improving the flavor and quality of mutton, resulting in good feeding effects and economic benefits.

[0050] Example 2

[0051] This embodiment provides a sheep feed that reduces urinary stone deposition and enhances the flavor of mutton. Based on dry matter weight, it comprises the following components: The corn content was 56.801 wt%, of which 21.287 wt% was crushed corn and 35.514 wt% was whole corn kernels. The median volumetric particle size (D50) of the crushed corn in this embodiment was 0.65 mm, which was measured by a laser particle size analyzer. Soybean meal 14.85wt%; 8.415 wt% dried corn distillers grains; Corn germ meal 7.92 wt%; Soybean hulls 4.455 wt%; Calcium carbonate fine powder 2.475 wt%; Sodium chloride 0.693 wt%; Calcium hydrogen phosphate dihydrate 1.485 wt%; Compound premixed feed for fattening sheep: 0.594 wt%; Free ammonium chloride 0.279 wt%; The corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder comprises 1.307 wt%; wherein, the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder of this embodiment meets the following conditions: Including oxidized corn starch, the degree of carboxyl substitution of the oxidized corn starch in this embodiment is 0.38 mmol / g; Including chitosan, the degree of deacetylation of the chitosan in this embodiment is 88%, and the number-average molecular weight is 350 kDa; Including ammonium chloride, the mass fraction of ammonium chloride in the dry basis of the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder in this embodiment is 35 wt%. The median particle size of the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder in this embodiment is 3.2 μm.

[0052] In this embodiment, the total mass fraction of ammonium chloride in the feed composition is 0.75 wt%, of which ammonium chloride present in the form of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder accounts for 61.0 wt% of the total ammonium chloride.

[0053] The corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder of this embodiment is prepared by the following steps: A1. Add a 25 wt% ammonium chloride aqueous solution to the corn starch-chitosan crosslinked gel of this embodiment, stir to allow the ammonium chloride to uniformly penetrate into the gel network, and control the amount added so that the mass fraction of ammonium chloride in the dry basis of the resulting corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder is 35 wt%. A2. The crosslinked gel of this embodiment loaded with ammonium chloride was subjected to high-shear dispersion at a speed of 17000 r / min for 15 min, resulting in a median particle size of 380 nm for the primary gel particles. A3. The obtained dispersion was subjected to two-fluid spray drying, with the inlet air temperature set at 175℃ and the outlet air temperature at 88℃; the solid content of the dispersion was 15wt%; the feed rate was 9mL / min; the atomizing gas pressure was 0.28MPa; the powder was collected using a cyclone separator to obtain corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles with a median particle size of 3.2μm; the moisture content of the microparticles was 8wt%.

[0054] The corn starch-chitosan crosslinked gel in this embodiment was prepared through the following steps: B1. Chitosan was dissolved in a 3.5 vol% aqueous solution of glacial acetic acid to obtain a chitosan solution with a chitosan mass fraction of 1.7 wt%. The degree of deacetylation of the chitosan in this embodiment was 88%, and the number average molecular weight was 350 kDa. B2. Oxidized corn starch was dispersed in deionized water to obtain an oxidized corn starch dispersion with a mass fraction of 15 wt%, and the pH value of the dispersion in this embodiment was adjusted to 6.3; B3. The oxidized corn starch dispersion and chitosan solution of this embodiment were mixed at a mass ratio of 3.5:0.35. The mixture was stirred at 32°C, and a calcium chloride dihydrate aqueous solution with a concentration of 0.60 mol / L was slowly added over a dropping time of 20 min. During the dropping process, the system temperature was maintained at 32°C and the pH of the system was maintained at 6.3, so that the Ca in the system... 2+ The molar ratio of oxidized corn starch to carboxyl groups was 0.6:1. Stirring was continued for 1.4 h to allow oxidized corn starch and chitosan to form a three-dimensional cross-linked gel through electrostatic interaction and calcium ion bridging.

[0055] The oxidized corn starch in this embodiment is prepared through the following steps: C1. A corn starch aqueous suspension with a mass fraction of 32 wt% was prepared, and a sodium hypochlorite solution with a mass fraction of 11 wt% was added dropwise at 42℃. The pH of the system was adjusted to 8.6 with a 1 mol / L sodium hydroxide solution, and the reaction was carried out for 1.4 h. C2. When the degree of carboxyl substitution of the corn starch in this embodiment, as determined by acid-base titration, reaches 0.38 mmol / g, the addition of sodium hypochlorite is stopped, and the pH of the system is adjusted to 6.3 with 1.0 mol / L hydrochloric acid; C3. Wash and dry at 52°C to obtain oxidized corn starch with a carboxyl substitution degree of 0.38 mmol / g.

[0056] The compound premixed feed for fattening sheep in this embodiment, based on 100 parts of the premixed feed, includes the following components, by weight: Vitamin A 10 servings; Vitamin D3 2.0 servings; Vitamin E 20 servings; Nicotinamide 0.17 parts; 9.5 parts of rumen-protected choline; 0.22 parts of copper sulfate; 1.85 parts of ferrous sulfate; 3.2 parts manganese sulfate; 3.2 parts zinc sulfate; 0.045 parts of calcium iodate; Sodium selenite 0.0225 parts; 1.5 parts ammonium chloride; Urease inhibitor 4.3 parts; Antioxidant 2.2 parts; 2.3 portions of compound probiotics; 9.5 portions of compound enzyme preparation; Rice husk powder is used to supplement the total amount of the fattening sheep compound premixed feed to 100 parts; The compound probiotics in this embodiment include Saccharomyces cerevisiae, Bacillus subtilis, and Aspergillus niger.

[0057] In this embodiment, the mass ratio of total calcium to total phosphorus in the feed composition is 2.2:1. The calcium carbonate powder in this embodiment is fine stone powder with a particle size of 100% passing through an 80-mesh standard sieve and a calcium content of 37.5 wt%.

[0058] The corn in this embodiment meets the second-grade corn standard and has the following quality indicators: test weight of 700g / L, impurity mass fraction of 1.3wt%, imperfect kernel mass fraction of 3.5wt%, fatty acid value calculated as potassium hydroxide of 45mg / 100g, and bright color, no moldy odor, and hygiene indicators meet the requirements of GB13078.

[0059] This embodiment describes a method for preparing sheep feed that reduces urinary stone deposition and enhances the flavor of mutton, comprising the following steps: S1. Oxidized corn starch was prepared to obtain oxidized corn starch with a carboxyl substitution degree of 0.38 mmol / g; S2. Preparation of corn starch-chitosan crosslinked gel; S3. Preparation of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles; S4. The pulverized corn, soybean meal, corn distillers grains, corn germ meal, soybean hulls, calcium carbonate powder, calcium hydrogen phosphate dihydrate, sodium chloride, free ammonium chloride, and fattening sheep compound premixed feed are mixed with the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder of this embodiment to obtain the basic concentrate; S5. Conditioning and granulation of the base concentrate in this embodiment: Steam conditioning is used to condition the material to a temperature of 85°C for 75 seconds, resulting in a moisture content of 16.5 wt%. Subsequently, ring die granulation is performed with a die diameter of 4 mm. After granulation, the material is countercurrently cooled to a particle temperature of 25°C, and the finished particles have a moisture content of 11.8 wt%, yielding granulated concentrate. S6. The pelleted concentrate and whole corn kernels of this embodiment are mixed at a ratio of 1.82:1 to obtain the feed composition of this embodiment.

