Feed for anadromous fish, method for producing the same, method for increasing seawater tolerance, growth, and feeding of anadromous fish, and fish feed used for preventing or reducing the severity of cataracts

Abstract

A fish feed for feeding anadromous fish in fresh water contains arginine in free amino acid form or dipeptide form, 0.1 to 7 wt% of histidine in free amino acid form or dipeptide form, and 0.2 to 5 wt% of Na+. The fish feed can be fed to anadromous fish to promote growth in fresh water and / or seawater periods, to promote feeding, and / or to prevent or reduce the severity of cataracts.

Description

Technical Field

[0001] The present invention relates to a feed for upstream fish, a method of using the feed, and a method of making the feed.

Background Art

[0002] Fish is an important source of protein for the world's population. It is recognized that per capita fish consumption should increase due to its beneficial effects on health.

[0003] However, due to the impact on fish resources, it is no longer possible to increase wild catches. Some resources of wild fish have already decreased sharply, and for other resources, the catch must be reduced in order for the resources to be sustainable.

[0004] Therefore, aquaculture (fish farming) is increasing in importance in supplying fish to the world's population.

[0005] Fish require protein, fat, minerals, and vitamins for growth and good health. The feed for carnivorous fish such as salmonids is particularly important.

[0006] Originally, in the farming of carnivorous fish, whole fish or minced fish was used to meet the nutritional requirements of the farmed fish. Minced fish mixed with various types of dry raw materials such as fish meal and starch was called soft or semi-moist feed. As aquaculture became industrialized, soft or semi-moist feed was replaced by compressed and shaped dry feed. This in turn has gradually been replaced by extruded dry feed.

[0007] Today, extruded feed is almost common in the farming of salmonids.

[0008] The main protein sources in fish dry feed are fish meals of different qualities. Fish meal and fish oil are obtained from so-called "industrial fish". The catch of industrial fish cannot be increased. Industrial fish can be, for example, fish caught off the coasts of northern Europe or South America, particularly off Peru and Chile. The production volumes of these countries vary to some extent every year. At intervals of about seven years, the El Niño weather phenomenon occurs, significantly reducing the production volume of industrial fish. This affects the availability of fish meal and fish oil on the world market, and the prices of these raw materials rise significantly.

[0009] For several years, the aquaculture industry and particularly the fish feed industry have predicted that there will be a relative shortage in the future for the demand for both fish meal and fish oil.

[0010] Other animal protein sources are also used in fish dry feed. Therefore, it is known to use blood meal, bone meal, feather meal, and other types of meals produced from other meat processing plant wastes, such as chicken meal. These are typically cheaper than fish meal and fish oil. However, in some regions such as Europe, there are regulations on the use of such raw materials in the production of feed for food-producing animals and fish. Insect powder and proteins from microorganisms and microalgae biomass are also known for this purpose, and macroalgae may be used in the future.

[0011] It is also known to use vegetable proteins, such as wheat gluten, corn gluten, soybean-based products, lupin meal, pea meal, soybean meal, rapeseed meal, sunflower meal, distillers dried grains with solubles (DDGS), fava bean products, and rice flour. Soybeans are low-cost raw materials with a high protein content and are available in very large quantities worldwide. Therefore, soybeans have been used in fish feed for many years.

[0012] Therefore, there is pressure to minimize the quantity of raw materials used in fish feed for aquaculture.

[0013] In addition, aquaculture is capital intensive. There is investment in cages, pens, or ponds, feeding robots, storage facilities, and other infrastructure. Since the fish are either purchased as juveniles (e.g., trout and salmon species) or caught wild, the fish themselves have associated costs.

[0014] The most important single cost in aquaculture is the cost of feed. Labor costs are also important.

[0015] The selling price of the fish and the number of fish harvested determine the profitability of the operation.

[0016] A faster turnover has several beneficial results. First, it helps cash flow. Second, it improves risk management. Fish diseases are common, and the likelihood of an outbreak is higher during long growth periods. There is also the risk that the fish will escape, for example, due to an accident when moving nets or due to bad weather that causes the destruction of the fish pens.

[0017] The turnover rate is determined by how quickly the fish grow to a harvestable size. As an example, it takes 12 - 18 or even 24 months to grow Atlantic salmon from smolt (the seawater transfer stage discussed in more detail below) to a harvestable size. The harvestable size depends on the fish species and the market. Some markets for Atlantic salmon prefer fish larger than 6 kg. Rainbow trout are sold in portion sizes in some markets, with a weight of 300 g. Larger rainbow trout are also farmed.

