Choledesmus sp. SYSU-A2024-1 and composition thereof, and application of Choledesmus sp. SYSU-A2024-1 in preparation of trachinotus ovatus low-fish-meal feed capable of improving lipid utilization rate

Abstract

The invention relates to the technical field of feed and feed additives. The invention provides an astaxanthin-rich cladophora sp. SYSU-A2024-1, the classification name of the cladophora sp. SYSU-A2024-1 is Oedacladium sp.SYSU-A2024-1, the cladophora sp. SYSU-A2024-1 is preserved in China Center for Type Culture Collection on June 3, 2024, the preservation address is Wuhan University, Wuhan, China, and the preservation number is CCTCC NO: M 20241138. The invention also provides a composition containing the cladophora sp. SYSU-A2024-1 and the chrysophyta laminarin, and an application of the composition in preparation of a low-fish-meal feed for aquatic animals. The trachinotus ovatus low-fish-meal feed containing the composition prepared by the invention can more comprehensively improve the lipid utilization rate of trachinotus ovatus, relieve oxidative stress and inflammatory injury, improve the liver health of fish bodies and remarkably improve the growth performance of the fish bodies through synergistic interaction, thereby ensuring the health and vitality of the fish bodies.

Description

Technical Field

[0001] The present invention relates to the technical field of feed and feed additives, in particular to Cladoscelis SYSU-A2024-1 and a composition thereof, and an application thereof in preparing a low-fishmeal feed for oval pomfret with improved lipid utilization. Background Art

[0002] As a typical carnivorous marine fish, the oval pomfret relies on a high-fat diet for rapid growth. However, excessive lipid intake in aquaculture can easily induce lipid deposition in the liver (fatty liver), leading to metabolic disorders and health risks. Aquaculture currently faces the severe challenge of fishmeal shortages, forcing feed formulations to shift to a high proportion of plant and animal protein sources (such as soybean meal and poultry meal). However, the amino acid imbalance and anti-nutritional factors of plant protein can impair liver function, while the saturated fatty acids in animal by-products exacerbate lipid accumulation. To compensate for the energy deficit of plant protein, excessive amounts of vegetable oil are often added to the feed, creating a vicious cycle of "low fishmeal, high fat, and liver damage." Astaxanthin, due to its unique lipid-lowering activity (activating fatty acid oxidation) and liver-protective properties, is an ideal additive for improving lipid metabolism. Furthermore, golden algae kelp polysaccharides have been shown to exhibit significant immunomodulatory, anti-inflammatory, hepatoprotective, and intestinal health-improving properties, alleviating metabolic stress by enhancing antioxidant capacity and inhibiting inflammatory responses. However, traditional single-use astaxanthin has certain limitations in improving lipid metabolism and comprehensively regulating health. Currently, astaxanthin used in aquatic feeds is primarily derived from chemical synthesis or from Haematococcus pluvialis. The former suffers from low bioavailability, controversial safety, and consumer acceptance issues, while the latter is limited by long cultivation cycles, demanding conditions, and high harvesting and processing costs. This study aims to provide a convenient, low-cost, and highly bioavailable astaxanthin-producing substance, combining it with kelp polysaccharides from golden algae as a novel additive. This combination has promising research implications for the comprehensive health regulation of high-fat aquatic animals and functional feeds. Summary of the Invention

[0003] The present invention aims to provide a Cladoscelis SYSU-A2024-1 and a composition thereof, as well as an application thereof in the preparation of a low-fishmeal feed for silver carp with improved lipid utilization. The low-fishmeal feed for silver carp containing the composition can more comprehensively improve the lipid utilization of silver carp through synergistic enhancement, alleviate oxidative stress and inflammatory damage, improve the liver health of fish, significantly improve the growth performance of fish, and thus ensure the health and vitality of fish.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides an astaxanthin-rich cladocladium SYSU-A2024-1, the classification name of which is Oedocladium sp. SYSU-A2024-1, which was deposited in the China Center for Type Culture Collection on June 3, 2024, with the deposit address being Wuhan University, Wuhan, China, and the deposit number being CCTCC NO: M20241138.

[0006] The present invention also provides a composition comprising chrysophyte laminarin and the clade algae SYSU-A2024-1, wherein the mass ratio of the clade algae SYSU-A2024-1 to the chrysophyte laminarin is (8-12):1.

[0007] The present invention also provides application of the composition in preparing low-fishmeal feed for aquatic animals for improving liver health.

[0008] The present invention also provides application of the composition in preparing low-fishmeal feed for aquatic animals for improving growth performance.

[0009] The present invention also provides application of the composition in preparing low-fishmeal feed for aquatic animals for improving lipid utilization.