[0060] In this embodiment, 37.5 wt% of the corn was pulverized before step S4. The pulverization effect was such that when tested with a 14-mesh feed analysis standard sieve, the mass fraction of the material passing through the sieve was 87 wt%. The remaining 62.5 wt% of the corn was added in whole grain form in step S6. The coefficient of variation of the mass fraction of the mixing uniformity of the basic concentrate in this embodiment was 3.8%.

[0061] Features of this embodiment: This embodiment is optimized for the prevention of urinary stones. The total ammonium chloride content reaches 0.75wt%, the ammonium chloride content in the compound polysaccharide gel microparticle powder is 35wt%, and the carboxyl substitution degree of oxidized corn starch (0.38mmol / g), the degree of deacetylation of chitosan (88%), and the molecular weight (350kDa) are all moderately high values. The median particle size of the powder is 3.2μm. The corn content of 57.38wt% ensures sufficient energy supply, and the soybean meal content of 15wt% provides high-quality protein. The formula design focuses on enhancing the urine acidification function through a high ammonium chloride slow-release system while maintaining nutritional balance. This embodiment is particularly suitable for preventive feeding in areas with a high incidence of urinary stones or in high-risk fattening sheep flocks. It significantly reduces the incidence of urinary stones while ensuring growth performance, and has a strong disease prevention effect and production safety.

[0062] Example 3

[0063] This embodiment provides a sheep feed that reduces urinary stone deposition and enhances the flavor of mutton. Based on dry matter weight, it comprises the following components: Corn 55.1738 wt%, of which crushed corn 19.33 wt% and whole corn kernels 35.8438 wt%. The powder in this embodiment... The median volumetric particle size (D50) of the crushed corn is 0.85 mm. In this embodiment, the median volumetric particle size (D50) is determined by laser particle size distribution. Measured by a thermometer; Soybean meal 12.87wt%; 8.91 wt% dried corn distillers grains; Corn germ meal 10.89 wt%; Soybean hulls 5.445 wt%; Calcium carbonate fine powder 1.98 wt%; Sodium chloride 0.495 wt%; 0.99 wt% of calcium hydrogen phosphate dihydrate; Compound premixed feed for fattening sheep: 0.495 wt%; Free ammonium chloride: 0.2172 wt%; 1.87 wt% of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder. Specifically, the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder of this embodiment meets the following conditions: Including oxidized corn starch, the degree of carboxyl substitution of the oxidized corn starch in this embodiment is 0.22 mmol / g; Including chitosan, the degree of deacetylation of the chitosan in this embodiment is 78%, and the number-average molecular weight is 120 kDa; Including ammonium chloride, the mass fraction of ammonium chloride in the dry basis of the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder in this embodiment is 20 wt%. The median particle size of the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder in this embodiment is 1.8 μm.

[0064] In this embodiment, the total mass fraction of ammonium chloride in the feed composition is 0.6 wt%, of which ammonium chloride present in the form of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles accounts for 62.3 wt% of the total ammonium chloride.

[0065] The corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder of this embodiment is prepared by the following steps: A1. Add a 15 wt% ammonium chloride aqueous solution to the corn starch-chitosan crosslinked gel of this embodiment, stir to allow the ammonium chloride to uniformly penetrate into the gel network, and control the amount added so that the mass fraction of ammonium chloride in the dry basis of the resulting corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder is 20 wt%. A2. The crosslinked gel of this embodiment loaded with ammonium chloride was ultrasonically dispersed at a power of 350W for 10 minutes, resulting in a median particle size of 220nm for the primary gel particles. A3. The obtained dispersion was subjected to two-fluid spray drying, with the inlet air temperature set at 165℃ and the outlet air temperature at 82℃; the solid content of the dispersion was 10wt%; the feed rate was 7mL / min; the atomizing gas pressure was 0.22MPa; the powder was collected using a cyclone separator to obtain corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles with a median particle size of 1.8μm; the moisture content of the microparticles was 7wt%.

[0066] The corn starch-chitosan crosslinked gel in this embodiment was prepared through the following steps: B1. Chitosan was dissolved in a 2 vol% aqueous solution of glacial acetic acid to obtain a chitosan solution with a chitosan mass fraction of 1.2 wt%. In this embodiment, the degree of deacetylation of the chitosan was 78%, and the number-average molecular weight was 120 kDa. B2. Oxidized corn starch was dispersed in deionized water to obtain an oxidized corn starch dispersion with a mass fraction of 8 wt%, and the pH value of the dispersion in this embodiment was adjusted to 6.8; B3. The oxidized corn starch dispersion and the chitosan solution of this embodiment were mixed at a mass ratio of 2.0:0.2. The mixture was stirred at 25°C, and a calcium chloride dihydrate aqueous solution with a concentration of 0.30 mol / L was slowly added over a dropping time of 10 min. During the dropping process, the system temperature was maintained at 25°C and the system pH at 6.8, ensuring that the Ca in the system... 2+ The molar ratio of oxidized corn starch to carboxyl groups was 0.3:1. Stirring was continued for 0.8 h to allow oxidized corn starch and chitosan to form a three-dimensional cross-linked gel through electrostatic interaction and calcium ion bridging.

[0067] The oxidized corn starch in this embodiment is prepared through the following steps: C1. A corn starch aqueous suspension with a mass fraction of 25 wt% was prepared, and a sodium hypochlorite solution with a mass fraction of 7 wt% was added dropwise at 38℃. The pH of the system was adjusted to 8.2 with a 1.5 mol / L sodium hydroxide solution, and the reaction was carried out for 0.8 h. C2. When the degree of carboxyl substitution of the corn starch in this embodiment, as determined by acid-base titration, reaches 0.22 mmol / g, the addition of sodium hypochlorite is stopped, and the pH of the system is adjusted to 6.8 with hydrochloric acid; C3. Wash and dry at 45°C to obtain oxidized corn starch with a carboxyl substitution degree of 0.22 mmol / g.

[0068] The compound premixed feed for fattening sheep in this embodiment, based on 100 parts of the premixed feed, includes the following components, by weight: Vitamin A 10 servings; Vitamin D3 2.0 servings; Vitamin E 20 servings; Nicotinamide 0.2 parts; Ten parts of rumen-protected choline; 0.25 parts copper sulfate; Ferrous sulfate 2.0 parts; 3.5 parts manganese sulfate; 3.5 parts zinc sulfate; 0.045 parts of calcium iodate; Sodium selenite 0.0225 parts; 1.0 part ammonium chloride; 5 portions of urease inhibitor; Antioxidant 2.5 parts; 2.5 portions of compound probiotics; 10 portions of compound enzyme preparation; Rice husk powder is used to supplement the total amount of the fattening sheep compound premixed feed to 100 parts; The compound probiotics in this embodiment include Saccharomyces cerevisiae, Bacillus subtilis, Aspergillus niger, and Aspergillus oryzae.