[0018] Growth rate is expressed as the daily percentage increase in body mass (specific growth rate, SGR). This is calculated as follows.

Equation

[0019] SGR does not take into account the amount of feed that is fed to obtain growth. It is a measure of growth rate only. A high SGR is dependent on the digestibility of the raw materials and how optimal the feed composition is with respect to the ratio of protein and fat, amino acid composition, as well as fatty acid composition. Trace components such as vitamins and minerals must also be present in sufficient quantities.

[0020] Therefore, it is desirable to produce fish feed that results in a good (high) SGR. A high feed intake, body weight, and weight gain are also all desirable.

[0021] For anadromous fish of the Salmonidae family, special consideration of feed applies. Anadromous fish hatch in fresh water and spend their juvenile stage in fresh water, but after smoltification (i.e., reaching the physiological stage of smolts where they can first migrate from fresh water to sea water), they move to brackish water and possibly sea water with the highest salinity concentration. The fish return to fresh water for spawning. Salmonidae refers to species belonging to the family Salmonidae. Examples of Salmonidae fish are salmon species such as the Atlantic salmon (Salmo salar) and trout species such as rainbow trout.

[0022] The smolt transformation of anadromous fish involves changes in behavior, morphology, and physiology that are preparations for migration and seaward movement and will improve its success.

[0023] Smoltification in aquaculture can be achieved by light manipulation, i.e., lighting management systems. Conventional methods are the "winter signal", i.e., part of the day is light and part of the day is dark, e.g., about 12 hours of dark and about 12 hours of light per day. However, the winter signal (i.e., keeping the fish in the dark for a period of the day) reduces the feed intake and thus growth compared to other lighting management systems, especially 24:0, i.e., continuous lighting. It is desirable to develop other feed and feeding methods that support feeding and / or growth during the freshwater period, for example using specific feeds.

[0024] Patent document 1 of Aquabio Products Sciences LLC (relating to a feed product known as "SUPERSMOLT") discloses a smoltification method that requires both a feed containing sodium salts and a polyvalent cation receptor regulator (PVCR), and the addition of Ca 2+ and Mg 2+ ions to water. The preferred PVCR is tryptophan in free amino acid form. Feeds containing histidine in free amino acid form as PVCR were tested but reported to give poor results (Table 19). This document outlines the physiology of smoltification.

[0025] Patent document 2 of Europharma A / S (relating to a feed product known as "SUPERSMOLT FeedOnly" and developing the initial SUPERSMOLT research) discloses a fish feed useful for a method for preventing smoltification and desmoltification in Salmonidae, and includes sodium salts, magnesium salts, and calcium salts, and a polyvalent cation receptor regulator (PVCR) that can be tryptophan in free amino acid form.

[0026] In the commercial farming of salmon and rainbow trout, it is well known that when they are suitable for seawater as smolts and migrate from fresh water to seawater, the fish lose their appetite. This is a stressful period and is associated with high mortality. The fish can be inactive for several weeks after migration. For fish farmers, this means a loss of growth. In particular, since growth has a daily compounding effect, it takes longer to bring the fish to a size suitable for slaughter. Therefore, in fish farming, there is a need for feed that is readily accepted by fish that have recently migrated to seawater.

[0027] Patent Document 3 of the applicant company group discloses a fish feed produced by extrusion molding and containing at least 3 weight percent of arginine. Some of the arginine can be provided in the form of free amino acids, for example, by adding 1 wt% of arginine crystals. The feed is used to prevent the growth decline of salmonids during the migration from fresh water to seawater. This document contains a review of the literature on the arginine requirements of salmon.

[0028] In addition, salmonid fish are prone to developing cataracts in their eyes (clouding of the lens and / or lens capsule). This can lead to a decrease in vision and cause a decrease in feeding. Patent Document 4 of BioMar Group discloses a feed for salmonid fish for reducing cataracts containing at least 1.15 wt% of histidine.

Prior Art Documents

Patent Documents

[0029]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0030] For example, it is desirable to develop a feed and feeding method, especially for the fresh water period, that uses a specific feed to reduce cataracts and / or support feeding and / or growth during the seawater period.

