Feed for improving reproductive performance of high-fetal-number sows and feeding method

Abstract

The invention discloses a feed for improving reproductive performance of high-fetal-number sows and a feeding method. The tryptophan disclosed by the invention is applied to preparation of the feed for improving the reproductive performance of the high-fetal-count sows. The feed for improving the reproductive performance of the high-fetal-number sows comprises a sow daily ration and the tryptophan, the feed comprises a feed for the sow in the estrus period and a feed for the sow in the early gestation period, the adding mass of tryptophan in the feed for the sow in the estrus period is 0.4-0.55% of the mass percentage of the daily ration of the sow, and the mass percentage of the feed for the sow in the early gestation period is 0.2-0.35% of the mass percentage of the daily ration of the sow. The feeding method for improving the reproductive performance of the high-fetal-number sows comprises the following steps that 1, tryptophan is added into daily ration of the sows in the estrus period for feeding, and 2, tryptophan is added into daily ration of the sows in the early gestation period for feeding The tryptophan is added into the daily ration of the sows, so that the reproductive performance of the high-fetal-number sows is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of animal feeding or feed feeding, and relates to a feed and a feeding method for improving the reproductive performance of high-parity sows. Background Art

[0002] At present, one of the key problems leading to low production efficiency in the pig industry is the relatively low reproductive performance of sows. How to improve the reproductive performance of sows has become a key means to improve breeding efficiency. The number of weaned piglets provided by each sow per year and the service life of the sow jointly determine the lifetime productivity of the sow. Sow culling data shows that the reasons for sow culling include reproductive-related diseases, common diseases, lameness, infertility, anestrus more than 7 days after weaning, and low litter size, all of which significantly increase the unplanned culling of sows. In the pig industry, more and more attention has been paid to the development of management solutions for lifetime reproductive performance and extending the reproductive period of sows.

[0003] In the actual pig production system, the annual culling rate of sows reaches about 50%, mainly due to culling for reproductive performance defects. At present, sows with a higher parity (>6) in the pig production system are usually called high-parity sows, and their proportion is usually less than 10%. However, these high-parity sows still have reproductive potential because, compared with young sows (the 2nd or 3rd parity), they can ovulate a similar (or even more) number of mature oocytes. High-parity sows are more likely to be culled due to low litter size and reduced litter weight, possibly due to early embryo loss caused by ovarian and uterine dysfunction, because when sows reach a higher parity, the aging of the uterus and ovaries also causes a decline in the quality of oocytes, thus affecting reproductive performance.

[0004] Therefore, there is an urgent need for a solution to improve the reproductive performance of high-parity sows. Summary of the Invention

[0005] The object of the present invention is to provide a feed and a feeding method for improving the reproductive performance of high-parity sows.

[0006] The present invention performs non-targeted metabolomics analysis on the serum of sows with different parities to screen out certain differential metabolites (tryptophan) in the serum of high-parity and lower-parity sows, thereby providing a theoretical basis for regulating the nutritional status of high-parity sows by nutritional means, improving embryo quality, and affecting the reproductive performance of sows.

[0007] The tryptophan provided by the present invention is applied to the preparation of a feed for improving the reproductive performance of high-parity sows.

[0008] In the above application, the high-parity sows are sows with 4 to 6 parities.

[0009] In the above application, the improvement of the reproductive performance of high-parity sows is manifested in the increase of the total number of piglets born and the number of live piglets born by high-parity sows.

[0010] In the above application, the improvement of the reproductive performance of high-parity sows is manifested in the increase of the serum hormone level of sows.

[0011] In the above application, the improvement of the reproductive performance of high-parity sows is manifested in the improvement of the quality of aging oocytes.

[0012] The present invention also provides a feed for improving the reproductive performance of high-parity sows, which feed comprises a sow diet and the tryptophan; The feed comprises a feed for the estrus period of sows and a feed for the early pregnancy period of sows. Among them, the added mass of tryptophan in the feed for the estrus period of sows is 0.4-0.55% of the mass percentage of the sow diet, and the feed for the early pregnancy period of sows is 0.2-0.35% of the mass percentage of the sow diet.

