Evaluation model and method for proper standard ileum digestible lysine demand amount of lactating sows under low-protein daily ration level

Abstract

The invention discloses a model and a method for evaluating the demand amount of standard ileum digestible lysine suitable for lactating sows under a low-protein daily ration level. The evaluation model comprises a broken line linear model and a broken line quadratic model; the broken line linear model is xlt; when R is, y = L + U * (R-x); when x is greater than or equal to R, y is equal to L + U * 0, and the quadratic model of the broken line is xlt; when R is, y = L + U * (R-x) 2; when x > = R, y = L + U * 0; wherein y is a sensitive effect index, and x is a standard ileum digestible lysine level; r is a suitable standard ileum digestible lysine level; l is an intercept; u is a slope; % is the mass percentage content.

Description

Technical Field

[0001] The present invention relates to the technical field of animal nutrition and feed science, and particularly relates to a model and method for evaluating the standardized ileal digestible lysine (SID Lys) requirement of lactating sows under low-protein diet conditions. Background Art

[0002] The low protein utilization efficiency and environmental pollution problems restrict the sustainable development of the pig industry. Adopting the formulation technology of low-protein diets (the crude protein level is 2-3 percentage points lower than the NRC recommended amount) and promoting the reduction and substitution of soybean meal and improving the utilization rate of nitrogen nutrients have become the key measures to break through the constraints. Using a suitable evaluation model to accurately evaluate the amino acid requirements of lactating sows for low-protein diets and establishing an ideal amino acid balance model are effective methods for accurately formulating low-protein diet formulas, saving feed protein raw materials, and maintaining the normal production and reproductive performance of sows.

[0003] Although many studies on the Lys nutrition of sows under conventional protein levels have been carried out currently, there are few studies on the SID Lys requirement of lactating sows under low-protein diet conditions, and the amino acid balance model has not been established. Therefore, using a suitable evaluation model to accurately evaluate the appropriate SID Lys requirement range of lactating sows under low-protein diet conditions and establishing an ideal amino acid balance model are effective methods for accurately formulating low-protein diet formulas, saving feed protein raw materials, and maintaining the normal production and reproductive performance of sows. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to evaluate the appropriate SID Lys requirement of lactating sows under low-protein diet conditions for the ideal amino acid model, combined with the net energy system, provide data support for constructing the balance model of multiple limiting amino acids for lactating sows, and promote the scientific application of low-protein diets for live pigs. For this purpose, an evaluation model and method for the appropriate standardized ileal digestible lysine requirement of lactating sows under low-protein diet levels are provided.

[0005] In order to achieve the above object, the technical solution provided by the present invention is as follows:

[0006] The evaluation model for the appropriate standardized ileal digestible lysine requirement of lactating sows under low-protein diet levels includes a broken-line linear model and a broken-line quadratic model:

[0007] Broken-line linear model: when x < R, y = L + U*(R - x); when x ≥ R, y = L + U*0,

[0008] Broken-line quadratic model: when x < R, y = L + U*(R - x) 2 ; when x ≥ R, y = L + U*0;

[0009] Wherein: y is the sensitive effect index, x is the standard ileum digestible lysine level (%); R is the appropriate standard ileum digestible lysine level (%); L is the intercept; U is the slope; and the % is the mass percentage content.

[0010] Preferably, the low-protein diet level is a diet in which the crude protein level is 2-3 percentage points lower than the NRC recommended amount. More specifically, the low-protein diet is a diet that reduces the protein level of the diet, the amount of dietary protein raw materials, and nitrogen emissions by adding appropriate types and amounts of industrial amino acids based on the essence of protein nutrition and the theory of amino acid nutritional balance without affecting animal production performance and product quality.

[0011] Preferably, the protein level of the low-protein diet is 15-18%, where % refers to the content in mass percentage.

[0012] More preferably, said low protein diet level is a protein level of 15%.

[0013] Preferably, the sensitive effect indicators include sow body loss, milk production, piglet 21d litter weight, 3-21d ADG, 21d body weight, 14d SUN, and 21d SUN.

