Feed additive capable of improving oxidation resistance of weaned piglets and improving intestinal morphological integrity and application of feed additive

Abstract

The invention discloses a feed additive for improving oxidation resistance of weaned piglets and improving intestinal morphological integrity and application of the feed additive. It is found for the first time that when gamma-PGA of different doses is added into weaned piglet feed, the growth performance of weaned piglets can be remarkably improved, the apparent digestibility of nutrient substances in the feed is improved, the intestinal morphological integrity of small intestines is improved, and jejunum antioxidant enzyme activity and gene expression are promoted. The application of the feed additive is expected to improve the oxidation resistance of the weaned piglets and promote the intestinal morphological integrity of the piglets, and the feed additive has a wide application prospect in actual breeding production. In addition, the invention provides a new solution thought and method for improving animal growth performance and maintaining intestinal morphological integrity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of feed additives, and particularly relates to a feed additive for improving the antioxidant capacity of weaned piglets and improving the intestinal morphological integrity and application thereof. BACKGROUND

[0002] China is the largest pig breeding country in the world. The intensive breeding system advances the weaning age to 3-4 weeks to improve the production capacity of sows, which can increase the annual number of piglets per sow. Early weaning leads to weaning stress in piglets, such as reduced feed intake, diarrhea and limited growth performance. Diarrhea after weaning of piglets seriously restricts the development of China's pig industry and is the main cause of piglet death. The mortality rate of piglets from birth to the nursery stage accounts for 80% of the whole breeding process, with a loss of 152 million heads. The post-weaning diarrhea rate of piglets is as high as 20%-30%, with a direct economic loss of 240 billion yuan. Under the dual pressure of feed antibiotic ban and African swine fever, the phenomenon of oxidative stress caused by weaning of piglets is more common. Finding new natural feed additives to alleviate oxidative stress, protect the health of piglets and ensure the sustainable development of green breeding will become an important problem faced by the industry.

[0003] Poly-γ-glutamic acid (γ-PGA) is a common biopolymer composed of D-glutamic acid or / and L-glutamic acid. In γ-PGA, multiple glutamic acid molecules are connected through the amide bond of γ-carboxyl to the α-amino group of adjacent molecules, forming a long chain structure. As an anionic polymer, γ-PGA has a large number of carboxyl anion groups, which endows it with strong cation metal chelating ability. When γ-PGA binds with metal ions, it can prevent the interaction of metal ions with lipid substances or peroxides, which provides the basis for its antioxidant properties. This chelation of metal ions not only prevents the generation of free radicals, but also maintains a relatively balanced metal ion environment in cells, which helps to protect cells from excessive oxidative stress. Especially in terms of antioxidant defense mechanisms, γ-PGA shows its unique advantages and becomes a potential natural antioxidant. As a natural source of high molecular compounds, γ-PGA has excellent antioxidant capacity and immunomodulatory biological activity functions, and has high safety and biocompatibility, leading to its wide application in the fields of food, health products and medicine, especially in the prevention and treatment of diseases caused by oxidative stress. At present, there are few reports on the application of γ-PGA in relieving oxidative stress of weaned piglets, improving growth performance and improving intestinal morphological integrity.

[0004] The patent document CN202510955217.6 discloses a preparation method of a gamma-PGA-rich feed additive for broilers and its application. A high-yield Bacillus licheniformis DY-0089 is screened from fermented foods such as fermented soy sauce, fermented bean curd, and natto, inoculated on a solid fermentation medium, fermented at 28-45 DEG C for 24-96 hours, dried in a drying oven at 55-70 DEG C, and crushed to prepare the gamma-PGA-rich feed additive. It is found through research that feeding 1% of the gamma-PGA-rich feed additive to broilers can enhance the immune function of the body, improve the cecal microbial population, regulate the cecal metabolomics, and thus improve the growth performance and feed conversion rate of the broilers, without affecting the serum biochemical indicators and antioxidant capacity of the broilers, slaughter performance, and nutritional ingredients of the breast muscle, thereby providing a theoretical basis for the development and application of the gamma-PGA-rich feed additive in animal breeding, especially broiler breeding. However, the patent document does not disclose the gamma-PGA-rich feed additive for improving the antioxidant capacity of weaned piglets and the intestinal morphological integrity. SUMMARY