[0010] The present invention also provides a low-fish meal feed for oval pomfret, comprising the following components in parts by weight: 55-63 parts of a protein source, 20-23 parts of a sugar source, 10.5-15.5 parts of a fat source, 0.5-1.5 parts of calcium dihydrogen phosphate, 0.8-1.2 parts of complex vitamins, 0.8-1.2 parts of complex minerals, 0.8-1.2 parts of single vitamins, 1.55-1.7 parts of essential amino acids, and 0.42-0.68 parts of the composition.

[0011] Preferably, the protein source comprises fish meal, soybean meal, soy protein isolate and chicken meal in a mass ratio of (16-19):(21-22):(6-8):(12-14).

[0012] The present invention also provides the use of the low-fishmeal feed for oval pomfret in improving the lipid utilization rate of oval pomfret, improving the liver health of oval pomfret and improving the growth performance of oval pomfret.

[0013] By adopting the above technical solution, the present invention has the following beneficial effects:

[0014] 1. The Cladoscelis SYSU-A2024-1 described in the present invention is a highly promising new source of natural astaxanthin. Compared to unicellular microalgae, this filamentous green algae has wider adaptability, relatively rapid growth potential, and the ability to easily form flocs or adhere to growth. This greatly simplifies large-scale harvesting and dehydration processes, reducing production costs. Furthermore, its cell structure is more conducive to the bioavailability of astaxanthin.

[0015] 2. The present invention fully utilizes the characteristics of the scaly algae SYSU-A2024-1 as a new source of natural, easy-to-harvest, and highly bioavailable astaxanthin, and synergistically compounds it with the golden algae laminarin polysaccharide, which has strong liver protection, anti-inflammatory and immunomodulatory functions. Through the multi-target and multi-pathway synergistic effects of astaxanthin and laminarin polysaccharide, it fundamentally solves the lipid metabolism disorders and liver health crisis caused by low-fishmeal, high-fat diets. It not only solves the growth and health problems caused by low-fishmeal diets, but also significantly improves feed conversion rate, reduces morbidity and mortality by improving lipid utilization efficiency and improving fish health, and helps improve fish meat quality and increase the economic benefits of breeding. This provides a natural, efficient, comprehensive and controllable innovative solution for the healthy, efficient and sustainable breeding of oval pomfret and even other high-fat aquatic animals in the context of limited fishmeal resources, which has great industrial application value and broad prospects.

[0016] Biological Deposit Description

[0017] The present invention relates to Oedocladium sp. SYSU-A2024-1, which has the classification name of Oedocladium sp. SYSU-A2024-1 and was deposited in the China Center for Type Culture Collection on June 3, 2024, with the deposit address being Wuhan University in Wuhan, China, and the deposit number being CCTCC NO: M 20241138. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a morphological structure diagram of Cladosporium SYSU-A2024-1;

[0019] Figure 2 The crude fat levels of liver and whole fish of oval pomfret in different treatment groups ( Figure 2 Different lowercase letters indicate significant differences, P < 0.05);

[0020] Figure 3 is the transcription level of genes related to fat transport and decomposition in the liver of oval pomfret in different treatment groups ( Figure 3 Different lowercase letters indicate significant differences, P < 0.05). DETAILED DESCRIPTION

[0021] The present invention provides an astaxanthin-rich cladocladium SYSU-A2024-1, the classification name of which is Oedocladium sp. SYSU-A2024-1, which was deposited in the China Center for Type Culture Collection on June 3, 2024, with the deposit address being Wuhan University, Wuhan, China, and the deposit number being CCTCC NO: M20241138.

[0022] The present invention also provides a composition comprising chrysolaminarin and the phyllodes alga SYSU-A2024-1. The chrysolaminarin of the present invention is extracted from Tribonema aequale, and the extraction method is described in the literature (Wang F, Yang R, Guo Y, Zhang C. Isolation, Characterization and Immunomodulatory Activity Evaluation of Chrysolaminarin from the Filamentous Microalga Tribonema aequale. Marine Drugs 2023, 21(1), 13.).

[0023] In the present invention, the mass ratio of the Cladosporium SYSU-A2024-1 and the laminarin is preferably (8-12):1, further preferably (9-11):1, and further preferably 10:1.

[0024] The present invention also provides application of the composition in preparing low-fishmeal feed for aquatic animals for improving liver health.

[0025] The present invention also provides application of the composition in preparing low-fishmeal feed for aquatic animals for improving growth performance.

[0026] The present invention also provides application of the composition in preparing low-fishmeal feed for aquatic animals for improving lipid utilization.

[0027] The present invention also provides a low-fish meal feed for oval pomfret, comprising the following components: a protein source, a sugar source, a fat source, calcium dihydrogen phosphate, complex vitamins, complex minerals, monomeric vitamins, essential amino acids and the composition.