[0014] More preferably,

[0015] When the sensitive effect indicator is sow body loss, the evaluation model is as follows:

[0016] Broken line linear model: y = 19.11 + 35.22 * (0.85-x),

[0017] Broken line quadratic model: y = 19.38 + 117.32 * (0.90-x) 2 ;

[0018] When the sensitive effect indicator is milk production, the evaluation model is as follows:

[0019] Broken line linear model: y = 239.17-322.67*(0.82-x),

[0020] Broken line quadratic model: y = 237.07-887.67*(0.90-x) 2 ;

[0021] When the sensitive effect index is the litter weight of piglets at 21 days, the evaluation model is as follows:

[0022] Broken line linear model: y = 73.52-88.28*(0.81-x),

[0023] Broken line quadratic model: y = 73.06-218.26*(0.90-x)2 ;

[0024] When the sensitive effect index is 3 - 21d ADG, the evaluation model is as follows:

[0025] Piecewise linear model: y = 264.81 - 283.56*(0.82 - x),

[0026] Piecewise quadratic model: y = 266.54 - 283.56*(0.90 - x) 2 ;

[0027] When the sensitive effect index is the body weight of an individual at 21d, the evaluation model is as follows:

[0028] Piecewise linear model: y = 6.80 - 5.92*(0.81 - x),

[0029] Piecewise quadratic model: y = 6.85 - 18.99*(0.89 - x) 2 ;

[0030] When the sensitive effect index is 14d SUN, the evaluation model is as follows:

[0031] Piecewise linear model: y = 5.51 + 12.47*(0.80 - x),

[0032] Piecewise quadratic model: y = 5.49 + 43.77*(0.86 - x) 2 ;

[0033] When the sensitive effect index is 21d SUN, the evaluation model is as follows:

[0034] Piecewise linear model: y = 4.34 + 18.27*(0.79 - x),

[0035] Piecewise quadratic model: y = 4.30 + 59.52*(0.90 - x) 2 。

[0036] The present invention also provides an evaluation method for the appropriate standardized ileal digestible lysine requirement of lactating sows under a low - protein diet level based on the above - mentioned evaluation model. The method is to measure the sensitive effect index y of lactating sows, calculate the standardized ileal digestible lysine level x according to the content of low - protein diet raw materials and the standardized ileal digestibility coefficient published by NRC; substitute y and x into the following evaluation model for fitting to determine the appropriate level of standardized ileal digestible lysine in the low - protein diet standard:

[0037] Piecewise linear model: When x < R, y = L + U*(R - x); when x ≥ R, y = L + U*0,

[0038] Piecewise quadratic model: when x < R, y = L + U * (R - x) 2 ; when x ≥ R, y = L + U * 0;

[0039] Where: y is the sensitive effect index, x is the standardized ileal digestible lysine level (%); R is the appropriate standardized ileal digestible lysine level (%); L is the intercept; U is the slope.

[0040] Preferably, the sensitive effect index includes sow body loss, milk yield, litter weight at 21 days of age of piglets, ADG from 3 to 21 days, individual weight at 21 days, SUN at 14 days, SUN at 21 days.

[0041] More preferably,

[0042] When the sensitive effect index is sow body loss, the evaluation model is as follows:

[0043] Piecewise linear model: y = 19.11 + 35.22 * (0.85 - x),

[0044] Piecewise quadratic model: y = 19.38 + 117.32 * (0.90 - x) 2 ;

[0045] When the sensitive effect index is milk yield, the evaluation model is as follows:

[0046] Piecewise linear model: y = 239.17 - 322.67 * (0.82 - x),

[0047] Piecewise quadratic model: y = 237.07 - 887.67 * (0.90 - x) 2 ;

[0048] When the sensitive effect index is litter weight at 21 days of age of piglets, the evaluation model is as follows:

[0049] Piecewise linear model: y = 73.52 - 88.28 * (0.81 - x),

[0050] Piecewise quadratic model: y = 73.06 - 218.26 * (0.90 - x) 2 ;

[0051] When the sensitive effect index is ADG from 3 to 21 days, the evaluation model is as follows:

[0052] Piecewise linear model: y = 264.81 - 283.56 * (0.82 - x),

[0053] Piecewise quadratic model: y = 266.54 - 283.56 * (0.90 - x) 2 ;

