Fish feed composition comprising a hydrolyzate with high levels of free amino acids and uses

Abstract

A composition for feeding fish containing from 0.05 to 2% by weight of a keratin hydrolyzate comprising at least 88% by weight of free amino acids relative to the total weight of the amino acids in the hydrolyzate, said composition comprising the following contents of the following amino acids in free form: aspartic acid from 0.009% to 0.074% by weight; serine from 0.016 to 0.132% by weight; glutamic acid from 0.013 to 0.106% by weight; glycine from 0.011 to 0.086% by weight; alanine from 0.006 to 0.050% by weight; arginine from 0.008 to 0.064% by weight; proline from 0.014 to 0.118% by weight relative to the total weight of the composition and uses for improving the quality and quantity of fish flesh. Figure to be published with the abstract: none

Description

Title of the invention: Food composition for fish comprising a hydrolyzate with high levels of free amino acids and uses

[0001] The present invention relates to the field of aquaculture and more particularly to fish farming. More specifically, the invention relates to a composition comprising a keratin hydrolyzate with high free amino acid contents for fish feed. Prior art

[0002] In the context of the current trend towards reducing meat intake in diets, particularly in Europe and North America, consumer demand for quality fish is growing. Aquaculture is intended to meet this growing demand and should therefore be considered as an alternative solution to overfishing and also to the disappearance of certain species.

[0003] Fish farming is generally practiced with the objective of optimizing nutritional intake to accelerate fish growth and also increase the feed / live weight gain conversion rate.

[0004] With this aim of accelerating growth, the applicant company has already presented the Kera Aqua range comprising 92% of amino acids in free form and a particularly low molecular weight.

[0005] Furthermore, patent application EP 3701802A1 of the applicant company already discloses a keratin hydrolysate with a high content of free amino acids as well as its use in animal feed.

[0006] However, there still remains a need for food compositions, in particular complete and complementary foods, which make it possible to improve specific properties of farmed fish such as the quantity or quality of the flesh as well as its composition.

[0007] Surprisingly and advantageously, the inventors have demonstrated that a solution to this problem could be provided by using, in fish feed, a particular composition containing a hydrolyzate of keratin materials comprising at least 88% by weight of free amino acids, said hydrolyzate providing in particular, and therefore in free form, amino acids recognized as non-essential in the animal kingdom.

[0008] By "non-essential amino acid" is meant an amino acid that can be synthesized by the body.

[0009] Description of the invention

[0010] A first object of the invention relates to a food composition for feeding fish containing from 0.05 to 2%, preferably from 0.1 to 1% by weight of a keratin hydrolyzate comprising at least 88% by weight of free amino acids relative to the total weight of the amino acids of the hydrolyzate, the remainder of the amino acids of the hydrolyzate being in the form of peptides having a molecular mass less than or equal to 800 Dalton, said composition comprising the following contents of the following amino acids in free form: an aspartic acid content ranging from 0.009% to 0.074% by weight, preferably ranging from 0.018 to 0.037% by weight; a serine content ranging from 0.016 to 0.132% by weight, preferably ranging from 0.032 to 0.066% by weight; a glutamic acid content ranging from 0.013 to 0.106% by weight, preferably ranging from 0.026 to 0.053% by weight; a glycine content ranging from 0.011 to 0.086% by weight, preferably ranging from 0.022 to 0.043% by weight;an alanine content ranging from 0.006 to 0.050% by weight, preferably ranging from 0.012 to 0.025% by weight; an arginine content ranging from 0.008 to 0.064% by weight, preferably ranging from 0.016 to 0.032% by weight; a proline content ranging from 0.014 to 0.118% by weight, preferably ranging from 0.029 to 0.059% by weight relative to the total weight of the composition. ;

[0011] In particular, the food composition according to the invention is a complete food comprising at least the following components: at least one fish meal, at least one fish oil, at least one source of starch chosen from cassava and cereals chosen from wheat, corn and rice, at least one source of protein chosen from soybean and rapeseed in the form of cake or flour, and a premix of vitamins chosen from the group consisting of vitamins A, group B, C, D3, E, K3, and trace elements chosen from the group consisting of iron, copper, manganese, zinc, cobalt and selenium.

