Use of slow-release methionine in the preparation of low-protein daily ration for egg-laying peak period hens

Abstract

The application discloses application of slow-release methionine in preparation of low-protein daily ration for laying hens in an egg production peak period and belongs to the technical field of poultry feed and animal nutrition. The application provides application of slow-release methionine in any one of the following aspects: (1) preparation of low-protein daily ration for laying hens in an egg production peak period; (2) preparation of a product for improving egg quality of laying hens in an egg production peak period under low-protein daily ration; (3) preparation of a product for improving liver antioxidant capacity of laying hens in an egg production peak period under low-protein daily ration; (4) preparation of a product for improving apparent digestibility of crude protein of laying hens in an egg production peak period under low-protein daily ration; and (5) preparation of a product for reducing nitrogen emission of laying hens in an egg production peak period under low-protein daily ration. The slow-release methionine is achieved by adding coated methionine and crystal methionine in the low-protein daily ration. The slow-release methionine method can alleviate the negative influence of low-protein daily ration on metabolism and immune function of the laying hens, and guarantee the health homeostasis of the laying hens in an egg production peak period.

Description

Technical Field

[0001] This invention relates to the field of poultry feed and animal nutrition technology, and in particular to the application of slow-release methionine in the preparation of low-protein diets for laying hens at peak egg production. Background Technology

[0002] In recent years, the livestock industry has developed significantly, with continuously expanding breeding scale and steadily improving production levels. The poultry industry is a key area for optimizing the livestock product structure, with nearly 20 billion birds raised annually, consuming approximately 180 million tons of feed annually. Its scale of operation exceeds 85%, and its production efficiency continues to lead the livestock industry. my country's dependence on imported protein feed has reached 64.4%, with annual soybean imports exceeding 100 million tons. The contradictions between livestock and grain crops for land and between livestock and humans for grain are acute, and feed resource shortages have become a core bottleneck for the development of the livestock industry. The bottleneck of high-quality protein feed is particularly prominent and has become a key constraint on the high-quality and sustainable development of the livestock industry.

[0003] Livestock farming is a significant source of agricultural carbon emissions, and manure discharge has become a major constraint on the green development of the livestock industry. Without addressing the issues of manure and carbon emissions, high-quality development of the livestock industry is impossible. Developing diversified low-protein, low-soybean meal diets using synthetic amino acids and miscellaneous grains and meals can reduce the use of soybean meal (a protein feed) and corn (an energy feed), alleviating the livestock industry's dependence on imported protein feeds and mitigating potential risks associated with energy feeds in the future. This contributes to the self-sufficiency and long-term stability of food security. Summary of the Invention

[0004] The purpose of this invention is to provide the application of slow-release methionine in the preparation of low-protein diets for laying hens during their peak egg production period, in order to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following solution: This invention provides the use of sustained-release methionine in any of the following: (1) Preparation of low-protein diets for laying hens during their peak egg production period; (2) To prepare products that improve the quality of eggs from laying hens in their peak laying period under low-protein diets; (3) Prepare products that enhance the liver antioxidant capacity of laying hens during their peak laying period under low-protein diets; (4) Prepare products that improve the apparent digestibility of crude protein in laying hens during their peak laying period under low-protein diets; (5) Prepare products that reduce nitrogen emissions from laying hens during their peak laying period on low-protein diets; The slow-release methionine is achieved by adding coated methionine and crystalline methionine to the low-protein diet.

[0006] Optionally, the protein content of the low-protein diet is 13%; The mass ratio of the coated methionine to the crystalline methionine is 4:6; The coated methionine and the crystalline methionine comprise 0.289% of the total mass of the low-protein diet.

[0007] Optionally, improving the egg quality of laying hens in their peak laying period under a low-protein diet includes improving the color of the egg yolk.

[0008] Optionally, improving the liver antioxidant capacity of laying hens in peak laying periods under low-protein diets includes increasing glutathione peroxidase activity, reducing malondialdehyde content, and enhancing total antioxidant capacity; upregulating genes SOD1 , NQO1 , HO-1 and Nrf2 The amount of expression.

[0009] The present invention also provides a low-protein laying hen feed, wherein the laying hen feed comprises coated methionine and crystalline methionine; The low protein content is 13%.

[0010] Optionally, the ratio of the actual effective levels of the coated methionine to the crystalline methionine is 4:6; The coated methionine and the crystalline methionine comprise 0.289% of the total mass of the low-protein diet.