[0005] In order to overcome the deficiencies of the prior art, the present application provides a feed additive for improving the antioxidant capacity of weaned piglets and the intestinal morphological integrity. The application of the feed additive gamma-PGA in the basic feed of piglets can effectively improve the growth performance of weaned piglets, improve the apparent digestibility of feed nutrients, improve the morphological structure integrity of the small intestine, and improve the antioxidant enzyme activity and the expression of antioxidant genes, thereby promoting the growth performance and intestinal health of weaned piglets. The feed additive has a broad application prospect in the feeding of weaned piglets.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] The first aspect of the present application provides a feed additive for improving the antioxidant capacity of weaned piglets and the intestinal morphological integrity. The feed additive is gamma-PGA.

[0008] The second aspect of the present application provides the application of the feed additive in the preparation of a feed for improving the antioxidant capacity of weaned piglets and the intestinal morphological integrity.

[0009] Further, the addition amount of the feed additive in the feed is 300-1200 mg / kg.

[0010] Further, the feed additive is used for improving the growth performance of weaned piglets; or / and for improving the apparent digestibility of feed nutrients; or / and for improving the morphological integrity of the small intestine; or / and for improving the antioxidant enzyme activity and gene expression of the jejunum, and relieving the damage of oxygen free radicals to the intestinal tract of the body.

[0011] Further, the feed additive is used for improving the growth performance of weaned piglets, significantly improving the average daily gain (ADG) of piglets, and with the addition of gamma-PGA in feed, the average daily gain presents a very significant quadratic curve effect, and the addition of 300-900 mg / kg gamma-PGA in feed can improve the average daily gain of weaned piglets.

[0012] Further, the feed additive is used for significantly improving the apparent digestibility of crude protein, and with the increase of the dose of gamma-PGA in feed, the apparent digestibility of crude protein in feed presents a very significant quadratic curve effect change; has a trend of significantly improving the apparent digestibility of crude fat; and the apparent digestibility of calcium and phosphorus in feed is linearly and significantly increased with the increase of the dose of gamma-PGA.

[0013] Further, the feed additive is used for very significantly reducing the jejunum crypt depth, significantly improving the jejunum villus crypt ratio, has a trend of reducing the ileum crypt depth, and can effectively improve the small intestinal morphological integrity of weaned piglets.

[0014] Further, the feed additive is used for significantly improving the total antioxidant capacity (T-AOC) and total superoxide dismutase (T-SOD) activity of the jejunum; has a trend of significantly improving the glutathione peroxidase (GSH-Px) activity and significantly reducing the content of malondialdehyde (MDA), which is a main component of lipid peroxidation product.

[0015] Further, the feed additive is used for significantly improving the relative expression amount of Keap1 and GPX4 genes; has a trend of improving the relative expression amount of NQO1 and SOD2 genes; and very significantly reduces the relative expression amount of Caspase 3 gene.

[0016] Compared with the prior art, the beneficial effects of the present application are:

[0017] In the present application, gamma-PGA can significantly improve the ADG of weaned piglets, improve the apparent digestibility of crude protein, crude fat and minerals in feed, improve the jejunum villus height, reduce the crypt depth of jejunum and ileum, improve the intestinal morphological integrity, improve the antioxidant enzyme activity of jejunum, reduce the content of malondialdehyde and promote the expression of antioxidant genes in jejunum. The application of the present application is expected to alleviate the oxidative stress of weaned piglets, promote the morphological structure of piglets, and has a broad application prospect in actual breeding production. In addition, the present application provides a new solution and method for improving the growth performance of animals and maintaining the morphological integrity of the intestinal tract. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Effect of adding gamma-PGA in feed on the growth performance of weaned piglets.