Means for Solving the Problems

[0031] The present invention relates to a fish feed for feeding anadromous fish in fresh water, which contains arginine in the free amino acid form or dipeptide form, 0.1 to 7 wt% of histidine in the free amino acid form or dipeptide form, and 0.25 to 5 wt% of Na + .

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3-1

Figure 3-2

Figure 4

Figure 5-1

Figure 5-2

Figure 5-3

Figure 6-1

Figure 6-2

Figure 6-3

Figure 7

Mode for Carrying Out the Invention

[0033] In a first aspect, the present invention relates to a fish feed for feeding anadromous fish in fresh water, wherein arginine is in the free amino acid form or dipeptide form, preferably in the free amino acid form, histidine is in the free amino acid form or dipeptide form, preferably in the free amino acid form, and 0.2 to 5 wt% of Na + is included.

[0034] Preferably, the fish feed contains 0.3 to 4.5 wt%, more preferably 0.4 to 4 wt%, even more preferably 0.6 to 3.5 wt%, for example 0.8 to 3 wt%, or 1 to 2.5 wt% of Na + is included.

[0035] Preferably, at least a part of the Na + is added to the feed in the form of NaCl, more preferably in the form of 1 to 10 wt%, or preferably 3 to 8 wt% of NaCl.

[0036] As used herein, the term "fish feed" includes the following compositions. Typically, fish feed includes fish meal as a component. Preferably, the fish feed is in the form of flakes or pellets, such as extruded pellets. Preferred pellet sizes (diameter) range from 1.5 to 6 mm, for example 2 to 5.5 mm, 2.5 to 5 mm, 3 to 4.5, or 3.5 to 4 mm.

[0037] References to the amino acids arginine and histidine each include D and L isomers, racemic or non-racemic mixtures, and their salts. Preferably, L-arginine and L-histidine, or their dipeptides or salts are used.

[0038] Preferably, the amounts of arginine and histidine in free amino acid form or dipeptide form are amounts added in addition to any contribution from unrefined components such as fish meal.

[0039] Preferably, each of arginine and histidine in free amino acid form or dipeptide form is synthetic and / or is provided in a form with a purity of more than 50%. Suitably, histidine may be provided in the form of histidine hydrochloride monohydrate.

[0040] Preferably, the fish feed contains 0.5 to 7 wt%, preferably 0.6 to 5 wt%, more preferably 0.7 to 4 wt%, even more preferably 0.75 to 3 wt%, even more preferably 0.8 to 2 wt%, for example 1 to 1.5 wt% of arginine in free amino acid form or dipeptide form, preferably in free amino acid form, and / or 0.1 to 7 wt%, preferably 0.15 to 5 wt%, more preferably 0.2 to 4 wt%, even more preferably 0.25 to 3 wt%, for example 0.3 to 2 wt%, or 0.35 to 1.5 wt% of histidine in free amino acid form or dipeptide form, preferably in free amino acid form.

[0041] Typically, fish feed, especially fish feed for application during the freshwater period, contains fish meal. Consequently, fish meal contains Ca 2+ ions and Mg 2+ ions. Tacon and Da Silva (Mineral composition of some commercial fish feeds available in Europe. Aquaculture. 1983, vol. 31: 11 - 20) provide an analysis of the mineral composition of 38 commercial fish feeds. Such feeds were found to contain Ca 2+ ions in the range of 2.5 to 37 g / kg and Mg 2+ ions in the range of 0.4 to 3.0 g / kg, preferably 1 to 2.5 g / kg. Suitably, the fish feed of the present invention has such conventional levels of Ca 2+ ions and Mg2+ It may contain ions.

[0042] In certain embodiments, in addition to conventional levels, up to 1 wt% of Ca 2+ salts and / or Mg 2+ salts are added to the feed, preferably, in addition to conventional levels, neither Ca 2+ salts nor Mg 2+ salts are added to the feed.

[0043] In a preferred embodiment, the fish feed contains 0.75 - 1.5 wt% of arginine in free amino acid form or dipeptide form, preferably in free amino acid form, 0.25 - 0.75 wt% of histidine in free amino acid form or dipeptide form, preferably in free amino acid form, and 1 - 3 wt% of Na + and contains.

[0044] Preferably, the anadromous fish are salmonids, more preferably salmon, such as Atlantic salmon.

