JP2024046898A - Mixed feed for farmed fish - Google Patents

Abstract

[Problem] To provide a new compound feed for farmed fish in which fish meal is partially or entirely replaced with other protein resource raw materials, which prevents a decrease in feed intake and enables efficient farming to be maintained. [Solution] The compound feed for farmed fish contains free proline and free alanine, and the amount of free proline is greater than the amount of free alanine in terms of mass ratio in the feed. [Selected Figure] Figure 1

Description

Application for application of Article 30, Paragraph 2 of the Patent Act has been filed. The contents of the poster displayed at the 56th Annual Meeting of the Japanese Society of Taste and Odor, held from August 22 to 24, 2022, have been announced. Prior to the 56th Annual Meeting of the Japanese Society of Taste and Odor, held from August 22 to 24, 2022, the contents described on page 67 of the proceedings sent to conference participants by the Society Secretariat on August 10, 2022, have been published.

The present invention relates to compound feed for farmed fish, and in particular to compound feed for farmed fish in which part or all of the fishmeal is replaced with other raw materials that serve as protein resources (hereinafter referred to as protein resource raw materials), which prevents a decrease in the feed intake of farmed fish and enables efficient farming to be maintained.

Animal protein resources such as fishmeal are often used as ingredients in compound feed for farmed fish, but with the recent trend towards SDGs, there is a demand for the development of compound feed that is less dependent on natural resources such as fishmeal.

Generally, reducing the fish meal content in feed leads to a problem of reduced feed intake by farmed fish and lower production efficiency, and methods to improve feeding of compound feed with reduced fish meal content are being investigated.

Methods for improving feeding include adding food organisms that fish like to eat, or adding feeding-promoting substances contained in the food organisms, and many attempts have been made to identify feeding-promoting substances from food organisms or synthetic extracts of such organisms (reviews are given in Non-Patent Documents 1 and 2).

For example, Takeda et al. reported on the identification of a substance that promotes feeding in juvenile eels. They found that when a synthetic extract of the sea worm was added to a basic feed containing fish meal and casein as protein sources (fish meal 40%, casein 30%), it promoted feeding in juvenile eels. They also showed that among the amino acid fraction, nucleic acid fraction, and other component fractions of the extract, the amino acid fraction promoted feeding the most, and that a mixture of glycine, alanine, proline, and histidine had activity equivalent to that of the amino acid fraction (Non-Patent Document 3).

Takii et al. also reported on the effect of adding a feeding promoter to feed on the feeding activity and growth of juvenile eels, showing that feeding glass eels is promoted when a mixture of alanine, glycine, proline, histidine and 5'-UMP is added to a basal feed containing fish meal and casein as protein sources (40% fish meal, 30% casein) (Non-Patent Documents 4 and 5).

Ikeda et al. have also reported on the search for feeding stimulants in Euphausia pacifica for horse mackerel, and have shown that adding a natural or synthetic extract of Euphausia pacifica to a basic diet containing casein as a protein source (casein content 69%) induces and promotes the feeding behavior of horse mackerel, whereas a mixture of alanine, glycine, valine, methionine, phenylalanine, and proline, or these amino acids alone, does not have a feeding stimulant effect (Non-Patent Document 6).

Sato also reported on the effect of adding krill extract and krill meal to feed on the rearing performance and protein digestibility of yellowtail during the low water temperature period, and showed that adding krill extract or krill meal to EP mainly made of fish meal (fish meal content 65%) improved the feeding and growth of yellowtail (Non-Patent Document 7).

Hosokawa et al. have also reported on a search for yellowtail feeding stimulants in synthetic extracts of Euphausia pacifica. They report that feeding yellowtail with 100 g of dried fish meal-free basic feed (casein content 65%) supplemented with synthetic extracts of Euphausia pacifica, its amino acid fraction, or a mixture of proline, alanine, and methionine in amounts equivalent to 50 g of krill increased their food intake, and that feeding these three amino acids in combination with inosinic acid further increased food intake (Non-Patent Document 8).

Fukuda et al. have also reported on the feeding stimulating effect of squid muscle extract on young yellowtail, and have shown that when an amino acid mixture of alanine, arginine, glycine, octopine, proline, taurine, and valine from a synthetic squid muscle extract is added to a pellet made of purified starch and carboxymethylcellulose and fed to the fish, it has a feeding stimulating effect, and when a pellet containing a nucleic acid mixture of 5'-ADP-Na, 5'-AMP-Na, and 5'-ATP-Na is added, it does not have a feeding stimulating effect, but when combined with the above amino acid mixture, it synergistically increases the feeding stimulating effect (Non-Patent Document 9).