[0013] In the present invention, the added mass of tryptophan in the feed for the estrus period of sows may specifically be 0.45% of the mass percentage of the sow diet, and the feed for the early pregnancy period of sows may specifically be 0.25% of the mass percentage of the sow diet.

[0014] The present invention further provides a feeding method for improving the reproductive performance of high-parity sows, comprising the following steps: 1) adding tryptophan to the diet of sows during the estrus period or feeding with the feed for the estrus period of sows as described; 2) adding tryptophan to the diet of sows during the early pregnancy period or feeding with the feed for the early pregnancy period of sows as described to improve the reproductive performance of high-parity sows.

[0015] In the above method, in step 1), the mass percentage of tryptophan added to the diet of sows during the estrus period may be 0.4-0.55%, and may specifically be 0.45%; The number of times of feeding the sows during the estrus period per day may be 2 times.

[0016] In the above method, in step 2), the mass percentage of tryptophan added to the diet of sows during the early pregnancy period may be 0.2-0.35%, and may specifically be 0.25%; The number of times of feeding the sows during the early pregnancy period per day may be 2 times; The early pregnancy period of the sows may be the 1st to 28th days of the gestation period.

[0017] The present invention has the following beneficial effects: Through non-targeted metabolomics analysis, the present invention screened out the specific differential metabolite tryptophan in the serum of high-parity sows, and further verified its regulatory effect on the reproductive performance of high-parity sows. The experimental results showed that adding tryptophan to the sow diet could significantly increase the litter size, number of live-born piglets and litter weight of high-parity sows, and improve their reproductive performance. The present invention provides a new nutritional regulation basis for improving the reproductive efficiency of high-parity sows and extending their service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 For the reproductive performance of sows with different parities, Figure 1 in (a) and (b), the litter size and number of live-born piglets are shown respectively.

[0019] Figure 2 The partial least squares discriminant analysis (PLS-DA) shows that the separation of the data depends on the parity.

[0020] Figure 3 For the enrichment analysis of different metabolites based on the KEGG database, Figure 3 in (a) and (b), the enrichment pathways of different metabolites in sows of the 3rd and 6th parities in the control group, and the enrichment pathways of different metabolites in sows of the 4th and 6th parities in the control group are shown respectively.

[0021] Figure 4 For the volcano plot of differential metabolites between the two groups, Figure 4 in (a) and (b), the volcano plots of differential metabolites in sows of the 3rd and 6th parities in the control group, and the volcano plots of differential metabolites in sows of the 4th and 6th parities in the control group are shown respectively.

[0022] Figure 5 For the effect of tryptophan on the reproductive performance of sows with different parities, Figure 5 in (a) and (b), the litter size and number of live-born piglets are shown respectively.

[0023] Figure 6 For the effect of tryptophan on the serum hormone levels of sows with different parities, Figure 6 in (a) and (b), the estrogen level and progesterone level are shown respectively.

[0024] Figure 7 For the in vitro maturation of porcine oocytes.

[0025] Figure 8 For the extrusion rate of the first polar body of porcine oocytes.

[0026] Figure 9 For the reproductive performance of sows with different parities, the means with different superscript letters in the same row in the figure are significantly different (P < 0.05). DETAILED DESCRIPTION OF THE INVENTION

[0027] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0028] Unless otherwise specified, the materials, reagents, etc. used in the following examples are all commercially available.

