Dual low rapeseed meal low protein diet and its application in improving egg laying performance and quality of laying ducks

Abstract

The application discloses a double-low rapeseed meal low-protein daily ration and application thereof in improving egg-laying performance and quality of egg ducks, and the low-protein daily ration comprises the following components: corn, wheat bran, brown rice, soybean meal, double-low rapeseed meal, stone powder, soybean oil, L-lysine sulfate, DL-methionine, L-threonine, tryptophan, isoleucine, L-arginine, phytase, anhydrous calcium hydrogen phosphate, sodium chloride, choline chloride, potassium magnesium sulfate, duck multi-vitamins and organic minerals. The application can ensure the balance of amino acid supply while reducing the crude protein level of the daily ration, replace part of the soybean meal with the double-low rapeseed meal, reduce the protein level of the daily ration and nitrogen emission, reduce the feed cost, and balance the economic benefits and ecological benefits of breeding.

Description

Technical Field

[0001] This invention belongs to the field of poultry feed formulation technology, specifically relating to a low-protein diet made from rapeseed meal and its application in improving the egg production performance and quality of laying ducks. Background Technology

[0002] Duck feed is highly dependent on soybean meal, which, as the main protein source, typically accounts for 20% to 30% of duck diets, leading to significant pressure from imported protein feed. This high dependence not only drives up breeding costs (feed costs account for over 70% of duck production costs) but also exacerbates environmental pressures: excessive soybean meal use leads to increased nitrogen emissions, highlighting ammonia and greenhouse gas emissions. Simultaneously, the development of unconventional protein resources lags behind, with low utilization rates of domestically produced protein sources such as rapeseed meal, cottonseed meal, and peanut meal. Anti-nutritional factors (such as glucosinolates and phytic acid) limit their large-scale application in duck diets. As high-yielding poultry, ducks are sensitive to protein and amino acid requirements; unstable protein levels in their diets directly affect egg production rate, egg weight, and egg quality, further amplifying the negative effects of resource shortages. Furthermore, under large-scale poultry production conditions such as duck farming, nitrogen load in excrement and the resulting ammonia emissions have become significant environmental issues hindering the industry's green development.

[0003] Low-erucic acid rapeseed meal has a high crude protein content and is a promising plant-based protein feed ingredient. Furthermore, as a major byproduct of rapeseed oil processing, it is abundant and can, to some extent, serve as a substitute protein source to alleviate soybean meal shortages. In the context of replacing part of soybean meal with low-erucic acid rapeseed meal and implementing a low-protein strategy, conducting a systematic evaluation from a nitrogen emission perspective is of significant practical importance for achieving cost reduction and efficiency improvement in laying duck farming and promoting green agriculture.

[0004] While low-erucic acid rapeseed meal has the potential to replace some soybean meal in livestock and poultry production, its application effectiveness is influenced by various factors, including animal species, production stage, addition ratio, raw material quality, and nutritional regulation measures. However, research on the application of low-erucic acid rapeseed meal in laying ducks is relatively limited. Existing studies mostly focus on its impact on production performance, failing to clarify its mechanism of action in reducing nitrogen emissions and improving egg quality by improving intestinal metabolism and gut microbiota structure. Furthermore, a stable low-protein diet formula using low-erucic acid rapeseed meal suitable for laying ducks has not been developed, thus limiting the large-scale promotion and application of this resource in the laying duck industry.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a low-protein diet with low-erucic acid rapeseed meal and its application in improving the egg production performance and quality of laying ducks. This invention solves the problems of high breeding costs and high nitrogen emission pressure caused by the high dependence on soybean meal in existing laying duck diets. This invention also fills the gap in the formulation of low-protein diets with low-erucic acid rapeseed meal suitable for laying ducks. It can maintain good egg production performance and ensure egg quality of laying ducks by adding an appropriate amount of low-erucic acid rapeseed meal to replace part of the soybean meal, while reducing nitrogen emissions and achieving green and sustainable development of the industry.

[0007] To achieve the above objectives, the present invention provides a low-protein diet made from low-erucic acid rapeseed meal, comprising the following components in parts by weight: 52.5-55.0% corn, 7.5-9.5% wheat bran, 6.5-9.5% brown rice, 7.5-19.0% soybean meal, 1.5-5.5% low-erucic acid rapeseed meal, 8.7-8.9% limestone powder, 0.09% soybean oil, 0.2-0.6% L-lysine sulfate, 0.1-0.3% DL-methionine, and 0.05-0.15%... L-Threonine, 0.05-0.1% Tryptophan, 0.06-0.19% Isoleucine, 0.13-0.37% L-Arginine, 0.03% Phytase, 1.08-1.1% Anhydrous Dicalcium Phosphate, 0.2% Sodium Chloride, 0.1% Choline Chloride, 0.9% Potassium Magnesium Sulfate, 0.1% Duck Multivitamins, and 0.1% Organic Minerals.

[0008] Preferably, the low-protein diet comprises the following components in parts by weight: 52.8-52.9% corn, 7.5-7.6% wheat bran, 6.5-6.7% brown rice, 18.8-18.9% soybean meal, 1.8-1.9% low-erucic acid rapeseed meal, 8.8-8.9% limestone powder, 0.09% soybean oil, 0.2-0.3% L-lysine sulfate, 0.1-0.2% DL-methionine, 0.05-0.06% L-threonine, 0.05-0.06% tryptophan, 0.06-0.07% isoleucine, 0.13-0.14% L-arginine, 0.03% phytase, 1.1% anhydrous dicalcium phosphate, 0.2% sodium chloride, 0.1% choline chloride, 0.9% potassium magnesium sulfate, 0.1% duck multivitamins, and 0.1% organic minerals.

[0009] The second objective of this invention is to provide the application of the aforementioned low-protein rapeseed meal diet in improving the egg production performance and quality of laying ducks.

[0010] Preferably, the low-protein diet made from rapeseed meal can ensure that the eggshell formation and egg white quality of laying ducks remain stable, and that the average daily feed intake of laying ducks remains stable.

[0011] Preferably, the low-protein diet made from rapeseed meal can ensure that the overall protein metabolism and liver function-related enzyme activity of the laying ducks remain stable.

[0012] Preferably, the low-protein diet made from low-erucic acid rapeseed meal can regulate the homeostasis of the intestinal environment in laying ducks.

[0013] Preferably, the low-protein diet made from low-erucic acid rapeseed meal can alter the cecal microbiota structure of laying ducks.

[0014] More preferably, the aforementioned low-protein diet made from low-erucic acid rapeseed meal can enrich... Actinobacteriota , Actinomycetia , Mycobacteriales , Mycobacteriaceae , Firmicutes D and Staphylococcales Microbial community.