[0012] The inventors have demonstrated that the food composition according to the invention has advantageous properties when used in fish feed, in particular; it makes it possible to improve the flesh of fish, and in particular that of fillets, in a quantitative and qualitative manner.

[0013] The fish fillet is a strip of flesh taken parallel to the backbone. Apart from a few specificities such as, for example, the cheeks in monkfish, the fillet corresponds to the bulk of the flesh, that is to say the edible part of the fish.

[0014] Thus a second object of the present invention aims at the non-therapeutic use of the food composition according to the invention to increase the quantity of flesh, in particular that of fish fillets.

[0015] Thus the inventors observed that the fish fed with the composition according to the invention develop a greater body mass of flesh, to the detriment of other non-utilizable parts of the fish such as the viscera and abdominal fat.

[0016] A third object of the present invention is the non-therapeutic use of the food composition according to the invention to improve the quality of fish flesh, in particular to modify the color of fish flesh, more particularly to obtain a whiter color.

[0017] The fish fed with the composition according to the invention have better quality flesh both in terms of its composition and its appearance and in particular its color. The flesh and in particular the fillets are whiter.

[0018] The lipid content of the flesh is higher and its water content is lower.

[0019] Fish fed with the food composition according to the invention exhibit therefore interesting properties for marketing in terms of color and size of the fillets.

[0020] Thus a fourth object of the present invention aims at the non-therapeutic use of the food composition according to the invention to modify the composition of the flesh, in particular that of fish fillets, and more particularly to increase the quantity of unsaturated fatty acids in the flesh, in particular the fillets.

[0021] A fifth object of the present invention is the non-therapeutic use of the food composition according to the invention to modify the composition of the intestinal flora of fish, in particular to increase the quantity of digestive enzymes in the intestinal flora of fish, in particular to increase the quantity of amylase.

[0022] It has thus been demonstrated that the food composition according to the invention allows the development of digestive enzymes such as amylases, lipases and proteases and therefore better assimilation of food.

[0023] Without wishing to be bound by any theory, it appears that the increase in the quantity of amylases, which allows better assimilation of starch, also leads to less significant deposition of fat in the viscera.

[0024] This use of the food composition according to the invention which makes it possible to contribute to the growth of digestive bacteria promoting intestinal balance is suitable for good absorption of nutrients in breeding conditions where the intake of diversified foods is limited.

[0025] The use of the food composition according to the invention - comprising in particular particular contents of the following non-essential amino acids, in free form: aspartic acid, serine, glutamic acid, glycine, alanine, arginine, proline - allows the production of a complete and balanced food, a source of free amino acids, and which allows better use of food proteins of plant and / or animal origin of complex molecular structure and high molecular weight. The use of the food composition according to the invention allows better assimilation of the nutrients present in the food and in particular in the complete food.

[0026] These uses, which fall within the conditions of breeding healthy fish, do not belong to the therapeutic field.

[0027] Other aspects, advantages, properties of the present invention are presented in the description and examples which follow.

[0028] Food composition

[0029] The subject of the present invention is a food composition for feeding fish at all stages of their development, in particular at the juvenile stage.

[0030] Preferably, the food composition according to the present invention comprises a hydrolyzate having the following distribution of total amino acids: an aspartic acid content ranging from 5 to 8% by weight, preferably ranging from 6 to 7% by weight; a threonine content ranging from 4 to 6% by weight, preferably from 4 to 5% by weight; a serine content ranging from 9 to 14% by weight, preferably ranging from 10 to 12% by weight; a glutamic acid content ranging from 9 to 11%; a glycine content ranging from 6 to 9% by weight, preferably ranging from 7 to 8% by weight; an alanine content ranging from 4 to 6% by weight, preferably from 4 to 5% by weight; a valine content ranging from 6 to 10% by weight, preferably ranging from 7 to 8% by weight; a methionine content ranging from 0.1 to 0.6% by weight; an isoleucine content ranging from 4 to 6% by weight, preferably ranging from 4 to 5% by weight;a leucine content ranging from 6 to 9% by weight, preferably ranging from 7 to 8% by weight; a phenylalanine content ranging from 2 to 5% by weight; a lysine content ranging from 1 to 3% by weight, a histidine content ranging from 0.4 to 1% by weight; an arginine content ranging from 5.5 to 6.5% by weight; a proline content ranging from 8.5 to 11% by weight, a tryptophan content of less than 0.1%, preferably 0% by weight relative to the total weight of the hydrolyzate.;

[0031] Free and total amino acids are measured by HPLC chromatography.