The inventors have also proposed a low-animal raw material feed for farmed fish such as yellowtail, which contains at least one amino acid selected from the group consisting of alanine, glutamic acid, glutamine, proline, ornithine, citrulline, and arginine, thereby preventing a decline in the growth efficiency and feed efficiency of farmed fish (Patent Document 1).

In addition, Izumi et al. reported on the effects of umami substances on the food intake and expression of neuropeptide Y in yellowtail, showing that inosinic acid and GMP increase both food intake and expression of neuropeptide Y, while MSG does not increase either, and SA does not increase food intake but does increase expression of neuropeptide Y (Non-Patent Document 10).

In addition, Izumi et al. reported on the effect of olfactory stimulation of amino acids on the feeding behavior of yellowtail and the expression levels of neuropeptide Y and c-Fos genes. Using alanine as the olfactory stimulus and proline as the gustatory stimulus, they showed that olfactory stimulation promotes foraging behavior, and gustatory stimulation promotes food intake behavior (Non-Patent Document 11).

Murofushi et al. also reported on the relationship between the feeding stimulating activity of neutral amino acids and their structure in red sea bream, and confirmed the feeding stimulating activity of amino acids such as alanine (Non-Patent Document 12).

On the other hand, Hosokawa et al. reported on the search for feeding stimulants for yellowtail in horse mackerel muscle extracts. They found that when a fraction of a synthetic horse mackerel muscle extract excluding nucleic acids was added to a fish meal-free basic diet (casein content 65%) and the fish were fed, the feeding stimulant activity was lost, but when a fraction excluding amino acids or organic bases was added, the feeding stimulant activity was demonstrated, and that among the nucleic acids, inosinic acid contributed to the feeding stimulant activity (Non-Patent Document 13).

WO2014/020925

Genetics 34, No. 9, 45-51 (1980) Fisheries Science Series 101, Feeding Stimulants for Fish and Shellfish, pp. 24-31, 41-45, and 55-63 Japanese Journal of Fisheries Science, Vol. 50, No. 4 Journal of the Japanese Society of Fisheries Science, Vol. 50, No. 6, 1039-1043 (1984) Journal of the Japanese Society of Fisheries Science 50, 645-651 (1984) Fisheries Aquaculture Vol. 51, No. 1, 93-99 (2003) Journal of the Japanese Society of Fisheries Science, Vol. 54, No. 2, 229-233 (1988) Abstracts of the Spring Meeting of the Japanese Society of Fisheries Science, 1977, 608 Journal of the Japanese Society of Fisheries Science, Vol. 55, No. 5, 791-797 (1989) Fisheries Aquaculture Vol. 68, No. 2, 159-162 (2020) Abstracts of the 2020 Autumn Meeting of the Japanese Society of Fisheries Science, 638 Journal of the Agricultural Chemical Society of Japan Vol. 56, No. 4, pp. 255-259, 1982 Fisheries Aquaculture Vol. 49, No. 2, 225-229 (2001)

The present invention aims to provide a new compound feed for farmed fish in which part or all of the fish meal is replaced with other protein resource raw materials, which suppresses a decrease in feed intake and enables efficient farming to be maintained.

The inventors verified the above-mentioned conventional findings and, while searching for new methods for promoting feeding, made an interesting discovery. That is, when raw materials that are sources of both amino acids are added to a compound feed in which part or all of the fish meal is replaced with other protein resource raw materials in a specific ratio such that the content of free proline is greater than that of free alanine, the inventors made the surprising discovery that a feeding promotion activity similar to that of a compound feed containing only fish meal as a protein resource raw material can be obtained without combining it with a nucleic acid such as inosinic acid. The present invention is based on this finding and provides the following compound feed.