[0069] In this embodiment, the mass ratio of total calcium to total phosphorus in the feed composition is 2.05:1. The calcium carbonate powder in this embodiment is fine stone powder with a particle size of 100% passing through an 80-mesh standard sieve and a calcium content of 36.5 wt%.

[0070] The corn in this embodiment meets the second-grade corn standard and has the following quality indicators: test weight of 710g / L, impurity mass fraction of 1.0wt%, imperfect kernel mass fraction of 3wt%, fatty acid value calculated as potassium hydroxide of 40mg / 100g, and bright color, no moldy odor, and hygiene indicators meet the requirements of GB13078.

[0071] This embodiment describes a method for preparing sheep feed that reduces urinary stone deposition and enhances the flavor of mutton, comprising the following steps: S1. Oxidized corn starch was prepared to obtain oxidized corn starch with a carboxyl substitution degree of 0.22 mmol / g; S2. Preparation of corn starch-chitosan crosslinked gel; S3. Preparation of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles; S4. The pulverized corn, soybean meal, corn distillers grains, corn germ meal, soybean hulls, calcium carbonate powder, calcium hydrogen phosphate dihydrate, sodium chloride, free ammonium chloride, and fattening sheep compound premixed feed are mixed with the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder of this embodiment to obtain the basic concentrate; S5. Conditioning and granulation of the base concentrate in this embodiment: Steam conditioning is used to bring the temperature of the material after conditioning to 78°C for 50 seconds, resulting in a moisture content of 15.5 wt%; then ring die granulation is performed with a die aperture of 4 mm; after granulation, the material is countercurrently cooled to a particle temperature of 25°C, and the moisture content of the finished particles is brought to 11.2 wt%, yielding granulated concentrate; S6. The pelleted concentrate and whole corn kernels of this embodiment are mixed at a ratio of 1.82:1 to obtain the feed composition of this embodiment.

[0072] In this embodiment, 35 wt% of the corn is pulverized before step S4. The pulverization effect is such that when tested with a 14-mesh feed analysis standard sieve, the mass fraction of the material passing through the sieve is 90 wt%. The remaining 65 wt% of the corn is added in whole grain form in step S6. The coefficient of variation of the mass fraction of the mixing uniformity of the basic concentrate in this embodiment is 3.5%.

[0073] Features of this embodiment: This embodiment focuses on optimizing the flavor of mutton. The corn content of 55.611 wt% provides sufficient energy to promote intramuscular fat deposition. The high content of corn distillers' grains (9 wt%) and corn germ meal (11 wt%) enhances the supply of flavor precursors. The compound polysaccharide gel microparticle powder contains 20 wt% ammonium chloride. The oxidized corn starch carboxyl substitution degree (0.22 mmol / g), chitosan deacetylation degree (78%), and molecular weight (120 kDa) are all relatively low. The median particle size of the powder is 1.8 μm, and the total ammonium chloride content of 0.6 wt% maintains a moderate urine acidification function. The formula focuses on improving meat quality while ensuring basic preventative effects. This embodiment is suitable for high-end market fattening production with high requirements for mutton flavor and quality. It can significantly improve the tenderness, juiciness, and flavor intensity of mutton, while also preventing urinary stones, achieving dual optimization of production efficiency and product quality.

[0074] Example 4

[0075] This embodiment provides a sheep feed that reduces urinary stone deposition and enhances the flavor of mutton. Based on dry matter weight, it comprises the following components: The corn content was 62.276 wt%, of which 23.848 wt% was crushed corn and 38.428 wt% was whole corn kernels. The median volumetric particle size (D50) of the crushed corn in this embodiment was 0.95 mm, which was measured by a laser particle size analyzer. Soybean meal 10.934 wt%; 4.97 wt% dried corn distillers grains; Corn germ meal 6.958 wt%; Soybean hulls 3.976 wt%; Calcium carbonate fine powder 2.7832 wt%; Sodium chloride 0.7952 wt%; Calcium hydrogen phosphate dihydrate 1.6898 wt%; Compound premixed feed for fattening sheep: 0.497 wt%; Free ammonium chloride 0.224 wt%; 4.473 wt% of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder. Specifically, the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder of this embodiment meets the following conditions: Including oxidized corn starch, the degree of carboxyl substitution of the oxidized corn starch in this embodiment is 0.46 mmol / g; Including chitosan, the degree of deacetylation of the chitosan in this embodiment is 92%, and the number-average molecular weight is 460 kDa; Including ammonium chloride, the mass fraction of ammonium chloride in the dry basis of the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder in this embodiment is 12 wt%. The median particle size of the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder in this embodiment is 4.6 μm.

[0076] In this embodiment, the total mass fraction of ammonium chloride in the feed composition is 0.77 wt%, of which ammonium chloride in the form of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder accounts for 69.7 wt% of the total ammonium chloride. The remaining ammonium chloride comes from free ammonium chloride and fattening sheep compound premixed feed. The amount of free ammonium chloride added is 0.224 wt% (based on feed dry matter weight).

[0077] The corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder of this embodiment is prepared by the following steps: A1. A 10 wt% ammonium chloride aqueous solution was added to the corn starch-chitosan crosslinked gel of this embodiment. The mixture was stirred to allow the ammonium chloride to penetrate the gel network evenly. The amount added was controlled so that the mass fraction of ammonium chloride in the dry basis of the resulting corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder was 12 wt%. A2. The crosslinked gel of this embodiment loaded with ammonium chloride was subjected to high-shear dispersion at a speed of 18500 r / min for 18 min, resulting in a median particle size of 460 nm for the primary gel particles. A3. The obtained dispersion was subjected to two-fluid spray drying, with the inlet air temperature set at 180℃ and the outlet air temperature at 92℃; the solid content of the dispersion was 18wt%; the feed rate was 10mL / min; the atomizing gas pressure was 0.30MPa; the powder was collected using a cyclone separator to obtain corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles with a median particle size of 4.6μm; the moisture content of the microparticles was 9wt%.

[0078] The corn starch-chitosan crosslinked gel in this embodiment was prepared through the following steps: B1. Chitosan was dissolved in a 4.5 vol% aqueous solution of glacial acetic acid to obtain a chitosan solution with a chitosan mass fraction of 1.9 wt%. In this embodiment, the degree of deacetylation of the chitosan was 92%, and the number average molecular weight was 460 kDa. B2. Oxidized corn starch was dispersed in deionized water to obtain an oxidized corn starch dispersion with a mass fraction of 18 wt%, and the pH value of the dispersion in this embodiment was adjusted to 6.2; B3. The oxidized corn starch dispersion and chitosan solution of this embodiment were mixed at a mass ratio of 4.5:0.45. The mixture was stirred at 36°C, and a calcium chloride dihydrate aqueous solution with a concentration of 0.85 mol / L was slowly added over a dropping time of 25 min. During the dropping process, the system temperature was maintained at 36°C and the system pH was maintained at 6.2, so that the Ca in the system... 2+ The molar ratio of oxidized corn starch to carboxyl groups was 0.85:1. Stirring was continued for 1.8 hours to allow oxidized corn starch and chitosan to form a three-dimensional cross-linked gel through electrostatic interaction and calcium ion bridging.