[0045] Salmonids are so-called oily fish. They require a high-fat diet to remain healthy. They accumulate fat in the fillet. Generally, they can utilize a large proportion of the fat in the feed for energy, and the protein in the feed accumulates in the muscle tissue. This means that a high proportion of the supplied protein is utilized for growth. This is advantageous. Because it gives a favorable ratio between the feed used and the marketable product. Thus, preferably, the fish feed contains at least 15 wt% of lipids, more preferably at least 20 wt% of lipids, such as 20 - 40 wt%, 20 - 35 wt%, or 20 - 30 wt% of lipids. The preferred range is 20 - 35 wt% of lipids.

[0046] Preferably, the fish feed contains a protein level of 30 to 60 wt%, preferably 35 to 55 wt%, more preferably 36 to 54 wt%, even more preferably 37 to 53 wt%, even more preferably 38 to 52 wt%, or 39 to 52 wt%, for example 40 to 52 wt%.

[0047] In a preferred embodiment, the fish feed has a general composition of 30 to 50 wt% protein, 3 to 15 wt% moisture, and the lipids as described above.

[0048] When comparing the nutrient content of different feeds and the types of feeds, it is important to take into account the moisture content. For pelleted and extruded feeds, in a commercial context and also in many scientific papers, it is normal to describe the feed composition on an "as-fed" basis, and this approach is used herein. For feeds containing large amounts and / or varying amounts of water, it is normal to describe the composition on a dry matter basis.

[0049] Preferably, the fish feed comprises one or more of the following: · Protein sources, carbohydrate sources, and lipid sources, discussed in more detail below, · Any binder (e.g., starch. Suitable sources are wheat, potato flour, tapioca flour, soybeans, pea starch, barley, and corn starch), · Vitamin premix, · Mineral premix, and · Colorants (e.g., canthaxanthin, astaxanthin. A mixed colorant source can be used), · Any additional functional components, such as immunostimulants, palatability enhancers, fecal binders.

[0050] Suitable protein sources, carbohydrate sources, and lipid sources include the following: · Fish meal and fish oil · Krill meal and krill oil · Microalgae and macroalgae · Animal powder (e.g., blood meal, feather meal, poultry meal such as chicken meal, bone meal, insect powder, and / or other types of meal produced from other meat processing plant wastes) · Animal fat (e.g., poultry oil) · Vegetable powder (e.g., soybean meal, lupin meal, pea meal, bean meal, rapeseed meal, rice meal, flaxseed meal, sunflower meal) · Vegetable oil (e.g., rapeseed oil, soybean oil, flaxseed oil, sunflower oil) · Gluten (e.g., wheat gluten or corn gluten) · Further additional amino acids (e.g., lysine, methionine).

[0051] In addition, some suitable protein sources, carbohydrate sources, and lipid sources are discussed in the introduction. Fish feed is preferably made by a method comprising the following steps: Mixing the components by a mixer, Extrusion or compression molding of the pellets, and Coating the pellets with oil.

[0052] Preferably, the fish feed is extruded.

[0053] Single - shaft and biaxial extruders are suitable. Preferably, a cooking extrusion process is used. This is typically as follows. The material to be extruded is a mixture of the above - mentioned components and water. Water can be added to the mixture in the form of water or steam. The mixture can be pre - heated by a so - called conditioner. Here, heating is carried out by adding steam to the mixture. Steam and water can also be added to the material within the extruder. In the extruder itself, the pasty material is pushed by a screw towards the die plate at the outlet end of the extruder, further through the die plate to form the desired cross - sectional shape. A rotating blade is usually positioned relative to the outside of the die plate to cut the string coming out of the die hole to the desired length. Usually, the pressure relative to the outside of the die plate will be equal to atmospheric pressure. The extruded product is called an extrusion. Due to the pressure created within the extruder and the addition of steam to the material, the temperature of the material before it is pushed out of the die opening can exceed 100 °C and the pressure will be above atmospheric pressure.

[0054] The cooking extrusion of starch - containing materials causes the starch granules to swell, as a result of which the starch crystals in the granules are released and can dissolve. This is called gelatinization of starch. Starch molecules will form a network and contribute to keeping the extrudate together. Especially in the case of feed for carnivorous fish, starch - containing raw materials are added due to their properties as binders in the finished fish feed. The natural prey for carnivorous fish does not contain starch. Carnivorous fish either do not have or have very little digestive enzymes that can change starch into digestible sugars. The cooking of starch makes it more digestible. This is, in part, because the starch is no longer raw and, in part, because the cooking process initiates the breakdown of starch into smaller sugar units that are easier to digest.

