Fish feed

Abstract

To provide a fish feed excellent in feedability and capable of simply raising the taste of fish meat in a short period.SOLUTION: A fish feed comprising sodium chloride crystals, wherein a time required for a dissolution rate of the sodium chloride crystals in water to reach 95% is 50 seconds or more and less than 150 seconds.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to fish feed suitable for enhancing the flavor of fish meat. [Background technology]

[0002] In recent years, various methods for improving the flavor of farmed fish by improving the umami of fish meat have been studied. It is known that the umami, sweetness, bitterness, etc. of fish meat are influenced by the amino acid components in the fish meat. One known method for improving the umami of fish meat is to feed fish and shellfish feed containing one or both of D-alanine and DL-alanine, with the aim of improving the umami of the edible parts of the fish and shellfish (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-218339 Summary of the Invention [Problem to be solved by the invention]

[0004] However, feeding amino acids to farmed fish does not necessarily mean that they are efficiently absorbed into the muscles. Simply feeding farmed fish feed containing amino acids to enhance flavor requires a certain period of time to sufficiently improve the amino acid content of the fish meat. Furthermore, during this period, it is necessary to continue feeding special feed containing amino acids different from the normal feed, which is cost-inefficient. Furthermore, long-term flavor enhancement can vary greatly depending on the size of the fish in the fish tank, making it difficult to determine the timing of shipment.

[0005] Furthermore, depending on the ingredients in the feed, the feeding behavior of farmed fish may decrease (hereinafter referred to as "feeding ability"). Therefore, one of the important characteristics of feed for farmed fish is that it has good feeding ability for farmed fish.

[0006] In order to solve the above-mentioned problems, an object of the present invention is to provide fish feed that has excellent feed intake and can easily improve the flavor of fish meat in a short period of time. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result, they have focused on the fact that fish can accumulate amino acids in their muscles by utilizing the mechanism of osmoregulation, and have found that the above-mentioned problems can be achieved by using sodium chloride having specific properties, which has led to the completion of the present invention.

[0008] <1> 1. A fish feed comprising sodium chloride crystals, The fish feed is such that the time required for the sodium chloride crystals to reach a dissolution rate of 95% by mass when added to water is 50 seconds or more and less than 150 seconds. <2> The content of the sodium chloride crystals is 3 to 20 mass% of the total feed. <1> The fish feed according to claim 1. <3> The sodium chloride crystals are rock salt. <1> or <2> The fish feed according to claim 1. <4> The particle size of the sodium chloride crystals is 5 mm or less. <1> ~ <3> The fish feed according to any one of the above. <5> Further, the above-mentioned <1> ~ <3> The fish feed according to any one of the above. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide fish feed that is excellent in feed intake and can easily improve the flavor of fish meat in a short period of time. [Brief explanation of the drawings]

[0010] [Figure 1] 1 shows the results of measuring the 95% dissolution time (change in sodium chloride concentration over time) in an example. DETAILED DESCRIPTION OF THE INVENTION

[0011] 《Fish feed》 The fish feed of this embodiment is a fish feed containing sodium chloride crystals, and the time required for the sodium chloride crystals to reach a dissolution rate of 95% when added to water (hereinafter sometimes referred to as the "95% dissolution time") is 50 seconds or more and less than 150 seconds.

[0012] The fish feed of this embodiment contains sodium chloride crystals with a 95% dissolution time of 50 seconds or more and less than 150 seconds, which makes the fish bite well (feedability) and allows the fish meat to be easily and quickly enhanced in flavor when ingested. Furthermore, because the fish feed of this embodiment uses sodium chloride crystals that satisfy a specific 95% dissolution time, it is possible to achieve excellent feedability and enhance the flavor of fish meat without requiring the feed to have a special structure (for example, a core-shell structure), and therefore can be easily prepared.