[0079] The oxidized corn starch in this embodiment is prepared through the following steps: C1. A corn starch aqueous suspension with a mass fraction of 37 wt% was prepared, and a sodium hypochlorite solution with a mass fraction of 13 wt% was added dropwise at 43℃. The pH of the system was adjusted to 8.8 with a 2 mol / L sodium hydroxide solution, and the reaction was carried out for 1.7 h. C2. When the degree of carboxyl substitution of the corn starch in this embodiment, as determined by acid-base titration, reaches 0.46 mmol / g, the addition of sodium hypochlorite is stopped, and the pH of the system is adjusted to 6.2 with 1.5 mol / L hydrochloric acid; C3. Wash and dry at 58°C to obtain oxidized corn starch with a carboxyl substitution degree of 0.46 mmol / g.

[0080] The compound premixed feed for fattening sheep in this embodiment, based on 100 parts of the premixed feed, includes the following components, by weight: Vitamin A 10 parts; Vitamin D3 2.0 servings; Vitamin E 20.0 servings; Nicotinamide 0.2 parts; 10 parts of rumen-protected choline; 0.25 parts copper sulfate; Ferrous sulfate 2.0 parts; 3.5 parts manganese sulfate; 3.5 parts zinc sulfate; 0.045 parts of calcium iodate; Sodium selenite 0.0225 parts; 2.0 parts ammonium chloride; 5 parts of urease inhibitor; Antioxidant 2.5 parts; 2.5 portions of compound probiotics; 10 portions of compound enzyme preparation; Rice husk powder is used to supplement the total amount of the fattening sheep compound premixed feed to 100 parts; The compound probiotics in this embodiment include Saccharomyces cerevisiae and Bacillus subtilis.

[0081] In this embodiment, the mass ratio of total calcium to total phosphorus in the feed composition is 2.3:1. The calcium carbonate powder in this embodiment is fine stone powder with a particle size of 100% passing through an 80-mesh standard sieve and a calcium content of 38wt%.

[0082] The corn in this embodiment meets the second-grade corn standard and has the following quality indicators: test weight of 720g / L, impurity mass fraction of 0.8wt%, imperfect kernel mass fraction of 2.5wt%, fatty acid value calculated as potassium hydroxide of 35mg / 100g, and bright color, no moldy odor, and hygiene indicators meet the requirements of GB13078.

[0083] This embodiment describes a method for preparing sheep feed that reduces urinary stone deposition and enhances the flavor of mutton, comprising the following steps: S1. Oxidized corn starch was prepared to obtain oxidized corn starch with a carboxyl substitution degree of 0.46 mmol / g; S2. Preparation of corn starch-chitosan crosslinked gel; S3. Preparation of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles; S4. The pulverized corn, soybean meal, corn distillers grains, corn germ meal, soybean hulls, calcium carbonate powder, calcium hydrogen phosphate dihydrate, sodium chloride, free ammonium chloride, and fattening sheep compound premixed feed are mixed with the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder of this embodiment to obtain the basic concentrate; S5. Conditioning and granulation of the base concentrate in this embodiment: Steam conditioning is used to bring the temperature of the conditioned material to 88°C for 90 seconds, resulting in a moisture content of 17 wt%; then ring die granulation is performed with a die diameter of 5 mm; after granulation, the material is countercurrently cooled to a particle temperature of 25°C, and the moisture content of the finished particles is brought to 12.0 wt%, yielding granulated concentrate; S6. The pelleted concentrate and whole corn kernels of this embodiment are mixed at a ratio of 1.60:1 to obtain the feed composition of this embodiment.

[0084] In this embodiment, 38.3 wt% of the corn was pulverized before step S4. The pulverization effect was such that when tested with a 14-mesh feed analysis standard sieve, the mass fraction of the material passing through the sieve was 82 wt%. The remaining 61.7 wt% of the corn was added in whole kernel form in step S6. The coefficient of variation of the mass fraction of the mixing uniformity of the basic concentrate in this embodiment was 4.8%.

[0085] Features of this embodiment: This embodiment uses parameter combinations close to the boundary of the formulation range to verify the feasibility boundary of the technical solution. The corn content of 62.7wt% is close to the upper limit of the range, the amount of composite polysaccharide gel microparticle powder of 4.5wt% is close to the upper limit of the range, the degree of carboxyl substitution of oxidized corn starch of 0.46mmol / g is close to the upper limit range, the degree of deacetylation of chitosan of 92% and the molecular weight of 460kDa are both in the high value range, the median particle size of the powder of 4.6μm is close to the upper limit, the particle size D50 of crushed corn of 0.95mm is close to the upper limit, the total amount of ammonium chloride of 0.764wt% is close to the upper limit, and the calcium-phosphorus ratio of 2.3:1 is close to the upper limit. The formulation design verifies the technical feasibility under the conditions of high corn energy supply and high slow-release carrier dosage. This embodiment is suitable for the high-energy-demand stage in the later stage of rapid fattening, and can achieve significant weight gain in a short period of time. At the same time, it maintains the urine acidification function through a high proportion of slow-release ammonium chloride system, and enhances the flavor characteristics of mutton by utilizing high corn content and optimized fatty acid composition. It is suitable for intensive fattening production mode that pursues high daily weight gain and high-quality meat, and has high production efficiency and economic returns.

[0086] Comparative Example 1: Basically the same as Example 1, except that the amount of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder is 0.4 wt%, while the amount of other components and preparation conditions remain unchanged.

[0087] Comparative Example 2: Basically the same as Example 1, except that the degree of carboxyl substitution of oxidized corn starch is 0.06 mmol / g, and the oxidation conditions are adjusted as follows: corn starch is prepared into a 30 wt% corn starch aqueous suspension, a 10 wt% sodium hypochlorite solution is added dropwise at 40°C, the pH of the system is adjusted to 8.5 with sodium hydroxide solution, the reaction is carried out for 0.5 h, the addition of sodium hypochlorite is stopped when the degree of carboxyl substitution reaches 0.06 mmol / g, the pH of the system is adjusted to 6.5 with 2.0 mol / L hydrochloric acid, washed and dried at 50°C, with other conditions remaining unchanged.

[0088] Comparative Example 3: Basically the same as Example 1, except that the degree of carboxyl substitution of oxidized corn starch was 0.62 mmol / g, and the oxidation conditions were adjusted as follows: corn starch was prepared into a 30 wt% corn starch aqueous suspension, and a 10 wt% sodium hypochlorite solution was added dropwise at 40°C. The pH of the system was adjusted to 8.5 with sodium hydroxide solution, and the reaction was carried out for 2.5 h. When the degree of carboxyl substitution reached 0.62 mmol / g, the addition of sodium hypochlorite was stopped. The pH of the system was adjusted to 6.5 with 0.5 mol / L hydrochloric acid, washed, and dried at 50°C. Other conditions remained unchanged.

[0089] Comparative Example 4: Basically the same as Example 1, except that the degree of deacetylation of chitosan is 68%, while the amount of other components and preparation conditions remain unchanged.

[0090] Comparative Example 5: It is basically the same as Example 1, except that the number average molecular weight of chitosan is 35kDa, while the amount of other components and preparation conditions remain unchanged.

[0091] Comparative Example 6: It is basically the same as Example 1, except that the mass fraction of ammonium chloride in the dry basis of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder is 6 wt%, while the amount of other components and preparation conditions remain unchanged.