That is, the present invention provides the following compound feed.
[1] A compound feed for farmed fish in which part or all of the fish meal is replaced with other protein resource raw materials, the compound feed for farmed fish containing free proline and free alanine, and the mass ratio of free proline in the feed being greater than the mass ratio of free alanine.
[2] The feed for farmed fish according to [1], wherein the mass ratio of free proline to free alanine (Pro:Ala) in the feed is 1.2:1 to 5:1.
[3] The feed for farmed fish according to [1], wherein the mass ratio of free proline to free alanine (Pro:Ala) in the feed is 1.5:1 to 3:1.
[4] The cultured fish compound feed according to any one of [1] to [3], wherein the content of free alanine in the feed is 300 ppm or more.
[5] A compound feed for farmed fish according to [4], in which the content of free alanine in the feed is 400 ppm or more and the content of free proline in the feed is 600 ppm or more.
[6] The feed for farmed fish according to any one of [1] to [5], containing 0.02 to 0.6 parts by mass of free proline and 0.02 to 0.3 parts by mass of free alanine per 100 parts by mass of the other protein resource raw materials.
[7] The farmed fish compound feed according to any one of [1] to [6], wherein the fish meal content in the feed is 50 mass% or less.
[8] The feed for farmed fish according to any one of [1] to [7], wherein the inosinic acid content is 1,500 ppm or less, preferably 1,200 ppm or less, or the free tryptophan content is 250 ppm or less.
[9] A compound feed for farmed fish according to any one of [1] to [8], in which the ratio of free alanine to the total amount of free amino acids in the feed is 6.5% by mass or less, preferably 5.0% by mass or less, and the ratio of free proline is 10% by mass or less.

The compound feed of the present invention can suppress the reduction in feed intake of farmed fish caused by replacing part or all of the fish meal with other protein resource raw materials, and achieve a feed intake similar to that of the compound feed before replacement.

1 is a graph showing the results of a test evaluating the total feed intake by juvenile yellowtail for each feed described in the Examples of the present application.

The following describes in detail the embodiments of the present invention. However, the present invention should not be understood as being limited to the following embodiments.

The cultured fish feed of the present invention is a cultured fish feed in which part or all of the fish meal is replaced with other protein resource raw materials, and is characterized by containing free proline and free alanine in a specific ratio.

In the compound feed of the present invention, when fish meal is contained, there is no particular limitation on the type of fish meal, and for example, fish meal of one or more fish selected from Clupeidae (Clupeidae), Engraulidae (Clupeidae), Carangidae (Perciformes), and Scombridae (Perciformes). Examples of fish belonging to these classes include sardines such as Japanese sardine, anchovy, and anchovy, mackerels such as chub mackerel and yellow mackerel, horse mackerel such as Japanese horse mackerel and round horse mackerel, and herrings such as Atlantic herring.
The fish meal may be ordinary fish meal that has not been subjected to a protein decomposition treatment, or may be enzyme-treated fish meal that has been treated with an enzyme such as peptidase, protease, or proteinase.

In the present specification, other protein resource raw materials are raw materials other than fish meal that can become protein resources when included in aquaculture fish feed, and include animal raw materials, vegetable raw materials, and other protein resource raw materials. Animal raw materials include, for example, processed products such as krill, shrimp, squid, etc. that have been dried or powdered (for example, krill meal, shrimp meal, squid meal, etc.), chicken meal, feather meal, fish soluble raw materials, etc. Vegetable raw materials include, for example, raw materials obtained by processing legumes such as soybeans, or corn, etc., such raw materials include soybean meal, corn gluten meal, concentrated soy protein, etc., and concentrated soy protein is preferred. Protein resources other than animal and vegetable sources include proteins synthesized in vitro, proteins derived from microorganisms (for example, feed yeast), and raw materials derived from insects.

The degree of substitution with other protein resource raw materials is preferably set to a degree that provides a feeding effect similar to that of a formula feed containing no fish meal replacement, taking into consideration the relationship between the feeding promotion effect of free proline and free alanine described below and the feed intake reduction due to substitution with other protein resource raw materials. Furthermore, the required fish meal content may differ depending on the fish species or whether the feeding subjects are adult fish or juvenile fish.
Therefore, the content of fish meal may vary depending on the content and ratio of free proline and free alanine as well as the feeding target, but can usually be 0 to 85% by mass in the mixed feed. From the viewpoint of promoting a mixed feed with reduced dependency on natural resources such as fish meal, it is preferably 0 to 50% by mass, more preferably 0 to 20% by mass, and particularly preferably 0 to 10% by mass. The content of other protein resource raw materials can usually be 10 to 70% by mass in the mixed feed, more preferably 30 to 70% by mass, and more preferably 50 to 70% by mass. The mass ratio of fish meal to other protein resource raw materials can usually be 9:1 to 0:10 (fish meal: other protein resource raw materials), preferably 5:5 to 0:10 (fish meal: other protein resource raw materials), and more preferably 2:8 to 0:10 (fish meal: other protein resource raw materials).