[0013] The reason why feeding fish meat with the fish feed of this embodiment can enhance its flavor is that when fish eat the fish feed of this embodiment, the sodium chloride crystals in the feed increase the amount of free amino acids in the cells of the fish (hereinafter, sometimes referred to as "intracellular amino acid content"). This allows the fish feed of this embodiment to enhance the overall flavor of the edible parts of the fish (so-called "enhanced flavor"). Therefore, fish fed with the fish feed of this embodiment have a deliciousness not found in fish (farmed fish or wild fish) that do not eat the fish feed of this embodiment. Here, flavor enhancement is achieved primarily by artificially increasing the amount of amino acids in the muscle and is different from aging (which can increase the amount of inosinic acid by aging fish meat). Therefore, further aging after flavor enhancement is expected to further enhance the synergistic effects of aging in the enhanced-flavored fish. The "edible parts" mentioned above are not particularly limited, but refer to parts that humans typically eat, such as muscle tissue and internal organs other than bone.

[0014] There is no particular reason why the fish feed of this embodiment can improve the flavor of fish meat, but one possible reason is that feeding the farmed fish with feed containing sodium chloride crystals increases the blood osmotic pressure of the farmed fish, which in turn increases the amount of amino acids inside the cells of the farmed fish.

[0015] Furthermore, by using the fish feed of this embodiment, it is possible to easily and inexpensively improve the flavor of farmed fish, etc. For example, by using the fish feed of this embodiment, existing offshore fish pens can be used as they are, and there is no need for a process such as transferring the fish to another tank with an increased salt concentration in the water to improve flavor. Therefore, for example, the labor and expense required to construct a new tank, or the labor and expense required to move farmed fish between the fish pen and the tank, is unnecessary, and further, stress and damage to farmed fish caused by movement between the fish pen and the tank can be prevented. Furthermore, the fish feed of this embodiment can increase the amount of amino acids in the cells of fish in a short period of time, which is advantageous in terms of time and cost compared to methods of continuously feeding fish directly with feed containing amino acids, etc.

[0016] In this specification, "farmed fish" refers to fish that are raised in a fish preserve or the like before shipping, regardless of the length of the period, and are fed the fish feed of this embodiment, and includes wild-caught fish and artificially hatched farmed fish. Furthermore, even wild fish caught at sea (including "livestock") are included in the concept of "farmed fish" in this embodiment, as long as they are fed the fish feed of this embodiment.

[0017] The fish feed of this embodiment will be described below.

[0018] (Sodium chloride crystals) The fish feed of this embodiment contains sodium chloride crystals. The 95% dissolution time of the sodium chloride crystals, i.e., the time required for the dissolution rate of sodium chloride crystals to reach 95% by mass when added to water, is 50 seconds or more but less than 150 seconds. Here, "the time required for the dissolution rate of sodium chloride crystals to reach 95% by mass when added to water" refers to the time required for a certain amount of sodium chloride crystals to dissolve in water at 95% by mass. Specifically, 2.0 g of sodium chloride crystals are added to 20 ml of water at 25°C, and the solution is stirred at a shaking speed of 15 rpm. The salt concentration of the resulting aqueous solution is measured every 10 seconds using a salinity meter. The value (mass%) obtained by dividing the salt content (g) in the aqueous solution by 2.0 g (the original amount of sodium chloride) by 100 is defined as the "dissolution rate of sodium chloride crystals when added to water" (hereinafter, sometimes simply referred to as "dissolution rate"). The time required for the dissolution rate to reach 95% by mass can be considered as the 95% dissolution time.

[0019] When the fish feed of this embodiment is introduced into water (e.g., seawater) to be fed to fish in a fish tank or the like, it is typically ingested by the fish within approximately 10 seconds. If the feed contains sodium chloride particles that are highly disintegrable in water (e.g., sodium chloride crystals that reach a dissolution rate of 70% by mass in 10 seconds or less when introduced into water), a large amount of sodium chloride component (i.e., "salt") will dissolve into the water before the fish ingest it. If a certain amount or more of salt dissolves into the water before the fish ingest it, the fish will spit it out immediately after ingesting it, resulting in poor feeding habits and a decrease in feeding ability. In contrast, the fish feed of this embodiment uses sodium chloride crystals that exhibit sustained release in water, with a 95% dissolution time of 50 to 150 seconds. This reduces the amount of salt that dissolves into the water before the fish ingest it, thereby improving feeding ability. Furthermore, if the 95% dissolution time of the sodium chloride crystals is 50 seconds or more but less than 150 seconds, the salt will be efficiently released into the fish's body after ingestion, effectively enhancing the flavor of the fish. From the viewpoints of feeding and flavor enhancement, the 95% dissolution time of the sodium chloride crystals is more preferably 50 seconds or more but 140 seconds or less, and particularly preferably 50 seconds or more but 100 seconds or less.