[0029] Example 1.1 Experimental animals The animal experiment procedures in this study have been approved by the Animal Experiment Ethics Committee of China Agricultural University. The animal experiments were conducted at the Fengning Sow Research Base of China Agricultural University (the academician workstation of Hebei Chengde Jiuyun Agriculture and Animal Husbandry Co., Ltd.). In order to study the differences in metabolism of sows of different parities and how to improve the reproductive performance of sows with high parities, 113 multiparous Large White × Landrace sows of different parities were first selected in this experiment, including sows of 2nd, 3rd, 4th, 5th, and 6th parities, and were divided into CON2, 3, 4, 5, 6 groups, with 21, 22, 25, 25, and 20 sows respectively. During the period from weaning to estrus, the dietary tryptophan level was 0.18% (calculated as the mass percentage of the total amount of the diet), and from the first day to the 28th day of pregnancy, the tryptophan level was 0.1% of the basal diet by mass percentage. On the 28th day of pregnancy, blood was collected by vein and serum was separated for subsequent metabolomics detection. During parturition, the sows were monitored and the start time of parturition was recorded. At the same time, the total number of piglets born, the number of live-born piglets, litter weight, piglet birth weight, number of stillborn piglets, and sex ratio of each litter were recorded.

[0030] Through serum metabolomics analysis, it was found that tryptophan might improve the reproductive performance of sows with high parities. Therefore, a second sow experiment was conducted to determine the optimal addition amount of tryptophan. From weaning to estrus until the 28th day of pregnancy, 128 Large White × Landrace crossbred sows with similar backfat thickness and parities were selected and randomly divided into a control group, a low-tryptophan group (LT), a medium-tryptophan group (MT), and a high-tryptophan group (HT). The dietary tryptophan level of the control group was 0.18% during the period from weaning to estrus and 0.1% from the first day to the 28th day of pregnancy (calculated as the mass percentage of the total amount of the diet, the same below); the tryptophan levels of the LT, MT, and HT groups were 0.27%, 0.36%, and 0.45% respectively during the period from weaning to estrus, and the tryptophan levels of the LT, MT, and HT groups from the first day to the 28th day of pregnancy were 0.15%, 0.20%, and 0.25% respectively (the number of feedings per day was 2 times, and the amount of diet each time was 1.25 kg, as shown in Table 2 specifically). Due to disease, 18 sows failed to give birth, and finally the actual number of sows that gave birth in the four groups were 29, 29, 25, and 27 respectively.

[0031] After determining the tryptophan addition amount, we also wanted to explore whether tryptophan could affect the reproductive performance of high-parity sows. A total of 159 Large White × Landrace crossbred multiparous sows with similar backfat thickness were selected in this experiment. They were divided into groups according to parity, including sows of parity 2, 3, 4, 5, and 6, and divided into Trp2, 3, 4, 5, and 6 groups, with 27, 33, 35, 35, and 29 sows respectively. During the period from weaning to estrus, the tryptophan level in the diet was 0.45%, and from the first day to the 28th day of pregnancy, the tryptophan level in the diet was 0.25% of the basal diet. Finally, due to diseases, abortions, etc., the actual number of sows giving birth was 22, 25, 22, 23, and 20 respectively. During parturition, the sows were monitored and the start time of parturition was recorded. At the same time, the total number of piglets born per litter, the number of live-born piglets, litter weight, piglet birth weight, number of stillborn piglets, and sex ratio were recorded.

[0032] Table 1 Composition of sows' diets during gestation and estrus (feeding basis, %)

[0033] In Table 1, 1 It means that the premix provides per kilogram of complete feed: vitamin A, 130 - 175 KIU; vitamin D3, 1000 Iu / kg; vitamin E, 500 IU; vitamin K3, ≥ 45 mg; vitamin B1, ≥ 50 mg; vitamin B2, ≥ 150 mg; vitamin B6, ≥ 100 mg; vitamin B12, ≥ 0.5 mg; niacin, 650 mg; pantothenic acid, ≥ 450 mg; folic acid, ≥ 80 mg; biotin, ≥ 10 mg; iron, 2.4 - 18 g; copper, 0.2 - 0.62 g; zinc, 1 - 2.5 g; manganese, 0.5 - 2 g; iodine, 10 - 50 mg; selenium, 5 - 12.5 mg; calcium, 80 g; phosphorus, 60 g; choline chloride, ≥ 10 mg; water, ≤ 10 %.