[0015] Preferably, the low-protein diet made from low-erucic acid rapeseed meal has the potential to reduce nitrogen emissions.

[0016] The low-protein rapeseed meal diet of the present invention and its application in improving the egg production performance and quality of laying ducks solve the problems of high breeding costs and high nitrogen emission pressure caused by the high dependence on soybean meal in existing laying duck diets, and has the following advantages: (1) This invention replaces part of the soybean meal with an appropriate amount of low-erucic acid rapeseed meal, thereby reducing the dietary protein level and balancing the amino acid composition by supplementing crystalline amino acids. It can alleviate the dependence on imported soybean meal without increasing the cost, thereby reducing the breeding cost. It is suitable for promotion and use in duck egg farming. (2) The low-protein rapeseed meal diet of the present invention will not affect the egg production performance of ducks, can maintain the egg production rate and egg weight, and at the same time ensure that the eggshell quality and egg white quality do not decline, can maintain the normal protein metabolism and liver function of ducks, and ensure the healthy production of ducks. (3) The low-protein rapeseed meal diet of the present invention can reduce nitrogen excretion by regulating the cecal flora structure of laying ducks, improving the intestinal environment homeostasis, reducing the environmental pressure caused by nitrogen emissions during the breeding process, and meeting the requirements of green and sustainable development of the laying duck industry. Attached Figure Description

[0017] Figure 1 The results of PCA analysis of the overall sample in positive and negative ion modes in Example 1 of this invention are shown below: (A) POS positive ion mode; (B) NEG negative ion mode.

[0018] Figure 2 The following are the OPLS-DA score diagrams (A~C) and displacement test diagrams (D~F) in positive and negative ion modes in Example 1 of the present invention: (A, F) CK vs LP; (B, E) CK vs MP; (C, F) CK vs HP.

[0019] Figure 3The following is a screening diagram of differential substances under positive and negative ion modes in Embodiment 1 of the present invention: (A) POS positive ion mode; (B) NEG negative ion mode.

[0020] Figure 4 This is a graph showing the differential enrichment analysis of substances in the positive ion mode in Example 1 of the present invention.

[0021] Figure 5 This is a graph showing the enrichment analysis of differential substances in the negative ion mode in Example 1 of the present invention.

[0022] Figure 6 This is the ASV Rank curve in Embodiment 1 of the present invention.

[0023] Figure 7 This is the ASV sparse curve in Embodiment 1 of the present invention.

[0024] Figure 8 The diagram shows the alpha diversity analysis of cecal microorganisms in ducks in Example 1 of this invention; (A) CK vs LP; (B) CK vs MP; (C) CK vs HP.

[0025] Figure 9 This invention investigates the effect of a low-protein diet containing low-erucic acid rapeseed meal on the relative abundance of cecal microbiota in laying ducks.

[0026] Figure 10 The following are bar charts showing the LDA scores in Embodiment 1 of the present invention: (A) CK vs LP; (B) CK vs MP; (C) CK vs HP. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that: Unless otherwise specified in the examples, conditions should be followed according to standard conditions or the manufacturer's recommendations. Instruments whose manufacturers are not specified are all commercially available products. Raw materials and reagents whose manufacturers are not specified are all commercially available goods or can be prepared using known methods.

[0029] In this invention, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are used only for simplicity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0030] The features mentioned in this invention can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification, provided that there is no contradiction in the combination of these features. Each feature disclosed in the specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0031] In the description of this invention, it should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Those skilled in the art will understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0032] Example 1: Effects of Low-protein Rapeseed Meal Diets on Egg Production and Other Performance of Ducks I. Feeding Experiment This experiment was conducted at Jiangsu Shunchang Agricultural Development Co., Ltd. Two hundred and eighty-eight 180-day-old Qingke No. 4 laying ducks with similar weight and egg production rate were randomly divided into four groups, corresponding to four dietary crude protein level gradients: 16.5% (control group, CK), 15.5% (LP group), 14.5% (MP group), and 13.5% (HP group), with six replicates per group and twelve ducks per replicate. The pre-trial period was four weeks, and the formal trial period was twelve weeks. The composition of the basal diet is detailed in Table 1. The main purpose of the pre-trial period was to allow the ducks to adapt to the experimental diet and feeding environment, while the formal trial period was used to measure various indicators. During the experiment, the feed intake, uneaten feed, number of eggs laid, and egg weight were recorded daily for each replicate to ensure the completeness and accuracy of the experimental data.

[0033] Table 1 Composition of the basic diet Corn (GB2 grade) 50 52.88 53.88 54.86 wheat bran 6.98 7.57 8.59 9.41 brown rice 6.98 6.65 7.9 9.3 soybean meal 24.33 18.86 13.35 7.92 Low-erucic acid rapeseed meal 0 1.88 3.66 5.47 stone powder 8.86 8.87 8.86 8.86 Soybean oil 0.1 0.09 0.09 0.09 L-Lysine sulfate 0.04 0.21 0.39 0.56 DL-methionine 0.15 0.17 0.2 0.22 L-threonine 0 0.05 0.1 0.14 Tryptophan 0.02 0.05 0.07 0.1 Isoleucine 0 0.06 0.13 0.19 L-arginine 0 0.13 0.25 0.37 Phytase 0.03 0.03 0.03 0.03 Anhydrous dicalcium phosphate 1.11 1.1 1.1 1.08 Sodium chloride 0.2 0.2 0.2 0.2 choline chloride 0.1 0.1 0.1 0.1 Potassium magnesium sulfate 0.9 0.9 0.9 0.9 Duck Multivitamin 0.1 0.1 0.1 0.1 Organic minerals 0.1 0.1 0.1 0.1 Note: The basal diets were formulated according to NRC (1994) and GB / T 41189-2021 "Nutritional Requirements for Laying Ducks"; each group was an isoenergetic diet with crude protein levels of 16.5% (CK), 15.5% (LP), 14.5% (MP), and 13.5% (HP), respectively; the diets used low-erucic acid rapeseed meal to replace part of the soybean meal, and supplemented with synthetic amino acids to balance essential amino acids. CK: control group; LP: low-protein group 1; MP: low-protein group 2; HP: low-protein group 3.

[0034] The experimental ducks were raised in a semi-open duck house using a floor-raising method. The temperature inside the house was controlled at 13-25℃, the relative humidity at 55-65%, and the daily light exposure was 16 hours. During the experiment, the ducks were guaranteed free access to feed and water, were fed twice a day at regular intervals, leftover feed and feces were promptly removed, the environment was kept clean, and the duck house was disinfected regularly.