[0028] In the present invention, the weight portion of the protein source is preferably 55-63 parts, further preferably 57-61 parts, and further preferably 59.64 parts; the weight portion of the sugar source is preferably 20-23 parts, further preferably 21-22 parts, and further preferably 21.18 parts; the weight portion of the fat source is preferably 10.5-15.5 parts, further preferably 12-14 parts, and further preferably 13 parts; the weight portion of the calcium dihydrogen phosphate is preferably 0.5-1.5 parts, further preferably 0.8-1.2 parts, and further preferably 1 part; the weight portion of the multivitamin is preferably 0.8-1.2 parts, and further preferably The weight proportion of the composite minerals is preferably 0.8-1.2 parts, further preferably 0.9-1.1 parts, further preferably 1 part; the weight proportion of the monomer vitamins is preferably 0.8-1.2 parts, further preferably 0.9-1.1 parts, further preferably 1 part; the weight proportion of the essential amino acids is preferably 1.55-1.7 parts, further preferably 1.6-1.65 parts, further preferably 1.63 parts; the weight proportion of the composition is preferably 0.42-0.68 parts, further preferably 0.5-0.6 parts, further preferably 0.55 parts.

[0029] In the present invention, the protein source preferably includes any one or more of fish meal, soybean meal, soy protein isolate, and chicken meal. When the protein source of the present invention is fish meal, soybean meal, soy protein isolate, and chicken meal, the mass ratio of the fish meal, soybean meal, soy protein isolate, and chicken meal is preferably (16-19):(21-22):(6-8):(12-14), further preferably (17-18.5):(21.1-21.5):(6.5-7.5):(12.5-13.8), and further preferably 18:21.14:7:13.5.

[0030] In the present invention, the sugar source preferably includes flour and / or tapioca starch. When the sugar source of the present invention is flour and tapioca starch, the mass ratio of flour to tapioca starch is preferably (19-20):(1-3), more preferably (19.1-19.5):(1.5-2.5), and even more preferably 19.18:2.

[0031] In the present invention, the fat source preferably includes any one or more of fish oil, soybean oil, and lecithin. When the fat source of the present invention is fish oil, soybean oil, and lecithin, the mass ratio of the fish oil, soybean oil, and lecithin is preferably (2-4):(8-10):(0.5-1.5), more preferably (2.5-3.4):(8.5-9.4):(0.8-1.2), and even more preferably 3:9:1.

[0032] In the present invention, the vitamin complex preferably includes 22-27 mg / kg vitamin B1, 43-47 mg / kg vitamin B2, 18-22 mg / kg pyridoxine hydrochloride, 0.08-0.12 mg / kg vitamin B12, 8-12 mg / kg vitamin K3, 780-820 mg / kg inositol, 55-65 mg / kg pantothenic acid, 180-220 mg / kg niacin, 18-22 mg / kg folic acid, 1-1.50 mg / kg biotin, 30-35 mg / kg retinyl acetate, 3-7 mg / kg cholecalciferol, 110-130 mg / kg α-tocopherol, 1800-2200 mg / kg ascorbic acid, 2300-2600 mg / kg choline chloride and 140-160 mg / kg ethoxyquin, further preferably including 24-26 mg / kg vitamin B1, 44-46 mg / kg vitamin B2, 19-21 mg / kg pyridoxine hydrochloride, 0.09-0.11 mg / kg vitamin B12, 9-11 mg / kg vitamin K3, 790-810 mg / kg kg inositol, 58-62 mg / kg pantothenic acid, 190-210 mg / kg niacin, 19-21 mg / kg folic acid, 1.10-1.30 mg / kg biotin, 31-33 mg / kg retinyl acetate, 4-6 mg / kg cholecalciferol, 115-125 mg / kg α-tocopherol, 1900-2100 mg / kg ascorbic acid, 2400-2550 mg / kg choline chloride and 145-155 mg / kg ethoxyquin, further preferably including 25 mg / kg vitamin B1, 45 mg / kg vitamin B2, 20 mg / kg pyridoxine hydrochloride, 0.1 mg / kg vitamin B12, 10 mg / kg vitamin K3, 800 mg / kg inositol, 60 mg / kg pantothenic acid, 200 mg / kg niacin, 20 mg / kg folic acid, 1.20 mg / kg biotin, 32 mg / kg retinyl acetate, 5 mg / kg cholecalciferol, 120 mg / kg alpha-tocopherol, 2000 mg / kg ascorbic acid, 2500 mg / kg choline chloride, and 150 mg / kg ethoxyquin.