[0011] Optionally, by weight percentage, the laying hen feed comprises 62.405% corn, 8.560% soybean meal, 8.050% wheat bran, 5.000% corn gluten meal, 3.480% corn starch, 8.810% limestone, 1.650% dicalcium phosphate, 0.300% salt, 0.478% L-lysine hydrochloride, 0.124% DL-methionine, 0.261% L-arginine, 0.147% L-threonine, 0.123% L-valine, 0.121% L-isoleucine, 0.101% L-glycine, 0.165% coated methionine, 0.100% choline chloride, 0.025% compound vitamins, and 0.100% compound trace elements. The DL-methionine contains 99% methionine, and the coated methionine contains 49.5% methionine.

[0012] Optionally, the compound vitamins per kilogram of laying hen feed include vitamin V. A 9000 IU, V D3 2000 IU, V E 11IU, V K 1.0 mg, V B1 1.2 mg, V B2 5.8 mg, V B62.6 mg, V B12 0.012 mg, 66.0 mg niacin, 10.0 mg pantothenic acid, 0.10 mg biotin and 0.70 mg folic acid; the complex trace elements include 100 mg manganese, 75 mg zinc, 80 mg iron, 0.65 mg iodine, 8.0 mg copper and 0.35 mg selenium.

[0013] The present invention discloses the following technical effects: (1) Improved production performance: Under the condition of a 3 percentage point reduction in dietary protein (from 16% to 13%), the use of a slow-release methionine ratio of M-Met:C-Met = 4:6 can significantly improve the feed conversion rate of laying hens during the peak laying period, effectively alleviate the problem of reduced egg production rate and egg production caused by low-protein diets, and maintain stable egg production performance.

[0014] (2) Significant antioxidant and liver-protective effects: This sustained-release formulation can significantly upregulate liver function. SOD1 , NQO1 , HO-1 and Nrf2 Antioxidant gene mRNA expression increases glutathione peroxidase activity, reduces malondialdehyde content, enhances the body's total antioxidant capacity, reduces liver lipid peroxidation damage caused by low-protein diets, and regulates lipid metabolism disorders in the body.

[0015] (3) Improve amino acid digestion and absorption: The reasonable slow-release ratio balances the rapid absorption of crystalline methionine and the slow release of coated methionine, optimizes the standard digestibility of amino acids at the end of the ileum, and avoids the drawbacks of low digestibility of fully coated methionine and overload oxidation of pure crystalline methionine.

[0016] (4) Reduce nitrogen emissions and improve protein utilization: This formula can be applied to low-protein diets, which can significantly reduce the daily nitrogen excretion of laying hens, improve the apparent digestibility of crude protein in the diet, reduce nitrogen pollution in breeding, and meet the needs of grain saving, emission reduction and green breeding development.

[0017] (5) Maintenance of physiological homeostasis: It can effectively regulate the development of organs and follicles in laying hens, stabilize the levels of serum biochemical, immune and inflammatory factors, reduce the negative impact of low-protein diets on the metabolism and immune function of laying hens, and ensure the health homeostasis of the body during the peak egg production period. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The effect of different amino acid slow-release ratios on the standard digestibility of methionine (A) and lysine (B) in the terminal duodenum of laying hens on low-protein diets; Figure 2 To investigate the effect of different amino acid slow-release ratios on the standard digestibility of methionine (A) and lysine (B) in the terminal jejunum of laying hens on low-protein diets; Figure 3 To investigate the effect of different methionine slow-release ratios on the expression level of antioxidant gene mRNA in the liver of laying hens at peak laying age under a low-protein diet (51 weeks of age). Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0023] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0024] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0025] This invention, based on the nutritional and metabolic characteristics of laying hens during peak egg production, first conducted preliminary experiments using a nitrogen-free diet combined with exogenous indicator methods. Gradual screening of MAA:CAA slow-release ratios of 0:10, 2:8, 4:6, 6:4, 8:2, and 10:0 was performed, with suitable ratios initially selected based on amino acid digestibility. Then, a formal feeding trial system was used to verify the effects of different slow-release ratios on laying hen performance, egg quality, organ development, blood biochemistry, antioxidant indicators, liver antioxidant gene expression, amino acid digestibility, and nitrogen emissions. Ultimately, a C-Met:M-Met ratio of 4:6 was determined to be the optimal methionine slow-release ratio. In a low-protein system with a 3 percentage point reduction in dietary protein, this ratio achieves segmented slow-release and stable supply of methionine, matching the amino acid absorption rhythm after feed intake in laying hens, balancing nutrient supply, antioxidant regulation, and nitrogen metabolism utilization. Without affecting the health of the laying hens, it achieves multiple benefits including protein conservation, stable egg production, and reduced emissions.