A problem with compound feed containing reduced fish meal is that the feed intake of farmed fish decreases, resulting in lower production efficiency. In the present invention, however, this decrease in feed intake is suppressed by including a specific ratio of free alanine and free proline in the feed, thereby achieving a feed intake that is close to that of the compound feed before the fish meal was replaced with other protein resource materials.
More specifically, as will be demonstrated in the Examples described later, by containing both free alanine and free proline and setting a specific ratio in which the content of free proline is higher than the content of free alanine, a significantly higher improvement in feed intake is achieved compared to a case in which almost only free alanine or free proline is contained, a case in which free alanine and free proline are contained in equal amounts, or a case in which the content of free alanine is much higher than the content of free proline.
Specifically, the mass ratio of free proline to free alanine (Pro:Ala) in the feed is preferably 1.2:1 to 5:1, more preferably 1.3:1 to 3:1, and particularly preferably 1.5:1 to 2.5:1.

The free proline and free alanine contents in the feed are preferably determined according to the contents of other protein resource raw materials, from the viewpoint of accurately responding to the decrease in feed intake caused by replacing fish meal. Specifically, they can usually be contained at 0.02 to 0.6 parts by mass and 0.02 to 0.3 parts by mass, respectively, per 100 parts by mass of other protein resource raw materials, but it is preferable to contain 0.08 to 0.4 parts by mass and 0.05 to 0.2 parts by mass, respectively, and more preferably 0.15 to 0.3 parts by mass and 0.09 to 0.15 parts by mass, respectively, per 100 parts by mass of other protein resource raw materials.

In order to fully exert the effect of promoting the feed intake of farmed fish, the free alanine content in the feed is preferably 100 ppm or more, more preferably 200 ppm or more, even more preferably 300 ppm or more, and particularly preferably 400 ppm or more. On the other hand, the free alanine content in the feed is preferably 2,000 ppm or less, more preferably 1,500 ppm or less, and even more preferably 1,000 ppm or less.
From the same viewpoint, the free proline content in the feed is preferably 150 ppm or more, more preferably 300 ppm or more, even more preferably 450 ppm or more, even more preferably 600 ppm or more, and particularly preferably 800 ppm or more. On the other hand, the free proline content in the feed is preferably 4,000 ppm or less, more preferably 3,000 ppm or less, and even more preferably 2,000 ppm or less.

In addition, free proline and free alanine may be salts such as salts with inorganic or organic acids, such as hydrochloride, sulfate, acetate, etc., or salts with alkali metals, such as sodium salt, potassium salt, etc. In this specification, when "proline" and "alanine" are mentioned, such salts are also included unless otherwise specified.

When the free proline and free alanine contents in the feed are set within the above-mentioned ranges, it is necessary to take into consideration that fish meal contains free proline and free alanine and has a higher content of free alanine relative to free proline, as shown in the example below.

Raw materials that are rich in free proline include crystalline products, krill, fungi, insects, etc. Raw materials that are rich in free alanine include crystalline products, fish meal, fish solubles, krill, fungi, insects, chicken meal, etc. Raw materials with a higher free proline content than alanine content include crystalline products, krill, fungi, insects, etc. Therefore, depending on the content of fish meal and other raw materials rich in free alanine in the feed, it is necessary to mix an appropriate amount of raw materials rich in free proline appropriately to achieve the above-mentioned free proline and free alanine contents.

The compound feed of the present invention may contain other free amino acids, for example, glycine, valine, methionine, phenylalanine, histidine, glutamic acid, glutamine, proline, ornithine, citrulline, arginine, octopine, aspartic acid, taurine, etc., and these free amino acids may be in the form of a salt, such as a salt with an inorganic or organic acid, such as a hydrochloride, sulfate, acetate, etc., or a salt with an alkali metal, such as a sodium salt, potassium salt, etc.
However, in the compound feed of the present invention, the feed intake promoting effect is increased by setting the above-mentioned free proline and free alanine contents, and free amino acids other than free proline and free alanine are not essential, and the composition may be such that does not contain some of the above-mentioned free amino acids.