[0033] In the present invention, the composite minerals preferably include 1.5-2.5 mg / kg sodium fluoride, 0.5-1.0 mg / kg potassium iodide, 45-55 mg / kg cobalt chloride hexahydrate, 8-12 mg / kg copper sulfate pentahydrate, 70-90 mg / kg ferrous sulfate monohydrate, 40-60 mg / kg zinc sulfate monohydrate, 50-70 mg / kg manganese sulfate monohydrate, 1150-1250 mg / kg magnesium sulfate heptahydrate, 2900-3100 mg / kg calcium dihydrogen phosphate monohydrate and 90-110 mg / kg sodium chloride, and further preferably include 1.8-2.2 mg / kg sodium fluoride, 0.7-0.9 mg / kg potassium iodide, 48-52 mg / kg cobalt chloride hexahydrate, 9-11 mg / kg copper sulfate pentahydrate. The present invention also provides the following ingredients: copper sulfate, 75-85 mg / kg ferrous sulfate monohydrate, 45-55 mg / kg zinc sulfate monohydrate, 55-65 mg / kg manganese sulfate monohydrate, 1180-1220 mg / kg magnesium sulfate heptahydrate, 2950-3050 mg / kg calcium dihydrogen phosphate monohydrate and 95-105 mg / kg sodium chloride, further preferably including 2 mg / kg sodium fluoride, 0.8 mg / kg potassium iodide, 50 mg / kg cobalt chloride hexahydrate, 10 mg / kg copper sulfate pentahydrate, 80 mg / kg ferrous sulfate monohydrate, 50 mg / kg zinc sulfate monohydrate, 60 mg / kg manganese sulfate monohydrate, 1200 mg / kg magnesium sulfate heptahydrate, 3000 mg / kg calcium dihydrogen phosphate monohydrate and 100 mg / kg sodium chloride.

[0034] In the present invention, the monomeric vitamin is preferably choline and / or vitamin C. When the monomeric vitamins of the present invention are choline and vitamin C, the mass ratio of choline to vitamin C is preferably (0.4-0.6):(0.4-0.6), more preferably (0.45-0.58):(0.43-0.58), and even more preferably 0.5:0.5.

[0035] In the present invention, the essential amino acid is preferably any one or more of methionine, lysine, and threonine (Thr), the methionine is preferably DL-methionine (DL-Met), and the lysine is preferably L-lysine hydrochloride (Lys-HCl). When the essential amino acids in the present invention are DL-methionine, Lys-HCl, and threonine, the mass ratio of DL-methionine, Lys-HCl, and threonine is preferably (0.4-0.45):(0.65-0.7):(0.5-0.55), further preferably (0.42-0.44):(0.67-0.69):(0.51-0.53), and further preferably 0.43:0.68:0.52.

[0036] The present invention also provides the use of the low-fishmeal feed for oval pomfret in improving the lipid utilization rate of oval pomfret, improving the liver health of oval pomfret and improving the growth performance of oval pomfret.

[0037] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0038] Example 1

[0039] A composition comprising chrysophyte laminarin and Cladosporium SYSU-A2024-1, wherein the mass ratio of Cladosporium SYSU-A2024-1 to chrysophyte laminarin is 10:1.

[0040] Example 2

[0041] A composition comprising chrysophyte laminarin and Cladosporium SYSU-A2024-1, wherein the mass ratio of Cladosporium SYSU-A2024-1 to chrysophyte laminarin is 8:1.

[0042] Example 3

[0043] A composition comprising chrysophyte laminarin and Cladosporium SYSU-A2024-1, wherein the mass ratio of Cladosporium SYSU-A2024-1 to chrysophyte laminarin is 12:1.

[0044] Example 4

[0045] A low-fishmeal feed for oval pomfret, comprising: 18 parts of fish meal, 21.14 parts of soybean meal, 7 parts of isolated soy protein, 13.5 parts of chicken meal, 19.18 parts of flour, 2 parts of cassava starch, 3 parts of fish oil, 9 parts of soybean oil, 1 part of lecithin, 1 part of monocalcium phosphate, 1 part of multivitamins, 1 part of multiminerals, 0.5 part of choline, 0.5 part of vitamin C, 0.43 part of DL-Met, 0.68 part of Lys-HCl, 0.52 part of Thr, 10.5 parts of SYSU-A2024-, and 0.05 part of chrysocolla polysaccharide.

[0046] The vitamin complex comprises 25 mg / kg vitamin B1, 45 mg / kg vitamin B2, 20 mg / kg pyridoxine hydrochloride, 0.1 mg / kg vitamin B12, 10 mg / kg vitamin K3, 800 mg / kg inositol, 60 mg / kg pantothenic acid, 200 mg / kg niacin, 20 mg / kg folic acid, 1.20 mg / kg biotin, 32 mg / kg retinyl acetate, 5 mg / kg cholecalciferol, 120 mg / kg α-tocopherol, 2000 mg / kg ascorbic acid, 2500 mg / kg choline chloride and 150 mg / kg ethoxyquin;

[0047] The complex minerals are 2 mg / kg sodium fluoride, 0.8 mg / kg potassium iodide, 50 mg / kg cobalt chloride hexahydrate, 10 mg / kg copper sulfate pentahydrate, 80 mg / kg ferrous sulfate monohydrate, 50 mg / kg zinc sulfate monohydrate, 60 mg / kg manganese sulfate monohydrate, 1200 mg / kg magnesium sulfate heptahydrate, 3000 mg / kg calcium dihydrogen phosphate monohydrate and 100 mg / kg sodium chloride.