[0026] Example 1 Forty-eight healthy 30-week-old Jingfen No. 6 laying hens were selected and divided into eight treatment groups, with six replicates in each treatment group and one hen per replicate. The pre-trial period was three days, and the formal trial period was one day.

[0027] Dietary Treatments: The control group was fed a basal diet; the nitrogen-free diet group was used to measure the basal endogenous loss of amino acids. The nitrogen-free diet was formulated using corn starch as the basal raw material, supplemented with minerals and vitamins, according to the NRC (1994) standard; the treatment groups, based on the nitrogen-free diet, had coated amino acids and crystalline amino acids added sequentially at ratios of 0:10, 2:8, 4:6, 6:4, 8:2, and 10:0, respectively, along with supplemental coating material. All diets were supplemented with exogenous TiO2 indicators. The composition and nutrient levels of the experimental diets are shown in Table 1. The coated amino acids were encapsulated using a composite coating material of palmitic stearic acid and monoglycerides (provided by Shandong Hemeihua Group Co., Ltd., with methionine content of 49.5%), allowing for slow release and stable supply in the middle and posterior digestive tracts of laying hens, achieving synchronous absorption with feed protein source amino acids.

[0028] The chickens were housed in three-tiered cages, with three chickens per cage. They received 16 hours of light daily, and all environmental indicators in the chicken house met the hygiene requirements for laying hen rearing. The chicken house was well-ventilated and kept clean. Throughout the trial, the chickens had free access to feed and water. Rearing and management were conducted according to the "Jingfen No. 6 Laying Hen 2022 Edition Rearing and Management Manual".

[0029] The animals were fasted for 12 hours before the trial period, then allowed free access to food for 1 hour. Samples were taken 4.5 hours later, and chyme from the duodenum and terminal jejunum was collected. The amino acid concentration of the chyme was determined using the exogenous indicator method.

[0030] Table 1. Composition and nutritional components of the experimental diet (air-dried basis) Note: 1 Multivitamins (provided per kilogram of feed): V A 9000 IU, V D3 2000 IU, V E 11 IU, V K 1.0 mg, V B1 1.2 mg, V B2 5.8 mg, V B6 2.6 mg, V B12 0.012 mg, niacin 66.0 mg, pantothenic acid 10.0 mg, biotin 0.10 mg and folic acid 0.70 mg. 2 Complex trace elements (provided per kilogram of feed): manganese 100 mg, zinc 75 mg, iron 80 mg, iodine 0.65 mg, copper 8.0 mg and selenium 0.35 mg. 3 The nutrient group was converted into the measured value. 4 The nutrient group is used as the calculated value. Same as Table 3.

[0031] Table 2 shows the TiO2 content and recovery rate in the experimental diets. The average recovery rate of TiO2 in this experiment reached 97.81%, indicating its good stability and suitability as an endogenous indicator for this study.

[0032] Table 2. TiO2 content and recovery rate in the experimental diets like Figure 1 As shown, with the increase of the proportion of coated amino acid slow release, the digestibility of Met and Lys in the terminal duodenum of laying hens showed a highly significant linear decrease and a quadratic change.

[0033] like Figure 2 As shown, the standard digestibility of Met in the terminal jejunum of laying hens exhibits highly significant linear and quadratic curve relationships with changes in the ratio of coated amino acids to crystalline amino acids. Based on the optimal results of amino acid standard digestibility, this experiment preliminarily screened and determined the MAA:CAA ratios to be 0:10, 2:8, 4:6, and 6:4 for subsequent experimental studies.

[0034] Example 2 Three hundred healthy Jingfen No. 6 laying hens of similar weight and egg production rate at 41 weeks of age were selected and divided into 5 treatments, with 5 replicates per treatment and 12 hens per replicate. The pre-trial period was 1 week and the formal trial period was 15 weeks. The basal diet control group (control group) was fed a basal diet (CP 16.0%); the amino acid slow-release treatment group (treatment group) was fed an isoenergetic low-protein diet (CP 13.0%), and coated methionine and crystalline methionine (M-Met:C-Met = 0:10, 2:8, 4:6, 6:4) were added according to the ratios screened in Example 1, while ensuring that the amino acid levels were consistent with the basal diet. Except for methionine, other amino acids Lys, Thr, Arg, Val, Ile, and Gly in the experimental diet were supplemented in crystalline form to reach the level of the control diet. The experimental diet was a corn-soybean meal diet, formulated according to the NRC (1994) nutritional requirements for laying hens. The composition and nutritional levels of the experimental diet are shown in Table 3.