[0019] Figure 2Effects of γ-PGA added in feed on the small intestine morphology of weaned piglets.

[0020] Figure 3 Effects of γ-PGA added in feed on the small intestine morphology of weaned piglets. DETAILED DESCRIPTION

[0021] The above content of the present application is further described in detail by the following examples, but this should not be understood as the scope of the above subject matter of the present application is limited to the following examples only, and any technology realized based on the above content of the present application falls within the scope of the present application.

[0022] The experimental methods in the following examples are all conventional methods, and the experimental materials used in the following examples are all commercially available, unless otherwise specified.

[0023] Example 1: Effects of 300 mg / kg γ-PGA added in feed on the growth performance, intestinal morphology and antioxidant capacity of weaned piglets.

[0024] Example 2: Effects of 600 mg / kg γ-PGA added in feed on the growth performance, intestinal morphology and antioxidant capacity of weaned piglets.

[0025] Example 3: Effects of 900 mg / kg γ-PGA added in feed on the growth performance, intestinal morphology and antioxidant capacity of weaned piglets.

[0026] Example 4: Effects of 1200 mg / kg γ-PGA added in feed on the growth performance, intestinal morphology and antioxidant capacity of weaned piglets.

[0027] 1. Materials and methods

[0028] 1.1 Test animals and materials

[0029] Test site: Henan Xinxiang Lv Fengyuan Agricultural Co., Ltd. Test animals: 30 weaned piglets (Duroc × Landrace × Yorkshire) of 28 days old, purchased from Henan Xinxiang Lv Fengyuan Agricultural Co., Ltd. Test reagents: γ-PGA from Xinxiang Bo Kai Biological Technology Co., Ltd.

[0030] 1.2 Test design and feeding management

[0031] A total of 30 weaned piglets with an average weight of 8.07 ± 0.09 kg and 28 days of age were selected and randomly divided into 5 groups according to a single factor randomized design, with 6 piglets in each group and single-pen feeding. The control group was fed with the basic diet, and the other treatment groups were added with 300 mg / kg, 600 mg / kg, 900 mg / kg and 1200 mg / kg of γ-PGA on the basis of the basic diet, respectively. The test period was 28 days.

[0032] During the test period, the piglets were free to eat and drink, and were fed five times a day (fixed time at about 06:30, 10:00, 13:30, 17:00 and 20:30). The piglets' feed intake and mental state were recorded every day, and corresponding treatment measures were taken for abnormal piglets and recorded. The pens were cleaned and disinfected regularly every day, and the temperature of the pig house was maintained at 25-28°C and the relative humidity was maintained at 50-70% during the test period. The daily management of the test site and the immunization measures for weaned piglets were carried out in accordance with the standard production procedures of the pig farm.

[0033] 1.3 Basic diet

[0034] Table 1 Composition of the diet and its nutritional ingredients

[0035]

[0036]

[0037] 1 The mixed additives provide, per kg of complete feed: 11,000 IU VA, 320 IU D3, 85 IU E, 1.95 mg VK3, 0.4 mg VB12, 11.5 mg riboflavin, 38 mg niacin, 24 mg pantothenic acid, 0.30 mg biotin, 1.65 mg folic acid, 3.2 mg thiamine, 2.30 mg VB6, 200 mg iron (FeSO4), 150 mg zinc (ZnSO4), 35 mg manganese (MnSO4), 28 mg copper (CuSO4), 0.6 mg iodine (KIO3), 0.3 mg cobalt (CoSO4), 0.35 mg selenium (Na2SeO3) and 4.5 mg ethoxyquin.

[0038] 2 SID: Standard ileal digestibility.