[0054] When the sensitive effect index is 21d body weight, the evaluation model is as follows:

[0055] Broken line linear model: y = 6.80-5.92*(0.81-x),

[0056] Broken line quadratic model: y = 6.85-18.99*(0.89-x) 2 ;

[0057] When the sensitive effect index is 14d SUN, the evaluation model is as follows:

[0058] Broken line linear model: y = 5.51 + 12.47 * (0.80-x),

[0059] Broken line quadratic model: y = 5.49 + 43.77 * (0.86-x) 2 ;

[0060] When the sensitive effect index is 21d SUN, the evaluation model is as follows:

[0061] Broken line linear model: y = 4.34 + 18.27 * (0.79-x),

[0062] Broken line quadratic model: y = 4.30 + 59.52 * (0.90-x) 2 .

[0063] According to the above-mentioned evaluation model corresponding to the sensitive effect index, the appropriate standard ileum digestible lysine requirement for lactating sows under the low-protein diet level is evaluated to be 0.79%-0.90%, where the % is the mass percentage content.

[0064] The present invention will be further described below:

[0065] The present invention provides a more accurate and more applicable SIDLys requirement assessment model for lactating sows under low-protein diet conditions, that is, using the nonlinear curve fitting program in Origin Pro 2022 software, the broken line linear model and the broken line quadratic model (curve platform model) are used to evaluate the appropriate low-protein diet amino acid requirement with key effect indicators. The broken line linear and broken line quadratic models are methods for studying the amino acid requirement in animals based on the dose-effect model.

[0066] When applying this method, the following points should be noted in the experimental design: (1) When preparing the basal diet, feed ingredients that lack the amino acid to be tested should be used to prepare the basal diet to ensure that the amino acid to be tested is limiting in the diet. This usually requires supplementing other amino acids in the basal diet to ensure that the amino acid to be tested becomes the first limiting amino acid; (2) Ensure nutrient balance. In addition to the amino acid to be tested, other nutrients in the basal diet should meet the needs of the animal to ensure that there are no other nutritional factors that limit the growth or physiological performance of the animal except the amino acid to be tested; (3) At least 4 gradient levels of the amino acid to be tested should be set, of which 2 levels are higher than the requirement and 2 levels are lower than the requirement to accurately depict the amino acid requirement curve; (4) The experimental period should be set according to the characteristics of the effect indicator, and an appropriate experimental period should be set to obtain accurate and reliable data; (5) Selecting an appropriate statistical model is the key to analyzing experimental results and determining requirements.

[0067] The differences and advantages between the present invention and the prior art are as follows:

[0068] Commonly used animal amino acid requirement assessment models include multiple comparisons (also known as mean comparisons), linear models, and nonlinear models. Multiple comparisons can only assess the dose level of a certain set value, but the animal's amino acid requirement may be between two set levels, so the exact requirement cannot be obtained; the linear model has no plateau period, so it is not suitable for dose-effect tests with inflection points. The quadratic curve model has low requirements for data types and dose levels (at least 3), and it is relatively easy to simulate the best assessment value (the dose corresponding to the extreme value of the quadratic function). Its limitation is that it can only be used for data with symmetrical effects on both sides of the optimal dose; for those data that increase linearly with increasing dose and then plateau, the broken line linear and broken line quadratic (curve platform) can fit well ( Figure 1 ), the latter further takes into account the variation between experimental groups and the dynamic needs of animals for nutrients, and the optimal dose evaluated is often higher than the former.

[0069] In summary, the present invention discloses a nonlinear model for evaluating the standard ileal digestible lysine (SID Lys) requirement of a low-protein diet for lactating sows based on a dose-effect method, wherein the effect indicators include but are not limited to sow milk production, sow body condition changes, sow serum urea nitrogen and piglet growth performance; the model includes a broken line linear model and a broken line quadratic model. The model described in the present invention is applied through feeding experiments and chemical detection methods, that is, by measuring the effect indicator data and substituting it into the model to fit the corresponding function graph, determine the inflection point of the function graph, and then describe the appropriate requirement range of SID Lys for a low-protein diet for lactating sows and evaluate the nutritional status of sows, thereby promoting the scientific application of low-protein diets for pigs. The present invention is obtained by analyzing American-style long-growing binary multiparous lactating sows, but the model can be extended to other pig strains, genders or growth stages, and other livestock and poultry species. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 The broken line linear and broken line quadratic model graphs are shown in Figure 1. In the figure, the solid points represent the effect data, and the dotted line represents the optimal dose.

