Feed for aquaculture

Abstract

This invention provides aquaculture feed with a high nitrogen content, which serves as an indicator of protein content. [Solution] The present invention provides a feed for aquaculture that contains crushed marine purple photosynthetic bacteria and has a nitrogen content of 8.0% by mass or more.

Description

Technical Field

[0001] The present invention relates to a feed for aquaculture.

Background Art

[0002] Many aquaculture feeds are manufactured using fish meal as a raw material. In recent years, due to the unstable catch of natural fish used as raw material for this fish meal and the soaring price of fuel required for fishing, attempts have been made to manufacture aquaculture feeds without using fish meal. As a method of manufacturing feed without relying on fish meal, a method of manufacturing feed using photosynthetic bacteria has been developed.

[0003] For example, Patent Document 1 discloses an aquaculture feed containing green sulfur bacteria as an active ingredient. According to Patent Document 1, such an aquaculture feed is said to be optimal as a feed additive for fish.

Prior Art Documents

Patent Documents

[0004] [[ID=J=26]]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, the problem of increasing the protein content of aquaculture feed has not been found, and it is considered that a high-protein aquaculture feed has not been provided yet. The problem to be solved by the present invention is to provide an aquaculture feed with a high protein content.

Means for Solving the Problems

[0006] As a result of diligent research to solve the above problems, the inventors of this invention discovered that aquaculture feed with a high protein content can be produced by using marine purple photosynthetic bacteria, and thus completed the present invention.

[0007] In other words, the present invention is as follows. [1] Aquaculture feed containing crushed marine purple photosynthetic bacteria and having a nitrogen content of 8.0% by mass or more. [2] The aquaculture feed according to [1], wherein the crushed marine purple photosynthetic bacteria are dried. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide aquaculture feed with a high protein content. [Brief explanation of the drawing]

[0009] [Figure 1] The feeding plan for the growth trial is shown. [Figure 2] This shows the survival rate of medaka fish. The minimum control and control groups were fed Otome B-2, while the example group (Photo B) was fed the aquaculture feed Photo B prepared as described above (n=17). [Figure 3](A) Changes in body length and (B) body weight of medaka are shown. The minimum control and control groups were fed Otome B-2, while the example group (Photo B) was fed the aquaculture feed Photo B prepared as described above. The sample size at the start of feeding was 17 for the minimum control, control, and example groups, and the sample sizes two weeks after the start of feeding were 14, 17, and 17, respectively. The bars in the graph represent the median. Differences between groups due to feeding period were analyzed using the Mann-Whitney U test, and differences between test intervals due to feeding feed were analyzed using one-way ANOVA and Dunnett's test. "*" and "**" indicate a statistically significant difference at the 5% and 1% significance levels, respectively. "ns" indicates no statistically significant difference at the 5% significance level. [Figure 4] These are photographs showing the typical appearance of medaka at the start of feeding and two weeks after the start of feeding. In the Minimum Control and Control groups, Otome B-2 was given, while in the Example (Photo B), the aquaculture feed Photo B prepared as described above was given. [Modes for carrying out the invention]

[0010] [Aquaculture feed] The aquaculture feed of this embodiment contains crushed marine purple photosynthetic bacteria and has a nitrogen content of 8.0% by mass or more. The aquaculture feed of this embodiment is a high-protein aquaculture feed that does not rely on raw materials derived from natural fish such as fishmeal. In this embodiment, a high protein content is achieved by having a nitrogen content of 8.0% by mass or more. In other words, in aquaculture feed, nitrogen content is an indicator of the protein content in the feed, and the higher the nitrogen content, the higher the protein content tends to be. For example, in official analytical methods such as the Japanese Standard Tables of Food Composition Analysis Manual, the crude protein content is estimated from the nitrogen content measured by component analysis using a nitrogen-to-protein conversion factor. While individual nitrogen-to-protein conversion factors are defined for major foods, in many cases, it is assumed that 16% of protein is nitrogen, and a nitrogen-to-protein conversion factor of 6.25 is used. In other words, in many cases, the crude protein content can be estimated by calculating the product of the nitrogen content and the conversion factor of 6.25. In this embodiment, the aquaculture feed has a nitrogen content of 8.0% by mass or more, but by using a nitrogen-to-protein conversion factor of 6.25, the crude protein content can be estimated to be 50% by mass or more. Thus, although these are estimated values, the fact that the nitrogen content of the aquaculture feed in this embodiment is 8.0% by mass or more means that the protein content of the aquaculture feed is high.