[0034] Table 2 Nutritional components corresponding to the composition of sows' diets during gestation and estrus (feeding basis, %)

[0035] During the experiment, the sows were individually housed in gestation stalls of 2.2 m × 0.65 m. By direct contact with boars, the estrus situation was checked every morning, and artificial insemination was carried out during estrus (with an interval of 12 hours between each insemination). Sows showing estrus return were excluded from the experiment. During the period from weaning to breeding, the sows were fed 2.00 kg of feed per day, and 2.5 kg of feed per day in the early pregnancy. The feed was provided twice, at 6:30 in the morning and 16:30 in the afternoon. During the whole experiment, they had free access to water. The experimental diet met the nutritional requirements of pregnant sows specified in "GB / T 39235 - 2020 Nutritional Requirements of Swine" (as shown in Tables 1 - 2).

[0036] 1.2 Test methods 1.2.1 Serum untargeted metabolomics detection Referring to the sample pretreatment method of Shanghai Majorbio Bio-pharm Technology Co., Ltd., 100 μL of sow serum sample was taken, 400 μL of extraction solution (methanol:acetonitrile volume ratio = 1:1, internal standard is L-2-chlorophenylalanine with a concentration of 2 μg / mL) was added, vortexed for 30 s, ultrasonically treated in an ice-water bath for 5 min, allowed to stand for 1 h, centrifuged for 15 min (4 °C, 12,000 r / min), the supernatant was taken and placed in a 1.5 mL EP tube, vacuum concentrated and dried, 150 μL of extraction solution (acetonitrile:water, volume ratio 1:1) was added for reconstitution, vortexed for 30 s, ultrasonically treated in an ice-water bath for 10 min, centrifuged for 15 min (4 °C, 12,000 r / min), 120 μL of the supernatant was taken and placed in a 2 mL injection vial, and 10 μL of each sample was taken and mixed into an OC sample for on-machine detection. Among them, methanol: CAS 67-56-1, purity LC-MS grade, brand Merck; acetonitrile: CAS 75-05-8, purity LC-MS grade, brand Merck; L-2-chlorophenylalanine: CAS 103616-89-3, purity > 98%, brand Shanghai Aladdin.

[0037] 1.2.2 Serum hormone level detection Commercially available radioimmunoassay reagents (purchased from Shanghai Hengyuan Bio, the product catalog numbers of progesterone and estradiol kits are HB035-Pg and HB317-Pg respectively) were used to detect the concentrations of progesterone and estradiol in sow serum. The concentrations of progesterone and estradiol in the PGC culture supernatant were also detected using commercially available radioimmunoassay kits. The brief steps were as follows: 100 μL of plasma sample was put into 0.9 mL of detection buffer, mixed well and centrifuged at 10,000 g and 4 °C for 10 minutes. The supernatant was transferred to a new centrifuge tube, and its absorbance at a wavelength of 585 nm was measured.

[0038] 1.2.3 Collection and in vitro maturation culture of porcine oocytes The fresh ovaries of young sows obtained from the slaughterhouse were placed in 0.9% NaCl solution (containing 75 μg / mL penicillin G and 50 μg / mL streptomycin) at 37 °C and brought back to the laboratory within 2 h, and then washed 3 times with the same solution to remove blood. The oocytes in follicles of 3 - 8 mm were aspirated into a 50 mL centrifuge tube with a 10 mL syringe with a needle, the supernatant was discarded after natural precipitation, washed 3 times with oocyte washing solution, and cumulus-oocyte complexes (COCs) with more than 3 layers of cumulus cells and uniform cytoplasm were selected under a microscope. After obtaining COCs, H 2 O 2 group and H 2 O2 +Trp group was treated with 100 μM H 2 O 2 Oocytes were treated with oocyte maturation medium for 0.5 h, then washed three times with the maturation medium to simulate the senescent state of oocytes, while the control group was treated with the maturation medium for 0.5 h. The control group and H 2 O 2 group COCs were placed in oocyte maturation medium, and H 2 O 2 +Trp group COCs were placed in oocyte maturation medium with a tryptophan concentration of 50 μM. The COCs were cultured in a 4-well plate (Nunc, Denmark, 60 mm), and about 60 COCs were cultured in 500 μL of maturation medium per well. Metaphase I oocytes were obtained after 44 h of culture. The status of COCs was observed and photographed, and then the cumulus cells were digested with 1% hyaluronidase to obtain oocytes, and the extrusion rate of the first polar body was observed and counted. Culture conditions: 5% CO 2 , 38.5 °C, in a carbon dioxide incubator with saturated humidity.