[0071] Figure 2 The broken line linear and broken line quadratic model fitting graphs of body loss and SID Lys;

[0072] Figure 3 The broken line linear and broken line quadratic model fitting graphs of milk yield and SID Lys;

[0073] Figure 4 The linear and quadratic model fitting diagrams of piglet litter weight on day 21 and SID Lys are shown in Figure 2.

[0074] Figure 5 The broken line linear and broken line quadratic model fitting diagrams of ADG and SID Lys of piglets from 3 to 21 days;

[0075] Figure 6 The broken line linear and broken line quadratic model fitting diagrams of individual weight and SID Lys of 21-day-old piglets;

[0076] Figure 7 The broken line linear and broken line quadratic model fitting diagrams of SUN and SID Lys of 14-day-old sows;

[0077] Figure 8 The broken line linear and broken line quadratic model fitting graphs of SUN and SID Lys in 21-day-old sows. DETAILED DESCRIPTION

[0078] 1 Experimental animals and diet

[0079] A total of 84 Landrace×Large White sows with similar parity (4.06±0.16), expected delivery date (7d) and body weight (260.65±1.25Kg) were selected and randomly divided into 6 treatments according to the principle of similar body weight. Each treatment had 14 replicates and each replicate had 1 pig. The formal experimental period was 28d (107d of gestation to 21d after delivery). The basic information of the experimental sows is shown in Table 1.

[0080] Table 1 Basic information of sows

[0081]

[0082] Note: Sows with insufficient feed intake, leg pain, whole-birth mortality, or death from disease will be eliminated.

[0083] The positive control group was prepared with the recommended dietary net energy and SID amino acids (90% dry matter) for lactating sows (2+ parities, piglet ADG about 230g / d) according to NRC (2012). The CP level was 18%. In addition, five low-protein (15%) groups with different SID Lys levels were set up. At the same time, the SID Met, Thr, Trp, Val, Ile, and Arg levels in the crystalline amino acid balanced diet were consistent with those in the positive control group (see Table 2), and the NE level was unified. The standard ileal digestible amino acids of the raw materials were calculated based on the raw material content and the standard ileal digestibility coefficients published by NRC (2012). The SID Lys levels of the five low-CP diets were 0.66%, 0.72%, 0.78%, 0.84%, and 0.90%, respectively. The diet composition and nutrient levels are shown in Table 3.

[0084] Table 2 Dietary SID Lys gradient design scheme

[0085]

[0086] Table 3 Composition and nutritional level of experimental diets

[0087]

[0088]

[0089] Note: 1) The premix provided the following per kg of diets: VA, 10000IU; VD3, 3000IU; VE, 10mg; VK3, 1mg; VB1, 1mg; VB2, 1mg; VB6, 1mg; VB12, 1mg; nicotinic acid, 30mg; pantothenic acid, 6.6mg; biotin, 0.172mg; folic acid, folic acid 1.58mg; Cu (as copper sulfate) 13.2mg; Fe (as ferrous sulfate) 120mg; Mn (as manganese sulfate) 70mg; Zn (as zinc sulfate) 68mg; I (as potassium iodide) 1.84mg; Se (as sodium selenite) 0.4mg.

[0090] 2)Crude protein, crude fiber, calcium and total phosphorus were measured valuesCP, CF, Ca and TP were measured values, while the others were calculated values.