[0032] Preferably, the amino acids are measured according to a method adapted from EC Regulation 152 / 2009. According to this method, for the determination of the quantities of total amino acids, hydrolysis using an acid is first carried out.

[0033] For the determination of the quantities of free and total amino acids, the amino acids are separated by HPLC chromatography, preferably with an ion exchange column, and assayed by reaction with ninhydrin and photometric detection, generally at 570 nm.

[0034] The hydrolyzate preferably used in the food composition according to the invention comprises the following free amino acids: at least 95% of aspartic acid in free form by weight relative to the total weight of aspartic acid in the hydrolyzate; at least 95% of threonine in free form by weight relative to the total weight of threonine in the hydrolyzate; at least 95% of serine in free form by weight relative to the total weight of serine in the hydrolyzate; at least 93% of glutamic acid in free form by weight relative to the total weight of glutamic acid in the hydrolyzate; at least 93% of glycine in free form by weight relative to the total weight of glycine in the hydrolyzate; at least 93% of alanine in free form by weight relative to the total weight of alanine in the hydrolyzate; at least 93% of methionine in free form by weight relative to the total weight of methionine in the hydrolyzate; at least 93% of phenylalanine in free form by weight relative to the total weight of phenylalanine in the hydrolyzate; at least 95% of proline in free form by weight relative to the total weight of proline in the hydrolyzate.

[0035] As shown in Table 1, the majority of amino acids are at least 95% in free form relative to the total weight of said amino acid in the hydrolyzate.

[0036] Advantageously, the total amino acid content (free and bound) of the hydrolyzate used according to the invention ranges from 40% to 95%, preferably 45% to 92% by weight relative to the total weight of the hydrolyzate, the hydrolyzate further comprising mineral matter and water. As already mentioned, the amino acids of the hydrolyzate according to the invention are essentially free amino acids.

[0037] Preferably, the mineral matter content of said hydrolyzate, preferably NaCl or KCl, is less than or equal to 9% by weight, preferably less than 8% by weight relative to the total weight of the hydrolyzate. This mineral matter content is determined after calcination of the hydrolyzate at 550°C for 4 hours.

[0038] The food composition according to the invention has the following distribution of total amino acids: an aspartic acid content ranging from 2.2% to 2.7% by weight, preferably ranging from 2.3% to 2.6% by weight; a threonine content ranging from 1.1% to 1.6% by weight, preferably from 1.2% to 1.5% by weight; a serine content ranging from 1.5% to 2.1% by weight, preferably ranging from 1.6% to 2.0% by weight; a glutamic acid content ranging from 4.8% to 5.4% by weight, preferably ranging from 4.9% to 5.3% by weight; a glycine content ranging from 2.1% to 2.7% by weight, preferably ranging from 2.2% to 2.6% by weight; an alanine content of 1.3% to 2.0% by weight, preferably ranging from 1.5% to 1.9% by weight; a valine content of 1.3% to 2.0% by weight, preferably ranging from 1.5% to 1.9% by weight; a cystine content of 0.3% to 0.7% by weight, preferably ranging from 0.4% to 0.6% by weight;a methionine content ranging from 0.4% to 1.0% by weight, preferably ranging from 0.6% to 0.8% by weight; a content of; isoleucine ranging from 1.1% to 1.8% by weight, preferably from 1.2% to 1.6% by weight; a leucine content ranging from 2.5% to 3.3% by weight, preferably from 2.6% to 3.1% by weight; a tyrosine content ranging from 0.6% to 1.3% by weight, preferably from 0.8% to 1.2% by weight; a phenylalanine content ranging from 1.0% to 1.8% by weight, preferably from 1.2% to 1.7% by weight; a lysine content ranging from 1.7% to 2.3% by weight, preferably from 1.8% to 2.2% by weight, a histidine content ranging from 0.4% to 0.9% by weight; an arginine content ranging from 1.8% to 2.6% by weight, preferably ranging from 2.0% to 2.4% by weight; a proline content ranging from 2.1% to 3.0% by weight, preferably ranging from 2.2% to 2.9% by weight; a tryptophan content ranging from 0.2% to 0.6% relative to the total weight of the composition.