[0020] Furthermore, from the viewpoints of feed intake and flavor enhancement, the amount of dissolved sodium chloride crystals 10 seconds after one pellet of fish feed (total amount 1000 mg; amount of sodium chloride crystals 100 mg with a 95% dissolution time of 50 seconds or more and less than 150 seconds) is added to 20 ml of water at 25°C (hereinafter, this may be referred to as the "amount of dissolved fish feed (10 seconds)") is preferably 4 mg or less, more preferably 3 mg or less, and particularly preferably 1 mg or less.

[0021] Furthermore, the "dissolution rate of sodium chloride crystals when added to water" after 20 seconds of sodium chloride crystals is preferably 35 to 70% by mass, more preferably 40 to 65% by mass, from the viewpoints of intake and improved taste.

[0022] The amount of sodium chloride crystals in the fish feed can be changed as appropriate taking into account the type and size of the fish, and can be set, for example, so that the salt concentration in the fish's blood is 0.95 to 1.20%. Specifically, the content of sodium chloride crystals in the fish feed is not particularly limited, but from the viewpoints of feed intake and flavor enhancement, it is preferably 20% by mass or less of the total feed, and from the viewpoint of the balance between the increase in intracellular amino acid content and the feed intake of the fish, it is preferably 2 to 20% by mass, more preferably 3 to 20% by mass, more preferably 3 to 15% by mass, and particularly preferably 3 to 10% by mass.

[0023] The shape of the sodium chloride crystals in the fish feed is not particularly limited, but from the viewpoint of improving the feedability of farmed fish by making them less likely to dissolve instantly when in contact with water, granular crystals are preferred, and for example, rock salt can be used as the sodium chloride crystals. Furthermore, from the viewpoint of reducing exposure from the surface of the fish feed of this embodiment and improving the feedability of farmed fish, granular rock salt is more preferred, and about 2 to 8 grains of rock salt per 1 g are even more preferred.

[0024] The particle size (diameter) of sodium chloride crystals in fish feed is not particularly limited, but from the viewpoint of feeding ability and flavor, it is preferably 5 mm or less, more preferably 0.5 mm to 5 mm, more preferably 0.5 mm to 1.0 mm, and even more preferably 1.0 mm to 2 mm. The particle size of sodium chloride crystals can be measured using a stainless steel test sieve in accordance with the Japanese Industrial Standards (JIS Z 8801:1994, General Rules for Sieving Test Methods). For example, sodium chloride crystals with a particle size of 1.0 to 2.0 mm can be obtained by combining stainless steel test sieves with mesh sizes of 1.0 mm and 2.0 mm (JIS Z 8801 STAINLESS TEST SIEVE). Specifically, sodium chloride crystals are first passed through a sieve with a mesh size of 2.0 mm to select sodium chloride crystals (sodium chloride particles) with a particle size of 2.0 mm or less, and then the obtained sodium chloride crystals are passed through a sieve with a mesh size of 1.0 mm to remove sodium chloride crystals (sodium chloride particles) with a particle size of 1.0 mm or less, thereby obtaining sodium chloride crystals with a particle size of 1.0 to 2.0 mm. When measuring the particle size of sodium chloride crystals from fish samples (products), the fish sample is crushed with a hammer, then separated into coarse and fine particles. The particle size of the coarse particle is measured using a sieving test method, and the particles obtained from the fine particle portion are subjected to particle size analysis using a dry laser diffraction / scattering method, allowing the particle size of the sodium chloride crystals to be measured.