[0055] A further effect of cooking extrusion is that the extrudate becomes porous. This is caused by the pressure drop and temperature drop at the die opening. The water in the extrudate will immediately expand and be released as steam, leaving a porous structure in the extrudate. This porous structure can be filled with oil in later process stages. The extruded feed will typically contain 18 - 30% water after extrusion. After extrusion, this feed undergoes a drying stage and subsequently an oil coating stage. The final product will typically contain approximately 10% or less water and will therefore be stable for storage. This is because the moisture content of such feed is low enough to prevent the growth of bacteria and mold and also avoid bacterial spoilage. After oil coating, the feed is typically cooled and packaged.

[0056] Therefore, the extrudate is different from compression - molded feed. Compression - molded feed means feed produced by feed compression molding. This process is different from extrusion in many respects and is typically as follows. Less water and steam are utilized in the process. The feed mixture is pushed through the die ring from the inside by a roller rotating against the inside of the die ring. The temperature and pressure are lower than in extrusion, and the product is not porous. The process has the effect that the starch is less digestible than after extrusion. Compression - molded feed will typically contain less than 15% water after compression molding and the assumed application of oil. Drying of compression - molded feed is usually not necessary, but post - adjustment can be applied. The feed is cooled before packaging.

[0057] It is common to feed only one type of feed, and in this case, each piece of feed should be nutritionally sufficient. However, two or more types of feed can be used in combination.

[0058] In a second aspect, the present invention relates to a method of feeding anadromous fish in fresh water, which includes feeding the above - mentioned fish feed to the fish over a feeding period.

[0059] As used herein, the term "freshwater" includes water having less than 3000 ppm total dissolved salts, for example, less than 0.05 ppt NaCl.

[0060] As used herein, the term "freshwater" includes water having a total dissolved salt content of less than 1 ppt.

[0061] As with the first aspect of the invention, the fish is preferably a salmonid, more preferably a salmon, most preferably Atlantic salmon.

[0062] Suitably, the feeding period is at least 250 days, preferably at least 350 days, such as at least 450 days, or at least 550 days, or at least 650 days, more preferably at least 750 days, or at least 850 days, at least 950 days, or at least 1000 days. Preferably, the feeding period is in the range of 420 to 1008 days.

[0063] As used herein, the term "daily degrees" (also referred to as "degree-days") refers to the number of days multiplied by the average water temperature in °C. As used herein, the term "seawater" includes water with a high salinity, e.g., brackish water. Seawater can include, for example, brackish water with a dissolved salinity of 3 ppt to 30 ppt, and seawater can include seawater with a maximum concentration of dissolved salinity of 30 ppt to 38 ppt.

[0064] Suitably, the feeding period is at least 5 weeks, preferably at least 12 weeks. The feeding period preferably ends within one week prior to seawater transfer of the fish, but may end earlier, for example 5 weeks prior to transfer. Alternatively, the feeding period may be until seawater transfer of the fish. At an average water temperature of 12°C, 420 days corresponds to 5 weeks, and 1008 days corresponds to 12 weeks.

[0065] An artificial winter signal may be applied during at least a portion of the feeding period and / or a continuous lighting signal may be applied during at least a portion of the feeding period.

[0066] As used herein, the term "winter signal" refers to the use of either light or dark other than continuous 24-hour lighting. Non-limiting examples of winter lighting signals are 6 to 12 hours of light and 18 to 12 hours of dark per day, or 12 to 18 hours of light and 6 to 12 hours of dark per day. Ordinarily, a 12:12 winter signal is used and is considered preferable. The lighting can be artificial lighting (artificial winter signal) or natural lighting (natural winter signal).

[0067] In one preferred embodiment, an artificial winter signal is initially applied, followed by a continuous lighting signal. Preferably, the artificial winter signal is applied for 5 to 9 weeks, for example 7 weeks, and then the continuous lighting signal is applied for 3 to 7 weeks, for example 5 weeks.

[0068] In another preferred embodiment, a continuous lighting signal is applied over the feeding period.