[0039] Advantageously, the food composition according to the invention has a total content of free amino acids ranging from 0.5 to 5% by weight, preferably ranging from 1 to 2.5% by weight, including a total content of the following free amino acids: aspartic acid, serine, glutamic acid, glycine, alanine, arginine and proline ranging from 0.08% to 1.5% by weight, preferably ranging from 0.15 to 0.75% by weight relative to the total weight of the composition.

[0040] The food composition may be a complete food or a complementary food, preferably the food is a complete food.

[0041] By "complete food" we generally mean a food providing in a balanced manner to the individual who ingests it all the materials and nutrients necessary for his life and development.

[0042] Complementary food refers to food distributed in addition to the usual food, generally to specifically supplement the diet with one or more particular ingredients.

[0043] The complete feed, respectively complementary feed, is formulated according to a classic recipe for complete feed, respectively complementary feed, for feeding fish.

[0044] Preferably, the feed is a complete feed comprising at least the following components: at least one fish meal, at least one fish oil, at least one source of starch chosen from cassava and cereals chosen from wheat, corn and rice, at least one source of protein chosen from soybean and rapeseed in the form of cake or flour, and a premix of vitamins chosen from the group consisting of vitamins A, group B, C, D3, E, K3, and trace elements chosen from the group consisting of iron, copper, manganese, zinc, cobalt and selenium.

[0045] Cereals also include cereal by-products chosen in particular from wheat bran, rice bran, rice husk, corn dregs, corn gluten also known as “corn gluten feed”.

[0046] In particular, the complete feed comprises fish meal, one or two terrestrial animal meals chosen from meat meal, generally bovine and / or pork, and poultry meal, calcium, phosphorus, sodium chloride and synthetic amino acids.

[0047] More particularly, the food composition is a complete food comprising at least the following components: fish meal, fish oil, corn gluten, rice bran, soy flour, cassava flour, soy oil, and a premix of vitamins chosen from the group consisting of vitamins A, group B, C, D3, E, K3, and trace elements chosen from the group consisting of iron, copper, manganese, zinc, cobalt and selenium.

[0048] Preferably, the complete feed comprises from 5 to 30% by weight of fish meal(s) relative to the total weight of said complete feed.

[0049] Preferably, the complete feed comprises from 10 to 40% by weight of at least one protein source chosen from soybean and rapeseed in the form of cake or flour, in particular soybean flour, relative to the total weight of said complete feed.

[0050] Preferably, the complete feed comprises from 5 to 25% by weight of corn gluten relative to the total weight of said complete feed.

[0051] Preferably, the complete feed comprises from 5 to 20% by weight of at least one source of starch chosen from cassava and cereals chosen from wheat, corn and rice relative to the total weight of said complete feed.

[0052] Preferably, the complete food comprises from 10 to 20% by weight of rice bran relative to the total weight of said complete food.

[0053] Preferably, the complete feed comprises from 0.05 to 2.5% by weight of at least one oil relative to the total weight of said complete feed.

[0054] As fat, the complete feed preferably comprises at least one fish oil or at least one fish oil and one soybean oil.

[0055] In addition, the complete feed advantageously comprises a premix of vitamins and trace elements, ready to be introduced into the final formulation, called Premix.

[0056] The premix includes in particular vitamins A, group B, C, D3, E and K3, as well as trace elements such as iron, copper, manganese, zinc, cobalt and selenium.

[0057] Preferably, the complete feed comprises an amount ranging from 0.05 to 5% by weight of Premix relative to the total weight of the complete feed.

[0058] Preferably, the food composition according to the present invention does not comprise any other hydrolysate than the keratin hydrolysate used according to the present invention, which comprises at least 88% by weight of free amino acids relative to the total weight of the amino acids of the hydrolysate, the remainder of the amino acids of the hydrolysate being in the form of peptides having a molecular mass less than or equal to 800 Dalton, in particular the composition according to the present invention does not comprise another hydrolyzate of marine origin.

[0059] The food composition according to the invention can be formulated with the ingredients usually used in compositions for feeding fish, in particular humectants, thickeners, texturizing agents, emulsifiers, flavoring agents, coating agents, preservatives, antioxidants, colorings, plant extracts, non-protein ingredients such as purified starches, plant fibers, minerals. Of course, those skilled in the art will take care to choose these excipients so as not to alter the properties of the complete food.