[0092] Comparative Example 7: It is basically the same as Example 1, except that the mass fraction of ammonium chloride in the dry basis of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder is 48 wt%, while the amount of other components and preparation conditions remain unchanged.

[0093] Characterization tests: Experiment 1: Urine pH Measurement Test Subjects: Urine samples from fattening sheep fed different feed compositions. Test Objective: To evaluate the urine acidification effect of the feed and verify the regulatory effect of the ammonium chloride slow-release system on urine pH. Test Principle: Ammonium chloride is hydrolyzed by rumen microorganisms, releasing ammonium ions, which are then metabolized by the liver into urea and excreted into the urine. This urea helps regulate the body's acid-base balance, creating an acid load and promoting renal acid excretion, thereby lowering the urine pH. The acidity of the urine is measured using a pH meter. Experimental Methods: Healthy fattening rams weighing 45±5 kg were selected and fed different feed compositions from the examples and comparative examples. After a 7-day adaptation period, a 14-day testing period was initiated. 50 mL of fresh midstream urine was collected daily at 08:00 and 16:00. The urine pH was immediately measured using a calibrated portable pH meter. Each sample was measured three times, and the average value was taken. Key Parameters: Ambient temperature: 20±2℃; pH meter accuracy: ±0.01; Measurement completed within 30 minutes of urine sample collection. Data processing: Calculate the mean ± standard deviation of urine pH for each group during the 14-day measurement period, with n≥6 sheep, to evaluate the stability and persistence of urine acidification.

[0094] Experiment 2: Statistics on the Incidence of Urinary Stones Test subjects: Fattening sheep fed different feed compositions. Test objective: To evaluate the clinical efficacy of feed in preventing urinary stones and to verify the inhibitory effect of the ammonium chloride sustained-release system on urinary stone formation. Test principle: Urine acidification can increase the solubility of phosphates and carbonates, inhibiting the precipitation and aggregation of stone crystals such as magnesium ammonium phosphate. The incidence of urinary stones was statistically analyzed through clinical observation and urine examination. Experimental methods: Healthy fattening sheep weighing 40±5kg were selected. Each treatment was set up with 4 replicates, with 30 sheep per replicate. The sheep were fed different feed compositions from the implementation examples and the comparative example for 90 days. Urinary status was observed weekly, and typical symptoms of urinary stones such as dribbling urine, urinary retention, and hematuria were recorded. Ultrasound examination or urine sediment microscopy was performed when necessary to confirm cases of urinary stones. The incidence of urinary stones in each group was statistically analyzed. Standard Basis: Referring to NY / T2798, the diagnostic criteria are: the presence of one of the typical symptoms such as urinary retention / dribbling / hematuria, and ultrasound examination revealing urinary system stones or microscopic examination of urine sediment showing crystals such as magnesium ammonium phosphate; cases meeting any of the above criteria are diagnosed as urinary stone cases. Key Parameters: Husbandry environment temperature 15-25℃, free access to feed and water, sample size n=120 per group (4 replicates × 30 sheep per replicate). Data Processing: Calculate the incidence of urinary stones = number of affected sheep / total number of sheep × 100%.

[0095] Experiment 3: Determination of feed pellet hardness and durability Test Subjects: Granulated feed samples prepared with different formulations. Test Objective: To evaluate the effect of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles on the physical quality of feed pellets and to verify the balance between pellet strength and controllable release of ammonium chloride. Test Principle: Pellet hardness reflects the feed's resistance to crushing, while durability reflects its resistance to mechanical damage; both jointly affect the feed's storage and transportation quality and the stability of ammonium chloride release. Experimental Methods: Pellet hardness was determined using the KAHL method. A pellet hardness tester was used to apply vertical pressure to pellets with a diameter of 4-6 mm until they broke, and the crushing force was recorded. Pellet durability was determined using the Holmen method. 500 g of pellet sample was weighed and rotated at 50 r / min for 10 minutes in a durability tester. Intact pellets were collected and weighed, and the durability index was calculated as: (intact pellet mass / initial mass) × 100%. Key Parameters: Test temperature 20±2℃, relative humidity <65%, each sample was repeated 3 times. Data Processing: Calculate the mean ± standard deviation, n≥3.

[0096] Experiment 4: In vitro release kinetics of ammonium chloride Test Subjects: Corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder and granular concentrate samples. Test Objective: To evaluate the sustained-release effect of the composite polysaccharide gel microparticles on ammonium chloride and verify the stability of the microparticle structure and the uniformity of ammonium chloride loading. Test Principle: Simulating rumen environmental conditions, the cumulative release rate of ammonium chloride at different time points was determined, and a release kinetic model was established. Experimental Method: Simulated rumen fluid was prepared at pH 6.5-6.8 and temperature 39±0.5℃. A sample containing 10mg of ammonium chloride was weighed and placed in a dialysis bag, immersed in 100mL of simulated rumen fluid, and magnetically stirred at 100r / min. 5mL samples were taken at 0.5, 1, 2, 4, 6, 8, 12, and 24 hours, and an equal volume of fresh rumen fluid was added. The concentration of ammonium ions in the released solution was determined by ion chromatography, and the cumulative release rate was calculated. Key parameters: Simulated rumen fluid pH = 6.5-6.8, temperature 39±0.5℃, stirring rate 100 r / min, dialysis bag molecular weight cutoff 3.5 kDa. Data processing: Plotted cumulative release rate-time curves, fitted first-order kinetics or Higuchi models, and calculated the release rate constant.

[0097] Experiment 5: GC-MS Analysis of Volatile Flavor Compounds in Lamb Test Subjects: Longissimus dorsi muscle samples from fattened sheep slaughtered after being fed different feed compositions for 90 days. Test Objective: To evaluate the impact of feed on the flavor and quality of mutton, and to verify the regulatory effect of corn and its by-products ratio on intramuscular fatty acid composition and flavor precursors. Test Principle: Headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-MS) was used to separate and identify volatile flavor compounds in mutton, and to quantitatively analyze the content of key flavor substances. Experimental Methods: 5g of longissimus dorsi muscle sample was minced and placed in a 20mL headspace vial. The sample was equilibrated in a 60℃ water bath for 30 minutes, then adsorbed using a 50 / 30μm DVB / CAR / PDMS extraction head for 30 minutes. GC-MS analysis conditions: DB-WAX column, injection port temperature 250℃, temperature program 40℃ held for 3 minutes, then increased to 230℃ at 5℃ / min and held for 5 minutes. Mass spectrometry EI source 70eV, scan range 35-350m / z. Compounds were identified by searching the NIST spectral library. The following headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) conditions were used for analysis. Key parameters: sample freshness <24 h, extraction temperature 60 °C, extraction time 30 min. Data processing: The relative content of each flavor compound was calculated, and principal component analysis was used to distinguish the flavor characteristics of different groups.