[0069] Further aspects of the present invention include the following: · A method for increasing the seawater tolerance of anadromous fish, comprising feeding the fish according to the above method. · A method for promoting the growth of anadromous fish during the freshwater and / or seawater period, comprising feeding the fish according to the above method. · A method for promoting the feeding of anadromous fish during the freshwater and / or seawater period, comprising feeding the fish according to the above method. · The above fish feed for use in preventing or reducing the severity of cataracts in fish, wherein the fish feed is optionally fed to the fish according to the above method. · A method for preparing the above fish feed, the method comprising mixing the components and optionally extruding pellets of the fish feed, wherein free amino acids are added to the components by mixing and / or overcoating.

[0070] As used herein, "promoting growth" means achieving good growth compared to fish that do not receive test feed.

[0071] Features described in relation to any aspect of the present invention may be used in any other aspect of the present invention.

[0072] The present invention will be further described with reference to non-limiting examples and drawings.

Example

[0073] The tests were carried out at the ARC-Lerang Research Institute for Screening in Norway from November 2020 to May 2021.

[0074] Atlantic salmon with an average starting weight of 40 g were distributed into 100 L experimental tanks. There were 80 fish per tank and 3 tanks per feed ration (24 tanks in total).

[0075] The type of feed, type and temperature of water, feeding time, and lighting management method were as shown in Tables 1 and 2 and Figures 1 and 2. Overall, there was a 3-month period in fresh water, followed by a seawater transition and a 3.5-month period in seawater. Different lighting management methods were used over the first 7 weeks in fresh water (12:12 dark:light i.e. winter signal, or 24:0 lighting i.e. continuous lighting). Thereafter, all groups were on continuous lighting.

[0076] Feeding after seawater transition (when the daily feed intake could not be measured) was targeted at 1.15% of body weight per day. Before seawater transition, the daily feed intake was measured. Reported below.

[0077] The average final weight after 3.5 months in seawater was 381 g.

[0078] [Feed] The feed was produced by extrusion. Arginine and histidine were added to the dry premix.

[0079] The feed used in the example is shown in Table 1.

[0080]

Table 1

[0081] The basic recipe corresponded to the corresponding control recipe with minimal necessary modifications.

[0082] The feed of S+T+Ca+Mg was designed to be similar to the "SUPERSMOLT FeedOnly" feed discussed above.

[0083] <Stage 1: Fresh water, 7 weeks, target weight range 40 - 90 g, initial average fish weight 40 g, final average fish weight 92 g, 2 mm feed> Ctrl 1 - Control Feed A - Basic recipe + 1.25 wt% Arg + 5 wt% NaCl Feed S+H - Basic recipe + 0.5 wt% His.HCl monohydrate (0.37 wt% His) + 5 wt% NaCl Feed S+A+H1 - Basic recipe + 1.25 wt% Arg + 0.5 wt% His.HCl monohydrate (0.37 wt% His) + 5 wt% NaCl (the feed of the present invention)

[0084] <Stage 2: Fresh water, 5 weeks, target weight range 90 - 120 g, initial average fish weight 92 g, final average fish weight 121 g, 2 mm feed> Ctrl 2 - Control Feed S+A+H2 - Basic recipe + 1.25 wt% Arg + 0.5 wt% His.HCl monohydrate (0.37 wt% His) + 5 wt% NaCl (the feed of the present invention) Feed S+T+Ca+Mg - Similar to "SUPERSMOLT FeedOnly", including 0.4 wt% L-Trp + 0.25 wt% MgCl2 + 0.75 wt% CaCl2 + 5 wt% NaCl (comparative example)

[0085] <Stage 3: Seawater, 3.5 months> In seawater for 3.5 months, the Ctrl SW feed according to Table 2.

[0086] The general component analysis of the feed is shown in Table 2.

[0087]

Table 2

[0088] In all treatment management methods, the mortality rates in both the fresh - water and sea - water periods were very low. There were no deaths in the first stage of the fresh - water period (stage 1), 1 - 2 fish per tank in the final stage of the fresh - water period (stage 2), no deaths in the first 6 weeks in sea - water, and 1 fish died in 1 tank during weeks 7 - 12 in sea - water (stage 3). No statistically significant differences were observed among any of the treatment management methods.