[0060] According to a first variant, the keratin hydrolyzate is incorporated into the food composition by mixing said hydrolyzate with the other components of the complete food.

[0061] According to a second variant, the keratin hydrolyzate is applied by coating on the surface of the food composition. The methods used to carry out these “coating” or “top-coating” steps, in particular by spray-coating, fall within the skills of a person skilled in the art.

[0062] The formulation of the food composition for animal feed in accordance with the invention uses conventional methods which are part of the general skills of those skilled in the art.

[0063] The food composition is introduced directly into the water.

[0064] Generally, the food composition is used in such a way as to allow administration of said composition ranging from 1% to 5% of the weight of the fish. Depending on its age, the weight of the fish ranges from 4 g to 1 kg.

[0065] Generally, the food composition is used in an amount ranging from 20 g / day to 1 kg / day per 100 fish, or a quantity of hydrolyzate used according to the invention ranging from 25 mg to 10 g per 100 fish.

[0066] The food composition according to the invention has advantageous nutritional properties, and high bioavailability and palatability for fish.

[0067] Hydrolyzate

[0068] According to a particular implementation, the hydrolyzate described below is used in the food compositions according to the invention.

[0069] According to a preferred embodiment, the hydrolyzate used according to the invention is obtained by a preparation process in which the keratin material is a keratin material, preferably from poultry, comprising at least the following steps, in this order: - subjecting the keratin material to at least one chemical hydrolysis by means of an acid under conditions capable of obtaining a hydrolyzate comprising at least 88% in weight of free amino acids relative to the total weight of amino acids in the hydrolyzate, the remainder of the amino acids in the hydrolyzate being in the form of peptides having a molecular mass less than or equal to 800 Dalton, - preferably extracting tyrosine and cystine from said hydrolyzate preferably using a base; - possibly dry.

[0070] This hydrolyzate is obtained from natural keratin materials, advantageously from poultry feathers. Examples of poultry include hens, chickens, turkeys, ducks, geese, etc. In particular, the hydrolyzate is not obtained from human keratin such as hair.

[0071] The process for preparing said keratin hydrolyzate implements at least one chemical hydrolysis using an acid under conditions capable of obtaining a hydrolyzate comprising at least 88% by weight of free amino acids relative to the total weight of the amino acids in the hydrolyzate, the remainder of the amino acids in the hydrolyzate being in the form of peptides having a molecular mass less than or equal to 800 Dalton.

[0072] The percentage of peptides - having a molecular mass less than or equal to 800 Dalton - in the hydrolyzate generally ranges from 5 to 12% by weight relative to the total weight of the hydrolyzate.

[0073] The chemical hydrolysis of keratin is carried out using an acid, preferably a strong acid chosen from hydrochloric, phosphoric and sulfuric acids, preferably hydrochloric acid. Preferably the strong acid is used in a concentration ranging from 10 to 30%, preferably from 15 to 25%.

[0074] The chemical hydrolysis is generally carried out for a period ranging from 1 hour to 8 hours, preferably from 6 to 7 hours at a temperature ranging from 100 to 115°C.

[0075] According to a particular variant, the chemical hydrolysis is carried out in two stages: - a first chemical hydrolysis carried out at a temperature ranging from 60 to 80°C for a period ranging from 4 to 5 hours then - a second chemical hydrolysis carried out at a temperature ranging from 100 to 115°C for a period ranging from 5 to 8 hours, both hydrolyses can be carried out without an intermediate pause step or by carrying out an intermediate pause step of between 1 hour and 7 days.

[0076] More precisely, the first chemical hydrolysis is carried out at 72°C for 4.5 hours and the second chemical hydrolysis is carried out at 107°C for 6 hours, an intermediate break of 24 to 80 hours being carried out between the two chemical hydrolyses.

[0077] Chemical hydrolysis, carried out in one or more stages, is advantageously followed by at least one step of extraction of cystine and tyrosine.

[0078] The step of extracting cystine and tyrosine is carried out using a base, preferably chosen from sodium hydroxide, potassium hydroxide, preferably sodium hydroxide. The addition of a base to the hydrolyzate makes it possible to precipitate the less soluble amino acids (mainly cystine, tyrosine), thus making them separable from the liquid phase by suitable techniques, such as filtration or spinning.