[0048] Test Example 1

[0049] A strain of filamentous microalgae was isolated from a stream in Daming Mountain. Microscopic observation revealed that the algal filaments were selected and placed in a 100mL Erlenmeyer flask. 20mL of BG-11 medium was added for propagation and culture. After 14 days of culture, the algal cells were observed for growth. Then, 1mL of the algal solution was transferred to BG-11 medium containing 100mg / L ampicillin. The antibiotic transfer culture was repeated in the 100mL Erlenmeyer flask to remove bacteria and protozoa associated with the filamentous algae. Slides of the algae were prepared and observed using a standard optical microscope, and their morphological and structural characteristics were recorded.

[0050] like Figure 1 The cells are branched and cylindrical, the chromatophores are reticular, and a certain amount of astaxanthin can be accumulated in the cells, which appear brown-red. Therefore, based on the morphological characteristics, SYSU-A2024-1 was classified as Oedocladium sp. SYSU-A2024-1, and the alga was named Oedocladium sp. SYSU-A2024-1 and stored in BG-11 liquid culture medium.

[0051] Test Example 2

[0052] Three experimental diets were set up: D1, D2, and D3. D1 served as the control diet, consisting of a normal fishmeal diet and a high-fat diet; D2 served as a low-fishmeal diet and a high-fat diet; and D3 served as a low-fishmeal diet and a high-fat diet supplemented with 0.5% Cladosporium and 0.05% chrysocolla polysaccharide. The specific composition of the experimental diets for each group is shown in Table 1.

[0053] Cladoscelis SYSU-A2024-1 was cultured using a modified BG-11 medium (also known as mBG11 medium). 1 L of the modified BG-11 medium contained 36 mg of calcium chloride dihydrate (CaCl2·2H2O), 75 mg of magnesium sulfate heptahydrate (MgSO4·7H2O), 20 mg of sodium carbonate (Na2CO3), 40 mg of potassium dihydrogen phosphate (K2HPO4), 3.15 mg of ferric chloride dihydrate (FeCl3·2H2O), 6.0 mg of citric acid, 4.36 mg of disodium ethylenediaminetetraacetic acid dihydrate (Na2EDTA·2H2O), and 1 mL of a mixed solution. The 1LA5 mixture consists of 1.81g manganese chloride tetrahydrate (MnCl2·4H2O), 79mg copper sulfate pentahydrate (CuSO4·5H2O), 2.86g boric acid (H3BO3), 222mg zinc sulfate heptahydrate (ZnSO4·7H2O), 0.39g sodium molybdate dihydrate (NaMoO4·2H2O), 49.4mg cobalt nitrate hexahydrate (Co(NO3)2·6H2O), and 1mL 98% sulfuric acid (H2SO4). Initially, the Cladosporium SYSU-A2024-1 strain was grown in mBG11 medium containing 9.0mM sodium nitrate (NaNO3) under a constant unilateral light intensity of 100 micromoles photons per square meter per second (mmol photons m -2 s -1 ) for 6 days. Then, the light intensity was adjusted to 500 micromoles photons per square meter per second (mmol photons m -2 s -1 ) and further cultured the algae for 10 days. Throughout the culture cycle, the glass tubular photobioreactor was maintained at 28°C and aerated with 1.0% carbon dioxide (CO2). Finally, the microalgae cells were harvested by filtration through gauze and then freeze-dried using a Christ EPSILON2-4 LSC plus freeze dryer at -60°C for 12 hours to obtain microalgae powder. The obtained Cladosporium algae powder contained 1.70% astaxanthin, 12.31% crude protein, and 38.15% crude fat.

[0054] Table 1 Composition of experimental diets in different groups

[0055]

[0056]

[0057] The vitamin complex comprises 25 mg / kg vitamin B1, 45 mg / kg vitamin B2, 20 mg / kg pyridoxine hydrochloride, 0.1 mg / kg vitamin B12, 10 mg / kg vitamin K3, 800 mg / kg inositol, 60 mg / kg pantothenic acid, 200 mg / kg niacin, 20 mg / kg folic acid, 1.20 mg / kg biotin, 32 mg / kg retinyl acetate, 5 mg / kg cholecalciferol, 120 mg / kg α-tocopherol, 2000 mg / kg ascorbic acid. The compound minerals include 2 mg / kg sodium fluoride, 0.8 mg / kg potassium iodide, 50 mg / kg cobalt chloride hexahydrate, 10 mg / kg copper sulfate pentahydrate, 80 mg / kg ferrous sulfate monohydrate, 50 mg / kg zinc sulfate monohydrate, 60 mg / kg manganese sulfate monohydrate, 1200 mg / kg magnesium sulfate heptahydrate, 3000 mg / kg calcium dihydrogen phosphate monohydrate and 100 mg / kg sodium chloride.