[0089] The daily feeding results are shown in Figure 3. The management method Ctrl1 / S+A+H2 / 24:0 gave the best feeding results in fresh - water (1.14% of body weight per day), sea - water (0.91 wt% of body weight), and overall fresh - water and sea - water (1.06% of body weight). These results were better than those of Ctrl1 / S+T+Ca+Mg / 24:0 (1.12%, 0.76%, and 1.00% of body weight per day in fresh - water, sea - water, and overall respectively). The best management methods for feeding with the initial 12:12 lighting were S+A+H1 / S+A+H2 (1.01% of body weight per day overall). Ctrl1 / S+A+H2 also had good results.

[0090] The cumulative feeding results are also shown in Figure 3. The management method Ctrl1 / S+A+H2 / 24:0 gave the best cumulative feeding results in fresh - water (3.153 kg in stage 1. 5.217 kg in overall fresh - water) and sea - water (8.375 kg in the first 6 weeks). These results were better than those of Ctrl1 / S+T+Ca+Mg / 24:0 (3.145 kg, 5.068 kg, and 7.562 kg respectively). The difference in the cumulative sea - water feeding amount was particularly large. Among the management methods with the initial 12:12 lighting, S+A+H1 / S+A+H2 gave good cumulative feeding results in sea - water (7.324 kg).

[0091] The weight results are shown in Fig. 4. The management regime Ctrl1 / S+A+H2 / 24:0 gave the best weight results after day 84. These results were better than Ctrl1 / S+T+Ca+Mg / 24:0. The best management regime for weight at the end of 3.5 months in seawater with initial 12:12 lighting was S+A+H1 / Ctrl2. The management regimes with initial 12:12 lighting were generally better or comparable to Ctrl1 / S+T+Ca+Mg with 24:0 lighting up to day 171.

[0092] The results of weight gain are shown in Fig. 5. Again, Ctrl1 / S+A+H2 / 24:0 gave the best growth results in fresh water (total weight gain in fresh water 92.9 g) and seawater (total weight gain in seawater 282 g). These results were better than the corresponding management regimes by Ctrl1 / S+T+Ca+Mg / 24:0 (90.5 g and 265 g respectively). The best management regime with initial 12:12 lighting was S+A+H1 / Ctrl2. This management regime gave a total weight gain of 79.2 g in fresh water and 261 g in seawater. During the first 6 weeks after seawater transfer (days 85 - 127), the management regime Ctrl1 / S+A+H2 gave a 26% higher weight gain than the control (67 g compared to 53 g). This is important as growth is often poor during this critical post-transfer period as described above.

[0093] The results of the Specific Growth Rate (SGR) are shown in Figure 6. Again, Ctrl1 / S+A+H2 / 24:0 gave the best SGR results in fresh water (1.48%), and better SGR in seawater (0.97% compared to 0.87% for Ctrl1 / S+T+Ca+Mg / 24:0) in the first 6 weeks after transfer (days 85 - 127). The management regime with initial 12:12 lighting and the feeds of the present invention (Ctrl1 / S+A+H2, S+A+H1 / Ctrl2, S+A+H1 / S+A+H2) gave good results for seawater SGR. In the first 6 weeks after seawater transfer (days 85 - 127), Ctrl1 / S+A+H2 gave a 24% higher SGR than the control (1.03% compared to 0.83%). As explained above, this is important as growth is often poor in this critical post-transfer period.

[0094] The cataract results are shown in Figure 7. Again, Ctrl1 / S+A+H2 / 24:0 gave the best cataract results (cataract score 0 in 79% of the fish). These results were better than the corresponding management regime by Ctrl1 / S+T+Ca+Mg / 24:0 (cataract score 0 in 34% of the fish). The best management regime with initial 12:12 lighting was Ctrl1 / S+A+H2. This management regime gave a cataract score 0 in 67% of the fish. This was comparable to the management regime using His-containing feed, i.e., S+H / Ctrl2 (cataract score 0 in 44% of the fish).

[0095] The results of the enzyme NaK ATPase were evaluated. Freshwater samples were analyzed by Sintef Norlab in Norway. All three management regimes by S+A+H2 at stage 2 (fresh water) gave high enzyme activity results on day 84 immediately before seawater transfer. This demonstrated that the fish were adapted to transfer to seawater. These results were better than the corresponding management regime by Ctrl1 / S+T+Ca+Mg / 24:0. Good results were achieved with both lighting management regimes. All the fish were adapted to transfer to seawater.