[0039] 2 Results 2.1 Reproductive performance of sows with different parities To determine the differences in reproductive performance of sows with different parities, multiparous sows were used as animal models, and five sows with different parities were selected to analyze their reproductive performance. The results showed that with the change of parity, the number of total born and number of live born per litter of sows both showed a trend of first increasing and then decreasing. Among them, compared with sows in the sixth parity, the number of total born per litter of sows in the third and fourth parities had an increasing trend (0.05 < P < 0.1) ( Figure 1 ). Specifically, the average number of total born per litter of sows in the third and fourth parities was 14.09 and 14.20, respectively, which was significantly higher than that of sows in the sixth parity (12.37), but there was no significant difference compared with the second parity. The number of live born also reached the peak in the third and fourth parities, which was 13.41 and 13.32, respectively, significantly higher than that of sows in high parities (11.68). Generally speaking, in line with previous reports, the reproductive performance of sows in the third and fourth parities was the best, while the reproductive performance of sows in high parities showed a downward trend.

[0040] 2.2 Serum metabolomics analysis of sows with different parities Serum from sows with different parities was subjected to untargeted metabolomics analysis to find differential metabolites and pathways that may affect the reproductive performance of sows in high parities. In the principal component analysis (PCA) plot, the metabolic profiles of sows with different parities were significantly separated ( Figure 2 ), indicating that parity has an important impact on the serum metabolic characteristics of sows. Subsequently, the metabolites in the groups with the largest differences in reproductive performance (CON3, CON4, and CON6) were analyzed. Figure 3In (a) and (b), respectively, are the enrichment analyses of different metabolites based on the KEGG database for CON3 and CON4 compared with CON6. Interestingly, in the differential metabolite enrichment analyses of CON3 and CON4 compared with CON6 respectively, it was found that both groups were enriched in the tryptophan metabolism pathway. Therefore, from the above results, it can be seen that the decline in the reproductive performance of high-parity sows may be related to tryptophan metabolism. Figure 4 In (a) is the volcano plot of all metabolites, and the red and blue dots represent the up-regulated and down-regulated metabolites in the CON3 group respectively. Figure 4 In (b) are the up-regulated and down-regulated metabolites in the CON4 group. Compared with low-parity sows, the metabolites related to tryptophan metabolism in high-parity sows were significantly reduced, suggesting that tryptophan may be a key metabolic factor for the decline in the reproductive performance of high-parity sows.

[0041] 2.3 Effects of Different Tryptophan Addition Levels on the Reproductive Performance of Sows To determine the effect of dietary tryptophan in early pregnancy on the reproductive performance of sows, multiparous sows were used as the animal model, and four diets with different tryptophan concentrations were selected to feed the sows. The results showed that compared with the control group, the litter weight of the HT group increased significantly (P<0.05), and there was an increasing trend in the number of live born piglets per litter (P = 0.06), while there were no significant differences in the number of live born piglets per litter or litter weight between the LT group and the MT group. There were no statistically significant differences among the four groups in backfat thickness, birth weight, sex ratio or number of stillborn piglets (as shown in Table 3).