[0035] The chickens were housed in three-tiered cages, with four chickens per cage. All environmental parameters within the chicken house met the hygiene requirements for laying hen rearing, and the house was well-ventilated and kept clean. They received 16 hours of light daily and were fed powdered feed. Throughout the trial, all chickens had free access to feed and water. Rearing management was conducted according to the "Jingfen No. 6 Laying Hen 2022 Edition Rearing Management Manual".

[0036] Table 3. Raw material composition and nutritional components of the experimental diet (air-dried basis) Note: Taking a 4:6 ratio as an example, here's a simplified explanation of how to calculate the addition amounts of coated methionine and crystalline methionine: The peak methionine requirement is 0.441%, while feed ingredients such as corn and soybean meal contain 0.237% methionine, leaving a deficit of 0.204%. Adding methionine at a 4:6 ratio requires 0.204% * 0.4 / 0.495 = 0.165% coated methionine and 0.204% / 0.6 / 0.99 = 0.124% crystalline methionine. Therefore, crystalline methionine accounts for 0.124% of the total feed mass, and coated methionine accounts for 0.165%.

[0037] During the experiment, feed intake, egg production rate, egg weight, egg production, and feed conversion ratio of laying hens at peak laying time were recorded for each group. The results are shown in Table 4. Throughout the experiment, compared with the control group, the low-protein diet group (treatment group) significantly reduced the egg production rate and egg production of laying hens at peak laying time. The slow-release ratio of methionine did not have a significant effect on the production performance of laying hens, and there was no significant change in the linearity and quadratic curve relationship. However, when M-Met : C-Met = 4:6, it improved feed conversion efficiency.

[0038] Table 4. Effects of different methionine slow-release ratios on the laying performance of hens at peak laying age under low-protein diets. Note: Different letters in each line indicate significant differences. P <0.05). Same as the table below.

[0039] The weight of each group of laying hens was measured every 5 weeks at the start of the experiment. The results are shown in Table 5. Compared with the control group, the weight of laying hens in the low-protein diet group was significantly reduced.

[0040] Table 5. Effects of different methionine slow-release ratios on body weight of laying hens at peak laying age under low-protein diets (g) Egg quality indicators (egg weight, egg shape index, eggshell thickness, eggshell strength, eggshell specific gravity, yolk specific gravity, albumen height, yolk color, and Haugh units) were measured in each group of laying hens at 46, 51, and 56 weeks of age. The results of egg quality at 46 weeks of age are shown in Table 6. The yolk color in the treatment group was significantly higher than that in the control group, and the egg shape index increased linearly with the increase of the methionine coating percentage. There were no significant differences in other indicators among the groups.

[0041] Table 6. Effects of different methionine slow-release ratios on egg quality in laying hens at peak laying age under low-protein diets (46 weeks of age) The results of egg quality at 51 weeks of age are shown in Table 7. Compared with the control group, the eggshell strength of the 0:10 ratio group was significantly improved, and the eggshell strength decreased linearly with the increase of the methionine coating ratio. The yolk color of the 2:8, 4:6, and 6:4 ratio groups was significantly higher than that of the control group. There were no significant differences among the groups in other indicators.

[0042] Table 7. Effects of different methionine slow-release ratios on egg quality in laying hens at peak laying age under low-protein diets (51 weeks of age) The results of egg quality at 56 weeks of age are shown in Table 8. At 56 weeks of age, the egg weight showed a linear decrease as the proportion of coated methionine increased. Compared with the control group, the albumen height of the 0:10, 2:8 and 6:4 ratio groups was significantly reduced, while the yolk color of the 2:8 and 6:4 ratio groups was significantly increased. The Haugh units of the treatment groups were significantly lower than those of the control group.