[0025] In addition to sodium chloride, potassium chloride can be used in fish feed to improve the amount of sodium chloride absorbed by fish. The amount of potassium chloride in the fish feed can be appropriately changed taking into account the type and size of the fish, etc., but from the viewpoint of the absorption mechanism of inorganic salts in the intestine, it is preferably 0.2 to 2.0 mass % of the total amount of the fish feed, and more preferably 0.5 to 1.0 mass %.

[0026] From the viewpoint of feeding ability, it is preferable that the fish feed contains water. The water content in the fish feed can be appropriately changed taking into consideration the type and size of the fish, etc., but is preferably 5 to 20 mass % and more preferably 8 to 12 mass % of the total amount of the fish feed.

[0027] Other components in the fish feed may include, for example, fish meal or other components contained in general fish feed depending on the type of fish. Examples of other components include protein components (e.g., fish meal, insect- or animal-derived feed, etc.), fat components, fibrous components, ash, calcium, phosphorus, animal-derived raw materials (e.g., live bait, etc.), plant-based raw materials, nutrients, binders, etc. For example, the fish feed of this embodiment may further contain fish meal. When the fish feed contains fish meal, the content of the fish meal in the fish feed is preferably 0 to 60% by mass, more preferably 0 to 40% by mass, of the total amount of the entire fish feed, from the viewpoint of suppressing the odor of the farmed fish after feeding is stopped.

[0028] The shape, size, and mass of each piece of fish feed are not particularly limited, and can be appropriately changed to a spherical, cylindrical, rectangular, or other shape taking into account the type and size of the fish. The mass of each piece of fish feed of this embodiment is preferably 0.1 to 3.0 g, more preferably 0.2 to 2.6 g, from the viewpoint of fish intake. Furthermore, the method for preparing the fish feed of this embodiment is not particularly limited, and general methods for preparing feed for farmed fish can be used as appropriate. As one example, the fish feed of this embodiment can be produced by kneading together sodium chloride salt, potassium chloride, water, a commercially available EP sample (trade name: Himezakura, manufactured by Higashimaru Co., Ltd.); ingredients (e.g., crude protein 46.0% or more (main ingredient: fish meal), crude fat 10.0% or more (main ingredient) shrimp meal, crude fiber 2.5% or less (main ingredient: krill meal), crude ash 15.0% or less, calcium 2.0% or more, phosphorus 1.0% or more, animal-derived ingredients 60%), and then extruding the resulting compound feed in a conventional manner to granulate it.

[0029] The amount of feed per fish is not particularly limited and can be changed as appropriate taking into account the type and size of the fish, etc. However, from the viewpoint of the feeding habits of the fish, it is preferable that the salt content in the fish feed be 10 to 50 g, and more preferably 20 to 30 g, based on the body weight of the fish (1 kg).

[0030] An example of how to use the fish feed of this embodiment will be described below, although the method of using the fish feed of this embodiment is not limited to the following embodiment.

[0031] <<How to use fish feed (aquaculture method)>> The method for using the fish feed of this embodiment (farming method) includes a feeding step of feeding the fish feed of this embodiment to farmed fish, a feeding stopping step of stopping feeding of the farmed fish that have been fed the fish feed of this embodiment in the feeding step for at least 6 hours but less than 48 hours, and a killing step of killing the farmed fish whose feeding has been stopped in the feeding stopping step.

[0032] <Feeding process> The feeding step is a step of feeding the fish feed of the present embodiment to farmed fish. According to the method of using the fish feed of the present embodiment, by feeding the fish feed of the present embodiment to farmed fish, the amount of amino acids inside the cells of the farmed fish can be increased easily and in a short period of time, and the edible parts can be improved in flavor.