[0058] The dry ingredients (fish meal, soybean meal, soy protein isolate, flour, chicken meal, and tapioca starch) were ground and filtered through a 200μm sieve. The sieve residue was collected. The mixture was then weighed and mixed according to the respective recipes to produce a mixture. Fish oil, soybean oil, lecithin, and water were then added to the mixture in sequence and stirred vigorously until uniform. The resulting mixture was then formed into extruded feed with a diameter of 2.5mm and dried in a ventilated oven at 40°C until the moisture content was reduced to below 10%. The experimental feed was then stored at -20°C. (one)

[0060] The nutritional composition of each experimental feed was analyzed and determined according to AOAC (1990) standard methods. Samples were oven-dried at 105°C to constant weight to determine moisture content. Protein content was determined using the Kjeldahl method, and fat content was determined using Soxhlet extraction. The results are shown in Table 2.

[0061] Table 2 Nutritional levels of experimental diets in different groups

[0062] (two)

[0064] The egg-shaped pomfret juveniles used in the experiment were purchased from a commercial hatchery in Ningde, Fujian Province, China (Ningde Lingling Fishery Technology Co., Ltd.). These fry were first acclimated for two weeks in floating seawater cages with dimensions of 4.0m×3.0m×2.5m to adapt to the experimental environment. Before the formal experiment, all individuals underwent a 24-hour fasting treatment. Subsequently, 480 healthy juveniles with an initial average weight of 6.49±0.02g were selected and randomly distributed to 12 small floating cages with dimensions of 1m×1m×1.5m, with 40 juveniles in each cage. Each experimental diet was randomly fed to the fish in 4 of the cages. During the 8-week rearing period, the fish were fed twice a day at 7 am and 6 pm.

[0065] After the feeding experiment, the experimental fish in each group were fasted for another 24 hours and then anesthetized with a 100 mg / L eugenol solution. The body weight of the fish in each group was measured to calculate growth and morphological indicators such as initial body weight (IBW), final body weight (FBW), specific growth rate (SGR), feed efficiency (FE), survival rate (SR), viscera-to-somatous ratio (VSI), and liver-to-somatous ratio (HSI). Specific data are shown in Table 3. Results are expressed as mean ± SD.

[0066] Specific growth rate (%) = (ln final weight - ln initial weight) / number of experimental days × 100;

[0067] Feed efficiency = (final weight - initial weight) / feed intake;

[0068] Survival rate (%) = final number of fish / initial number of fish × 100;

[0069] Visceral to body ratio (%) = 100 × (visceral mass weight, g) / (body weight, g)

[0070] Liver to body weight ratio (%) = 100 × (liver weight, g) / (body weight, g)

[0071] Table 3 Growth performance of juvenile pomfret in different treatment groups

[0072]

[0073]

[0074] Table 3 shows that compared with the control group (D1), the low-fishmeal diet group (D2) significantly reduced terminal body weight, specific growth rate, feed efficiency, and survival rate of oval pomfret (P < 0.05). Notably, the addition of Cladophora spp. and Chrysophyta laminarin to the low-fishmeal diet (D3) significantly improved these growth and survival indicators compared with the D2 group (P < 0.05), even surpassing the D1 group. Furthermore, the organ-to-body ratio and liver-to-body ratio of the D2 group were significantly higher than those of the D1 group (P < 0.05). The addition of Cladophora spp. and Chrysophyta laminarin to the D3 group significantly reduced these fat deposition-related indicators (P < 0.05 compared with the D2 group). The above results show that although low fishmeal feed can significantly inhibit the growth performance and feed utilization efficiency of oval pomfret and lead to fat deposition in the viscera and liver, the addition of Cladosporium and Chrysophyll laminarin can effectively alleviate these negative effects, not only restoring the growth performance to the level of the control group, but also significantly reducing fat accumulation in the viscera and liver.

[0075] Test Example 3

[0076] After the growth performance measurements were completed, tissue sampling was performed on 10 juvenile scads randomly selected from each experimental cage. The sampling process involved collecting blood via the tail vein using a sterile syringe containing sodium heparin. The resulting blood sample was centrifuged at 4000 × g for 10 minutes at 4°C to separate serum for biochemical analysis. Liver tissue was also isolated, snap-frozen in liquid nitrogen, and stored for subsequent analysis of liver crude fat content, antioxidant markers, and gene expression levels. In addition, four fish were randomly selected from each cage for whole-body crude fat content determination.