[0035] II. Measurement Indicators and Methods All experimental data were statistically analyzed using SPSS 27.0 software. Production performance data were analyzed on a replicate basis, while egg quality, blood biochemical indicators, intestinal metabolomics, cecal microbiota, and excrement-related indicators were analyzed on an individual basis. One-way ANOVA was used for single-sample measurements, and Duncan's multiple comparison method was used for inter-group comparisons when significant differences were found. Results are expressed as mean ± standard error. P <0.05 indicates a significant difference.

[0036] 1. Production performance testing 1) The main production performance indicators include: average daily feed intake (ADFI), egg production rate, average egg weight and feed conversion ratio. All measurements were repeated and statistically analyzed once a week for a total of 12 weeks during the trial period. 2) Average Daily Feed Intake (ADFI): Record the amount of feed and leftover feed for each replicate daily, and calculate the daily feed intake of each laying duck. The calculation formula is: ADFI (g / duck) = (total feed amount - total leftover feed amount) / (number of replicates). 3) Egg production rate: Record the number of eggs produced in each replicate daily and calculate the egg production rate. The calculation formula is: Egg production rate (%) = Number of eggs produced / Number of replicates × 100%; 4) Average egg weight: Collect duck eggs from each replicate daily, weigh them using an electronic analytical balance (accuracy 0.01g), and calculate the average egg weight of each replicate. The calculation formula is: Average egg weight (g) = Total egg weight / Total number of eggs laid. 5) Feed intake to egg ratio: The total feed intake and total egg weight of each cycle are summarized each week, and the feed intake to egg ratio is calculated. The formula is: Feed intake to egg ratio = Total feed intake per week / Total egg weight per week.

[0037] Table 2. Effects of low-protein diets containing low-erucic acid rapeseed meal on the production performance of laying ducks. 0w Average egg weight / g 65.64±1.05 65.91±0.84 66.14±2.05 66.20±1.82 0.92 Egg production rate / % 1.00±0.00 0.92±0.09 0.89±0.07 0.95±0.10 0.11 Average daily feed intake 142.04±5.35 131.50±14.58 132.83±13.13 138.89±8.85 0.33 Egg ratio 2.17±0.08 2.18±0.05 2.26±0.16 2.25±0.16 0.69 2w Average egg weight / g 67.74±2.13 66.21±1.26 65.73±1.27 66.79±1.34 0.16 Egg production rate / % 0.95±0.09 0.96±0.10 0.92±0.11 0.96±0.09 0.84 Average daily feed intake 145.83±0.00 140.75±10.40 140.10±7.68 145.03±1.51 0.33 Egg ratio 2.3±0.2 2.23±0.25 2.35±0.23 2.28±0.21 0.86 4w Average egg weight / g <![CDATA[67.40±0.74 a ]]> <![CDATA[65.70±1.60 b ]]> <![CDATA[65.67±0.85 b ]]> <![CDATA[65.68±1.15 b ]]> 0.04 Egg production rate / % <![CDATA[1.00±0.00 a ]]> <![CDATA[0.86±0.11 b ]]> <![CDATA[0.90±0.09 ab ]]> <![CDATA[0.99±0.03 a ]]> 0.01 Average daily feed intake 145.83±0.00 128.12±20.53 133.23±10.28 139.12±7.98 0.10 Egg ratio 2.17±0.02 2.28±0.38 2.27±0.21 2.15±0.22 0.63 6w Average egg weight / g <![CDATA[67.27±2.41 a ]]> <![CDATA[63.84±1.71 b ]]> <![CDATA[63.10±1.94 b ]]> <![CDATA[63.34±1.66 b ]]> 0.01 Egg production rate / % <![CDATA[1.00±0.09 a ]]> <![CDATA[0.88±0.10 ab ]]> <![CDATA[0.87±0.09 b ]]> <![CDATA[0.86±0.05 b ]]> 0.04 Average daily feed intake 143.80±4.96 141.59±5.80 144.31±2.37 145.51±0.78 0.41 Egg ratio <![CDATA[2.15±0.14 b ]]> <![CDATA[2.56±0.31 a ]]> <![CDATA[2.66±0.31 a ]]> <![CDATA[2.64±0.18 a ]]> 0.01 8w Average egg weight / g <![CDATA[67.87±2.08 a ]]> <![CDATA[65.89±1.33 ab ]]> <![CDATA[63.49±4.18 b ]]> <![CDATA[66.35±1.47 ab ]]> 0.05 Egg production rate / % <![CDATA[0.96±0.04 a ]]> <![CDATA[0.72±0.13 b ]]> <![CDATA[0.84±0.11 ab ]]> <![CDATA[0.89±0.10 a ]]> 0.01 Average daily feed intake 136.33±7.28 132.69±9.8 144.49±15.91 144.09±4.25 0.15 Egg ratio <![CDATA[2.10±0.16 b ]]> <![CDATA[2.89±0.64 a ]]> <![CDATA[2.73±0.40 a ]]> <![CDATA[2.46±0.19 ab ]]> 0.02 10w Average egg weight / g 66.53±1.44 65.79±1.81 66.06±1.13 66.33±2.57 0.90 Egg production rate / % <![CDATA[0.86±0.09 ab ]]> <![CDATA[0.79±0.04 b ]]> <![CDATA[0.80±0.04 b ]]> <![CDATA[0.93±0.14 a ]]> 0.05 Average daily feed intake 141.66±7.21 140.96±6.25 137.40±11.54 145.35±5.56 0.41 Egg ratio 2.51±0.34 2.72±0.28 2.60±0.12 2.40±0.33 0.28 12w Average egg weight / g 65.60±3.47 66.56±2.82 64.76±1.83 64.67±2.49 0.61 Egg production rate / % 0.70±0.12 0.67±0.05 0.78±0.12 0.83±0.15 0.10 Average daily feed intake 121.86±11.15 120.95±11.46 124.95±10.00 131.89±6.54 0.25 Egg ratio 2.77±0.84 2.75±0.38 2.51±0.38 2.52±0.39 0.75 Note: Data in the same row with no letter or the same letter above the header indicates that the difference is not significant. P >0.05), different lowercase letters indicate significant differences ( P <0.05).