[0011] In the aquaculture feed of this embodiment, the nitrogen content is 8.0% by mass or more, preferably 9.0% by mass or more, and more preferably 10% by mass or more. The upper limit of the nitrogen content is not particularly limited and may be, for example, 30% by mass, 20% by mass, 15% by mass, or 14% by mass. The nitrogen content may be between 8.0% by mass and 30% by mass, and within this range, the lower and upper limits may be arbitrarily selected. The nitrogen content in aquaculture feed is measured by the dry combustion method and determined as the total nitrogen content in the aquaculture feed.

[0012] Crude protein content can be calculated by dividing the nitrogen content of aquaculture feed by the standard nitrogen content of protein, or by multiplying the nitrogen content by a nitrogen-to-protein conversion factor. For example, the standard nitrogen content is 16%, and the nitrogen-to-protein conversion factor is 6.25. In the feed for aquaculture of the present embodiment, the crude protein content is, for example, 50% by mass or more, more preferably 56% by mass or more, and even more preferably 63% by mass or more. The upper limit value of the crude protein content is not particularly limited, and may be, for example, 88% by mass, 81% by mass, or 75% by mass. The crude protein content may be 50% by mass or more and 88% by mass or less, and within this range, it may also be a range obtained by arbitrarily selecting the above lower limit value and upper limit value.

[0013] (Marine purple photosynthetic bacteria) Purple photosynthetic bacteria can be roughly classified into freshwater purple photosynthetic bacteria and marine purple photosynthetic bacteria according to their habitats. In the present embodiment, marine purple photosynthetic bacteria that inhabit seawater areas are used. Marine purple photosynthetic bacteria are bacteria that can use seawater, nitrogen, carbon dioxide, and light, which are abundant on the earth, for growth. Under near-infrared light, they perform non-oxygen-generating photosynthesis using carbon dioxide and can fix atmospheric nitrogen with nitrogenase. Examples of marine purple photosynthetic bacteria include marine purple sulfur bacteria and marine purple non-sulfur bacteria. Purple sulfur bacteria are bacteria that perform photosynthesis using near-infrared light and grow photoautotrophically in the presence of hydrogen, sulfide, and carbon dioxide. Purple non-sulfur bacteria are photosynthetic bacteria that grow photoheterotrophically in the presence of organic substances and the like.

[0014] Examples of marine purple sulfur bacteria include bacteria of the genera Allochromatium (which may also be written as Allochromatium sp.; the same applies hereafter), Ectothiorhodospira, Halochromatium, Halorhodospira, Marichromatium, Thiocapsa, Thiohalocapsa, and Thiophaeococcus. Examples of marine purple non-sulfur bacteria include bacteria of the genera Rhodobaca, Rhodobacter, Rhodobium, Afifella (Rhodobium), Rhodothalassium, Rhodovulum, and Roseospira.

[0015] Furthermore, examples of marine purple photosynthetic bacteria include those disclosed in PLOS ONE | DOI:10.1371 / journal.pone.0160981. Specifically, the following purple photosynthetic bacteria, disclosed as Table 1 in that paper, are examples of those that inhabit marine environments. The marine red photosynthetic bacterium may be the marine red photosynthetic bacterium described as Organism in Table 1 below. Specifically, it may be Thiohalocapsa marina, Thiophaeococcus mangrovi, Marichromatium bheemlicum, Afifella marina, Rhodovulum euryhalinum, Rhodovulum imhoffii, Rhodovulum sulfidophilum, Rhodovulum tesquicola, Rhodovulum visakhapatnamense, Roseospira marina, or Roseospira goensis. If the classification changes and the bacterial name changes, it may also be the marine red photosynthetic bacterium as the name of the new bacterium. Also, it may be bacteria of the genus Thiohalocapsa, Thiophaeococcus, Marichromatium, Afifella, Rhodovulum, Roseospira, and Roseospira in terms of these genus names.