[0077] (1) Antioxidant capacity test

[0078] The collected liver tissue was mixed with pre-chilled saline at a ratio of 1:10 (w / v) and homogenized in an ice bath. The homogenate was centrifuged at 2000 rpm at 4°C for 30 minutes, and the supernatant was collected for analysis of liver antioxidant parameters, including catalase (CAT) and superoxide dismutase (SOD) activities, total antioxidant capacity (T-AOC), and malondialdehyde (MDA) content. These parameters were measured using the corresponding kits purchased from the Nanjing Jiancheng Bioengineering Research Institute, strictly following the manufacturer's instructions. The results are shown in Table 4.

[0079] Table 4 Antioxidant capacity of juvenile pomfret in different treatment groups

[0080]

[0081]

[0082] As shown in Table 4, compared with the control group (D1), the liver SOD, CAT activities, and T-AOC of the oval pomfret in group D2 (low-fishmeal diet) were significantly reduced, while the MDA content was significantly increased (P < 0.05). After the addition of Cladosporium and Laminaria japonica polysaccharides (D3), all antioxidant indices were significantly improved compared with group D2 (P < 0.05), and the SOD, CAT activities, and T-AOC were superior to those of the other experimental groups. These results suggest that a low-fishmeal diet can weaken the antioxidant capacity of fish and induce oxidative damage, but this additive combination can effectively alleviate this negative impact, laying an important foundation for optimizing the functionality of low-fishmeal diets. (two)

[0084] Serum biochemical parameters, including total cholesterol (TC), triglycerides (TG), alanine aminotransferase (ALT), aspartate aminotransferase (AST), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C), were measured using a fully automatic biochemical analyzer (Chemray 240, Rayto Life Science Co., Ltd.). The results are shown in Table 5.

[0085] Table 5 Serum biochemical parameters of juvenile pomfret in different treatment groups

[0086]

[0087] As shown in Table 5, serum levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol, aspartate aminotransferase, and alanine aminotransferase were significantly increased in the low-fishmeal group (D2) compared with the control group (D1) (P < 0.05). The addition of Cladosporium and Chrysophyll laminarin to the low-fishmeal diet (D3) significantly reduced these elevated parameters (TC, TG, LDL-C, AST, and ALT) compared with the D2 group (P < 0.05). Notably, TC, TG, and LDL-C levels in the D3 group were even significantly lower than those in the control group (D1) (P < 0.05). Furthermore, high-density lipoprotein cholesterol (HDL-C) was significantly reduced in the D2 group compared with the D1 group (P < 0.05). However, the addition of Cladosporium and Chrysophyll laminarin (D3) significantly increased HDL-C levels compared with the D2 group (P < 0.05). These results indicate that low-fishmeal feed may lead to increased fat deposition and weakened cholesterol transport capacity, causing blood lipid accumulation and liver damage; however, the addition of Cladosporium and Laminaria japonica polysaccharides can effectively reverse these adverse effects, providing an important basis for the functional improvement of low-fishmeal feed.

[0088] (3) Crude fat levels in liver and whole fish

[0089] Soxtec System HT6 Soxhlet fat extraction system was used to quantitatively analyze the crude fat content in the liver tissue (Liver) and whole-body samples of experimental fish. The results are shown in Figure 1 .

[0090] like Figure 2 As shown, compared with the control group (D1), the crude fat content of liver tissue and whole fish in the low-fishmeal group (D2) was significantly increased (P>0.05). When Cladosporium and Laminaria japonica polysaccharides were added to the low-fishmeal diet (D3), these indices were significantly reduced compared with the D2 group (P>0.05) and returned to levels comparable to those in the D1 group (P>0.05). This suggests that the composite additive can effectively regulate lipid metabolism in fish and alleviate the abnormal fat accumulation induced by the low-fishmeal diet.

[0091] (IV) Transcription levels of lipolysis-related genes in the liver

[0092] Liver samples of juvenile pomfret in each cage were collected and RNA was extracted using Trizol reagent (TaKaRa, Dalian, China) according to the manufacturer's instructions. The concentration and purity of the extracted RNA were then quantified using a Nanodrop 2000 spectrophotometer (Thermo, Wasserhaus, USA) and further confirmed by 1% agarose gel electrophoresis. TMTotal RNA was reverse transcribed into cDNA using a RT assay kit (TaKaRa, Dalian, China) and prepared for qRT-PCR analysis. The qRT-PCR procedure and specific primer sequences used were based on the reference "Impacts of dietary konjac glucomannan supplementation on growth, antioxidant capacity, hepatic lipid metabolism and inflammatory response in golden pompano (Trachinotus ovatus) fed a high fat diet" (Li Yang, Luang Shusheng, Shao Yiru, Li Yuanyou, Chen Cuiying, You Cuihong, Monroig Oscar, Rahimnejad Samad, Tocher Douglas R., Wang Shuqi. Impacts of dietary konjac glucomannan supplementation on growth, antioxidant capacity, hepatic lipid metabolism and inflammatory response in golden pompano (Trachinotus ovatus) fed a high fat diet[J]. Aquaculture, 2021, 545, 737113). -ΔΔCt Methods The expression levels of target genes were calculated, and all results were normalized with the expression of the housekeeping gene β-actin to ensure consistency and accuracy.