[0043] Table 8. Effects of different methionine slow-release ratios on egg quality in laying hens at peak laying age under low-protein diets (56 weeks of age) Organ indices of laying hens were measured at 46, 51, and 56 weeks of age. As shown in Table 9, at 46 weeks of age, compared with the control group, the liver index and abdominal fat index of the low-protein diet group were significantly increased; there were no significant differences in other indicators among the groups. At 51 weeks of age, compared with the 2:8 ratio group, the liver index of the 0:10 and 6:4 ratio groups was significantly increased; compared with the control group, the abdominal fat index and jejunal organ index of the low-protein diet group were significantly increased, the ovarian index of the 2:8 and 4:6 ratio groups was extremely significantly increased, the oviduct index of the 4:6 ratio group was extremely significantly decreased, and the oviduct length of the 0:10 and 2:8 ratio groups was significantly decreased. Furthermore, with the increase of the methionine coating ratio, the oviduct length showed a linear increase and a quadratic change. At 56 weeks of age, with the increase of the methionine coating ratio, the spleen index showed a linear decrease; there were no significant differences in other indicators among the groups.

[0044] Table 9. Effects of different methionine slow-release ratios on organ indices of laying hens at peak egg production under low-protein diets. Serum antioxidant parameters (catalase, superoxide dismutase, total antioxidant capacity, malondialdehyde, and glutathione peroxidase) of laying hens were measured using kits at 46 and 51 weeks of age. As shown in Table 10, at 46 weeks of age, the serum T-AOC level in the treatment group was significantly lower than that in the control group, while other antioxidant parameters showed no significant differences among the groups. At 51 weeks of age, there were no significant differences in any of the parameters among the groups.

[0045] Table 10. Effects of different methionine slow-release ratios on serum antioxidant parameters of laying hens in peak laying period under low-protein diets. At 46 and 51 weeks of age, the liver antioxidant parameters (catalase, superoxide dismutase, total antioxidant capacity, malondialdehyde, and glutathione peroxidase) of laying hens in each group were measured using a kit. As shown in Table 11, at 46 weeks of age, compared with the control group, the liver GSH-Px activity in the 0:10 diet group was significantly lower than that in the other three diet groups; with the increase of the proportion of coated methionine, the liver MDA content decreased linearly, while the liver GSH-Px activity increased linearly and underwent a quadratic change. At 51 weeks of age, compared with the control group, the liver SOD activity in the low-protein diet group was significantly increased, and the liver GSH-Px activity in the 4:6 diet group was significantly higher than that in the other three diet groups; with the increase of the proportion of coated methionine, the liver T-AOC content showed a linear decreasing trend.

[0046] Table 11 Effects of different methionine slow-release ratios on liver antioxidant indices in laying hens at peak laying period under low-protein diets At 51 weeks of age, real-time quantitative PCR was used to detect liver antioxidant-related genes in each group of laying hens. HO-1 , SOD1 , SOD2 , AKT , Nrf2 and NQO1 The gene primer sequences were derived from the NCBI database, synthesized and verified by Shanghai Sangon Biotech Co., Ltd., and showed over 99% homology with the target product. The primer sequences used in the experiment are shown in Table 12. The reverse transcription reaction system consisted of: dNTPMix, 2.5 mM, 4 μL each; Primer Mix, 12 μL; RNA Template, x μL; 5×RT Buffer, 1 μL; DTT, 0.1 M, 2 μL; and HiFiScript, 200 U / μL, 1 μL; with RNase-free H2O added to a final volume of 20 μL. PCR reaction system: 10 μL 2×Magic SYBR Mixture, 0.4 μL F primer (10 μM), 0.4 μL R primer (10 μM), 2 μL Template DNA, 0.2 μL ROX Reference Dye, and 7 μL ddH2O. Reaction program: Two-step qPCR amplification program, 95℃ pre-denaturation for 30 s, 1 cycle; 95℃ denaturation for 5 s → 60℃ annealing / extension for 30 s, 40 cycles. GAPDH As an internal reference gene, based on "average relative content = 2" -ΔΔCt Calculate the relative gene expression level.

[0047] Table 12 Primer Sequences The results are as follows Figure 3 As shown, compared with the control group, the 2:8, 4:6, and 6:4 ratio groups significantly upregulated [the condition / effects]. SOD1 , NQO1 The expression levels of [the substance] were significantly upregulated in the 2:8 and 4:6 ratio groups. HO-1 The expression levels of [the substance] were significantly upregulated in the 2:8 and 6:4 ratio groups. SOD2 Expression levels; 4:6 ratio group Nrf2 mRNA expression levels were significantly upregulated compared to the control group, the 0:10 ratio group, and the 2:8 ratio group.