[0091] 2. Feeding and management

[0092] A feeding experiment was carried out at the Dongchong Phase II breeding base of Longhua Agriculture and Animal Husbandry Co., Ltd. in Zhuzhou, Hunan Province. The experimental sows were raised in a limited stall in a closed and well-ventilated conventional delivery room. The temperature in the delivery room was controlled between 22-28°C by a wet curtain-fan combination. During the experiment, artificial feeding was performed, sows were restricted to feeding one week before delivery, and the feeding amount was gradually reduced 3 days before delivery. No feed was added on the day of delivery. Sows were fed 1kg of feed on the first day after delivery, 2kg on the second day, 3kg on the third day, and 4kg on the fourth day. From the fifth day to weaning, piglets were fed freely. Routine delivery was performed on the day of sow delivery to ensure that newborn piglets ingested colostrum. Within 3 days after delivery, piglets were fostered in groups to ensure that the number of piglets carried by sows was consistent, and excess piglets were transferred to non-experimental pigs for fostering. The pens were inspected at irregular intervals every day to record the humidity and temperature of the delivery room, and the feeding, defecation, health status of the experimental pigs and the growth of the piglets. Daily hygiene management in the delivery room (air quality, floor cleaning, feed trough cleaning, feces disposal) and pig immunization procedures (sow anti-inflammation, piglet tail docking, iron supplementation, vaccine injection, etc.) are all carried out normally in accordance with the requirements of the pig farm where the experiment is located.

[0093] 3. Index determination and methods

[0094] 3.1 Sow performance measurement

[0095] Sow weight and backfat thickness: Sows were weighed on a floor scale at 107 days of gestation (G107 d) and 21 days after farrowing (L21 d), and the backfat thickness at the P2 point (about 6.5 cm above the last rib from the midline of the back) on 107 days of gestation (for grouping) and 21 days after farrowing was measured with an ultrasonic backfat meter (Renco, USA) to calculate the backfat loss of sows.

[0096] Sow milk production: It is generally believed that the milk production of lactating sows is four times the weight gain efficiency of lactating piglets. The total milk production of each lactating sow within the 21 days of lactation can be calculated, that is, the total milk production of lactating sows = piglet ADG × 4 × litter size × number of lactation days.

[0097] 3.2 Piglet performance measurement

[0098] Within 3 days after farrowing, the number of piglets carried by each sow in the same group was adjusted to ensure that there was no difference in the average litter size and average piglet weight among sows in each group.

[0099] The litter weight and litter size of piglets at 3d, 7d, 14d, and 21d after farrowing, the age and weight of piglets that died during lactation, and the individual weight and ADG of piglets at each stage of lactation were calculated. Piglet ADG (g / head / day) = (weaning litter weight - initial litter weight + dead piglet weight - piglet weight + transferred piglet weight) / (number of pigs remaining after transfer × number of experimental days + number of dead pigs × number of days participating in the experiment + number of pigs sent × number of days participating in the experiment).

[0100] 3.3 Serum biochemical index determination

[0101] Serum samples were thawed at 4°C and centrifuged at 1000 g for 15 min. 200 μL of supernatant was collected in a sample cup and analyzed by Roche automatic biochemical analyzer ( c311, Switzerland) was used to measure the concentrations of serum total protein (TP), albumin (ALB), glucose (GLU), triglycerides (TG), SUN, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and the activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT).

[0102] 4 Statistical analysis methods

[0103] After the data was preliminarily sorted by Excel 2021, IBM SPSS Statistics 27 was used for statistical analysis of the data. Kolmogorov-Smirnov and Levene tests were used to test the normality and homogeneity of variance of the data. If satisfied, one-way ANOVA was used. If not satisfied, non-parametric tests (Kruskal-Wallis test) were used, and Duncan's multiple comparison method was used to compare the differences between groups. The orthogonal polynomial contrast method was used to evaluate the linear and quadratic effects of the SID Lys level (low-protein group) added to the diet on the indicators. The results were presented as mean and standard error. P<0.05 was considered significantly different, P<0.01 was considered extremely significantly different, and 0.05≤P<0.10 was considered to have a significant trend of difference. Different superscript letters for the same row of numerical values indicated significant differences (P<0.05). It should be noted that the data of the 18% CP + 0.78% SID Lys group and the 15% CP + 0.78% SID Lys group were separately subjected to an independent samples t-test. The nonlinear curve fitting program in Origin Pro 2022 software was used to evaluate the appropriate SID Lys requirement of the low-protein diet with the key effect indicators by the broken-line linear model and the broken-line quadratic model respectively. The general form of the model is as follows:

[0104] Broken-line linear model: if x<R, y = L + U*(R - x); when x≥R, y = L + U*0

[0105] Broken-line quadratic model: if x<R, y = L + U*(R - x) 2 ; when x≥R, y = L + U*0

[0106] In the formula: y is the sensitive effect index; x is the standardized ileal digestible lysine level (SID Lys level) (%); R is the appropriate standardized ileal digestible lysine level (SID Lys level) (%); L is the intercept; U is the slope.

[0107] 5 Experimental results

[0108] 5.1 Effects of different SID Lys levels in low-protein diets on the body weight and backfat thickness of lactating sows

[0109] As shown in Table 4, reducing the dietary CP level to 15% had no significant effect on the body weight loss and backfat loss of sows (t-test, P>0.05). At the low dietary protein level, with the increase of the dietary SID Lys level, the body weight loss decreased (linear and quadratic, P<0.05).

[0110] Table 4 Effects of different SID Lys levels in low-protein diets on the body weight and backfat thickness of lactating sows

[0111]

[0112]

[0113] Note: The data of 18% CP+0.78% SID Lys group and 15% CP+0.78% SID Lys group were subjected to independent sample t test, one-way analysis of variance was used between all groups, and linear or quadratic effect was analyzed between low protein groups. The same numerical values ​​with different letters on the shoulders indicate significant differences (P<0.05), the same as the following table.

[0114] 5.2 Effects of different SID Lys levels in low-protein diets on growth performance of suckling piglets

[0115] As shown in Table 5, a 3 percentage point decrease in dietary CP level had a tendency to reduce sow milk production (t test, P = 0.06), piglet 14d (t test, P = 0.08) and 21d litter weight (t test, P = 0.09), and piglet 3-21d ADG (t test, P = 0.06). Further reduction in SID Lys level significantly affected sow milk production and piglet growth performance (P < 0.05). Under low protein levels, with the increase of dietary SID Lys level, sow milk production, piglet 14 and 21d litter weight, individual weight, piglet 7-14d and 3-21d ADG significantly increased (linear and quadratic, P < 0.05).

[0116] Table 5 Effects of different SID Lys levels in low-protein diets on growth performance of suckling piglets

[0117]

[0118] 5.3 Effects of different SID Lys levels in low-protein diets on serum biochemical parameters in lactating sows

[0119] The effects of different SID Lys levels in low-protein diets on serum biochemical indices of lactating sows are shown in Table 6. (1) By observing serum biochemical indices on the day of farrowing, we found that reducing the CP level in the diet had no significant effect on the serum biochemical indices of sows (t-test, P>0.05). Under low protein levels, the SID Lys level significantly affected the TP and ALB contents (linear and quadratic, P<0.05). Specifically, reducing the CP level and increasing the SID Lys level increased the TP and ALB contents. When the SID Lys level was 0.72%, it was significantly reduced (P<0.05); when the SID Lys level was 0.84% ​​and 0.90%, it was significantly higher than the control group (P<0.05). The TC content was significantly different among the groups (P<0.05), but there was no obvious pattern. When the SID Lys level was 0.66%, the LDL-C content was significantly increased (P<0.05). (2) The results of serum biochemistry at 14 days after delivery showed that reducing the CP level in the diet significantly reduced the SUN content (t test, P<0.05). Under low protein levels, as the SID Lys level in the diet increased, the SUN content decreased (linear and quadratic, P<0.05). The TC content was significantly different among the groups (P<0.05). When the SID Lys in the diet was 0.84%, its content was significantly lower than that in the control group, the low protein SID Lys 0.66% and 0.90% groups (P<0.05). (3) The results of serum biochemistry at 21 days after delivery showed that reducing the CP level in the diet significantly reduced the SUN content (t test, P<0.05), and there was a trend of reducing the VLDL content (t test, P=0.09). Under low protein levels, as the SID Lys level in the diet increased, the SUN content decreased (linear and quadratic, P<0.01). The level of dietary SID Lys significantly affected the serum VLDL content (linear and quadratic, P<0.05), and the lowest value was found when the dietary SID Lys level was 0.84%.