[0033] <Bait stopping process> The feed cessation step is a step of halting feeding of the farmed fish that have been fed the fish feed of this embodiment in the feeding step for 6 hours or more but less than 48 hours. Hereinafter, the period during which feeding is halted may be referred to as the "feed cessation period." The amount of intracellular amino acids increases as blood pressure osmotic pressure increases due to the feeding of the fish feed of this embodiment, reaches a peak value after a predetermined period, and then gradually decreases over time. In the method of using the fish feed of this embodiment, the feed cessation period is 6 hours or less than 48 hours, so that the effect of increasing intracellular amino acids obtained by feeding the fish feed of this embodiment can be fully exerted, and farmed fish can be shipped with intracellular amino acid amounts near their peak.

[0034] The feeding stop period in the feeding stop step is preferably 12 hours or more and 36 hours or less, more preferably 24 hours or more and 36 hours or less, from the viewpoint of further fully exerting the flavor-improving effect.

[0035] <Tightening process> The killing process is a process of killing the farmed fish whose feeding has been stopped in the feed stopping process. In the method of using fish feed of this embodiment, by killing the farmed fish promptly after a specific feed stopping period has elapsed, the farmed fish can be shipped with the amount of amino acids in the muscle cells in the edible parts at their peak. In the killing process, it is preferable to kill the farmed fish promptly after the feed stopping period has elapsed without feeding them again.

[0036] (amino acid) As described above, when the fish feed of this embodiment is fed to the farmed fish, the total intracellular amino acids increase over time until a certain period of time has passed. Examples of amino acids that increase in the cells of farmed fish (e.g., red sea bream) include aspartic acid, glutamic acid, etc., which are related to umami components; serine, glycine, threonine, proline, glutamine, asparagine, etc., which are related to sweet components; and histidine, arginine, tyrosine, etc., which are related to bitter components.

[0037] There are no particular limitations on the means for killing farmed fish, and any known method can be used depending on the type of farmed fish. Examples of such methods include ice killing, live killing, nerve killing, etc. After killing, farmed fish can be subjected to treatments such as bleeding, if necessary.

[0038] <Other processes> The method for using the fish feed of this embodiment is not particularly limited, but a normal farming method is carried out depending on the type of farmed fish, and a feeding step is carried out before the feeding stopping step before shipping. Note that the method for using the fish feed of this embodiment may include a step of stopping normal feeding before the feeding step in order to increase the fish's tendency to eat the fish feed of this embodiment.

[0039] In one example of the above-mentioned typical aquaculture method, farmed fish are transferred to dedicated cages or tanks and managed under breeding management conditions, adjusting the feeding, water temperature, fish density, etc. For example, the number of times and amount of feeding per day to farmed fish before the feeding step in this embodiment is not particularly limited and can be set appropriately depending on the type of farmed fish, etc., but it is preferable to feed the farmed fish at least once a day by scattering the food inside the cage. The feed may be live fish feed or compound feed such as pellets, or feed prepared by crushing live feed and mixing it with compound feed for moist pellets. The ingredients of the compound feed are not particularly limited, but typically include animal feed, grains, vegetable oil cakes, oils and fats, various vitamins, minerals, etc.

[0040] As an example of a method of using the fish feed of this embodiment, the water temperature in a fish pen or tank is not particularly limited and can be set appropriately depending on the type of farmed fish, etc. In the case of a tank, the water temperature can be adjusted by using a heater or the like, but in the case of a fish pen installed on the sea for, for example, red sea bream or yellowtail, the farmed fish can be managed under desired temperature conditions by appropriately selecting the installation location and region of the fish pen.

[0041] As an example of a method of using the fish feed of this embodiment, the rearing density of the farmed fish in the fish pen or tank is not particularly limited and can be set appropriately depending on the type of farmed fish, etc. For example, in consideration of the work efficiency in the feeding process, the relationship between the weight of the farmed fish and the capacity of the fish pen, etc., is set to 1 to 6 kg / m. 3 is preferable, and 2 to 5 kg / m 3 The size of the fish preserve or tank is not particularly limited as long as it allows the farmed fish to swim without touching each other, but for example, it can be about 5 to 10 m long x 5 to 10 m wide and 5 to 10 m deep.