[0096] The examples show that the feed for freshwater Atlantic salmon according to the preferred embodiments of the present invention has led to good and efficient growth (measured by feed intake, body weight, weight gain, and relative growth rate) in both freshwater and seawater, timely smoltification / good fitness for seawater transfer, and prevention of cataracts. Growth was particularly good during the critical six-week period after seawater transfer. Good results were achieved with both the 12:12 and 24:0 initial lighting management regimes. Feeding the feed of the present invention during the period immediately prior to seawater transfer gave good results. The results were better or equivalent to the management regime by Ctrl1 / S+T+Ca+Mg / 24:0.

[0097] Although the present invention has been described with reference to preferred embodiments, it will be understood that various modifications are possible within the scope of the present invention.

Claims

1. Arginine in free amino acid form or dipeptide form, 0.1-7 wt% histidine in free amino acid form or dipeptide form, and 0.6-5 wt% Na ＋ A fish feed for feeding anadromous fish in freshwater, including [specific ingredient / material].

2. The fish feed according to claim 1, comprising 0.5 to 7 wt%, preferably 0.75 to 2 wt%, of arginine in the form of free amino acids or dipeptides, and / or 0.2 to 1.5 wt% of histidine in the form of free amino acids or dipeptides.

3. Maximum 1 wt% Ca ２＋ salt and / or Mg ２＋ Salt is added to the feed, preferably Ca ２＋ Salt also contains magnesium ２＋ The fish feed according to claim 1, wherein salt is not added to the feed.

4. 0.6–1.25 wt% arginine in free amino acid form, 0.2–0.75 wt% histidine in free amino acid form, and 1–3 wt% Na ＋ The fish feed according to claim 1, comprising:

5. The fish feed according to claim 1, comprising at least 15 wt% of lipids, preferably at least 20 wt% of lipids, and more preferably 20 to 35 wt% of lipids.

6. The fish feed according to claim 1, wherein the fish feed is in the form of extruded pellets.

7. A method for feeding anadromous fish in freshwater, comprising: arginine in free amino acid form or dipeptide form; histidine in free amino acid form or dipeptide form; and 0.6 to 5 wt% Na ＋ A method comprising feeding fish a fish feed containing the following over a feeding period, wherein the fish feed is optionally as described in claim 1.

8. The method according to claim 7, wherein the fish is a salmonid fish, preferably salmon, and more preferably Atlantic salmon.

9. The method according to claim 7, wherein the feeding period is at least 250 days, preferably at least 650 days.

10. The method according to claim 7, wherein artificial and / or natural winter signals are applied for at least a portion of the feeding period, and / or a continuous lighting signal is applied for at least a portion of the feeding period.

11. The method according to claim 10, wherein an artificial winter signal is applied initially, followed by a continuous illumination signal.

12. The method according to claim 10, wherein a continuous lighting signal is applied over the feeding period.

13. A method for increasing the saltwater tolerance of anadromous fish, comprising feeding the fish in freshwater a fish feed containing arginine in free amino acid form or dipeptide form, histidine in free amino acid form or dipeptide form, and 0.25 to 5 wt% of Na+ over a feeding period, wherein the method optionally follows the method of any one of claims 7 to 12.

14. A method for promoting the growth of an anadromous fish in freshwater and / or saltwater seasons, comprising feeding the fish according to the method of any one of claims 7 to 12.

15. A method for promoting feeding of anadromous fish in freshwater and / or saltwater seasons, comprising feeding the fish in freshwater a fish feed containing arginine in free amino acid form or dipeptide form, histidine in free amino acid form or dipeptide form, and 0.25 to 5 wt% Na+ over a feeding period, wherein the method optionally follows the method of any one of claims 7 to 12.

16. Arginine in free amino acid form or dipeptide form, histidine in free amino acid form or dipeptide form, and 0.25-5 wt% Na, used to prevent or reduce the severity of cataracts in fish. ＋ A fish feed comprising, wherein the fish feed is optionally as described in any one of claims 1 to 6, and the fish feed is optionally fed to the fish according to the method described in any one of claims 7 to 12.

17. A method for preparing a fish feed according to any one of claims 1 to 6, wherein the method comprises mixing components and optionally extruding the fish feed into pellets, wherein the free amino acids are added to the components by mixing and / or coating.

18. A method for preparing the fish feed according to claim 17, wherein the arginine and histidine, in free amino acid form or dipeptide form, are provided in a synthetic and / or pure form of more than 50%.

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