[0038] Production performance is an important indicator for evaluating the effectiveness of low-protein diets. Average daily feed intake, egg production rate, average egg weight, and feed conversion ratio (FCR) can directly reflect the adaptability of laying ducks to changes in dietary protein levels. Table 2 shows that there was no significant difference in average daily feed intake among the groups throughout the experiment (P > 0.05), indicating that under the conditions of partially replacing soybean meal with low-erucic acid rapeseed meal and moderately reducing the crude protein level in the diet, the overall feeding behavior of the laying ducks remained stable, and the palatability of the diet was not significantly adversely affected. Egg production rate did not differ significantly among the groups at the beginning of the experiment (week 0), week 2, and week 12 (P > 0.05), but significant differences were observed at weeks 4, 6, 8, and 10 (P < 0.05). Specifically, at week 4, the LP group was significantly lower than the CK and HP groups; at week 6, the MP and HP groups were significantly lower than the CK group; at week 8, the LP group was significantly lower than the CK and HP groups; and at week 10, the LP and MP groups were significantly lower than the HP group. Average egg weight did not differ significantly among the groups at weeks 0, 2, 10, and 12 (P > 0.05), but showed significant differences at weeks 4, 6, and 8 (P < 0.05). Specifically, at weeks 4 and 6, the CK group had significantly higher average egg weight than the other groups, while at week 8, the MP group had significantly lower average egg weight than the CK group. The LP and HP groups did not differ significantly from the CK and MP groups. The feed conversion ratio (FCR) did not differ significantly among the groups at weeks 0, 2, 4, 10, and 12 (P > 0.05), but showed significant differences at weeks 6 and 8 (P < 0.05). Specifically, at week 6, the LP, MP, and HP groups were significantly higher than the CK group, while at week 8, the LP and MP groups were significantly higher than the CK group. The HP group did not differ significantly from the other groups. Clearly, egg production rate, average egg weight, and FCR are more sensitive to changes in dietary protein levels, and their effects are mainly manifested as periodic fluctuations in the middle of the experiment, rather than a continuous decline throughout the entire period. Overall, a diet with a crude protein level of 15.5% has a relatively small impact on the production performance of laying ducks. However, when the crude protein level is further reduced to 14.5% and 13.5%, the egg production rate decreases, the average egg weight decreases, and the feed conversion ratio increases in some stages.

[0039] 2. Egg quality determination At the end of the 12th week of the experiment, 10 fresh duck eggs (laid within 24 hours) were randomly selected from each replicate for the determination of egg quality indicators, including egg shape index, eggshell thickness, eggshell strength, Haugh unit and yolk color.

[0040] 1) Egg shape index: Measure the major and minor diameters of the duck egg with vernier calipers (accuracy 0.01mm) and calculate the egg shape index. The calculation formula is: Egg shape index = major diameter / minor diameter; 2) Eggshell thickness: After removing the inner membrane of the eggshell, use an eggshell thickness measuring instrument (accuracy 0.01mm) to measure the eggshell thickness at three points: the tip, middle, and blunt end of the duck egg. Take the average value of the three points as the eggshell thickness of the duck egg. 3) Eggshell strength: The eggshell strength of duck eggs was measured using an eggshell strength tester (unit: kg / cm²). The test site was the middle of the duck egg, and each duck egg was measured once. 4) Haugh unit: After breaking a duck egg, place it in a petri dish and use an egg quality analyzer to measure the height of the egg white and the weight of the egg. The instrument automatically calculates the Haugh unit; the higher the Haugh unit, the better the quality of the egg white. 5) Egg yolk color: The egg yolk color is measured using an egg yolk color meter (Lovibond color fan). The color grade range is 1 to 15, with the higher the grade, the darker the egg yolk color.

[0041] Table 3. Effects of low-protein diets with low-erucic acid rapeseed meal on egg quality in ducks. Egg-shaped index 1.31±0.02b 1.34±0.03ab 1.34±0.02ab 1.36±0.03a 0.047 Eggshell thickness (mm) 0.45±0.04 0.45±0.03 0.45±0.06 0.44±0.06 0.748 Eggshell strength (kg / cm²) 4.24±1.04ab 3.73±1.15b 4.50±0.87a 4.17±1.11ab 0.043 Egg weight (g) 66.55±6.28 65.92±6.93 63.67±4.34 64.06±5.60 0.167 Egg yolk color 5.37±1.30b 5.20±0.89b 6.33±1.27a 5.13±1.28b 0.002 Huff unit 59.67±17.33 65.35±14.88 61.99±19.79 67.65±11.46 0.236 Note: Data in the same row with no letter or the same letter above the header indicates that the difference is not significant. P >0.05), different lowercase letters indicate significant differences ( P <0.05).

[0042] As shown in Table 3, among the egg quality indicators at the end of the experiment, there were no significant differences in eggshell thickness and Haugh units among the groups. P >0.05); the egg shape index of the HP group was significantly higher than that of the CK group ( P <0.05, with no significant difference from the LP and MP groups; eggshell strength showed significant differences among the groups ( P <0.05%, with the LP group significantly lower than the MP group, but not significantly different from the CK and HP groups; egg yolk color showed significant differences among the groups ( P <0.05%, with the MP group showing significantly higher values ​​than the CK, LP, and HP groups; no significant difference was found in egg weight among the groups. P >0.05). This indicates that under the conditions of this experiment, the low-protein diet with low-erucic acid rapeseed meal had a relatively small overall impact on eggshell thickness and egg white quality, but some appearance indicators and egg yolk color were more sensitive to changes in diet composition.

[0043] 3. Blood biochemical index measurement At the end of week 12 of the experiment, two ducks were randomly selected from each replicate. After fasting for 12 hours, 5 mL of blood was collected from the subwing vein and placed in a centrifuge tube. The tube was left to stand at room temperature for 2 hours, and then centrifuged at 3000 r / min for 15 minutes at 4°C. The serum was separated and stored in a -80°C freezer for the determination of blood biochemical indicators.

[0044] The measured indicators include: total protein (TP), albumin (ALB), globulin (GLB), uric acid (UA), urea (UREA), and liver function-related enzyme activities (AST, ALT, and ALP).

[0045] Table 4. Effects of low-protein diets containing low-erucic acid rapeseed meal on blood biochemical parameters in laying ducks. TP 62.91±11.03 58.75±9.11 56.33±8.23 53.85±6.51 0.093 ALB 14.59±3.14 14.84±2.71 14.27±2.42 13.94±1.73 0.838 GLB 48.32±8.75a 43.91±8.47ab 42.06±6.12ab 39.91±5.05b 0.045 UREA 0.53±0.16a 0.38±0.17ab 0.29±0.13b 0.28±0.14b 0.002 UA 169.49±33.99 227.81±100.73 184.65±84.66 165.83±60.97 0.171 AST 80.54±29.19 78.36±28.42 84.62±30.88 81.21±21.48 0.957 ALT 61.72±27.56 64.40±23.34 71.17±45.53 79.59±24.69 0.519 ALP 195.57±179.30 200.78±94.68 227.26±186.07 276.62±220.28 0.664 Note: TP: Total protein (g / L); ALB: Albumin (g / L); GLB: Globulin (g / L); UREA: Urea (mmol / L); UA: Uric acid (μmol / L); AST: Aspartate aminotransferase (U / L); ALT: Alanine aminotransferase (U / L); ALP: Alkaline phosphatase (U / L). No letter or the same letter in the superscript of data from the same row indicates no significant difference. P >0.05), different lowercase letters indicate significant differences ( P <0.05).