[0016]

Table 1

[0017] Examples of marine red sulfur bacteria include Marichromatium bheemlicum, Thiohalocapsa marina, and Thiophaeococcus mangrovi. Examples of marine red non-sulfur bacteria include Afifella pfennigii (Rhodobium pfennigii), Afifella marina (Rhodobium marinum), Rhodovulum euryhalinum, Rhodovulum imhoffii, Rhodovulum sulfidophilum, Rhodovulum tesquicola, Rhodovulum visakhapatnamense, Roseospira goensis, and Roseospira marina. The marine purple photosynthetic bacteria used in this embodiment may be marine purple photosynthetic bacteria isolated from the sea off Kyoto from among the above bacterial species, for example, bacteria of the genus Marichromatium. These marine purple photosynthetic bacteria may be obtained from each depositary institution through prescribed procedures. The marine purple photosynthetic bacteria described above may also be mutant strains. Mutant strains include those obtained by genetic methods, such as recombination, transduction, and transformation.

[0018] In this embodiment, it is preferable to use marine purple photosynthetic bacteria that can grow under photosynthetic heterotrophic or photoautotrophic conditions, and R. sulfidophilum is preferably used.

[0019] (Manufacturing of feed for aquaculture) In this embodiment, the crushed marine purple photosynthetic bacteria are produced by the following method, as one embodiment thereof. Marine purple photosynthetic bacteria are cultured under artificial light suitable for photosynthesis and then collected. The collected marine purple photosynthetic bacteria are crushed or crushed and dried to obtain the crushed product of marine purple photosynthetic bacteria in this embodiment. The resulting crushed marine purple photosynthetic bacteria can be used as feed for aquaculture. To obtain the crushed material, in addition to cultivation, bacterial collection, crushing, and drying, one or more processes such as extraction, desalting, granulation, sizing, and acid / alkali treatment may be performed. It is preferable that the marine purple photosynthetic bacteria are included in aquaculture feed as a powder after undergoing crushing and subsequent drying. Feed for aquaculture is preferably granulated or sized depending on the target aquatic product. In this embodiment, each process from culturing marine purple photosynthetic bacteria to obtaining the crushed product can be carried out by combining conventionally known methods as appropriate, but it is preferable to carry it out by the method described below.

[0020] In this embodiment, aquaculture feed with a high nitrogen content, which is an indicator of protein content, can be produced through the cultivation process of marine purple photosynthetic bacteria. In this specification, "cultivation" refers to the process of increasing the number of bacteria and accumulating nutrients such as proteins within the bacterial cells by culturing bacteria under specific conditions. The culture method used in this embodiment can be a method known as a large-scale culture method, but examples include continuous culture methods and batch culture methods. The cultivation of the starter culture and the cultivation of marine purple photosynthetic bacteria to obtain crushed marine purple photosynthetic bacteria can be carried out as appropriate and are not particularly limited, but in this embodiment, it is preferable that the marine purple photosynthetic bacteria are grown by culturing them under specific conditions during the cultivation process.

[0021] The culture may be carried out under the irradiation of near-infrared light, which marine purple photosynthetic bacteria use to grow autotrophically, or under far-red light. Far-red light can be light with a peak wavelength in the range of 700 nm to 860 nm. The method of irradiation with far-red light is not particularly limited; conventional irradiation methods used when culturing marine purple photosynthetic bacteria can be used.