On the other hand, the present inventors have found that the content of free alanine and free proline relative to the total amount of free amino acids can be made relatively low in order to exert the effect of promoting the feed intake of farmed fish. Specifically, the content of free alanine in the feed can be 6.5% by mass or less relative to the total amount of free amino acids, preferably 1 to 5.0% by mass, more preferably 1 to 4% by mass, and particularly preferably 2 to 3% by mass.
Similarly, the free proline content in the feed can be 10% by mass or less, preferably 2 to 8% by mass, and particularly preferably 3 to 6% by mass.
In the compound feed of the present invention, the total amount of free amino acids is preferably 10,000 ppm or more, and more preferably 10,000 ppm to 50,000 ppm.

The compound feed of the present invention may contain various nucleic acids such as inosinic acid. However, in the compound feed of the present invention, the feeding promotion effect can be increased by setting the above-mentioned free proline and alanine contents, and nucleic acids such as inosinic acid are not essential components. Therefore, in the present invention, it is possible to reduce various nucleic acid components such as inosinic acid compared to conventional compound feeds, and for example, the content of inosinic acid can be 1,500 ppm or less, preferably 1,200 ppm or less, and more preferably 300 to 1,000 ppm.

In addition to the above, the compound feed for farmed fish of the present invention may contain vegetable carbohydrate resource raw materials such as wheat flour, pregelatinized starch, or cellulose, animal fats and oils such as fish oil, squid liver oil, or chicken oil, vegetable fats and oils such as palm oil, soybean oil, or rapeseed oil, vitamins, minerals, antioxidants, and binders such as carboxymethylcellulose or guar gum.

The cultured fish compound feed of the present invention can be produced by a general method using the above-mentioned raw materials, and may be in the form of pellets, crumbles, granules, powder, moist pellets, paste, etc. The cultured fish compound feed of the present invention may also be produced by preparing the feed using general cultured fish feed raw materials, and then spreading a raw material containing a large amount of proline and alanine (for example, an aqueous solution of proline or alanine) on the feed.

The compound feed of the present invention may be fed to cultured fish in the same manner as conventional compound feed for cultured fish.
The feeding promotion effect of proline and alanine is expected in a wide range of fish species (e.g., Non-Patent Documents 7, 1 and 2), and the effect of the present invention, which contains them in a specific ratio in the feed, is also expected to be exerted in a wide range of fish species. As the cultured fish to be fed with the compound feed of the present invention, for example, fish belonging to the family Carangidae, such as amberjack, yellowtail, horse mackerel, and striped jack, fish belonging to the family Anguilla, such as Japanese eel, European eel, giant mottled mottle moth, and New Guinea eel, fish belonging to the family Sparidae, such as black porgy, red sea bream, and crimson sea bream, fish belonging to the family Oplegnathidae, such as scorpionfish, bluefin tuna, Pacific bluefin tuna, Atlantic bluefin tuna, southern bluefin tuna, chub mackerel, and sesame mackerel, and fish belonging to the family Carangidae are preferable.
There is no particular restriction on the timing of feeding the feed, but it is preferable to use it for feeding the fry or juvenile fish.

The present invention will be explained in more detail below with reference to examples, but the present invention should not be understood in a limiting manner by the following examples.

1. Preparation of test feeds In order to evaluate the compound feed according to the present invention, each feed having the composition shown in Table 2 below was prepared.

The free amino acid composition of each feed is as follows:

The FM group is a control feed containing fish meal as a protein source and no other protein source materials. In order to clarify the effect of adding free alanine and free proline, in this test, a basic feed (casein group) was prepared containing only casein as a protein source without fish meal. Alanine and proline crystals were added to this basic feed, either alone or together, to prepare test feed. The ALA and PRO groups were prepared as test feeds by adding each of them alone. The A=P group was a sample with the same concentration of free alanine and free proline in the feed, the A>P group was a sample with a higher concentration of free alanine than the free proline (P/A ratio = 0.52/1), and the A<P group was a sample with a higher concentration of free proline than the free alanine (P/A ratio = 2.09/1).
The alanine and proline crystals were dissolved in the purified water used for preparing the feed, and the resulting solution was added to the feed ingredients listed in the table. Next, 400 mL of purified water was added per 1 kg of the feed ingredients, and the mixture was thoroughly mixed in a mixer and then molded into single moist pellets (diameter 2 mm) using a small pelleter (N022VR-1500DX, α Royal, Kobe). The resulting pellets were stored frozen at -20°C, and the required amount was thawed and used when feeding.