[0042] As an example of a method for using the fish feed of this embodiment, the period of aquaculture up to the feeding step is not particularly limited, and can be determined appropriately depending on the aquaculture fish.

[0043] <Farmed fish> The type of farmed fish that can be used in the method of using the fish feed of this embodiment is not particularly limited, and may be any of saltwater fish, freshwater fish, and amphidromous fish. Examples of farmed fish that can be used in the method of using the fish feed of this embodiment include fish belonging to the Sparidae family of the order Perciformes (e.g., red sea bream, yellow sea bream, black porgy, etc.), fish belonging to the Carangidae family of the order Perciformes (e.g., yellowtail, striped jack, horse mackerel, etc.), fish belonging to the Carangidae genus of the order Perciformes (e.g., yellowtail, amberjack, yellowtail, etc.), fish belonging to the Thunnus genus of the order Perciformes (scommon family Scomberidae) (e.g., bluefin tuna, yellowfin tuna, bigeye tuna, etc.), fish belonging to the Salmonidae family of the order Salmoniformes (e.g., rainbow trout, etc.), and fish belonging to the Tetraodontiformes family of the genus Pufferfish (e.g., tiger pufferfish, etc.). Preferred examples of fish that can be used in the method of using the fish feed of this embodiment include at least one species selected from red sea bream, yellowtail, tuna, striped jack, rainbow trout, and tiger pufferfish.

[0044] For example, the fish feed of this embodiment contains sodium chloride crystals, and when the sodium chloride crystals are added to water, the time required for the dissolution rate to reach 95% or more is 50 seconds or more but less than 150 seconds, and the fish feed can be used as fish feed that is added to farmed fish 6 hours or more but less than 48 hours before slaughter.

[0045] Although one aspect of this embodiment has been described above, the present invention is not limited to the above description. [Example]

[0046] The present invention will be specifically described below using examples, but the present invention is not limited to the following examples.

[0047] [Examples 1 and 2, Comparative Examples 1 and 2] [Seasoning test] Twenty test fish (red sea bream) weighing an average of 1,000 g were housed in a 5-ton oval test tank (longer diameter 320 cm, shorter diameter 100 cm, depth 115 cm). They were fed a standard diet (Hime Sakura EP Feed, Higashimaru Co., Ltd.) once a day until satiation. After feeding, the fish were fasted for two days. After that, they were given a satiating amount of salty feed listed in Table 1 below (satiating feeding). Satiating feeding was defined as when the fish had ingested a satiating amount of salty feed, as determined by confirming that no food had been expelled from the fish 5 to 15 minutes after feeding. The amount of salty feed consumed was generally approximately 0.8 to 1% of their body weight. After feeding the fish feed of this embodiment, the red sea bream were not fed any other food for one day. After one day had passed, the red sea bream were caught and killed.

[0048] (Composition of fish feed of this embodiment) Sodium chloride crystals 5% by mass (5.7% by mass when the amount of sodium chloride in the EP sample below is taken into account; see Table 1 below for particle size) Potassium chloride 1% by mass ·Moisture 11% by mass Remaining amount of commercially available EP sample (product name: Himezakura, manufactured by Higashimaru Co., Ltd.; ingredients (crude protein 46.0% or more (main ingredient: fish meal), crude fat 10.0% or more (main ingredient) shrimp meal, crude fiber 2.5% or less (main ingredient: krill meal), crude ash 15.0% or less, calcium 2.0% or more, phosphorus 1.0% or more, animal-derived ingredients 60%)