[0039] 1.4 Sample collection

[0040] Digestion experiment was conducted on the 22nd day of the experiment, using 0.25wt% Cr2O3 as an exogenous indicator, and about 200g of feed samples were collected after mixing evenly for proximate nutrient determination, and stored at -20℃. The digestion experiment was conducted on a per pen basis, with 2 days of pre-feeding, 5 days of formal period, and fecal collection after adding acid to fix nitrogen, mixing evenly, and drying in a 65±5℃ forced air oven. After rehydrating at room temperature, the samples were ground and sieved, sealed in bags, and stored for apparent digestibility testing. After the experiment, all piglets were fasted for 12 hours, weighed, and euthanized, with blood collection from the neck, dissection, exposure of the abdominal cavity, and careful flushing of the jejunum and ileum tissue with pre-cooled physiological saline. A portion of the intestinal segment was placed in a 4wt% paraformaldehyde solution for fixation for intestinal morphology analysis. The remaining jejunum segment was scraped for mucosa, stored in tin foil paper, and stored at -80℃ after quick freezing in liquid nitrogen for determination of jejunum antioxidant enzyme activity and mRNA expression.

[0041] 1.5 Measurement indicators and methods

[0042] (1) Effect of γ-PGA on growth performance of weaned piglets

[0043] The piglets were weighed on the 0th and 29th days, and the feed weight was measured daily to calculate the average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (F:G) of the piglets.

[0044] (2) Effect of γ-PGA on apparent digestibility of weaned piglets

[0045] The contents of DM, OM, CP, EE, Ca, and P in the feed and fecal samples were determined according to "Feed Analysis and Feed Quality Detection Technology" (Zhang Liying, 5th edition). The Cr2O3 content in the feed and fecal samples was determined by mixed acid (perchloric acid: concentrated nitric acid = 1:4) heating digestion, transfer to constant volume, and using atomic absorption spectrophotometry to determine the content and calculate the feed nutrient digestibility. The calculation of apparent digestibility of feed nutrients is shown in formula 1:

[0046]

[0047] In the formula, A d is the chromium trioxide content in the feed (%); A f is the chromium trioxide content in the feces (%); B f is the nutrient content in the feces (%); B d is the nutrient content in the feed (%).

[0048] (3) Intestinal morphology

[0049] The intestinal tissue immersed in 4wt% paraformaldehyde was trimmed of excess mesentery and fat, then placed in a tissue embedding box, labeled, and washed overnight. Then it was sequentially immersed in 75% volume fraction, 85% volume fraction, and 95% volume fraction ethanol for 2 hours each, and then immersed in anhydrous ethanol twice for 30 minutes each for gradient dehydration. The completely dehydrated tissue was transparentized in a xylene solution. When the tissue appeared crystal clear and amber, the tissue was immersed in a wax tank for waxing, with low melting point wax (58-60°C) for 1 hour, high melting point wax (60-62°C) for 1 hour, and embedding on a tissue embedding machine. The embedded wax block was placed in a freeze dryer for cooling treatment. The embedded wax block was cut into 5 μm sections on a paraffin sectioning machine, and the sections were placed in a water bath at 41.5°C for sectioning. After the tissue was unfolded, it was placed on a slide using a glass slide, and then placed in an oven for 4 hours or more.

[0050] The paraffin sections were placed in a 55°C oven for 20 minutes, and then immersed in a xylene solution three times for 10 minutes each to remove the paraffin on the tissue. The paraffin-removed sections were immersed in anhydrous ethanol, 95% volume fraction, 85% volume fraction, and 75% volume fraction ethanol for 3 minutes each, and then immersed in distilled water for 3 minutes, and then immersed in hematoxylin staining solution for 7 minutes. After washing with running water for 5 minutes to remove excess hematoxylin staining solution, the sections were immersed in 1wt% hydrochloric acid differentiation solution for 20 seconds, and then allowed to reblue under running water. After microscopic examination, the sections were immersed in 75% and 85% volume fraction ethanol for 2 minutes each, stained with eosin for 30 seconds, and then sequentially immersed in 85% and 95% volume fraction ethanol, anhydrous ethanol for 1 minute each. After microscopic examination, the sections were immersed in xylene for 15 minutes, and then mounted with neutral balsam. After the neutral balsam solidified, the sections were observed and photographed, and the villus length, crypt depth, and villus width were measured using image-J software, and the villus-crypt ratio and villus surface area were calculated. The calculation of the villus surface area is shown in Equation 2:

[0051]

[0052] (4) Effect of γ-PGA on antioxidant enzyme activity in the jejunum of weaned piglets

[0053] The jejunum mucosa was ground with a pre-cooled mortar using liquid nitrogen, and an appropriate amount of powder was scraped into a centrifuge tube. The powder was mixed with physiological saline at a mass ratio of 1:9, vortexed, and then centrifuged at 2500g for 10 minutes at 4°C. The supernatant was collected for testing. The T-AOC, T-SOD, GSH-Px, and MDA contents in the jejunum were determined according to the Nanjing Jiancheng Reagent Kit instructions.

[0054] (5) Effect of γ-PGA on antioxidant genes in the jejunum of weaned piglets

[0055] ① RNA extraction and reverse transcription

[0056] The jejunum mucosa was ground into powder under liquid nitrogen environment, 100 mg sample was added with 1 mL Trizol solution, and after uniform shaking, it was placed on ice. After no precipitation, 200 μL chloroform was added, and the solution was shaken vigorously to become milky white. After centrifugation at 12000 g at 4°C for 10 min, the supernatant was taken, and an equal volume of isopropanol was added, mixed uniformly, and placed on ice for 10 min. After centrifugation at 12000 g at 4°C for 10 min, the supernatant was discarded, and 1 mL of 75% ethanol prepared with DEPC water was added to wash the precipitate, and the washing was repeated once. The DNA was dissolved with DEPC water, and after measuring the concentration, 1% agarose gel electrophoresis was used to detect the integrity of RNA. After all qualified, the mRNA reverse transcription kit (TaKaRa, Japan) was used to reverse the RNA to cDNA, and the cDNA was diluted with high-pressure sterilized water according to the volume ratio of 1:4.

[0057] 2. Primer sequence and RT-PCR analysis

[0058] The primer sequence was designed using Primer Premier 5, and was synthesized by Shengong. The primer sequence is shown in Table 2. β-actin was used as an internal reference, and 2 –ΔΔCt The gene expression amount was calculated.

[0059] Table 2 RT-PCR primer sequence

[0060]

[0061] According to Table 3, the reaction solution was prepared using TaKaRa TB Premix Ex Taq TM II (Tli RNaseH Plus) kit, and the sample gene expression level was detected using QuantStudio TM 6 Flex real-time fluorescent quantitative PCR system, with 2 repeats for each sample.

[0062] Table 3 RT-PCR reaction system and procedure

[0063]

[0064]

[0065] 1.6 Statistical analysis

[0066] In this experiment, Excel 2019 was used for data statistics, and SPSS 22 was used for data processing by one-way analysis of variance. When all data met the homogeneity of variance (P﹥0.05), one-way analysis of variance (One Way ANOVA) combined with the Duncan method was used for multiple comparisons; when the data did not meet the homogeneity of variance, the Welch test was used. The orthogonal polynomial comparison method was used to perform linear and quadratic curve regression analyses on different dose groups. The results were presented as the mean and standard error. 0.05 < P < 0.10 was considered as no significant difference but with a trend, 0.01 < P < 0.05 was regarded as a significant difference, and P < 0.01 was regarded as an extremely significant difference. In the tables and figures, different letters (a, b, c) reflected significant differences. All charts were drawn and combined using GraphPad Prism 8 and Adobe Illustrator 2022.