[0079] The steps of chemical hydrolysis and extraction of cystine and tyrosine can be followed by optional steps of purification of the hydrolyzate obtained.

[0080] The steps of chemical hydrolysis and extraction of cystine and tyrosine can be followed by optional drying steps, for example by atomization.

[0081] The purification and drying steps are conventional steps, the implementation of which falls within the skills of a person skilled in the art.

[0082] The step of extracting cystine and tyrosine can be followed by an optional step of recovering certain amino acids from the precipitate by redissolving it in acid, then reprecipitating it with a base, the amino acids to be recovered then being in the liquid phase.

[0083] Preferably, the hydrolyzate used comprises less than 1% by weight of tyrosine relative to the total weight of the hydrolyzate, preferably less than 0.5%, more preferably, the hydrolyzate does not contain tyrosine. The only traces of tyrosine being due to the limits of the operating conditions and the equipment used during the extraction step.

[0084] Preferably, the hydrolyzate comprises less than 2.5%, preferably less than 1.5% and more preferably less than 1% by weight of cystine relative to the total weight of the hydrolyzate, more preferably, the hydrolyzate does not contain cystine.

[0085] Furthermore, the hydrolyzate does not comprise cysteine.

[0086] It has also been observed that the amino acids of the hydrolyzate exhibit good diffusion in water, which allows good detection of the food compositions according to the invention by the fish, which promotes the attraction capacities of the food on said fish.

[0087] The following examples are intended to illustrate the invention without limiting its scope.

[0088] Examples

[0089] Example 1- Hydrolyzate 1

[0090] Preparation of hydrolyzate 1

[0091] 4,500 kg of poultry feathers are introduced into a 50,000 litre reactor / hydrolyser. A first stage of chemical hydrolysis is carried out by adding 18,000 litres of hydrochloric acid (24%), the hydrolysis is carried out at 72°C for 4.5 hours. The product obtained is stored for 48 hours at room temperature (interval break Then a second chemical hydrolysis is carried out in a 20,000 liter reactor by heating at 107°C for 6 hours without adding acid. The product obtained is left to cool.

[0092] Next, a step of extraction of tyrosine and cystine is carried out, adjusting the pH to 5 using sodium hydroxide. The amino acids which precipitate (mainly cystine and tyrosine) are separated by spinning. The spinning waters are recovered. The precipitate is redissolved in dilute hydrochloric acid, then reprecipitated by adding sodium hydroxide solution, and spun again. The waters from this second spinning are added to those from the first spinning.

[0093] The amino acid solution obtained is separated from the sodium chloride by a membrane process and then dried by atomization.

[0094] 4,200 kg of hydrolyzate are obtained in dry form.

[0095] Results - Determination of the composition of the hydrolyzate

[0096] Table 1 shows, for each amino acid present, the content of total amino acids (free and bound) relative to the total weight of the hydrolyzate, as well as the weight fraction of free amino acids (AA) / total amino acids (AA).

[0097] [Tables 1] Content (% wt) in the composition of the hydrolyzate Weight fraction Free AA / Total AA Aspartic Acid 6.87 99% Threonine 4.55 100% Serine 12.14 100% Ac. Glutamic Acid 10.33 96% Glycine 7.84 98% Alanine 4.64 98% Valine 7.42 73% Cystine 1.71 71% Methionine 0.40 96% Isoleucine 4.18 82% Leucine 7.09 95% Tyrosine 0.26 72% Phenylalanine 2.33 97% Lysine 1.80 93% Histidine 0.58 89% Arginine 5.69 94% Proline 10.90 100% Total 88.73%

[0098] The free amino acid content is 94.3% by weight relative to the weight of total amino acids (free and bound).

[0099] Furthermore, the free amino acids of this hydrolyzate are not denatured.

[0100] The dry matter content of the hydrolyzate is 98.6% by weight.

[0101] An advantage of this hydrolysate is that it is very digestible. The true digestibility of amino acids is 96.8%, which gives it rapid assimilation by fish. Digestibility is measured in vivo according to the method described by ZM Larbier, AM Chagneau and M. Lessire in “Effect of protein intake on true digestibility of amino acids in rapeseed meals for adult roosters force fed with moistened feed”. Animal Feed Science and Technology. 34 (1991) 255-260.

