Medicinal plant extract for improving anti-stress capability of micropterus salmoides as well as preparation method and application of medicinal plant extract

Abstract

The invention discloses a medicinal plant extract for improving the anti-stress capability of micropterus salmoides as well as a preparation method and application of the medicinal plant extract. Belongs to the technical field of aquaculture. The rosemary extract is prepared from rosemary, astragalus membranaceus and liquorice according to a specific proportion through an innovative process of composite enzymolysis, ultrasonic-assisted extraction and macroporous resin purification, and can effectively relieve temperature, water quality and transportation stress; the resistance of the micropterus salmoides to novel stress sources such as low-oxygen stress and salinity sudden change can be obviously improved. Experiments prove that the extract can significantly reduce serum cortisol and lactic acid levels and improve superoxide dismutase activity and immunoglobulin concentration under the addition amount of 0.1%, the survival rate under hypoxia stress is improved by 35% or above, the regulation recovery time under salinity sudden stress is shortened by 50%, and the content of the superoxide dismutase is reduced by 50% or above. The obvious synergistic interaction effect and the unexpected technical effect are shown.

Description

Technical Field

[0001] This invention relates to the field of aquaculture technology, and more specifically to a medicinal plant extract for improving the stress resistance of largemouth bass, its preparation method, and its application. Background Technology

[0002] Largemouth bass is one of my country's important freshwater aquaculture fish species. However, in intensive aquaculture, fish inevitably suffer from various stressors, such as sudden changes in water temperature (temperature stress), excessive ammonia / nitrite levels (water quality stress), and harvesting and transportation (transportation stress). In addition to the aforementioned common stressors, hypoxia stress and sudden salinity changes have also constrained the industry's development to some extent in recent years. Hypoxia stress usually occurs in high-density aquaculture, when water quality deteriorates, or when weather changes suddenly. When dissolved oxygen concentration is below 2 mg / L, fish will exhibit symptoms such as rapid breathing, metabolic disorders, and decreased immunity, leading to mass mortality in severe cases. Sudden salinity changes are more common in coastal aquaculture, during heavy rains, or due to human mismanagement. These events severely impact the fish's osmotic pressure regulation system, causing ion regulation imbalances and neuroendocrine disorders. These stressors activate the hypothalamic-pituitary-renal axis in fish, leading to the release of large amounts of stress hormones such as cortisol. This, in turn, causes metabolic disorders, immune suppression, and damage to the antioxidant system, resulting in slow growth, susceptibility to disease, and even mass mortality, causing significant economic losses to the aquaculture industry.

[0003] Currently, stress relief measures in aquaculture mainly rely on adding nutrients such as vitamin C and vitamin E to feed, or some chemical sedatives. However, vitamin products have limited effectiveness, while chemical sedatives pose risks such as drug residues, food safety concerns, and environmental pollution. Therefore, developing green, safe, and highly effective natural anti-stress drugs has become a current research hotspot.

[0004] Plant extracts are favored due to their natural properties, low toxicity, and low likelihood of inducing drug resistance. While there are reports of using extracts from single plants such as astragalus, rhubarb, and pine needles for stress relief in aquaculture, these methods often suffer from limited effectiveness, instability, or the need for large dosages. For example, the research progress on the application of astragalus and its polysaccharides in aquaculture, by Meng Muhan, discloses the application of astragalus polysaccharides in aquaculture, but its main focus is on promoting aquatic animal growth, enhancing disease resistance, antioxidant capacity, and immunity, inhibiting the growth of harmful bacteria, and improving the intestinal flora structure. No reports have been found on improving related stress resistance. Furthermore, existing technologies lack comprehensive solutions that can effectively address multiple stressors simultaneously (including traditional and novel stressors). Most anti-stress products have limited effects, and their efficacy under different stressors is unstable.

[0005] Therefore, how to develop new medicinal plant extracts with broad-spectrum anti-stress properties, so that they not only have good effects on traditional stressors, but also have excellent anti-stress effects on novel stressors such as hypoxia stress and sudden changes in salinity, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The primary objective of this invention is to provide a medicinal plant extract that enhances the stress resistance of largemouth bass, effectively improving its resistance to temperature stress, water quality stress, transportation stress, hypoxia stress, and sudden salinity change stress.