[0093] The results are as follows Figure 3As shown in the results, compared with the control group (D1), the transcription levels of fat transport-related genes (apolipoprotein B100 (apob100), fatty acid translocase 36 (cd36), fatty acid binding protein 1 (fabp1)) and lipolysis-related genes (peroxisome proliferator-activated receptor α (pparα), carnitine palmitoyltransferase 1 (cpt1), hormone-sensitive lipase (hsl)) in the liver tissue of the low fish meal group (D2) were significantly decreased (P<0.05); after the addition of Cladosporium-Chrysophyte Laminaria polysaccharide complex to the low fish meal feed (D3 group), the expression levels of the above genes were significantly increased compared with the D2 group (P<0.05), and even significantly higher than those in the D1 group (P<0.05), indicating that the compound additive effectively reversed the transcriptional inhibition of liver lipid metabolism genes induced by the low fish meal feed by synergistically activating the fatty acid transport and decomposition pathways, thereby inhibiting the formation of fatty liver.

[0094] In summary, it can be seen that fish meal and high-fat feed (D2 group) has many significant disadvantages in the farming of oval pomfret, specifically, low fish meal and high fat feed increases the burden of liver lipid metabolism, which in turn leads to inhibited growth performance, reduced survival rate, severe deposition of fat in the viscera and liver, decline in antioxidant capacity, dyslipidemia and obvious liver damage, forming a typical "low fish meal-high fat-liver damage" vicious cycle, posing a serious threat to fish health and farming benefits; and the composite additive scheme of Cladoscelis SYSU-A2024-1 and golden algae kelp polysaccharide (D3 group) provided by the present invention, under the same low fish meal and high fat basic feed conditions, showed excellent improvement effects, significantly reversed growth inhibition, efficiently alleviated fatty liver, strongly enhanced antioxidant defense, comprehensively improved lipid metabolism and liver function, and activated lipid decomposition metabolism pathways. The low-fishmeal feed for silver carp containing the composition of the cladocerus SYSU-A2024-1 and golden algae laminarin described in the present invention fundamentally solves the lipid metabolism disorder and liver health crisis caused by the low-fishmeal and high-fat feed for silver carp. It not only solves the growth and health problems caused by the low-fishmeal feed, but also significantly improves the feed conversion rate and reduces the incidence and mortality rate by improving the lipid utilization efficiency of silver carp and improving the health of silver carp. It provides a natural, efficient, comprehensively controllable and easy-to-scale innovative solution for the healthy, efficient and sustainable breeding of silver carp under the background of limited fishmeal resources.

[0095] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A Cladosporium SYSU-A2024-1 rich in astaxanthin, characterized in that: The classification name is Oedocladium sp.SYSU-A2024-1, and it was deposited in the China Center for Type Culture Collection on June 3, 2024, with the deposit address being Wuhan University, Wuhan, China, and the deposit number is CCTCC NO:M20241138.

2. A composition comprising chrysophyte laminarin and the cladodesmacus SYSU-A2024-1 of claim 1, characterized in that: The mass ratio of the cladosa SYSU-A2024-1 and the golden algae laminarin is (8-12):

1.

3. Use of the composition according to claim 2 in preparing a low-fishmeal feed for aquatic animals for improving liver health.

4. Use of the composition according to claim 2 in preparing a low-fishmeal feed for aquatic animals for improving growth performance.

5. Use of the composition according to claim 2 in preparing a low-fishmeal feed for aquatic animals for improving lipid utilization.

6. A low-fishmeal feed for oval pomfret, characterized in that: The invention comprises the following components in parts by weight: 55-63 parts of a protein source, 20-23 parts of a sugar source, 10.5-15.5 parts of a fat source, 0.5-1.5 parts of calcium dihydrogen phosphate, 0.8-1.2 parts of complex vitamins, 0.8-1.2 parts of complex minerals, 0.8-1.2 parts of single vitamins, 1.55-1.7 parts of essential amino acids, and 0.42-0.68 parts of the composition according to claim 2; The protein source includes fish meal, soybean meal, soy protein isolate and chicken meal in a mass ratio of (16-19):(21-22):(6-8):(12-14).

7. Use of the low-fishmeal feed for oval pomfret according to claim 6 in improving lipid utilization, improving liver health and improving growth performance of oval pomfret.

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