[0022] Regarding the culture time, it should be sufficient to allow the marine purple photosynthetic bacteria to accumulate biomolecules such as proteins, and the culture temperature can be set appropriately according to the optimal culture temperature for marine purple photosynthetic bacteria. For example, the culture temperature may be 20-40°C. Regarding the culture time, for example, the culture may be performed until the intermediate logarithmic growth phase is reached, and then the culture medium may be changed and the culture may be continued until the stationary phase is reached. Regarding the growth of marine purple photosynthetic bacteria, the absorbance at 660 nm (OD) is used. 660 The measured optical cell density in ) may also be used as an indicator.

[0023] Cultivation can be carried out under suitable atmospheric conditions, but by carrying it out under nitrogen-containing conditions, nitrogen from the atmosphere can be fixed, and a nitrogen-rich feed for aquaculture can be provided without adding a nitrogen source to the culture medium. The nitrogen concentration in the culture medium may also be increased by bubbling nitrogen gas into it.

[0024] The culture medium used is not particularly limited as long as it is a medium capable of culturing marine purple photosynthetic bacteria; conventionally known growth media may be used. The culture medium used is not particularly limited, but natural seawater may be used, or a seawater-based medium utilizing natural seawater may be used. The growth medium may contain an organic carbon source or an inorganic carbon source. If an inorganic carbon source is present, the medium does not need to contain an organic carbon source. In this embodiment, carbon fixation may be promoted by culturing in a culture medium in which an inorganic carbon source is preferably used, and in some cases, an organic carbon source is not used. Examples of organic carbon sources include carbohydrates such as glucose, fructose, sucrose, and molasses containing these, starch, and starch hydrolysates; organic acids such as acetic acid and propionic acid; and alcohols such as ethanol and propanol. Examples of inorganic carbon sources include carbon dioxide, carbonate ions, bicarbonate ions, and carbon monoxide. Carbonate ions and bicarbonate ions may be added to the culture medium as metal salts. Carbon dioxide and carbon monoxide may be bubbled together with or separately from nitrogen gas. If the culture atmosphere contains nitrogen, the growth medium does not need to contain a nitrogen source. The growth medium may contain a nitrogen source. Examples of nitrogen sources include ammonia, ammonium salts of inorganic or organic acids such as ammonium chloride, ammonium sulfate, ammonium acetate and ammonium phosphate, other nitrogen-containing compounds, as well as peptone, meat extract, yeast extract, corn steep liquor, casein hydrolysate, soybean meal and soybean meal hydrolysate, various fermentation microorganisms and their digests. For organic carbon sources, inorganic carbon sources, and nitrogen sources, one type may be used, or two or more types may be used.

[0025] The growth medium may further contain inorganic salts. Examples of inorganic salts include monopotassium phosphate, dipotassium phosphate, magnesium phosphate, magnesium sulfate, sodium chloride, sodium thiosulfate, ferrous sulfate, manganese sulfate, copper sulfate, and calcium carbonate.

[0026] Suitable culture media include, for example, the Marine Broth medium described in the examples. Alternatively, nutrient-poor media may be used. Examples of nutrient-poor media include, for example, M6 medium and media prepared by adding appropriate additives to natural seawater. Additives that may be added to natural seawater include, for example, lignin-containing wastewater discarded during the papermaking process of Japanese paper (so-called lignin wastewater), sodium thiosulfate, and the nitrogen source mentioned above.

[0027] The composition of M6 medium is, for example, 5g sodium malate; 0.75g KH2PO4; 0.78g K2HPO4; 0.029g CaCl2·2H2O; 0.247g MgSO4·7H2O; 1g (NH4)2SO4; 0.011g FeSO4·7H2O; 10mL vitamin solution; 10μL trace element solution. Here, the composition of the vitamin solution per 100mL is 0.1g nicotinic acid, 0.1g thiamine, 0.005g biotin, 0.05g para-aminobenzoic acid, and vitamin B. 12The amounts are 0.001g of nitrate, 0.05g of vitamin B5, 0.05g of pyridoxine hydrochloride, 0.2g of EDTA-3Na, 0.05g of folic acid, 70μg of ZnCl2-5H2O, 100μg of MnCl2-4H2O, 360μg of H3BO, 200μg of CoCl2-6H2O, 20μg of CuCl2-2H2O, 20μg of NiCl2-6H2O, and 40μg of Na2MoO4-H2O. Furthermore, the trace element composition per liter is as follows: MnSO4·4H2O 11.16g, ZnSO4·7H2O 2.88g, Co(NO3)2·6H2O 2.92g, CuSO4·5H2O 2.52g, Na2MoO4·2H2O 2.42g, H3BO3 3.10g, and EDTA·3Na 41.20g.