[0007] The second objective of this invention is to provide a method for preparing the plant extract of the drug, which significantly improves the yield and purity of the active ingredients and enhances its anti-stress effect through process innovation.

[0008] The third objective of this invention is to provide the application of the plant extract of this drug in the preparation of anti-multiple stress feed additives and drugs.

[0009] To achieve the above objectives, this application adopts the following technical solution: A medicinal plant extract for improving the stress resistance of largemouth bass, the active ingredients of which are composed of rosemary extract, astragalus extract and licorice extract, wherein the weight ratio of the raw materials of rosemary, astragalus and licorice is 1-3:2-5:1-2, and the extract can simultaneously improve the resistance of largemouth bass to hypoxia stress and sudden salinity change stress.

[0010] As a preferred technical solution, the weight ratio of rosemary, astragalus and licorice is 2:3:1.

[0011] Another object of this application is to provide: a method for preparing the medicinal plant extract, characterized by comprising the following steps: a) Weigh out the rosemary leaves, astragalus root, and licorice root according to the raw material weight ratio, and grind them separately; b) Mix the crushed rosemary, astragalus, and licorice, add 10-15 times the total weight of water, adjust the pH to 4.5-5.5, add compound cellulase and pectinase, and enzymatically hydrolyze at 45-50℃ for 1-2 hours. c) After enzymatic hydrolysis, the enzyme is inactivated, and the mixture is filtered to obtain the filter residue; d) Add 8-10 times the total weight of the raw material to the filter residue in 60%-70% ethanol solution, and perform ultrasonic-assisted extraction. The ultrasonic power is 300-500W, the temperature is 50-60℃, and the time is 30-45min. e) Filter the extract, combine the solutions, and concentrate under reduced pressure until no alcohol odor remains, to obtain the crude extract; f) Pass the crude extract through an AB-8 type macroporous adsorption resin column, first wash with water to remove impurities, then perform gradient elution with 70%-80% ethanol solution, and collect the eluent. g) Concentrate the eluent under reduced pressure and spray dry to obtain the plant extract of the drug.

[0012] As a preferred technical solution, in step b), the mass ratio of the composite cellulase and pectinase is 1:1, the total addition amount is 1%-2% of the total weight of the raw materials, and xylanase is added at the same time during the enzymatic hydrolysis process at 0.1%-0.3% of the total weight of the raw materials.

[0013] As a preferred technical solution, in step d), two-stage ultrasonic extraction is used: the first stage ultrasonic power is 500W and the time is 20min; the second stage ultrasonic power is 300W and the time is 25min, and the ethanol concentration is 65%.

[0014] Another object of this application is to provide the use of the aforementioned medicinal plant extract in the preparation of a feed additive for improving the hypoxic stress resistance of largemouth bass, wherein the hypoxic stress is a stress response caused by a dissolved oxygen concentration ≤2 mg / L for 6 hours.

[0015] Another object of this application is to provide the use of the aforementioned medicinal plant extract in the preparation of a feed additive for improving the resistance of largemouth bass to sudden salinity change stress, wherein the sudden salinity change is a stress response triggered by a salinity increase from 0‰ to 12‰ within 2 hours.

[0016] Another object of this application is to provide the use of the aforementioned medicinal plant extract in the preparation of a medicament for simultaneously enhancing the resistance of largemouth bass to multiple stressors, including temperature stress, water quality stress, transport stress, hypoxia stress, and sudden salinity change stress.

[0017] Another object of this application is to provide a feed that enhances the resistance of largemouth bass to multiple stresses, the feed containing the aforementioned medicinal plant extract at an addition amount of 0.05%-0.2% of the total weight of the feed, and the feed that can simultaneously enhance the adaptability of largemouth bass to low-oxygen environments and sudden changes in salinity.

[0018] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: (1) This invention is the first to discover that a specific extract of rosemary-astragalus-licorice exhibits significant resistance to hypoxia and sudden salinity changes. This characteristic has never been reported in the prior art and represents an unexpected technical effect. Experiments have shown that the extract of this invention is significantly more than 35% more effective than the individual extracts under hypoxia stress, and effectively shortens the recovery time under sudden salinity changes. This synergistic effect cannot be predicted from the individual components.