[0046] As shown in Table 4, there were no significant differences in serum total protein (TP), albumin (ALB), uric acid (UA), and liver function-related enzyme activities (AST, ALT, ALP) among the groups. P >0.05), AST, ALT, and ALP levels showed no significant abnormal increases, indicating that when the quality of the low-erucic acid feed was good, the limiting amino acid supplementation was relatively sufficient, and the substitution level was within a controllable range, the laying ducks did not exhibit obvious liver stress. The contents of globulin (GLB) and urea (UREA) decreased with decreasing dietary crude protein levels, with the HP group showing significantly lower GLB levels than the CK group. P <0.05), the UREA levels in the MP and HP groups were significantly lower than those in the CK group ( P <0.05). This indicates that under the conditions of this experiment, after using low-erucic acid rapeseed meal as an important alternative protein source and appropriately reducing the crude protein level, the overall protein metabolism status and liver function-related enzyme activities of laying ducks remained stable, while nitrogenous metabolic end products and some serum protein components were more sensitive to the decrease in dietary protein.

[0047] 4. Intestinal non-targeted metabolomics analysis At the end of week 12 of the experiment, two laying ducks were randomly selected from each replicate (12 ducks in total per group). After slaughter, the contents of the small intestine (jejunum segment) were quickly separated, placed in sterile centrifuge tubes, flash-frozen in liquid nitrogen, and stored in a -80°C freezer for intestinal metabolomics determination.

[0048] 1) Metabolomics sample pretreatment: Take an appropriate amount of small intestinal contents sample, add a pre-cooled methanol-acetonitrile-water mixed solution (volume ratio 2:2:1), vortex for 10 minutes, let stand at 4℃ for 30 minutes, then centrifuge at 12000 r / min at 4℃ for 15 minutes, take the supernatant, freeze dry under vacuum, reconstitute with methanol, filter through a 0.22 μm filter membrane, and collect the filtrate for UPLC-MS / MS detection.

[0049] 2) UPLC-MS / MS detection conditions: The chromatographic column was a Waters ACQUITY UPLC BEH C18 column (100 mm × 2.1 mm, 1.7 μm); mobile phase A was 0.1% formic acid aqueous solution, and mobile phase B was acetonitrile; gradient elution program: 0–2 min, 5% B; 2–10 min, 5%–95% B; 10–13 min, 95% B; 13–13.1 min, 95%–5% B; 13.1–16 min, 5% B; flow rate was 0.3 mL / min; column temperature was 40 °C; injection volume was 2 μL. Mass spectrometry conditions: Electrospray ionization (ESI) was used, with simultaneous detection in positive and negative ion modes, scan range of m / z 50–1000; ion source temperature was 150 °C; desolvation gas temperature was 500 °C; desolvation gas flow rate was 800 L / h.

[0050] Based on the total ion overlap spectrum results under both positive and negative ion modes, the retention times and peak intensities of the total ion chromatograms for each QC sample were generally consistent, with largely overlapping chromatographic peaks and no significant drift observed. This indicates that the instrument operated stably during this metabolomics assay, the sample detection showed good repeatability, and the data quality was reliable, making it suitable for subsequent multivariate statistical analysis.

[0051] 3) Metabolomics Data Processing: Progenesis QI software was used for data preprocessing (peak identification, peak alignment, noise reduction, etc.) to screen effective metabolite peaks. These peaks were then matched against the Human Metabolomics Database (HMDB) and the METLIN database to identify metabolites. SIMCA 14.1 software was used for multivariate statistical analysis, including principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA), with peaks ≥ 1 being the most significant. P A value <0.05 was used as the screening criterion to identify differentially metabolites among the groups. KEGG pathway enrichment analysis was performed on the differentially metabolites to clarify the main metabolic pathways involved.

[0052] Depend on Figure 1 It was found that in positive ion mode, the first two principal components explained 22.2% and 9.6% of the total variance, respectively; in negative ion mode, the first two principal components explained 28.0% and 10.4% of the total variance, respectively. There was some overlap and intersection between the two modes, indicating differences in the intestinal metabolic profiles among the different treatment groups, but the overall separation was incomplete. In contrast, the distribution trend between groups was clearer in negative ion mode. Meanwhile, the QC samples showed good clustering, further indicating the stability of the detection system and high data repeatability.

[0053] Depend on Figure 2It was found that under both positive and negative ion modes, the CK group showed a significant separation trend from the LP, MP, and HP groups, indicating that different low-protein diets based on low-erucic acid rapeseed meal could induce changes in the intestinal metabolic characteristics of laying ducks. The separation was even stronger between the CK group and the MP and HP groups, suggesting that metabolic differences gradually increased with changing treatment levels. The results of 200 permutation tests showed that the R0 values ​​of each comparative group model were... 2 and Q 2 The values ​​are all relatively high, and Q 2 An intercept less than 0 indicates that the established OPLS-DA model is stable and reliable, with no obvious overfitting, and can be used for subsequent differential metabolite screening and pathway analysis.

[0054] Depend on Figure 3 Further analysis revealed that a large number of differentially expressed metabolites were detected in each comparative group under both positive and negative ion modes, with both upregulated and downregulated metabolites present, indicating that the low-protein diet containing low-erucic acid rapeseed meal significantly altered the expression characteristics of intestinal metabolites in laying ducks. Under positive ion mode, 330 differentially expressed metabolites were screened in the CK vs HP group, with 117 upregulated and 213 downregulated; 260 differentially expressed metabolites were screened in the CK vs LP group, with 109 upregulated and 151 downregulated; and 277 differentially expressed metabolites were screened in the CK vs MP group, with 127 upregulated and 150 downregulated. Under negative ion mode, 328 differentially expressed metabolites were screened in the CK vs HP group, with 150 upregulated and 178 downregulated; 306 differentially expressed metabolites were screened in the CK vs LP group, with 161 upregulated and 145 downregulated; and 354 differentially expressed metabolites were screened in the CK vs MP group, with 246 upregulated and 108 downregulated. The results showed that different treatment levels could significantly affect the gut metabolome of laying ducks, but the degree of influence and the direction of change differed to some extent.