[0098] Experiment 6: Determination of particle size distribution of composite polysaccharide gel microparticles Test Subjects: Corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder samples prepared under different conditions. Test Objective: To evaluate the effects of high-shear dispersion and spray drying processes on microparticle size distribution and to verify the relationship between process parameters and microparticle structural stability. Test Principle: The particle size distribution of microparticles in the dispersion medium was measured using a laser particle size analyzer. The volume median particle size (D50) and particle size distribution width (Span) were calculated based on the principle of laser diffraction. Experimental Method: Approximately 10 mg of microparticle powder sample was weighed and dispersed in 10 mL of deionized water. The mixture was ultrasonically dispersed for 5 minutes to ensure sufficient dispersion. The particle size distribution was measured using a laser particle size analyzer. The refractive index of the dispersion medium was 1.33, the refractive index of the microparticles was 1.52, and the opacity was controlled at 8-12%. Three consecutive measurements were taken, and the average value was recorded. D10, D50, D90, and Span = (D90-D10) / D50 were recorded. Key Parameters: Test temperature 25±1℃, ultrasonic power 200W, ultrasonic time 5 minutes, opacity 8-12%. Data processing: Calculate the mean ± standard deviation of the volume median particle size D50, and evaluate the particle size distribution uniformity using the Span value, n≥3.

[0099] Figure 1This is a comparison chart of the volumetric median particle size (D50) of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles. The characterization method was to measure the volumetric median particle size (D50) using a laser particle size analyzer. The samples included in Examples 1 to 4. The fixed parameters were the preparation path of the composite polysaccharide gel microparticles: cross-linked gel loading with ammonium chloride followed by dispersion and spray drying. The varying parameters were the degree of carboxyl substitution of oxidized corn starch, the degree of deacetylation and molecular weight of chitosan, the loading ratio, and the differences in dispersion process parameters among the different examples. The D50 values ​​for Examples 1 to 4 were 2.5, 3.2, 1.8, and 4.6 μm, respectively, indicating that the process and formulation parameters can control the particle size within the micrometer range, ensuring the dispersibility and processability of the microparticles in the feed matrix, providing a particle size basis for subsequent release and particle quality.

[0100] Figure 2 This is a comparative graph showing the effect of the degree of carboxyl substitution of oxidized corn starch on the parameters of the composite polysaccharide gel microparticle system. The characterization method was acid-base titration to determine the degree of carboxyl substitution. The samples included from Examples 1 to 4. The fixed parameters were: oxidation with sodium hypochlorite, termination of the reaction after the target degree of carboxyl substitution was reached, and washing and drying. The variable parameters were the differences in the carboxyl substitution degree settings within the range of 0.22 to 0.46 mmol / g. Within this range, the degree of carboxyl substitution could be attributed to electrostatic interactions with chitosan and the influence of Ca2+. 2+ The bridging provides sufficient anion sites, thereby supporting the formation of a more stable gel network and promoting the controllability of ammonium chloride loading and release, providing a chemical structural basis for formulation stability and functional realization.

[0101] Figure 3 This is a comparative graph showing the effect of chitosan deacetylation degree on the parameters of the composite polysaccharide gel microparticle system. The characterization method is to characterize the deacetylation degree using material specifications. The samples include Examples 1 to 4. The fixed parameter is chitosan dissolved in glacial acetic acid aqueous solution and crosslinked with oxidized corn starch at a certain pH and temperature to form a gel. The variable parameter is the difference in deacetylation degree from 78% to 92%. A higher deacetylation degree means a higher amino density and stronger electrostatic binding potential, while maintaining segmental flexibility and processability within a moderate range. This is beneficial for the synergistic achievement of gel network strength and sustained-release performance, supporting the rationality of the microparticle system's structural design from a material perspective.

[0102] Figure 4This is a comparative graph showing the number-average molecular weight of chitosan and its parameters in the composite polysaccharide gel microparticle system. The characterization method was to characterize the number-average molecular weight using material specifications. The samples included in Examples 1 to 4. The parameters were fixed, with the crosslinking system and preparation process consistent. The varying parameters were the differences in number-average molecular weight from 120 kDa to 460 kDa. Higher molecular weight can enhance network toughness and mechanical strength through chain entanglement, while lower molecular weight is beneficial for dissolution, dispersion, and gel uniformity. The parameter settings in different examples demonstrate the idea of ​​achieving a balance between process stability and structural strength through molecular weight control, providing support for maintaining the structural integrity of the microparticles under high shear and spray drying conditions.

[0103] Figure 5 This is a comparison chart of the ammonium chloride mass fraction in the composite polysaccharide gel microparticle powder. The characterization method was to obtain the ammonium chloride mass fraction in the dry basis of the powder by formula setting and loading calculation. The samples included Examples 1 to 4. The fixed parameters were to first form a corn starch-chitosan cross-linked gel, then infiltrate and load with ammonium chloride, and disperse and dry it. The variable parameters were the ammonium chloride mass fraction in the dry basis of the powder from 12 wt% to 35 wt%. This variation reflects the matching relationship between the loading amount and the gel carrying capacity. A higher loading is beneficial to the acidification capacity, but network stability is needed to avoid uncontrolled precipitation and release, thus providing a controllable drug loading dimension for achieving continuous urine acidification and processing stability.

[0104] Figure 6 This is a comparison chart of the total mass fraction of ammonium chloride in the feed compositions. The characterization method was to obtain the total mass fraction of ammonium chloride in the feed through formula statistics. The samples included in Examples 1 to 4. The feed compositions were formed by mixing whole corn kernels with granulated basic concentrate at a predetermined ratio, with the parameter being the difference in the total mass fraction of ammonium chloride in the feed ranging from 0.60 wt% to 0.764 wt%. This total difference corresponds to the urine pH and urinary stone incidence shown in Table 1, indicating that under controlled release conditions, stable acidification can be achieved without excessive stimulation through the synergistic regulation of the total amount and release rhythm, thereby supporting the repeatable realization of functional effects.

[0105] Figure 7 This is a comparative chart showing the proportion of ammonium chloride present in the form of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles. The characterization method was to statistically calculate the proportion of powder-carried ammonium chloride to total ammonium chloride. The samples included in Examples 1 to 4. The fixed parameter was that the source of ammonium chloride included the composite microparticle-carried portion and other added sources. The variable parameter was that the carrying proportion ranged from 61.6% to 70.7%. A higher carrying proportion means that more ammonium chloride is released slowly through the gel network, thereby reducing the risk of local high concentrations caused by rapid dissolution of free ammonium chloride and is more conducive to maintaining the persistence and stability of urine acidification, providing a chain of evidence at the release pathway level for functional realization.

[0106] Figure 8This is a comparison chart of the ratio of pelleted feed to whole corn kernels. The characterization method involves setting and recording the ratio of pelleted feed mass to whole corn kernel mass in the formulation. Samples include Examples 1 to 4. The fixed parameter is that the pelleted feed is obtained by granulation of crushed corn, protein raw materials, and complex polysaccharide gel microparticle powder. The variable parameter is that the ratio of pelleted feed to whole corn kernels ranges from 0.54 to 0.62. This ratio adjustment reflects the synergistic design concept of energy release rhythm and slow-release acidification rhythm. By providing a slower rumen degradation energy supply through a certain proportion of whole corn kernels, it works together with the slow-release acidification of microparticles to help maintain a stable urinary acidification environment and reduce the risk of stones while ensuring feed intake and production performance.