[0067] 2 Results

[0068] 2.1 Effects of γ-PGA addition in feed on the growth performance of weaned piglets<Object: word / embeddings / 2 / 157><Object: word / embeddings / 2 / 158>The effects of γ-PGA addition in feed on the growth performance of weaned piglets are shown in <Object: word / embeddings / 2 / 163>. From <Object: word / embeddings / 2 / 164>, it can be seen that compared with the control group, 600 mg / kg γ-PGA can significantly improve the ADG of piglets (P = 0.017). With the addition of γ-PGA, the ADG showed a significant quadratic curve effect (quadratic, P = 0.028), indicating that 300 - 900 mg / kg γ-PGA in feed can improve the growth performance of weaned piglets. <Object: word / embeddings / 2 / 165><Object: word / embeddings / 2 / 166>2.2 Effects of γ-PGA addition in feed on the apparent digestibility of weaned piglets<Object: word / embeddings / 2 / 167><Object: word / embeddings / 2 / 168>Table 4 Effects of γ-PGA on the apparent digestibility of weaned piglets<Object: word / embeddings / 2 / 169><Object: word / embeddings / 2 / 170><Object: word / embeddings / 2 / 171><Object: word / embeddings / 2 / 172><Object: word / embeddings / 2 / 173>Note: Different lowercase letters in the same row of data indicate significant differences (P < 0.05), and no superscript or the same superscript lowercase letters indicate no significant differences (P > 0.05). The same below. <Object: word / embeddings / 2 / 174><Object: word / embeddings / 2 / 175>The effect of γ-PGA in feed on apparent digestibility of weaned piglets is shown in Table 4. As shown in Table 4, compared with the control group, the apparent digestibility of crude protein in 300 mg / kg, 600 mg / kg and 900 mg / kg γ-PGA groups was significantly increased (P = 0.038), and the apparent digestibility of crude protein showed a significant quadratic curve effect change with the increase of γ-PGA dose (quadratic, P = 0.008). Compared with the control group, the apparent digestibility of crude fat in 600 mg / kg γ-PGA group had a significant increasing trend (P = 0.070). The apparent digestibility of calcium (linear, P = 0.023) and phosphorus (linear, P = 0.027) was linearly significantly increased with the increase of γ-PGA dose. These results showed that the addition of γ-PGA in feed could promote the digestibility of nutrients such as crude protein, crude fat and minerals in feed of weaned piglets, and further explained that the addition of γ-PGA could promote the growth performance of weaned piglets.

[0075] 2.3 Effect of γ-PGA in feed on small intestinal morphology of weaned piglets