[0102] The hydrolyzate used according to the invention is also soluble in water, in fact 1 g hydrolyzate is soluble in 5 mL of water. This solubility gives it interesting properties for the implementation and development of organoleptic characteristics within the final product, in particular a high palatability.

[0103] Example 2 - Food compositions

[0104] The food compositions presented in Table 2 below are prepared.

[0105] To obtain the formulations in accordance with the invention, containing the hydrolysate, the raw materials presented in Table 2: soy flour, fish flour, corn gluten, rice bran, are ground, then mixed with the cassava flour, hydrolysate 1, half the quantities of soy and fish oils and the premix. The final mixture is extruded through a 3 mm mesh sieve.

[0106] For each formulation, the required quantity of hydrolyzate is incorporated as a substitute for the same quantity of cassava flour so as to obtain the compositions F AA 0.125; FAA 0.25; FAA 0.375; FAA 0.50 and FAA 1.0.

[0107] Comparative composition FAA 0, was prepared without hydrolyzate 1.

[0108] Then after drying, the remaining part of the soybean and fish oils is applied to each composition to ensure its stability. The prepared food compositions were stored at -20 °C

[0109] [Tables2] Raw materials FAA0 Compar. FAA 0.125 FAA 0.25 FAA 0.375 FAA 0.50 FAA 1.0 Fish meal (a) 26.0 26.0 26.0 26.0 26.0 26.0 Soy flour (b) 30.0 30.0 30.0 30.0 30.0 30.0 Corn gluten (c) 24.0 24.0 24.0 24.0 24.0 24.0 Rice bran 14.5 14.5 14.5 14.5 14.5 14.5 soybean oil 0.125 0.125 0.125 0.125 0.125 0.125 fish oil 0.125 0.125 0.125 0.125 0.125 0.125 Premix (d) 0.25 0.25 0.25 0.25 0.25 0.25 Cassava flour 5.00 4.875 4.75 4.625 4.50 4.00 Hydrolyzate of example 1 0.00 0.125 0.25 0.375 0.50 1.00

[0110] Fish meal (a) marketed by the Thai company Nivat fishmeal Industry Co. Ltd (55% Protein, 90% dry matter, 12% lipids, 23% ash)

[0111] Soybean meal (b) marketed by the Thai company Portoh animal feed Co. Ltd

[0112] Corn gluten (c) marketed by the Thai company Portoh animal feed Co. Ltd.

[0113] Premix (d) is marketed by the Thai company Atlantic pharmaceutical Co. Ltd, its composition is presented in table 3.

[0114] [Tables 3] Vitamins Quantity / kg of feed Minerals Quantity / kg of feed A 4000000 IU Calcium D-pantothenate 2.0 mg D 400000 IU Magnesium acetate 11.2 mg E 1.3 g Sodium acetate 75 mg K 0.9 g Calcium gluconate 290 mg C 300 mg Sodium chloride 150 mg B1 2.5 g Sodium citrate 275 mg B2 2.5 g Calcium acetate 75 mg B6 0.5 g Potassium chloride 112.5 mg B12 5.0 mg Nicotinamide 5.0 mg Folic acid 0.5 mg

[0115] Table 4 shows the nutritional values ​​of the compositions.

[0116] [T ables 4] Raw materials FAA0 Compar. FAA 0.125 FAA 0.25 FAA 0.375 FAA 0.50 Humidity % 8.20 8.30 8.30 8.60 8.60 Mineral matter % 9.70 9.33 8.96 8.85 8.81 Lipids % 4.20 4.20 4.40 4.20 4.20 Proteins % 31.30 31.90 32.00 32.00 31.90 Fibers % 2.79 2.57 2.57 2.82 2.62

[0117] Table 5 shows the total amino acid contents of the food compositions- supplementary in g / kg of composition, in raw material.