[0042] Table 3 Effects of Dietary Addition of Different Concentrations of Tryptophan on the Reproductive Performance of Sows from Weaning to Estrus and in Early Pregnancy

[0043] In Table 3, the means with different superscript letters in the same row of a and b are significantly different (P<0.05). 2.4 Effects of Tryptophan on the Reproductive Performance of Sows with Different Parities To verify that the decline in the reproductive performance of high-parity sows may be related to tryptophan, tryptophan-supplemented diets were fed from estrus to early pregnancy (tryptophan content was 0.45% during estrus and 0.25% during early pregnancy; the feeding amount and frequency of the daily diet were 1.25 kg twice a day; feeding was carried out on days 1-28 of early pregnancy), and the reproductive performance of the sows was counted. As Figure 9 The results in showed that the addition of tryptophan in the diet significantly increased the total number of piglets born to high-parity sows ( P <0.01), and the number of sixth-parity sows increased from 12.37 in the control group to 13.68. The number of live born piglets in the tryptophan treatment group was significantly higher than that in the control group ( P(< 0.05), the number of high parity sows increased from 11.68 in the control group to 13.37. Tryptophan supplementation significantly increased the litter weight of high parity sows ( P (< 0.01), especially significant in the fifth and sixth parities. As Figure 5 can be seen, sow parity had a significant effect on total litter size and number of live born piglets ( P (< 0.05), reaching a peak at the 4th parity, and also had a significant effect on average litter weight ( P (< 0.05). No interaction between parity and dietary treatment was observed on these indicators ( Figure 9 ). The results showed that tryptophan significantly improved multiple reproductive performance indicators of high parity sows, supporting its potential as a nutritional intervention measure.

[0044] 2.5 Effects of tryptophan on serum hormone levels of sows with different parities Since during pregnancy, hormonal regulation is crucial for reproductive performance, the serum estrogen and progesterone levels of sows were subsequently detected. Figure 6 It showed that both parity and dietary treatment had a significant effect on serum estrogen levels (P < 0.05). The estrogen level of high parity sows increased significantly after tryptophan supplementation, approaching that of the low parity group. Similarly, tryptophan treatment at 0.45% during estrus and 0.25% during early pregnancy significantly increased progesterone levels ( P (< 0.05). The changes in hormone levels further indicated that tryptophan might improve the reproductive ability of high parity sows through an endocrine regulation mechanism.

[0045] 2.6 Effects of tryptophan on the quality of aging oocytes Through in vitro oocyte maturation experiments, it was explored whether tryptophan improved the reproductive performance of sows by improving the quality of aging oocytes. In this experiment, 100 μM H 2 O 2 oocyte maturation medium was used to treat cumulus-oocyte complexes for 0.5 h to simulate oocyte aging. As Figure 7 can be seen, after in vitro culture of normal cumulus-oocyte complexes, the granulosa cells spread well, while the granulosa cells in the H 2 O 2 group did not spread well, and adding 50 μM tryptophan after H 2 O 2 treatment could improve this situation. The oocyte maturation rate was expressed by the extrusion rate of the first polar body. As Figure 8 can be seen, compared with the control group, the oocyte maturation rate in the H 2 O 2 group was significantly reduced ( P (< 0.05), while in the H 2 O2 Adding tryptophan after treatment can restore the oocyte maturation rate to the control group level.

[0046] Discussion 1. Due to the degeneration of ovarian and uterine functions, the reproductive performance of high-parity sows is usually low, manifested as a decrease in litter size, litter weight, and an increase in stillbirth rate. This study found abnormal tryptophan metabolism in the serum of high-parity sows, suggesting that the tryptophan metabolic pathway may play an important role in the decline of their reproductive performance, providing a new perspective for revealing the molecular mechanism of the decline in sow reproductive performance.