[0120] Table 6 Effects of different SID Lys levels in low-protein diets on serum biochemical parameters of lactating sows

[0121]

[0122]

[0123] 5.4 Effect index and SID Lys broken line linear and broken line quadratic model fitting chart (Table 7)

[0124] Figures 2 to 8The broken line linear and broken line quadratic (curve platform) simulation diagrams between sensitive effect indicators and dietary SID Lys show that when sow body loss, milk production, piglet 21d litter weight, 3-21d ADG, 21d individual weight, 14d SUN and 21d SUN are used as effect indicators, the suitable levels of SID Lys in the low-protein diet for sows obtained by broken line linear simulation are 0.85%, 0.82%, 0.81%, 0.82%, 0.81%, 0.80% and 0.79%; the suitable levels of SID Lys in the low-protein diet obtained by broken line quadratic simulation are 0.90%, 0.90%, 0.90%, 0.90%, 0.89%, 0.86% and 0.86%. Finally, it is concluded that the suitable range of SID Lys requirement is between 0.79% and 0.90%.

[0125] It can be seen from Table 7 that under the condition of 15% low-protein diet level, the fitting results of the effect indicators are good, and it is finally concluded that the appropriate range of SID Lys requirement is between 0.79% and 0.90%, which has practical guiding significance for the preparation and promotion of low-protein diets for lactating sows.

[0126] Table 7 Information table of broken line linear and broken line quadratic models of effect indicators

[0127]

Claims

1. A model for evaluating the appropriate standard ileal digestible lysine requirement of lactating sows under low protein diet level, characterized in that: The model includes a broken-line linear model and a broken-line quadratic model: Broken-line linear model: when x < R, y = L + U*(R - x); when x ≥ R, y = L + U*0, Piecewise quadratic model: when x < R, y = L + U * (R - x) 2 ; when x ≥ R, y = L + U * 0; where: y is the sensitive effect index, x is the standardized ileal digestible lysine level (%); R is the appropriate standardized ileal digestible lysine level (%); L is the intercept; U is the slope; the % is the mass percentage content.

2. The evaluation model for the appropriate standard ileal digestible lysine requirement for lactating sows under low protein diet level as claimed in claim 1, characterized in that: The low-protein diet level is that the crude protein level is 2 - 3 percentage points lower than the NRC recommended amount.

3. The evaluation model for the appropriate standard ileal digestible lysine requirement for lactating sows under low protein diet level as claimed in claim 2, characterized in that: The low-protein diet level is a protein level of 15 - 18%, and the % is the mass percentage content.

4. The evaluation model for the appropriate standard ileal digestible lysine requirement for lactating sows under low protein diet level as claimed in claim 3, characterized in that: The low-protein diet level is a protein level of 15%.

5. The evaluation model for the appropriate standard ileal digestible lysine requirement for lactating sows under low protein diet level as claimed in claim 1, characterized in that: The sensitive effect index includes sow body loss, milk yield, litter weight at 21 days of age of piglets, ADG from 3 to 21 days, individual weight at 21 days, serum urea nitrogen (SUN) at 14 days, SUN at 21 days.