[0049] (Sorting of sodium chloride crystal particle size) The sodium chloride crystals used in each of the Examples and Comparative Examples were prepared as follows. First, four stainless steel test sieves with mesh sizes of 0.3 mm, 0.5 mm, 1.0 mm, and 2.0 mm (JIS Z 8801 STAINLESS TEST SIEVE) were used, and the samples were processed in combinations of 1.0-2.0 mm, 0.5-1.0 mm, 0.3-0.5 mm, and 0.0-0.3 mm. (a) Place the sieve with the largest mesh size among the sieves to be used on top of the receiver. (b) The sample was gently placed into the sieve and the lid was closed. (c) This was held in both hands and vibrated in one direction in the horizontal plane with an amplitude of 10 cm at a rate of approximately 60 back and forth movements per minute. After sorting through the sieve, the obtained sodium chloride crystals were sieved using the next largest mesh sieve by methods (a) to (c) to prepare sodium chloride crystals with particle sizes of 1.0 mm or more and 2.0 mm or less (Example 1), 0.5 mm or more and 1.0 mm or less (Example 2), 0.3 mm or more and 0.5 mm or less (Comparative Example 1), and 0.3 mm or less (Comparative Example 2).

[0050] (Measurement of 95% dissolution time) The 95% dissolution time (change in sodium chloride concentration over time) was measured for the sodium chloride crystals obtained for each of the Examples and Comparative Examples. First, 2.0 g of sodium chloride crystals were added to 20 ml of water at 25°C, and the aqueous solution was stirred at a shaking speed of 15 rpm. The salt concentration of the resulting aqueous solution was measured every 10 seconds using a salt concentration meter, and the value (mass %) obtained by dividing the salt content (g) in the aqueous solution by 2.0 g (the original amount of sodium chloride) by 100 was calculated. The results are shown in Figure 1. The time required for the sodium chloride crystals used in each Example and Comparative Example to reach a dissolution rate of 95% (95% dissolution time) is also shown in the table below.

[0051] [Evaluation of palatability] When salted bait was given, all the fish were caught and the amount of salted bait remaining in the tank was counted to determine whether the fish were interested in the bait and biting it, and whether they regurgitated it after biting. The results were then evaluated comprehensively according to the following criteria. (standard) A: There were less than three grains of salt left in the tank. B: There were more than 3 grains but less than 10 grains of salt food remaining in the tank. C: There were more than 10 grains of salt food remaining in the tank.

[0052] The amount of free amino acids (intracellular amino acids) per 100 g of fish meat (mg / 100 g) was measured for 20 red sea bream (control) before feeding the fish feed (salt feed) of this embodiment and for red sea bream fed the salt feed of each Example and Comparative Example by simultaneous analysis using a high-performance liquid chromatograph triple quadrupole mass spectrometer (product name: High-Performance Liquid Chromatograph Mass Spectrometer LCMS-8060, manufactured by Shimadzu Corporation). The average total amino acid concentration, including umami components (aspartic acid, glutamic acid), sweet components (serine, glycine, threonine, proline, glutamine, asparagine), and bitter components (histidine, arginine, tyrosine), was calculated for each Example and Comparative Example, and the degree of increase compared to the control was evaluated according to the following criteria. (standard) A: The average total amino acid concentration increased by 1.4 times or more compared to the control. B: The average total amino acid concentration increased by 1.2 to less than 1.4 times compared to the control. C: The mean increase in total amino acid concentration was less than 1.2-fold compared to the control.

[0053] [Table 1]

[0054] As a result, the red sea bream fed the fish feed (salty bait) of this embodiment had a high feed intake and a high preference for the salty bait. Furthermore, the salty baits of Comparative Examples 1 and 2, which had a 95% dissolution time of less than 50 seconds, were found to be salty enough for the red sea bream to easily perceive, resulting in significantly low feed intake and the phenomenon of the red sea bream spitting out the bait. Furthermore, the increase in total amino acid content was limited and was not different from the control.

Claims

1. A fish feed comprising sodium chloride crystals, The fish feed is such that the time required for the sodium chloride crystals to reach a dissolution rate of 95 mass % when added to water is 50 seconds or more and less than 150 seconds.

2. The fish feed according to claim 1, wherein the content of the sodium chloride crystals is 3 to 20% by mass based on the total mass of the feed.

3. 2. The fish feed of claim 1, wherein the sodium chloride crystals are rock salt.

4. 2. The fish feed according to claim 1, wherein the particle size of the sodium chloride crystals is 5 mm or less.

5. The fish feed of claim 1 , further comprising fish meal.

Images