The composition of the feed was analyzed as follows.
Crude protein content: Measured by semi-micro Kjeldahl method (N x 6.25).
Crude lipid content: The method of Folch et al. (Folch et al., 1957) was modified to extract the feed with a chloroform:methanol mixture (2:1 v/v) and measure the crude lipid content according to the method of Folch et al.
Moisture content: The feed was dried at 110°C for 10 hours and measured from the difference in mass before and after drying.
Ash content: measured after burning at 550° C. for 5 hours.
Free amino acids: The feed was extracted with pure water, deproteinized, and then lipid-removing. Measurements were performed using a JLC-500/V2 fully automated amino acid analyzer (JEOL Ltd.) with post-column derivatization/ninhydrin colorimetry at measurement wavelengths of 440 nm, 570 nm, and 690 nm.
The concentration of each component in the table is the value in the molded pellets converted into a dry matter value.

2. Feeding Test Using each of the feeds prepared as described above, the feed intake by the cultured fish was measured, and the feeding effect of adding alanine and proline was evaluated.
The test fish used were artificial seedling yellowtail juveniles transferred from Feed One Co., Ltd. in January 2022. They were pre-bred with commercially available EP feed (Feed One Co., Ltd., Kanagawa) until the start of the test. Randomly selected yellowtails were housed in 0.6 ton FRP tanks with aeration and water exchange, and 3 tanks per test area were set up for a total of 18 tanks. The average weight of the yellowtails used for breeding was 48.7 g at the start of the test. The test period was 8 days from March 21 to March 28, 2022, during which the test feed was given once a day until the fish were satiety (until the fish lost interest in the food or spit it out after eating it once). During the breeding period, the water temperature was 16.4 to 17.1 degrees. All breeding tests were conducted at the Konan City Fisheries Promotion Facility (Kochi).

The amount of food fed was calculated by measuring the weight of the container containing the food before and after each feeding, and the weight was subtracted from the weight of the container. The calculated amount of food fed was considered to be the amount of food consumed. Figure 1 shows the average total amount of food fed over 8 days (i.e., 8 times) in each tank (average of 3 tanks ± standard error).

All values obtained were subjected to one-way ANOVA followed by Tukey-Kramer multiple comparison test to determine significant differences at a risk level of 5%. Statistical processing was performed using GraphPad Prism ver. 9.0 (GraphPad Software, Inc.).

3. Test results As shown in Figure 1, the yellowtails in the A<P group achieved a feed intake similar to that of the yellowtails in the FM group.
Although the feed intake of the yellowtails in the Ala, Pro, A=P, and A>P groups was greater than that of the yellowtails in the casein group fed with the basic diet containing neither free alanine nor free proline, the feed intake of the yellowtails in the A<P group was significantly greater than that of the yellowtails in the ALA, PRO, A=P, and A>P groups. This demonstrated that it is extremely important, in order to promote feeding, not only to add alanine and/or proline but also to set the ratio of the proline concentration to be significantly higher than that of the alanine concentration (P/A ratio = 2.10/1).

Claims (9)

A compound feed for farmed fish in which part or all of the fish meal is replaced with other protein resource materials (hereinafter referred to as protein resource materials), which contains proline and alanine and in which the mass ratio of free proline in the feed is greater than the mass of free alanine. The compound feed for farmed fish according to claim 1, in which the mass ratio of free proline to free alanine (Pro:Ala) in the feed is 1.2:1 to 5:1. The compound feed for farmed fish according to claim 1, in which the mass ratio of free proline to free alanine (Pro:Ala) in the feed is 1.5:1 to 3:1. The compound feed for farmed fish according to claim 1, in which the content of free alanine in the feed is 300 ppm or more. The compound feed for farmed fish according to claim 4, wherein the content of free alanine in the feed is 400 ppm or more and the content of free proline in the feed is 600 ppm or more. The compound feed for farmed fish according to claim 1, which contains 0.02 to 0.6 parts by mass of free proline and 0.02 to 0.3 parts by mass of free alanine per 100 parts by mass of the other protein resource raw materials. The compound feed for farmed fish according to any one of claims 1 to 6, in which the fish meal content in the feed is 50% by mass or less. The compound feed for farmed fish according to claim 7, wherein the inosinic acid content is 1,500 ppm or less, or the free tryptophan content is 250 ppm or less. The compound feed for farmed fish according to claim 5, in which the ratio of free alanine to the total amount of free amino acids in the feed is 5.0% by mass or less, and the ratio of free proline is 10% by mass or less.