[0047] 2. In the feeding experiment, dietary supplementation of tryptophan significantly improved the reproductive performance of high-parity sows. This indicates that tryptophan can optimize the physiological state of sows and thus improve reproductive ability by restoring damaged metabolic pathways. This result shows the potential application value of tryptophan in the reproductive management of old sows. Further in vitro cell experiments showed that tryptophan could significantly increase the maturation rate of senescent oocytes. The decline in the quality of senescent oocytes is an important reason limiting the reproductive performance of old sows, and tryptophan may protect oocytes through multiple mechanisms, such as enhancing mitochondrial function, reducing oxidative stress, and regulating metabolic homeostasis. In particular, tryptophan, as an important precursor for the synthesis of NAD⁺ (nicotinamide adenine dinucleotide), has attracted extensive attention for its role in anti-aging.

[0048] 3. NAD⁺ is a key molecule in intracellular energy metabolism and signal transduction, and is closely related to DNA repair, mitochondrial function, and anti-inflammatory responses. With the increase of age in high-parity sows, the level of NAD⁺ in their bodies gradually decreases, which will lead to a decrease in metabolic efficiency, an increase in oxidative stress, and an exacerbation of inflammatory responses, thus accelerating the decline of reproductive performance. Tryptophan may activate NAD⁺-dependent deacetylases such as SIRT1 by providing precursors for NAD⁺ synthesis, thereby improving cell metabolism, inhibiting inflammation, and delaying age-related functional degradation. The research results of this application show that tryptophan supplementation may improve the reproductive performance of high-parity sows by increasing the level of NAD⁺, restoring the metabolic activity of oocytes, and improving their maturation rate and quality.

[0049] Summary Through non-targeted metabolomics analysis, the present invention screened out the specific differential metabolite tryptophan in the serum of high-parity sows, and further verified its regulatory effect on the reproductive performance of high-parity sows. The experimental results showed that adding tryptophan to the sow diet could significantly increase the litter size, number of live-born piglets, and litter weight of high-parity sows, and improve their reproductive performance. This discovery provides a new nutritional regulation plan for improving the reproductive efficiency of high-parity sows and extending their service life.

Claims

1. Application of tryptophan in the preparation of feed for improving the reproductive performance of high-parity sows.

2. The use according to claim 1, characterized in that: The high-parity sows are sows that reproduce 4 to 6 parities.

3. The use according to claim 1 or 2, characterized in that: The improvement of the reproductive performance of high-parity sows is manifested in increasing the total number of piglets born and the number of piglets born alive by high-parity sows.

4. The use according to claim 1 or 2, characterized in that: The improvement of reproductive performance of high-parity sows is manifested in improving the serum hormone level of sows.

5. The use according to claim 1 or 2, characterized in that: The improvement of reproductive performance of high-parity sows is manifested in improving the quality of aging oocytes.

6. A feed for improving the reproductive performance of high-parity sows, characterized in that: The feed comprises a sow diet and the tryptophan; The feed includes feed for sows in estrus and feed for sows in early pregnancy, wherein the added mass of tryptophan in the feed for sows in estrus is 0.4-0.55% of the mass percentage of the sow's daily diet, and the feed for sows in early pregnancy is 0.2-0.35% of the mass percentage of the sow's daily diet.

7. A feeding method for improving the reproductive performance of high-parity sows, characterized in that: The method comprises the following steps: 1) adding tryptophan to the diet of sows in estrus or feeding the sows with the feed for sows in estrus as claimed in claim 6; 2) Adding tryptophan to the diet of sows in early pregnancy or feeding the sows with the feed for early pregnancy as claimed in claim 6 to improve the reproductive performance of high-parity sows.

8. The method according to claim 7, characterized in that In step 1), the mass percentage of tryptophan added to the diet of the sow in estrus period is 0.4-0.55%; The sow is fed twice a day during the estrus period.

9. The method according to claim 7 or 8, characterized in that: In step 2), the weight percentage of tryptophan added to the diet of the sow in early pregnancy is 0.2-0.35%; The sow is fed twice a day in the early stage of pregnancy; The early pregnancy of the sow is the 1st to 28th day of the pregnancy period.

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