[0019] (2) The three-enzyme complex hydrolysis system (cellulase, pectinase, xylanase) used in this invention can more thoroughly destroy plant cell walls, especially for rhizomes and other medicinal materials that are difficult to extract, such as licorice. The two-stage ultrasonic extraction process achieves efficient dissolution of active ingredients while avoiding thermal damage through a combination of high and low power.

[0020] (3) Through in-depth research, this invention has discovered that the extract exerts its anti-stress effect through multiple mechanisms: it not only alleviates neuroendocrine stress by regulating cortisol levels, but also reduces oxidative damage by enhancing the activity of antioxidant enzymes, and further enhances osmotic pressure regulation by regulating the expression of ion transport proteins. This multi-target mechanism is the fundamental reason why it can cope with a variety of stressors.

[0021] (4) Hypoxia stress and sudden changes in salinity are increasingly prominent problems in aquaculture, but there is a lack of effective solutions. This invention provides for the first time an effective product targeting these new stressors, solving a bottleneck problem in the industry's development and having significant practical application value. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1

[0024] Preparation of medicinal plant extracts

[0025] (1) Weigh 2.0 kg of dried rosemary leaves, 3.0 kg of dried astragalus root, and 1.0 kg of dried licorice root, pulverize them separately and pass them through a 40-mesh sieve, then mix them evenly.

[0026] (2) Add 60 kg of water to the mixed powder, adjust the pH to 5.0 with citric acid, add the compound enzyme (30 g of cellulase, 30 g of pectinase, 12 g of xylanase), and stir at 48 °C for 1.5 hours for enzymatic hydrolysis.

[0027] (3) After enzymatic hydrolysis, the enzyme is inactivated by heating in a water bath at 90°C for 10 minutes, and then filtered by a filter press to obtain the filter residue.

[0028] Add 54 kg of 65% ethanol solution to the filter residue, perform a first-stage ultrasonic extraction (500 W, 55°C, 20 minutes), followed by a second-stage ultrasonic extraction (300 W, 55°C, 25 minutes), and collect the filtrate. Repeat the extraction with 54 kg of 65% ethanol, and combine the two filtrates.

[0029] (4) The filtrate was concentrated under reduced pressure at 60°C until it became a paste (without alcohol odor).

[0030] (5) Dissolve the extract in water to about 1 L and load it onto an AB-8 macroporous resin column (resin volume is 2 L) at a flow rate of 2 BV / h. First, elute with 8 L of deionized water (flow rate 3 BV / h) and discard the water wash. Then elute with 8 L of 75% ethanol solution at a flow rate of 2 BV / h and collect this ethanol eluent.

[0031] (6) After the ethanol eluent is concentrated under reduced pressure, it is spray dried (inlet air temperature 180℃, outlet air temperature 90℃) to obtain 480g of brownish-yellow powder, which is the plant extract of the present invention.

[0032] Feed preparation

[0033] The medicinal plant extract powder obtained in Example 1 was thoroughly mixed with basic feed ingredients (fish meal, soybean meal, flour, vitamin premix, mineral premix, etc.) at weight ratios of 0.05%, 0.1%, and 0.2%, respectively. The mixture was then processed into pellets with a diameter of 2.0 mm using a pellet mill, dried at 60°C, and packaged for later use. Example 2

[0034] Preparation of medicinal plant extracts

[0035] (1) Weigh 1.0 kg of dried rosemary leaves, 2.0 kg of dried astragalus root, and 1.0 kg of dried licorice root, pulverize them separately and pass them through a 40-mesh sieve, then mix them evenly.

[0036] (2) Add 60 kg of water to the mixed powder, adjust the pH to 4.5 with citric acid, add the compound enzyme (20 g of cellulase, 20 g of pectinase, 4 g of xylanase), and stir at 45 °C for 1.0 hour for enzymatic hydrolysis.

[0037] (3) After enzymatic hydrolysis, the enzyme is inactivated by heating in a water bath at 90°C for 10 minutes, and then filtered by a filter press to obtain the filter residue.

[0038] Add 32 kg of 60% ethanol solution to the filter residue, perform a first-stage ultrasonic extraction (500 W, 55 °C, 20 min), followed by a second-stage ultrasonic extraction (300 W, 55 °C, 25 min), and collect the filtrate. Repeat the extraction with 32 kg of 60% ethanol once more, and combine the two filtrates.