[0028] Marine purple photosynthetic bacteria are cultured under artificial light suitable for photosynthesis, and then preferably collected by harvesting and washing. During collection, the bacteria may be washed before collection, or they may be collected first and then washed. Collection may be performed from one or more culture tanks. Furthermore, collection and washing may be repeated multiple times. The recovery of marine purple photosynthetic bacteria can be carried out by conventionally known methods for recovering bacteria from culture media. The washing of marine purple photosynthetic bacteria may also be carried out by suspending the recovered bacterial cells in a desired solution, or by washing while desalting using conventionally known methods such as ultrafiltration. The number of times the marine purple photosynthetic bacteria are collected and / or washed for collection is not particularly limited, but one or more times is sufficient. Acid / alkali treatment may be performed using conventionally known methods to remove salts present in the culture medium or washing solution, or to adjust the pH of the culture medium or washing solution.

[0029] Marine purple photosynthetic bacteria are included in aquaculture feed as crushed material after being subjected to crushing treatment. Crushing may be carried out, for example, by using an ultrasonic crushing device, a homogenizer, or a bead crushing device, or by enzymatic crushing, or a combination thereof. The crushing treatment may be carried out, for example, by homogenizing the material once or more (for example, 5 to 10 times, preferably 8 times) using a high-pressure homogenizer at a pressure of 800 to 1500 bar.

[0030] When manufacturing feed for aquaculture, drying treatment may be performed. The drying treatment may include, for example, aeration drying using a blower or the like to apply hot or cold air, airless drying by heating to evaporate moisture, spray drying in which the slurry is suspended in a suitable buffer and then sprayed into a gas for rapid drying, freeze-drying, vacuum drying in which the air is removed using a vacuum pump or the like in a sealed container, natural drying (including sun-drying) by leaving it exposed to the open air, or a combination thereof. The drying treatment may be, for example, freeze-drying.

[0031] The crushed marine purple photosynthetic bacteria may be sized by sieving or similar methods after the above treatment, or granulated to an appropriate size. The crushed marine purple photosynthetic bacteria may exist in particulate form after being sized or granulated. The buoyancy and particle size of the crushed marine purple photosynthetic bacteria, which are in particulate form, can be adjusted as appropriate depending on the type and growth stage of the aquatic products being cultivated. For example, when the target is fish, it is preferable to adjust the buoyancy and particle size of the crushed marine purple photosynthetic bacteria when feeding, taking into consideration the size of the fish and whether it is a larva, juvenile, young fish, or adult. In particular, for saltwater fish such as yellowtail and sea bream, a small-particle, floating type is preferred during the juvenile stage, and as the fish matures, it is preferable to increase the particle size and use a sinking type. For freshwater fish such as carp and trout, a floating type is generally preferred. When the target is crustaceans such as shrimp, it is generally preferable that the material sinks, and that it maintains its shape well so that it can be picked up with claws. The particle size of the crushed marine purple photosynthetic bacteria may be, for example, 2.8 mm or less, 2.0 mm or less, or 1.2 mm or less. The lower limit of the particle size is not particularly limited and may be, for example, 0.1 mm or more, 0.3 mm or more, or 0.5 mm or more. The particle size may be between 0.1 mm and 2.8 mm, and within this range, the lower and upper limits may be arbitrarily selected to obtain the desired range.