[0055] Correlation analysis of differentially expressed metabolites revealed significant positive and negative correlations among the differentially expressed metabolites in each comparison group, forming several related modules. This indicates that the effects of low-protein diets containing rapeseed meal on the intestinal metabolome of laying ducks are not independent changes in a single metabolite, but rather the result of synergistic regulation by multiple metabolites. Under positive ion mode, acylcarnitines, fatty acids, sphingolipids, and glycerophospholipids showed strong correlations, suggesting that lipid metabolism and cell membrane lipid remodeling may be jointly regulated. Under negative ion mode, bile pigments, porphyrins, and some secondary metabolites also showed strong correlations, indicating that low-protein dietary treatment may regulate intestinal homeostasis through multiple metabolic pathways.

[0056] To further compare the commonality and specificity of differentially expressed metabolites among the three comparison groups (CK vs LP, CK vs MP, and CK vs HP), Venn analysis was performed on the differentially expressed metabolites screened under both positive and negative ion modes. The results showed that under positive ion mode, 91 common differentially expressed metabolites were found among the three groups (CK vs LP, CK vs MP, and CK vs HP). The number of differentially expressed metabolites specific to each group was 149, 96, and 77, respectively, with the CK vs HP group having the highest number of specific differentially expressed metabolites. Among the pairwise common differentially expressed metabolites, CK vs HP and CK vs MP had 63, higher than the 46 between CK vs LP and CK vs MP, and the 27 between CK vs HP and CK vs LP. Under negative ion mode, a total of 119 differentially expressed metabolites were found across the three groups. Among the group-specific differentially expressed metabolites, the CK vs HP, CK vs LP, and CK vs MP groups had 119, 86, and 110 metabolites, respectively. The CK vs HP and CK vs MP groups had a relatively large number of specific differentially expressed metabolites, indicating that these two treatment levels had a more significant impact on the intestinal metabolome. In terms of pairwise intersections, CK vs LP and CK vs MP had the most differentially expressed metabolites, with 68, followed by CK vs HP and CK vs MP with 57, and CK vs HP and CK vs LP with 33.

[0057] To further clarify the effects of low-protein diets containing low-erucic acid rapeseed meal on the intestinal metabolism of laying ducks, KEGG pathway enrichment analysis was performed on differentially expressed metabolites in three comparison groups: CK vs LP, CK vs MP, and CK vs HP (see [link to KEGG pathway analysis]). Figures 4-5The results showed that, under positive ion mode, the enriched pathways in each comparative group were generally consistent, mainly involving metabolic, cellular processes, environmental information processing, genetic information processing, and systemic functions. Sphingolipid metabolism showed high enrichment levels in all three comparative groups, and necroptosis was also significant, suggesting that low-protein diets may affect intestinal lipid metabolism balance and cell survival regulation. The LP group was also mainly enriched in pathways such as arginine and proline metabolism, tyrosine metabolism, pantothenic acid and coenzyme A biosynthesis, β-alanine metabolism, mTOR signaling pathway, apoptosis, aminoacyl-tRNA biosynthesis, and ABC transporters. The MP group further involved α-linolenic acid metabolism, arginine biosynthesis, lipoic acid metabolism, primary bile acid biosynthesis, cysteine ​​and methionine metabolism, and D-amino acid metabolism. The HP group was mainly enriched in pathways such as ABC transporters, primary bile acid biosynthesis, aminoacyl-tRNA biosynthesis, arginine biosynthesis, arginine and proline metabolism, pantothenic acid and coenzyme A biosynthesis, β-alanine metabolism, mTOR signaling pathway, and neuroactive ligand-receptor interactions. Under negative ion mode, the enriched pathways in each comparison group were relatively dispersed, but were still mainly metabolic-related pathways. The LP group was mainly enriched in pathways such as pyrimidine metabolism, folic acid-mediated one-carbon unit metabolism, purine metabolism, ABC transporters, cysteine ​​and methionine metabolism, steroid hormone biosynthesis, and glycerol metabolism; the MP group was mainly involved in pathways such as purine metabolism, folic acid-mediated one-carbon unit metabolism, arachidonic acid metabolism, glycine / serine / threonine metabolism, phenylalanine metabolism, pyrimidine metabolism, and glyoxylic acid and dicarboxylic acid metabolism; the HP group was mainly enriched in pathways such as alanine, aspartic acid and glutamate metabolism, porphyrin metabolism, glyoxylic acid and dicarboxylic acid metabolism, arachidonic acid metabolism, oxidative phosphorylation, purine metabolism, TCA cycle, carbon metabolism, and taurine and taurine metabolism.

[0058] The results of this study indicate that low-protein diets based on low-erucic acid rapeseed meal can regulate the intestinal homeostasis of laying ducks by influencing multiple pathways, including sphingolipid metabolism, amino acid sensing, bile acid / transport system, nucleotide metabolism, and mitochondrial energy metabolism. The metabolic changes were relatively limited at 15.5% crude protein levels, while the metabolic remodeling was more pronounced at 14.5% and 13.5% crude protein levels.

[0059] 5. Cecal microbiota 16S rRNA sequencing At the end of week 12 of the experiment, two laying ducks were randomly selected from each replicate (12 ducks in total per group). After slaughter, the cecum was quickly separated, impurities on the surface of the cecum contents were removed, and the contents were rinsed with sterile physiological saline. The contents of the cecum were collected, placed in sterile centrifuge tubes, flash-frozen in liquid nitrogen, and stored in a -80°C freezer for cecal flora determination.

[0060] 1) Cecal microbiota DNA extraction: Total microbial DNA was extracted from cecal contents samples using an Omega Bio-tek DNA extraction kit, strictly following the kit's instructions. DNA purity and integrity were assessed using 1% agarose gel electrophoresis, and DNA concentration was determined using a Nanodrop 2000 spectrophotometer.

[0061] 2) PCR amplification and sequencing of the 16S rRNA gene: Using extracted total DNA as a template, PCR amplification was performed on the V3-V4 region of the bacterial 16S rRNA gene using specific primers 338F (5'-ACTCCTACGGGAGGCAGCAG-3') and 806R (5'-GGACTACHVGGGTWTCTAAT-3'). The PCR amplification reaction system (25 μL) consisted of: 2.5 μL of 10×PCR Buffer, 2 μL of dNTP Mix, 0.5 μL each of forward and reverse primers, 0.25 μL of Taq enzyme, 1 μL of DNA template, and 18.25 μL of sterile water. PCR amplification conditions: 95℃ pre-denaturation for 5 minutes; 95℃ denaturation for 30 seconds, 55℃ annealing for 30 seconds, 72℃ extension for 30 seconds, for a total of 30 cycles; final extension at 72℃ for 10 minutes; storage at 4℃. After PCR amplification products were detected by 1% agarose gel electrophoresis, high-throughput sequencing was performed using the Illumina MiSeq platform.