[0039] (4) The filtrate was concentrated under reduced pressure at 60°C until it became a paste (without alcohol odor).

[0040] (5) Dissolve the extract in water to about 1 L and load it onto an AB-8 macroporous resin column (resin volume is 2 L) at a flow rate of 2 BV / h. First, elute with 8 L of deionized water (flow rate 3 BV / h) and discard the water wash. Then elute with 8 L of 75% ethanol solution at a flow rate of 2 BV / h and collect this ethanol eluent.

[0041] (6) After the ethanol eluent is concentrated under reduced pressure, it is spray dried (inlet air temperature 180℃, outlet air temperature 90℃) to obtain 318g of brownish-yellow powder, which is the plant extract of the drug of the present invention.

[0042] Feed preparation

[0043] The medicinal plant extract powder obtained in Example 2 was thoroughly mixed with basic feed ingredients (fish meal, soybean meal, flour, vitamin premix, mineral premix, etc.) at weight ratios of 0.05%, 0.1%, and 0.2%, respectively. The mixture was then processed into pellets with a diameter of 2.0 mm using a pellet mill, dried at 60°C, and packaged for later use. Example 3

[0044] Preparation of medicinal plant extracts

[0045] (1) Weigh 3.0 kg of dried rosemary leaves, 5.0 kg of dried astragalus root, and 2.0 kg of dried licorice root, pulverize them separately and pass them through a 40-mesh sieve, then mix them evenly.

[0046] (2) Add 150 kg of water to the mixed powder, adjust the pH to 5.5 with citric acid, add the compound enzyme (100 g of cellulase, 100 g of pectinase, 30 g of xylanase), and stir at 50 °C for 2.0 hours for enzymatic hydrolysis.

[0047] (3) After enzymatic hydrolysis, the enzyme is inactivated by heating in a water bath at 90°C for 10 minutes, and then filtered by a filter press to obtain the filter residue.

[0048] Add 100 kg of 70% ethanol solution to the filter residue, perform a first-stage ultrasonic extraction (500 W, 55 °C, 20 min), followed by a second-stage ultrasonic extraction (300 W, 55 °C, 25 min), and collect the filtrate. Repeat the extraction with 100 kg of 70% ethanol once more, and combine the two filtrates.

[0049] (4) The filtrate was concentrated under reduced pressure at 60°C until it became a paste (without alcohol odor).

[0050] (5) Dissolve the extract in water to about 1 L and load it onto an AB-8 macroporous resin column (resin volume is 2 L) at a flow rate of 2 BV / h. First, elute with 8 L of deionized water (flow rate 3 BV / h) and discard the water wash. Then elute with 8 L of 75% ethanol solution at a flow rate of 2 BV / h and collect this ethanol eluent.

[0051] (6) After the ethanol eluent is concentrated under reduced pressure, it is spray dried (inlet air temperature 180°C, outlet air temperature 90°C) to obtain about 795g of brownish-yellow powder, which is the plant extract of the drug of the present invention.

[0052] Feed preparation

[0053] The medicinal plant extract powder obtained in Example 3 was thoroughly mixed with basic feed ingredients (fish meal, soybean meal, flour, vitamin premix, mineral premix, etc.) at weight ratios of 0.05%, 0.1%, and 0.2%, respectively. The mixture was then processed into pellets with a diameter of 2.0 mm using a pellet mill, dried at 60°C, and packaged for later use.