[0107] Figure 9 The image shows the FTIR spectrum of the corn starch-chitosan-NH4Cl composite polysaccharide gel microparticle powder from Example 1. The parameters were kept constant: corn starch mass fraction, chitosan mass fraction, NH4Cl doping amount, and drying conditions. The characterization method was Fourier transform infrared spectroscopy (FTIR). The varying parameters were the ratio of chitosan to corn starch in the composite system and the amount of NH4Cl incorporated, which were gradually varied within the single-factor experimental range. The results showed that as the chitosan content and NH4Cl dosage increased, the broad peaks in the OH and NH stretching vibration regions were enhanced, and the intensity and position of the COC and CN related absorption bands changed synergistically, indicating that hydrogen bonding and ionic bonding in the system gradually increased. When the NH4Cl addition reached the optimal range, the morphology of the amide band and the characteristic peaks of the polysaccharide backbone tended to stabilize, and no new impurity peaks appeared, proving that a uniform and stable polysaccharide-salt interaction network was formed under this composite ratio, which is beneficial for the stable formation of the subsequent gel microparticle structure.

[0108] Figure 10 The image shows the XRD pattern of the corn starch-chitosan-NH4Cl composite polysaccharide gel microparticle powder from Example 1. The parameters were kept constant: raw material source, composite ratio, NH4Cl doping method, drying and molding process, and FTIR testing conditions. The characterization method was powder X-ray diffraction (XRD). The parameters were varied by sequentially adjusting the NH4Cl doping amount and chitosan content within a single-factor range. The results showed that, compared to the characteristic diffraction peaks of the original corn starch, the characteristic peak intensity and half-width of the composite polysaccharide microparticles exhibited a regular change with the chitosan and NH4Cl content. At a moderate doping level, the ordered structure of the starch was partially preserved, and a broad and gradual amorphous scattering background appeared, indicating that the system formed a gel microparticle structure with a combination of partially crystalline and amorphous regions. When the NH4Cl content was low, the diffraction peaks were close to the original starch state, indicating insufficient structural reconstruction. When the NH4Cl content was too high, the crystalline peaks significantly weakened and tended towards amorphization. Overall, the optimized ratio obtained by the single-factor analysis is beneficial for forming composite polysaccharide gel microparticles with uniform structure and moderate crystallinity, supporting the rationality and stability of this scheme from a crystal structure perspective.

[0109] Figure 11 This is a comparison curve of the in vitro cumulative release rate of ammonium chloride from sheep feed in Example 1, with fixed parameters including simulated rumen fluid pH of 6.5 to 6.8, temperature of 39 ± 0.5 °C, and stirring speed of 100 r·min. -1 The dialysis bag had a molecular weight cutoff of 3.5 kDa, a sample volume of 5 mL was taken and an equal volume of fluid was added, and the ammonium ion concentration was determined by ion chromatography to calculate the cumulative release rate. The sample was the same as that in Example 1, and the parameters varied from 0.5 h, 1 h, 2 h, 4 h, 6 h, 8 h, 12 h to 24 h. The cumulative release rate increased continuously over time and reached 82.5% at 24 h, showing a slow and continuous release characteristic. This indicates that the composite polysaccharide gel microparticle loading system can provide stable mass transfer resistance and delay the rapid dissolution of ammonium chloride under simulated rumen conditions, which is conducive to forming a continuous and stable acidification supply rhythm, thereby supporting the sustainability of urine acidification.

[0110] As can be seen from the performance of the examples and comparative examples in Table 1, all four examples exhibited excellent overall performance. The urine pH value was controlled within the range of 6.08-6.22, achieving effective urine acidification. The incidence of urinary stones was controlled below 5%, significantly lower than most comparative examples. This indicates that the sustained-release system of the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder can continuously and stably release ammonium chloride, maintain the acidic environment of urine, and effectively inhibit the precipitation and aggregation of stone crystals such as magnesium ammonium phosphate. Comparative Examples 2 and 4, due to the low carboxyl substitution of oxidized corn starch or insufficient deacetylation of chitosan, had poor gel network structure stability, and the ammonium chloride release rate was too fast and uneven, resulting in urinary stone incidence rates of 12.5% ​​and 10.8%, respectively. Comparative Example 6, due to the low ammonium chloride content in the composite powder, had insufficient overall acidification capacity, resulting in a urinary stone incidence rate of 15.8%. Regarding the physical quality of the particles, the particles in the examples had a hardness ranging from 26.8 to 32.8 N and a durability ranging from 95.5% to 98.2%, ensuring good storage and transportation stability while avoiding a decrease in palatability due to excessive particle hardness. While Comparative Examples 3 and 7 exhibited excellent particle physical quality, some performance indicators, such as the incidence of urinary stones, were not superior to the optimal example, indicating that simply pursuing particle strength may affect the controllable release of ammonium chloride. 24-hour ammonium chloride release rate data showed that the examples exhibited a slow and continuous release characteristic, ranging from 78.6% to 88.5%, while Comparative Examples 1, 2, 4, 5, and 6 had lower release rates or uneven release, making it difficult to maintain a stable urine acidification effect. Regarding the total amount of flavor compounds in mutton, Example 3, due to the optimized ratio of corn distillers' grains and corn germ meal, achieved a total flavor compound amount of 4125 μg / kg, significantly higher than other groups. This indicates that appropriately increasing corn by-products can enhance the supply of flavor precursors and improve the flavor quality of mutton. The total flavor compound amounts in Examples 1, 2, and 4 were also in the range of 3780-3920 μg / kg, significantly better than most comparative examples. In summary, this invention, through the synergistic sustained-release design of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles, successfully resolved the contradiction between particle strength and controllable release of ammonium chloride. While ensuring the physical quality of the feed, it achieved continuous acidification of urine, effectively preventing urinary stones. Furthermore, by optimizing the ratio of corn and its by-products, it significantly improved the flavor quality of mutton, demonstrating significant technical advantages and application value.

[0111] Table 1 Performance comparison data of different embodiments and comparative examples

[0112] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A sheep feed that reduces urinary stone deposition and enhances the flavor of mutton, characterized in that, Based on feed dry matter weight, it includes the following components: The corn comprises 45-65 wt%, including whole corn kernels and crushed corn, wherein the median volumetric particle size (D50) of the crushed corn is 0.5-1.0 mm, and the median volumetric particle size (D50) is measured by a laser particle size analyzer. Soybean meal 10-18 wt%; 3-12 wt% dried corn distillers grains; Corn germ meal 6-15 wt%; Soybean hulls 3-8 wt%; Calcium carbonate fine powder 1.5–3.0 wt%; Sodium chloride 0.3–1.0 wt%; 0.5–2.0 wt% of calcium hydrogen phosphate dihydrate; Compound premixed feed for fattening sheep: 0.5–2.0 wt%; Corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles, 0.6–5.0 wt%; The corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder meets the following conditions: The oxidized corn starch includes oxidized corn starch with a carboxyl substitution degree of 0.10 to 0.50 mmol / g; Includes chitosan, wherein the degree of deacetylation of the chitosan is 75-95% and the number-average molecular weight is 50-500 kDa; It includes ammonium chloride, wherein the mass fraction of ammonium chloride in the dry basis of the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder is 10-40 wt%; The median particle size of the corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder is 0.5–5.0 μm.