6. The evaluation model for the appropriate standardized ileal digestible lysine requirement of lactating sows under the low-protein diet level as described in claim 5, characterized in that when the sensitive effect index is sow body loss, the evaluation model is as follows: Broken-line linear model: y = 19.11 + 35.22*(0.85 - x), Broken line quadratic model: y = 19.38 + 117.32 * (0.90-x) 2 ; when the sensitive effect index is milk yield, the evaluation model is as follows: Broken-line linear model: y = 239.17 - 322.67*(0.82 - x), Broken line quadratic model: y = 237.07-887.67*(0.90-x) 2 ; when the sensitive effect index is litter weight at 21 days of age of piglets, the evaluation model is as follows: Broken-line linear model: y = 73.52 - 88.28*(0.81 - x), Broken line quadratic model: y = 73.06-218.26*(0.90-x) 2 ; when the sensitive effect index is ADG from 3 to 21 days, the evaluation model is as follows: Broken-line linear model: y = 264.81 - 283.56*(0.82 - x), Broken line quadratic model: y = 266.54-283.56*(0.90-x) 2 ; when the sensitive effect index is individual weight at 21 days, the evaluation model is as follows: Broken-line linear model: y = 6.80 - 5.92*(0.81 - x), Broken line quadratic model: y = 6.85-18.99*(0.89-x) 2 ; when the sensitive effect index is SUN at 14 days, the evaluation model is as follows: Broken-line linear model: y = 5.51 + 12.47*(0.80 - x), Broken line quadratic model: y = 5.49 + 43.77 * (0.86-x) 2 ; when the sensitive effect index is SUN at 21 days, the evaluation model is as follows: Broken-line linear model: y = 4.34 + 18.27*(0.79 - x), Broken line quadratic model: y = 4.30 + 59.52 * (0.90-x) 2 .

7. A method for evaluating the appropriate standard ileal digestible lysine requirement of lactating sows under low protein diet level, characterized in that: The method is to measure the sensitive effect index y of lactating sows, calculate the standardized ileal digestible lysine level x according to the content of low-protein diet raw materials and the standardized ileal digestibility coefficient published by NRC; substitute y and x into the following evaluation model for fitting to determine the appropriate level of standardized ileal digestible lysine in the low-protein diet: Broken-line linear model: when x < R, y = L + U*(R - x); when x ≥ R, y = L + U*0, Piecewise quadratic model: when x < R, y = L + U * (R - x) 2 ; when x ≥ R, y = L + U * 0; where: y is the sensitive effect index, x is the standardized ileal digestible lysine level (%); R is the appropriate standardized ileal digestible lysine level (%); L is the intercept; U is the slope.

8. The method for evaluating the appropriate standard ileal digestible lysine requirement for lactating sows under low protein diet level according to claim 7, characterized in that: The sensitive effect index includes sow body loss, milk yield, litter weight at 21 days of age of piglets, ADG from 3 to 21 days, individual weight at 21 days, SUN at 14 days, SUN at 21 days.

9. The method for evaluating the appropriate standard ileal digestible lysine requirement for lactating sows under low protein diet level according to claim 8, characterized in that: When the sensitive effect indicator is sow body loss, the evaluation model is as follows: Broken line linear model: y = 19.11 + 35.22 * (0.85-x), Broken line quadratic model: y = 19.38 + 117.32 * (0.90-x) 2 ; When the sensitive effect indicator is milk production, the evaluation model is as follows: Broken line linear model: y = 239.17-322.67*(0.82-x), Broken line quadratic model: y = 237.07-887.67*(0.90-x) 2 ; When the sensitive effect index is the litter weight of piglets at 21 days, the evaluation model is as follows: Broken line linear model: y = 73.52-88.28*(0.81-x), Broken line quadratic model: y = 73.06-218.26*(0.90-x) 2 ; When the sensitive effect index is 3-21d ADG, the evaluation model is as follows: Broken line linear model: y = 264.81-283.56*(0.82-x), Broken line quadratic model: y = 266.54-283.56*(0.90-x) 2 ; When the sensitive effect index is 21d body weight, the evaluation model is as follows: Broken line linear model: y = 6.80-5.92*(0.81-x), Broken line quadratic model: y = 6.85-18.99*(0.89-x) 2 ; When the sensitive effect index is 14d SUN, the evaluation model is as follows: Broken line linear model: y = 5.51 + 12.47 * (0.80-x), Broken line quadratic model: y = 5.49 + 43.77 * (0.86-x) 2 ; When the sensitive effect index is 21d SUN, the evaluation model is as follows: Broken line linear model: y = 4.34 + 18.27 * (0.79-x), Broken line quadratic model: y = 4.30 + 59.52 * (0.90-x) 2 .

10. The method for evaluating the appropriate standard ileal digestible lysine requirement for lactating sows under low protein diet level according to claim 9, characterized in that: The suitable standard ileum digestible lysine requirement for lactating sows under the low-protein diet level is 0.79%-0.90%, where the % is the mass percentage content.

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