[0054] Verification of anti-multiple stress effects

[0055] 1. Experimental Grouping Example 1 (2:3:1 ratio, complete process); Example 2 (1:2:1 ratio, complete process); Example 3 (3:5:2 ratio, complete process); Comparative Example 1: Rosemary alone group (2.0 kg rosemary, without astragalus or licorice); Comparative Example 2: Astragalus membranaceus alone (3.0 kg Astragalus membranaceus, without rosemary or licorice); Comparative Example 3: Single-ingredient licorice group (1.0 kg licorice, without rosemary or astragalus); Comparative Example 4: Physical Mixing Group (Rosemary, Astragalus and Licorice were extracted, purified and dried independently using the same single-component extraction method as in Example 1 to obtain three independent single-component extract powders, and then these three powders were simply physically mixed in the optimal ratio (2:3:1 by weight). Comparative Example 5: Different ratio groups (rosemary:astragalus:licorice = 1:1:1); Comparative Example 6: Simplified process group (lacking complex enzymatic hydrolysis step); Blank control group (basal feed); 2. Laboratory animals and their care Laboratory animals: Healthy largemouth bass, with an initial weight of 50±5g; Aquaculture system: Indoor recirculating aquaculture system, water temperature 25±1℃; Experiment duration: 8 weeks; Grouping settings: Each group has 4 repetitions, and each repetition contains 25 fish; Feeding management: Feed twice a day, with the amount of feed being 3-5% of the fish's body weight; The formal experiment was conducted in an indoor recirculating aquaculture system for 8 weeks. After the experiment, the following stress test was performed.

[0056] Traditional stress experiment (1) Temperature stress experiment: 20 fish were taken from each group and transferred from 25℃ to 15℃ water. After 2 hours of cold stress, samples were taken for testing.

[0057] (2) Water stress experiment: 20 fish were taken from each group and exposed to water with 5 mg / L total ammonia nitrogen for 48 hours before sampling and testing.

[0058] (3) Transportation stress experiment: 20 fish were taken from each group, and the survival rate was recorded and samples were taken after 8 hours of simulated transportation.

[0059] Novel stress experiment (1) Hypoxia stress experiment: 20 fish were taken from each group and placed in water with dissolved oxygen of 1.5±0.2mg / L for 6 hours. The survival rate was recorded and samples were taken from the surviving fish for testing.

[0060] (2) Salinity change experiment: 20 fish were taken from each group, and the salinity was gradually increased from 0‰ to 12‰ within 2 hours and maintained for 24 hours. Serum cortisol, ion concentration and other indicators were sampled and detected.

[0061] The survival rate of largemouth bass under different stress treatments was determined, and the experimental results are shown in Table 1.

[0062] Table 1: Comparison of survival rates of largemouth bass under different stress models (%)

[0063] Note: * indicates P<0.05 compared with the blank control group; # indicates P<0.05 compared with all comparative groups.

[0064] Results analysis: Example 1 of the present invention (rosemary: astragalus: licorice = 2:3:1) exhibits excellent broad-spectrum anti-stress effects, with a comprehensive survival rate as high as 94.4%. Its synergistic effect is significantly better than that of individual extracts, physical mixtures and existing technologies, especially in dealing with novel stressors such as hypoxia and sudden changes in salinity.

[0065] Furthermore, this invention also measured the changes in physiological and biochemical indicators of each group after temperature stress, and the experimental results are shown in Table 2.

[0066] Table 2: Changes in physiological and biochemical indicators after temperature stress

[0067] Note: * indicates P<0.05 compared with the blank control group; # indicates P<0.05 compared with all comparative groups.

[0068] Results analysis: Example 1 of the present invention showed the best performance under temperature stress, and could most significantly reduce the levels of stress hormones cortisol and lactate, while maximally increasing the activity of antioxidant enzyme SOD and the concentration of immunoglobulin IgM, fully demonstrating its excellent anti-stress efficacy and synergistic effect.

[0069] Furthermore, this invention also measured the changes in physiological and biochemical indicators of each group after hypoxia stress, and the experimental results are shown in Table 3.

[0070] Table 3: Changes in specific indicators of hypoxia stress

[0071] Note: * indicates P<0.05 compared with the blank control group; # indicates P<0.05 compared with all comparative groups.

[0072] Results Analysis: As shown in Table 3, Example 1 of the present invention exhibits comprehensive advantages under hypoxic stress: significantly increasing gill Na+. + / K + - ATPase activity (3.45 U / mg prot) enhances ion regulation, increases hemoglobin concentration (108.6 g / L) to improve oxygen-carrying capacity, and significantly upregulates HIF-1α gene expression (2.15) to activate hypoxia adaptation mechanisms. At the same time, it effectively reduces lactate dehydrogenase (165.8 U / L), indicating that it can significantly reduce anaerobic metabolic load and comprehensively enhance the body's tolerance and adaptation to hypoxia environment.

[0073] Furthermore, this invention also measured the changes in physiological and biochemical indicators of each group after a sudden change in salinity stress, and the experimental results are shown in Table 4.