[0062] 3) Cecal microbiota data processing: QIIME 2 software was used for data preprocessing to filter low-quality and chimeric sequences and obtain high-quality sequences. QIIME 2 was used for quality control and noise reduction to obtain amplicon sequence variants (ASVs), and species annotation was performed. The species classification information corresponding to each ASV was determined with reference to the Silva database (v138).

[0063] 4) Microbial community diversity and structure analysis: The Alpha diversity index (Shannon, Simpson, and Chao1 indices) was calculated using QIIME 2 software to assess the richness and evenness of the cecal microbiota. Rank-abundance curves, ASV sparsity curves, and Venn diagrams were plotted using R software to analyze the species distribution characteristics of the microbiota. Principal coordinate analysis (PCoA) and non-metric multidimensional scaling (NMDS) were used to assess the differences in cecal microbiota structure among the groups. LEfSe analysis (LDA score ≥ 4) was used to screen for dominant genera in each group.

[0064] To evaluate the reliability of the cecal microbiota 16S rRNA sequencing data, ASV Rank abundance curves and ASV dilution curves were plotted. The results are as follows: Figures 6-7As shown in the figure, the ASV Rank abundance curves show that the curves for each sample extend far to the right and the decreasing trend is relatively gentle, indicating that the cecal microbiota of each sample has high species richness and good community evenness. The overall trends of the curves among different samples are relatively similar, but there are still some differences, suggesting that there are some fluctuations in the microbiota composition among individuals. The ASV dilution curves show that as the number of sequencing sequences increases, the number of ASVs in each sample increases rapidly, then gradually flattens out and reaches a plateau, indicating that the sequencing depth in this study is sufficient to cover most of the microbial information in the samples, and the obtained sequencing data can reflect the species composition of the cecal microbiota of laying ducks relatively accurately. In summary, the 16S sequencing data are of good quality and can meet the needs of subsequent microbiota diversity and community structure analysis.

[0065] To compare the commonalities and specificities of cecal microbiota (ASVs) in different treatment groups of laying ducks, Venn analysis was performed on the CK, LP, MP, and HP groups. The results showed that the CK and LP groups shared 7806 ASVs, with 17590 and 19499 specific ASVs, respectively; the CK and MP groups shared 5503 ASVs, with 19893 and 20710 specific ASVs, respectively; and the CK and HP groups shared 5405 ASVs, with 19991 and 22562 specific ASVs, respectively. These results indicate the presence of a certain number of common ASVs among the groups, suggesting the existence of a relatively stable core microbiota in the cecum of laying ducks. With increasing treatment levels of low-protein diets containing low-erucic acid rapeseed meal, the number of common ASVs gradually decreased, while the number of specific ASVs gradually increased, with the HP group having the highest number of specific ASVs.

[0066] To evaluate the effects of low-protein diets containing low-erucic acid rapeseed meal on the richness and diversity of cecal flora in laying ducks, the Chao1, Goods coverage, Simpson, and Shannon indices of each group were analyzed. The results are as follows: Figure 8 As shown in the figure. Compared with the LP group, the differences in Chao1, Goods coverage, Simpson, and Shannon indices were not significant (P>0.05), with corresponding P values ​​of 0.59, 0.44, 0.38, and 0.85, respectively. Compared with the MP group, the differences in each index were also not significant (P>0.05), with corresponding P values ​​of 0.51, 0.38, 0.38, and 0.97, respectively. Compared with the HP group, none of the indices reached a significant level (P>0.05), with corresponding P values ​​of 0.58, 0.81, 0.35, and 0.26, respectively. The results indicate that the low-protein diet treatment with low-erucic acid rapeseed meal did not significantly affect the richness, evenness, or overall diversity of the cecal microbiota in laying ducks. The Goods coverage index for each group was close to 1, indicating high sequencing coverage and that the data could comprehensively reflect the composition of the sample microbiota.

[0067] To evaluate the effects of different low-protein, low-erucic acid rapeseed meal diets on the cecal microbiota structure of laying ducks, PCoA and NMDS were used to perform Beta diversity analyses on the CK, LP, MP, and HP groups. PCoA results showed that the CK and LP groups explained 20.1% and 11.0% of the first two principal axes, respectively, indicating a certain trend of separation between the two groups, but some overlap remained. The CK and MP groups explained 17.9% and 9.2% of the first two principal axes, respectively, with more significant separation between the groups than the LP group. The CK and HP groups explained 14.2% and 13.3% of the first two principal axes, respectively, with the most significant separation along the PC1 direction. NMDS analysis results were largely consistent with PCoA; the LP, MP, and HP groups all showed some degree of separation from the CK group, with the HP group exhibiting the most significant separation trend. This indicates that low-protein, low-erucic acid rapeseed meal diets can alter the cecal microbiota structure of laying ducks, and this effect is dose-dependent. The results showed that the low-protein diet with low-erucic acid rapeseed meal could alter the cecal microbiota structure of laying ducks, and the difference between the microbiota composition and the control group gradually increased with the increase of treatment level.

[0068] To analyze the effects of low-protein diets containing low-erucic acid rapeseed meal on the phylum-level composition of the cecal flora in laying ducks, the relative abundance of flora in the CK group was compared with that in the LP, MP, and HP groups. The results are as follows: Figure 9 As shown in the figure, Bacteroidota was the dominant phylum in the cecal flora of all groups, followed by Firmicutes A, Actinobacteriota, Firmicutes C / Firmicutes D, Spirochaetota, Desulfobacterota I, Deferribacterota, Fusobacteriota, and Proteobacteria. Compared with the CK group, the relative abundance of Bacteroidota generally decreased in the LP, MP, and HP groups, while the relative abundance of Actinobacteriota and some Firmicutes subgroups (Firmicutes C / Firmicutes D) increased, with the changes being more pronounced in the MP and HP groups. The results indicate that the low-protein diet with low-erucic acid rapeseed meal did not change the composition of the main dominant phyla in the cecal flora of laying ducks, but it could regulate the relative abundance distribution of each phylum, and the differences in phylum-level flora structure gradually increased with the increase of treatment level.