[0076] The effect of γ-PGA in feed on small intestinal morphology of weaned piglets is shown in Table 5. Figure 2 . As shown in Table 5, compared with the control group, the villus height in 300 mg / kg, 600 mg / kg and 900 mg / kg γ-PGA groups was significantly increased (P = 0.038), and the villus height showed a significant quadratic curve effect change with the increase of γ-PGA dose (quadratic, P = 0.008). Compared with the control group, the crypt depth in 600 mg / kg γ-PGA group had a significant increasing trend (P = 0.070). The villus height to crypt depth ratio (linear, P = 0.023) and the villus height to crypt depth ratio (linear, P = 0.027) were linearly significantly increased with the increase of γ-PGA dose. These results showed that the addition of γ-PGA in feed could promote the small intestinal morphology of weaned piglets, and further explained that the addition of γ-PGA could promote the growth performance of weaned piglets. Figure 2HE staining results showed that the jejunum villi of the control group were sparse, and the crypt depth was relatively deep, and the intestinal epithelial cells were exfoliated, and the villus structure was damaged. Compared with the control group, the jejunum structure of the 600 mg / kg γ-PGA group was complete, the villus epithelial structure was arranged in order, and the morphology was relatively complete. The HE staining results of the ileum showed that the villi of each group were relatively complete, and the intestinal morphology was relatively clear. The statistical results of the jejunum data showed that compared with the control group, the 600 mg / kg, 900 mg / kg and 1200 mg / kg γ-PGA groups significantly reduced the jejunum crypt depth (P<0.001), and the linear significant reduction was presented with the addition of the dose (linear, P<0.001). Compared with the control group, the 600 mg / kg and 1200 mg / kg γ-PGA groups significantly improved the jejunum villus-crypt ratio (P=0.022), and the linear significant increase of the jejunum villus-crypt ratio was presented with the addition of the dose of γ-PGA in feed (linear, P=0.020); the jejunum villus-crypt ratio (quadratic, P=0.089) and the villus surface area (quadratic, P=0.072) showed a quadratic curve effect change trend. There was no significant difference in the jejunum villus width between different groups (P>0.05). The statistical results of the ileum data showed that compared with the control group, the 900 mg / kg and 1200 mg / kg γ-PGA groups had a trend to reduce the ileum crypt depth (P=0.068), and the linear significant reduction of the ileum crypt depth was presented with the addition of γ-PGA (linear, P=0.010), and the ileum villus-crypt ratio showed a quadratic curve change effect trend (quadratic, P=0.073). There was no significant difference in the ileum villus width and the ileum villus surface area between different groups (P>0.05). These results showed that the addition of γ-PGA in feed could reduce the crypt depth of the intestinal tract and promote the intestinal health.

[0077] 2.4 Effect of γ-PGA added in feed on the antioxidant enzyme activity of the jejunum of weaned piglets

[0078] The effect of γ-PGA added in feed on the antioxidant enzyme activity of the jejunum of weaned piglets is shown in Figure 3 . By Figure 3It was found that the addition of γ-PGA could significantly increase the T-AOC in jejunum (P = 0.048). Compared with the control group, the 1200 mg / kg γ-PGA group could significantly increase the T-SOD activity in jejunum of weaned piglets (P = 0.043), and the T-SOD showed a very significant linear increase with the increase of γ-PGA dose (linear, P = 0.003). Compared with the control group, the 600 mg / kg γ-PGA group could increase the GSH-Px activity in jejunum (P = 0.056), and there was a trend of linear increase of GSH-Px in jejunum of weaned piglets with the increase of γ-PGA dose (linear, P = 0.066). The addition of γ-PGA could significantly reduce the MDA content in jejunum (P = 0.031) and very significantly reduce with the addition of γ-PGA dose (linear, P = 0.004). The addition of γ-PGA could reduce the malondialdehyde content and increase the antioxidant enzyme activity.

[0079] 2.5 Effect of γ-PGA addition in feed on the antioxidant genes in jejunum of weaned piglets

[0080] The effects of γ-PGA on the antioxidant genes of the jejunum of weaned piglets in feed are shown in Table 5. As shown in Table 5, compared with the control group, the relative expression of Keap1 in the 300 mg / kg γ-PGA group can be significantly improved (P = 0.011); with the increase of the dose of γ-PGA in the feed, the relative expression of Keap1 presents a quadratic curve effect change (quadratic, P = 0.016). Compared with the control group, the relative gene expression of NQO1 in the 600 mg / kg γ-PGA group has a tendency to increase (P = 0.067); the relative gene expression of SOD2 in the 300 mg / kg γ-PGA group has a tendency to increase (P = 0.087); with the increase of the dose of γ-PGA in the feed, the relative expression of SOD2 presents a significant quadratic curve effect change (quadratic, P = 0.036). Compared with the control group, the relative gene expression of GPX4 in the 300 mg / kg and 600 mg / kg γ-PGA groups can be significantly improved (P = 0.037); the relative gene expression of GPX4 presents a very significant quadratic curve effect change (quadratic, P = 0.008) with the increase of γ-PGA. Compared with the control group, the relative expression of Caspase 3 in the 300 mg / kg, 600 mg / kg, 900 mg / kg and 1200 mg / kg γ-PGA groups is very significantly reduced (P = 0.002); with the increase of the dose of γ-PGA, the relative expression of Caspase 3 linearly and significantly increases (linear, P = 0.012) and presents a very significant quadratic curve effect (quadratic, P = 0.004). Different groups have no significant effect on the relative expression of other antioxidant genes (P > 0.05). The addition of γ-PGA in the feed can promote the relative expression of antioxidant genes, reduce the relative expression of apoptosis genes, improve the antioxidant level of the body, and thus reduce the damage caused by oxygen free radicals to the body.