[0074] Table 4: Indicators of Osmotic Pressure Regulation under Salinity Change Stress

[0075] Note: * indicates P<0.05 compared with the blank control group; # indicates P<0.05 compared with all comparative groups.

[0076] Results Analysis: As shown in Table 4, under sudden salinity change stress, Example 1 of this invention exhibited excellent osmolarity regulation capability: the lowest serum osmolarity (245.8 mOsm / kg), Na... + / K + - The highest ATPase activity (3.42 U / mg prot), the shortest cortisol recovery time (18 hours), and the strongest expression of ion regulation genes (2.35) comprehensively demonstrate that it can rapidly rebuild the body's osmotic balance and significantly improve the salinity adaptation ability of largemouth bass.

[0077] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0078] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A medicinal plant extract for enhancing the stress resistance of largemouth bass, characterized in that, Its active ingredients consist of rosemary extract, astragalus extract and licorice extract, wherein the weight ratio of the raw materials of rosemary, astragalus and licorice is 1-3:2-5:1-2, and the extracts can simultaneously improve the resistance of largemouth bass to hypoxia stress and sudden salinity change stress.

2. The medicinal plant extract according to claim 1, characterized in that, The weight ratio of rosemary, astragalus, and licorice is 2:3:

1.

3. A method for preparing the medicinal plant extract according to any one of claims 1-2, characterized in that, Includes the following steps: a) Weigh out the rosemary leaves, astragalus root, and licorice root according to the raw material weight ratio, and grind them separately; b) Mix the crushed rosemary, astragalus, and licorice, add 10-15 times the total weight of water, adjust the pH to 4.5-5.5, add compound cellulase and pectinase, and enzymatically hydrolyze at 45-50℃ for 1-2 hours. c) After enzymatic hydrolysis, the enzyme is inactivated, and the mixture is filtered to obtain the filter residue; d) Add 8-10 times the total weight of the raw material to the filter residue in 60%-70% ethanol solution, and perform ultrasonic-assisted extraction. The ultrasonic power is 300-500W, the temperature is 50-60℃, and the time is 30-45min. e) Filter the extract, combine the solutions, and concentrate under reduced pressure until no alcohol odor remains, to obtain the crude extract; f) Pass the crude extract through an AB-8 type macroporous adsorption resin column, first wash with water to remove impurities, then perform gradient elution with 70%-80% ethanol solution, and collect the eluent. g) Concentrate the eluent under reduced pressure and spray dry to obtain the plant extract of the drug.

4. The method according to claim 3, characterized in that, In step b), the mass ratio of the compound cellulase and pectinase is 1:1, and the total amount added is 1%-2% of the total weight of the raw materials. At the same time, xylanase is added at 0.1%-0.3% of the total weight of the raw materials during the enzymatic hydrolysis process.

5. The method according to claim 3, characterized in that, In step d), two-stage ultrasonic extraction was used: the first stage had an ultrasonic power of 500W and a time of 20min; the second stage had an ultrasonic power of 300W and a time of 25min, and the ethanol concentration was 65%.

6. The use of the medicinal plant extract of any one of claims 1-2 in the preparation of a feed additive for improving the ability of largemouth bass to resist hypoxia stress, wherein the hypoxia stress is a stress response caused by a dissolved oxygen concentration ≤2 mg / L for 6 hours.

7. The use of the medicinal plant extract of any one of claims 1-2 in the preparation of a feed additive for improving the ability of largemouth bass to withstand sudden salinity change stress, wherein the sudden salinity change is a stress response caused by the salinity increasing from 0‰ to 12‰ within 2 hours.

8. The use of the medicinal plant extract according to any one of claims 1-2 in the preparation of a drug for simultaneously improving the resistance of largemouth bass to multiple stressors such as temperature stress, water quality stress, transportation stress, hypoxia stress and sudden salinity change stress.

9. A feed for improving the resistance of largemouth bass to multiple stresses, characterized in that, The feed contains the medicinal plant extract as described in any one of claims 1-2, and the amount added is 0.05%-0.2% of the total weight of the feed. The feed can simultaneously enhance the adaptability of largemouth bass to low-oxygen environments and sudden changes in salinity.

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