[0048] At 56 weeks of age, nitrogen emission-related indicators (feed intake, feed nitrogen content, daily nitrogen intake, daily fresh manure output, fecal moisture content, daily dry matter output, fecal nitrogen content, daily fecal nitrogen excretion, and apparent digestibility of crude protein) were measured in each group of laying hens, as shown in Table 13. Different methionine slow-release ratios had no significant effect on feed intake, daily fresh manure output, fecal moisture content, and daily dry matter output of laying hens. The feed nitrogen content, daily nitrogen intake, fecal nitrogen content, and daily fecal nitrogen excretion of the low-protein diet group were significantly lower than those of the control group, while the apparent digestibility of crude protein in the 2:8 and 4:6 ratio groups was significantly higher than that of the control group.

[0049] Table 13 Effects of different methionine slow-release ratios on nitrogen emissions in laying hens during peak laying period under low-protein diets At 56 weeks of age, the apparent digestibility of amino acids in the terminal ileum of laying hens in each group was measured. The results are shown in Table 14. Compared with the control group, the digestibility of Asp and Glu in the 4:6 ratio group was significantly reduced, while the digestibility of Cys in the 0:10 ratio group was significantly increased. With the increase of the proportion of coated methionine, the digestibility of Cys and Met showed a linear decrease and a quadratic change.

[0050] Table 14 Effects of different methionine slow-release ratios on the apparent digestibility of amino acids in the terminal ileum of laying hens during peak egg production under low-protein diets (dry matter basis) The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. Application of sustained-release methionine in any of the following: (1) Preparation of low-protein diets for laying hens during their peak egg production period; (2) To prepare products that improve the quality of eggs from laying hens in their peak laying period under low-protein diets; (3) Prepare products that enhance the liver antioxidant capacity of laying hens during their peak laying period under low-protein diets; (4) Prepare products that improve the apparent digestibility of crude protein in laying hens during their peak laying period under low-protein diets; (5) Prepare products that reduce nitrogen emissions from laying hens during their peak laying period on low-protein diets; The slow-release methionine is achieved by adding coated methionine and crystalline methionine to the low-protein diet.

2. The application as described in claim 1, characterized in that, The protein content of the low-protein diet is 13%; The ratio of the actual effective levels of the coated methionine to the crystalline methionine is 4:6; The coated methionine and the crystalline methionine comprise 0.289% of the total mass of the low-protein diet.

3. The application as described in claim 1, characterized in that, Improving egg quality in peak-laying hens on low-protein diets includes improving egg yolk color.

4. The application as described in claim 1, characterized in that, The proposed methods for enhancing the liver antioxidant capacity of peak-laying hens on low-protein diets include increasing glutathione peroxidase activity, reducing malondialdehyde content, and enhancing total antioxidant capacity; upregulating genes SOD1 , NQO1 , HO-1 and Nrf2 The amount of expression.

5. A low-protein laying hen feed, characterized in that, The laying hen feed contains coated methionine and crystalline methionine; The low protein content is 13%.

6. The laying hen feed as described in claim 5, characterized in that, The ratio of the actual effective levels of the coated methionine to the crystalline methionine is 4:6; The coated methionine and the crystalline methionine comprise 0.289% of the total mass of the low-protein diet.

7. The laying hen feed as described in claim 5, characterized in that, By weight percentage, the laying hen feed comprises 62.405% corn, 8.560% soybean meal, 8.050% wheat bran, 5.000% corn gluten meal, 3.480% corn starch, 8.810% limestone, 1.650% dicalcium phosphate, 0.300% salt, 0.478% L-lysine hydrochloride, 0.124% DL-methionine, 0.261% L-arginine, 0.147% L-threonine, 0.123% L-valine, 0.121% L-isoleucine, 0.101% L-glycine, 0.165% coated methionine, 0.100% choline chloride, 0.025% compound vitamins, and 0.100% compound trace elements. The DL-methionine contains 99% methionine, and the coated methionine contains 49.5% methionine.

8. The laying hen feed as described in claim 7, characterized in that, The compound vitamins per kilogram of laying hen feed include vitamin V A 9000 IU, V D3 2000 IU, V E 11 IU, V K 1.0 mg, V B1 1.2 mg, V B2 5.8 mg, V B6 2.6 mg, V B12 0.012 mg, 66.0 mg niacin, 10.0 mg pantothenic acid, 0.10 mg biotin and 0.70 mg folic acid; the complex trace elements include 100 mg manganese, 75 mg zinc, 80 mg iron, 0.65 mg iodine, 8.0 mg copper and 0.35 mg selenium.

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