[0069] To screen for differentially significant bacteria between different treatment groups and the control group, LEfSe was used to analyze the CK group, LP group, MP group, and HP group. The results are as follows: Figure 10 As shown. In the comparison between the CK and LP groups, the differentially enriched bacterial communities in the CK group mainly included... Bacteroidota , Firmicutes A , Fusobacteriota , Fusobacteriaceae , Fusobacteriales , Fusobacterium A and Coriobacteriia And so on, while the LP group is mainly enriched Actinobacteriota , Actinomycetia , Mycobacteriales , Mycobacteriaceae , Bacilli , Firmicutes D , Staphylococcales and Staphylococcus arlettae In the comparison between the CK and MP groups, the differentially enriched bacterial communities in the CK group were still mainly... Bacteroidota , Firmicutes A , Fusobacteriota , Fusobacterium A and Phocaeicola A The main components are α and β, while the MP group is mainly enriched. Deferribacterota , Deferribacterales , Mucispirillaceae , Mucispirillum , Mucispirillum schaedleri and Staphylococcaceae In comparison between the CK and HP groups, the CK group was mainly enriched. Bacteroidota , Phocaeicola A , Fusobacteriota , Fusobacteriaceae and Fusobacterium A And so on, while the HP group is mainly enriched Spirochaetia , Mycobacteriales , Mycobacteriaceae and Paraprevotella The results showed that low-protein diets with low rapeseed meal significantly altered the composition of differentially expressed marker bacteria in the cecal flora of laying ducks, and different treatment levels showed enrichment patterns of their respective characteristic bacterial communities.

[0070] 6. Fecal nitrogen emissions At the end of the 12th week of the experiment, one experimental duck was randomly selected from each replicate in each group. All excrement from the duck was collected twice daily, and impurities such as feathers and feed scraps were removed. Collection continued for 3 days, and the excrement was treated with 10% sulfuric acid for nitrogen fixation. The collected samples were dried to constant weight at 65℃, pulverized, and stored for later use. The nitrogen content in the excrement samples was determined according to GB / T 6432—2018 standard.

[0071] Table 5. The impact of low-protein rapeseed meal on nitrogen emissions from laying ducks. Nitrogen emissions in feces (%) 3.88±1.02 3.60±2.03 2.43±0.29 1.83±0.40 0.086 Nitrogen emissions are an important indicator for evaluating the environmental effects of low-protein diets, and can directly reflect the level of nitrogenous nutrient excretion by the body after a decrease in dietary crude protein. Table 5 shows that there were no significant differences in nitrogen emissions among the groups (P > 0.05), but nitrogen emissions generally decreased with decreasing dietary crude protein levels. Compared with the CK group, the nitrogen emissions in the LP group decreased slightly, while the decreases were more significant in the MP and HP groups. This indicates that under the condition of partially replacing soybean meal with low-erucic acid rapeseed meal, moderately reducing dietary crude protein levels has a certain potential for reducing nitrogen emissions, but under the conditions of this experiment, it has not yet reached a statistically significant level.

[0072] In summary, this invention demonstrates that low-protein diets, while supplementing limiting amino acids and maintaining nutritional balance, have the potential to reduce nitrogen emissions from laying hens and alleviate environmental nitrogen load. It also indicates that the core advantage of a low-protein strategy is primarily reflected in its nitrogen reduction effect on the environmental side; however, whether this effect is significant depends on factors such as the degree of crude protein reduction, the precision of amino acid supplementation, and the composition of the diet ingredients. Under the condition of partially replacing soybean meal with low-erucic acid rapeseed meal, moderate protein reduction has already shown a clear direction towards nitrogen reduction, providing a basis for its application in green farming of laying ducks.

[0073] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A low-protein diet made from low-erucic acid rapeseed meal, characterized in that, This low-protein diet contains the following components by weight: 52.5–55.0% corn, 7.5–9.5% wheat bran, 6.5–9.5% brown rice, 7.5–19.0% soybean meal, 1.5–5.5% low-erucic acid rapeseed meal, 8.7–8.9% limestone, 0.09% soybean oil, 0.2–0.6% L-lysine sulfate, 0.1–0.3% DL-methionine, 0.05–0.15% L-threonine, 0.05–0.1% tryptophan, 0.06–0.19% isoleucine, 0.13–0.37% L-arginine, 0.03% phytase, 1.08–1.1% anhydrous dicalcium phosphate, 0.2% sodium chloride, 0.1% choline chloride, 0.9% potassium magnesium sulfate, 0.1% duck multivitamins, and 0.1% organic minerals.

2. The low-protein rapeseed meal diet according to claim 1, characterized in that, This low-protein diet contains the following components by weight: 52.8–52.9% corn, 7.5–7.6% wheat bran, 6.5–6.7% brown rice, 18.8–18.9% soybean meal, 1.8–1.9% low-erucic acid rapeseed meal, 8.8–8.9% limestone powder, 0.09% soybean oil, 0.2–0.3% L-lysine sulfate, 0.1–0.2% DL-methionine, 0.05–0.06% L-threonine, 0.05–0.06% tryptophan, 0.06–0.07% isoleucine, 0.13–0.14% L-arginine, 0.03% phytase, 1.1% anhydrous dicalcium phosphate, 0.2% sodium chloride, 0.1% choline chloride, 0.9% potassium magnesium sulfate, 0.1% duck multivitamins, and 0.1% organic minerals.

3. The application of the low-protein rapeseed meal diet as described in claim 1 or 2 in improving the egg production performance and quality of laying ducks.

4. The application according to claim 3, characterized in that, The aforementioned low-protein diet made from rapeseed meal can ensure that eggshell formation and egg white quality of laying ducks remain stable, and that the average daily feed intake of laying ducks remains stable.

5. The application according to claim 3, characterized in that, The aforementioned low-protein diet made from rapeseed meal can ensure that the overall protein metabolism and liver function-related enzyme activity of laying ducks remain stable.

6. The application according to claim 3, characterized in that, The aforementioned low-protein diet made from rapeseed meal can regulate the homeostasis of the intestinal environment in laying ducks.

7. The application according to claim 3, characterized in that, The aforementioned low-protein diet made from rapeseed meal can alter the cecal microbiota structure of laying ducks.

8. The application according to claim 7, characterized in that, The aforementioned low-protein diet made from low-erucic acid rapeseed meal can enrich... Actinobacteriota , Actinomycetia , Mycobacteriales , Mycobacteriaceae , Firmicutes D and Staphylococcales Microbial community.

9. The application according to claim 3, characterized in that, The aforementioned low-protein rapeseed meal diet has the potential to reduce nitrogen emissions.

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