[0081] Table 5 Effects of γ-PGA on the antioxidant genes of the jejunum of weaned piglets

[0082]

[0083] In summary, the addition of 300-900 mg / kg γ-PGA in the feed can significantly improve the growth performance of weaned piglets, improve the apparent digestibility of feed nutrients, improve the morphological integrity of the small intestine, improve the antioxidant enzyme activity and the relative expression of antioxidant genes in the jejunum, enhance the antioxidant capacity, and relieve the oxidative stress level of the body, so as to promote the intestinal health of piglets.

[0084] The embodiments of the present application are described in detail above, but the present application is not limited to the described embodiments. For those skilled in the art, various changes, modifications, replacements and variations of the embodiments can be made without departing from the principles and spirits of the present application, and still fall within the protection scope of the present application.

Claims

1. A feed additive for improving the antioxidant capacity and intestinal morphological integrity of weaned piglets, characterized in that, The feed additive is γ-PGA.

2. Use of the feed additive of claim 1 in the preparation of feed for improving the antioxidant capacity and intestinal morphological integrity of weaned piglets.

3. Use according to claim 2, characterized in that, The feed additive is added in the feed in an amount of 300-1200 mg / kg.

4. Use according to claim 2, characterized in that, The feed additive is used for improving the growth performance of weaned piglets; or / and for improving the apparent digestibility of feed nutrients; or / and for improving the intestinal morphological integrity of small intestine; or / and for improving the antioxidant enzyme activity and gene expression of jejunum, and relieving the damage of stress to the intestinal tract of piglets.

5. Use according to claim 2, characterized in that, The feed additive is used for improving the growth performance of weaned piglets, significantly improving the average daily gain of piglets, and with the addition of γ-PGA in the feed, the average daily gain shows a very significant quadratic curve effect, and the addition of 300-900 mg / kg γ-PGA in the feed can improve the average daily gain of weaned piglets.

6. Use according to claim 2, characterized in that, The feed additive is used for improving the apparent digestibility of crude protein in the feed, and with the increase of the dose of γ-PGA, the apparent digestibility of crude protein in the feed shows a quadratic curve effect; it has a trend of significantly improving the apparent digestibility of crude fat in the feed; the apparent digestibility of calcium and phosphorus in the feed is linearly and significantly increased with the increase of the dose of γ-PGA.

7. Use according to claim 2, characterized in that, The feed additive is used for reducing the jejunum crypt depth, improving the jejunum villus-crypt ratio, and has a trend of reducing the ileum crypt depth, which can effectively improve the intestinal morphological integrity of small intestine of weaned piglets.

8. Use according to claim 2, characterized in that, The feed additive is used for significantly improving the total antioxidant capacity (T-AOC) and total superoxide dismutase (T-SOD) activity of jejunum; it has a trend of significantly improving the glutathione peroxidase (GSH-Px) activity and significantly reducing the content of malondialdehyde (MDA), the main component of lipid peroxidation product.

9. Use according to claim 2, characterized in that, The feed additive is used for significantly increasing Keap1 and GPX4 The relative expression amount of the gene; the relative expression amount of the gene has a tendency to increase; NQO1 and SOD2 The relative expression amount of the gene has a tendency to increase; Caspase 3 The relative expression amount of the gene is extremely significantly reduced.

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