[0032] The aquaculture feed of this embodiment is preferably obtained as a solid feed. The crushed marine purple photosynthetic bacteria may be used alone as aquaculture feed, or they may be combined with other components and processed as needed to form aquaculture feed. The aquaculture feed of this embodiment may be used in combination with conventionally known aquaculture feeds.

[0033] [Aquaculture Methods] One aspect of this embodiment is a method for cultivating aquatic products, i.e., fish and shellfish, using the above-described aquaculture feed. In this method, examples of target fish and shellfish are as follows, and the aquaculture feed may be any of the embodiments described above. This method involves feeding aquaculture feed to fish and shellfish. The aquaculture feed in this embodiment may be fed at appropriate intervals, for example, once to three times a day.

[0034] The target species for which the aquaculture feed of this embodiment is given is not particularly limited, and may include, for example, fish and shellfish, such as various fish, shellfish, and crustaceans. Specifically, examples include the family Adrianichthyidae (e.g., Japanese rice fish), the family Balistidae (e.g., filefish), the family Tetraodontidae (e.g., tiger pufferfish), the family Anguillidae (e.g., eel), the family Sparidae (e.g., red sea bream), the family Pleuronectidae (e.g., flounder), the family Soleidae (e.g., flathead flounder), the family Serranidae (e.g., grouper), the family Carangidae (e.g., horse mackerel, yellowtail), the family Scombridae (e.g., mackerel, tuna, skipjack tuna), and shrimp. The organisms to be raised may be fish, for example, the family Adrianichthyidae (especially medaka), the family Monacanthidae (especially filefish), or shrimp, or any of these. The target fish for growth may be larvae, juveniles, young fish, or adult fish. The aquaculture feed of this embodiment can be fed at appropriate intervals, for example, once to three times a day.

[0035] The aquaculture feed of this embodiment may promote the growth of the target fish and shellfish. The aquaculture feed of this embodiment may promote growth, that is, it may shorten the period in which larvae, juveniles, and young fish mature and transition to the next stage, and may increase the weight and / or length of adult fish. [Examples]

[0036] The present invention will be described more specifically below using examples and comparative examples. The present invention is not limited in any way by the following examples.

[0037] (Bacterial culture) The marine purple photosynthetic bacterium R. sulfidophilum was obtained from the American Type Culture Collection (ATCC). Marine Broth 2216 medium (Sigma Aldrich) was used to culture marine purple photosynthetic bacteria. The composition of Marine Broth medium per liter was as follows: NH4NO3 1.6 mg, H3BO3 22.0 mg, CaCl 2 1.8 g, Na2HPO4 8.0 mg, ferric citrate 0.1 g, MgCl 2 5.9 g, MgSO4 3.24 g, peptone 5.0 g, KBr 0.08 g, KCl 0.55 g, NaHCO3 0.16 g, NaCl 19.45 g, NaF 2.4 mg, sodium silicate 4.0 mg, SrCl2 3 4.0 mg, yeast extract 1.0 g.

[0038] For the preparation of the inoculum culture, one agar culture colony of bacteria was cultured in 50 mL of Marine Broth 2216 medium in a sterile screw-cap tube (under atmospheric conditions). Absorbance at 660nm (OD 660Until the optical cell density in ) reaches 1 to 1.5 (intermediate logarithmic growth phase), use far-red light LEDs (730nm, 20Wm). -2 The culture was maintained under static conditions at 30°C using a CCS (Cellular Control System). Next, the culture was transferred to 0.5-1 L of Marine Broth medium and maintained under the same conditions while stirring with a magnetic stirrer at a stirring speed of 200 rpm until the cells reached the intermediate logarithmic growth phase. After that, the culture was transferred to 10 L of Marine Broth medium and stirred at a stirring speed of 450 rpm until the cells reached the stationary phase (OD). 660 The cells were cultured under the same conditions until the optical cell density reached 1.8–2.0.