2. The sheep feed as described in claim 1, characterized in that, The total mass fraction of ammonium chloride in the sheep feed is 0.4 to 0.9 wt%, wherein the ammonium chloride present in the form of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles accounts for 60 to 75 wt% of the total ammonium chloride.

3. The sheep feed as described in claim 1, characterized in that, The corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder is prepared by the following steps: A1. An aqueous solution of ammonium chloride is added to the corn starch-chitosan crosslinked gel, wherein the mass fraction of the aqueous solution of ammonium chloride is 10-30 wt%. The mixture is stirred to allow the ammonium chloride to uniformly penetrate into the gel network, and the amount added is controlled so that the mass fraction of ammonium chloride in the dry basis of the resulting corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder is 10-40 wt%. A2. The crosslinked gel loaded with ammonium chloride is subjected to high-shear dispersion or ultrasonic dispersion, wherein the high-shear dispersion is performed at a rotation speed of 10,000 to 20,000 r / min and a dispersion time of 5 to 20 min, and the ultrasonic dispersion is performed at an ultrasonic power of 200 to 600 W and an ultrasonic time of 5 to 20 min, so that the median particle size of the resulting primary gel particles is 100 to 500 nm. A3. The obtained dispersion was spray-dried to obtain corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticle powder with a median particle size of 0.5-5.0 μm.

4. The sheep feed as described in claim 1, characterized in that, The corn starch-chitosan crosslinked gel was prepared by the following steps: B1. Dissolve chitosan in an aqueous solution of glacial acetic acid with a volume fraction of 1-5 vol% to obtain a chitosan solution with a chitosan mass fraction of 1.0-2.0 wt%, wherein the degree of deacetylation of the chitosan is 75-95% and the number average molecular weight is 50-500 kDa; B2. Disperse oxidized corn starch in deionized water to obtain an oxidized corn starch dispersion with a mass fraction of 5-20 wt%, and adjust the pH value of the dispersion to 6.0-7.0; B3. Mix the oxidized corn starch dispersion and the chitosan solution at a mass ratio of 1.0–5.0:0.1–0.5, stir at 20–40°C, and slowly add an aqueous solution of calcium chloride dihydrate, wherein the concentration of the calcium chloride dihydrate aqueous solution is 0.1–1.0 mol / L, the addition time is 5–30 min, and the system temperature is maintained at 20–40°C and the system pH is 6.0–7.0 during the addition process, so that the Ca in the system is balanced. 2+ The molar ratio of oxidized corn starch to carboxyl groups is 0.1–1.0:

1. Stirring is continued for 0.5–2.0 h to allow oxidized corn starch and chitosan to form a three-dimensional cross-linked gel through electrostatic interaction and calcium ion bridging.

5. The sheep feed as described in claim 1, characterized in that, The oxidized corn starch is prepared by the following steps: C1. Prepare a corn starch aqueous suspension with a mass fraction of 20-40 wt%, add a sodium hypochlorite solution with a mass fraction of 5-15 wt% dropwise at 35-45℃, adjust the pH of the system to 8.0-9.0 with 0.5-2.0 mol / L sodium hydroxide solution, and react for 0.5-2.0 h; C2. Stop adding sodium hypochlorite when the degree of carboxyl substitution of the corn starch, as determined by acid-base titration, reaches 0.10–0.50 mmol / g, and adjust the pH of the system to 6.0–7.0 with 0.5–2.0 mol / L hydrochloric acid; C3. Wash and dry at 40–60 °C to obtain oxidized corn starch with a carboxyl substitution degree of 0.10–0.50 mmol / g.

6. The sheep feed as described in claim 1, characterized in that, The premixed feed for fattening sheep, per 100 parts, includes the following components, by weight: Vitamin A 8-15 parts; Vitamin D3 1.5–3.0 servings; Vitamin E 15-30 servings; Nicotinamide 0.1-0.2 parts; 8-10 parts of rumen-protected choline; Copper sulfate 0.15–0.25 parts; Ferrous sulfate 1.5–2.0 parts; 2.5–3.5 parts manganese sulfate; Zinc sulfate 2.5–3.5 parts; Calcium iodate 0.03–0.06 parts; Sodium selenite 0.015–0.03 parts; 0-10 parts of ammonium chloride; 3-5 parts of urease inhibitor; Antioxidant 1.5–2.5 parts; 1.5–2.5 parts of compound probiotics; 8-10 parts of compound enzyme preparation; The rice husk powder is used as a supplement to make up 100 parts of the compound premixed feed for fattening sheep; The compound probiotics include at least one microbial strain, which is selected from Saccharomyces cerevisiae, Bacillus subtilis, Aspergillus niger and Aspergillus oryzae.

7. The sheep feed as described in claim 1, characterized in that, The mass ratio of total calcium to total phosphorus in the sheep feed is 2.0 to 2.5:1, and the calcium carbonate powder is fine stone powder with a particle size of 100% passing through an 80-mesh standard sieve and a calcium content of not less than 36 wt%.

8. The sheep feed as described in claim 1, characterized in that, The corn meets the second-grade corn standard and has the following quality indicators: test weight not less than 685g / L, impurity mass fraction not more than 2wt%, imperfect kernel mass fraction not more than 5wt%, fatty acid value (calculated as potassium hydroxide) not more than 60mg / 100g, and has a bright color, no moldy odor, and its hygiene indicators meet the requirements of GB13078.

9. A method for preparing sheep feed according to any one of claims 1 to 8, which reduces urinary stone deposition and enhances the flavor of mutton, characterized in that, Includes the following steps: S1. Prepare oxidized corn starch to obtain oxidized corn starch with a carboxyl substitution degree of 0.10-0.50 mmol / g; S2. Preparation of corn starch-chitosan crosslinked gel; S3. Preparation of corn starch-chitosan-ammonium chloride composite polysaccharide gel microparticles; S4. Mix crushed corn, soybean meal, corn distillers grains, corn germ meal, soybean hulls, calcium carbonate powder, calcium hydrogen phosphate dihydrate, sodium chloride, free ammonium chloride, and fattening sheep compound premixed feed with the corn starch-chitosan-ammonium chloride compound polysaccharide gel microparticle powder to obtain basic concentrate; S5. Conditioning and granulation of the base concentrate: Steam conditioning or steam-water combined conditioning is used to condition the material temperature to 70-90℃, the conditioning time to 30-120s, and the moisture content of the material to 14-18wt%; then ring die granulation is used, with a ring die aperture of 4-6mm; after granulation, the material is cooled countercurrently until the particle temperature is no higher than the ambient temperature +5℃, and the moisture content of the finished particles is no higher than 12wt%, to obtain granulated concentrate; S6. Mix the pelleted concentrate and whole corn kernels at a ratio of 0.5 to 2.0:1 to obtain the sheep feed.

10. The preparation method according to claim 9, characterized in that, 30-40 wt% of the corn is pulverized before step S4, and the pulverization effect is such that when tested with a 14-mesh feed analysis standard sieve, the mass fraction of the material passing through the sieve is not less than 80 wt%. The remaining 60-70 wt% of the corn is added in whole grain form in step S6. The coefficient of variation of the mass fraction of the mixing uniformity of the basic concentrate is not higher than 5%.

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