[0039] (Manufacturing of feed for aquaculture) Aquaculture feed (hereinafter referred to as "Photo B") was manufactured using bacteria cultured as described above. First, bacteria cultured for 6 days were collected by centrifugation, and the resulting pellets were suspended in 1.5 mL of distilled water per 1 g FW. The suspension was homogenized eight times at 1000 bar using a high-pressure homogenizer Panda Plus 1000, and then freeze-dried for 36 to 48 hours. Next, it was thawed at 4°C for 12 to 16 hours, and then freeze-dried again for more than 24 hours. The resulting freeze-dried material was crushed and sieved to the following particle sizes: 1.2 mm or less, 1.2 to 2.0 mm, and 2.0 to 2.8 mm.

[0040] (component analysis) The aquaculture feed with a particle size of 1.2 mm or less obtained in this manner was subjected to the following analysis. The results of the component analysis are shown in Table 2, along with the values ​​indicated in the component table of Otohime B-2 (manufactured by Nisshin Marubeni Feed Co., Ltd.), a commercially available feed used as a control in the growth experiment described later. The nitrogen content of Otohime B-2 was calculated from the crude protein content listed in the component table, assuming a standard nitrogen content of 16% for protein. Similarly, the crude protein content of Photo B above was calculated from the nitrogen content, assuming a standard nitrogen content of 16% for protein. The content of each component in Table 2 is shown in mass percent. • Total nitrogen: Dry combustion method • Total phosphoric acid: Nitrate decomposition (microwave decomposition) and spectrophotometric method (ammonium vanadomolybdate method) • Total potassium: Nitrate decomposition (microwave decomposition) and atomic absorption spectrophotometry

[0041] [Table 2]

[0042] (Growth experiment) A growth trial was conducted using the feeding plan shown in Figure 1. The minimum control group was given 2 mg (=0.16 mgN) of Otohime B-2 (manufactured by Nisshin Marubeni Feed Co., Ltd.) per medaka fish every two days. The control group was given 2 mg (=0.16 mgN) of Otohime B-2 (manufactured by Nisshin Marubeni Feed Co., Ltd.) per medaka fish every two days. In the example (Photo B), 2 mg (=0.16 mgN) of Otohime B-2 (manufactured by Nisshin Marubeni Feed Co., Ltd.) per medaka fish every two days, and the feed prepared as described above (sieved to 1.2 mm or less) was given 2 mg (=0.22 mgN) per medaka fish every two days, three times a day.

[0043] Figure 2 shows the survival rate of medaka after two weeks of continuous feeding. In the minimum control group, the survival rate decreased over time, while in the control group and the example group containing marine purple photosynthetic bacteria, the survival rate was 100%. Furthermore, no contamination (unexpected bacterial growth) from marine purple photosynthetic bacteria was observed.

[0044] Furthermore, Figure 3 shows the changes in body length and weight of the medaka after two weeks of continuous feeding. It was found that when the medaka were fed the feed containing marine purple photosynthetic bacteria, their growth was promoted on average compared to the minimum control group. Figure 4 shows representative photographs of medaka taken at the start of feeding and two weeks after the start of feeding.

[0045] Similarly, filefish were fed aquaculture feed containing the marine purple photosynthetic bacteria produced as described above. As with medaka, favorable growth effects were obtained in filefish as well. Furthermore, the aquaculture feed containing the marine purple photosynthetic bacteria produced as described above can also be used in the cultivation of pufferfish and shrimp. From these results, it was found that marine purple photosynthetic bacteria can be used to suitably produce feed for aquaculture. [Industrial applicability]

[0046] The aquaculture feed of the present invention is expected to be supplied as a new alternative to fishmeal as a feed ingredient, thereby preventing the destruction of marine resources and ecosystems due to overfishing of wild fish, promoting sustainable next-generation aquaculture, and revitalizing local and Japanese fisheries.

Claims

1. Aquaculture feed containing crushed marine purple photosynthetic bacteria and having a nitrogen content of 8.0% by mass or more.

2. The aquaculture feed according to claim 1, wherein the crushed marine purple photosynthetic bacteria are dried.

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