[0118] [Tables 5] FAA0 FAA 0.1 25 FAA 0.25 FAA 0.3 75 FAA 0.50 FAA 1.00 Aspartic acid 24.4 24.5 24.5 24.6 24.7 25.1 Threonine 13.3 13.4 13.5 13.5 13.6 13.8 Serine 17.1 17.2 17.4 17.6 17.7 18.4 Glutamic acid 50.1 50.2 50.4 50.5 50.6 51.2 Glycine 23.1 23.2 23.3 23.4 23.5 24.0 Alanine 16.2 16.3 16.4 16.4 16.5 16.7 Valine 16.1 16.2 16.3 16.4 16.5 16.9 Cystine 4.8 4.8 4.9 4.9 4.9 5.0 Methionine 7.0 7.0 7.1 7.1 7.1 7.1 Isoleucine 13.6 13.7 13.8 13.8 13.9 14.1 Leucine 28.2 28.3 28.4 28.5 28.6 29.0 Tyrosine 9.7 9.7 9.7 9.7 9.7 9.7 Phenylalanine 14.1 14.2 14.3 14.3 14.4 14.6 Lysine 20.1 20.1 20.1 20.2 20.2 20.3 Histidine 6.6 6.6 6.6 6.6 6.6 6.6 Arginine 22.1 22.2 22.3 22.4 22.4 22.8 Proline 25.9 26.0 26.2 26.3 26.5 27.1 Tryptophan 3.9 3.9 3.9 3.9 3.9 3.9

[0119] Example 3 - Study on farmed fish

[0120] a. Materials and methods

[0121] The study involved 450 healthy fish. The fish used were Nile carp (Nile Tilapia) with an average initial individual weight of 4.76 g + 0.05 g.

[0122] During the two weeks preceding the start of the experiments, the fish were acclimatized to laboratory conditions, they were randomly distributed in 15 floating cages of dimensions 2.0x1.5x1.5 m3, placed in a cement tank with the following dimensions 7x10x1.5 m3 with a density of 30 fish per cage.

[0123] The fish were fed with a commercial product comprising 32% protein and 4% fat in a daily quantity corresponding to 5% of their weight.

[0124] The food compositions FAA 0; FAA 0.125; FAA 0.25; FAA 0.375 and FAA 0.50 used were formulated.

[0125] Water quality parameters were measured and were consistent with fish farming: dissolved oxygen level was 9.61+0.7 mg / L, temperature 27.2+0.70°C, pH 8.37+0.3, alkalinity 215.33+0.03 mg / L and ammonia nitrogen less than 0.02 mg / L).

[0126] b. Blood and tissue sampling

[0127] In order to evaluate the functional capacity of several organs, such as the liver and kidneys, of the fish fed with the feed compositions according to the invention, the biochemical profile of the blood of said fish was analyzed. At the end of the feeding trial, all fish were fasted for 24 hours after the last feeding, blood samples were taken from the caudal vein of the fish after anesthesia (5% 2-phenoxyethanol) using sterile syringes. The blood samples were taken from twelve fish per treatment and were centrifuged to obtain serum. The serum samples were stored at -20 °C until their use in the biochemical and immune tests.

[0128] In parallel, fish samples from each treatment were dissected and livers and intestines were aseptically removed on ice and then rinsed with cold PBS, pH 7.5. The liver tissue was ground in a glass homogenizer (0.1 g of liver was added to 0.9 ml of PBS, pH 7.5), then centrifuged at 5000 g for 15 min at 4 °C to obtain the supernatant, which was stored at -20 °C before being used for the measurement of antioxidant activities. The midgut (3 fish / cage) was immediately homogenized in 10 volumes of ice-cold Tris-HCl (pH 7.5) and centrifuged at 5000 g for 15 min at 4 °C. The supernatant was retained for the measurement of digestive enzyme activities.

[0129] c - Biochemical analyses

[0130] Total proteins were determined by the Biuret method according to Zheng et al. (2017).

[0131] Example 3.1 - Zootechnical performance, carcass yield and body composition index

[0132] In order to evaluate the effect of the feed compositions according to the invention on the growth performance of the fish, after 8 weeks of feeding, the following growth performance parameters were measured.

[0133] Thus, the initial body weight IBW, the final body weight FBW as well as the average daily gain (ADG) were measured.

[0134] All fish in each tank were weighed and growth parameters, for each replicate, were calculated according to the following formulas:

[0135] Weight gain in % (WG%) = 100 x (FBW - IBW) / IBW;

[0136] Specific growth rate (SGR; % / day) = 100 x (Ln FBW - Ln IBW) / day, Ln being the natural logarithm;

[0137] Feed conversion ratio or feed conversion ratio (FCR) = dry feed consumption / wet weight gain;

[0138] Protein Efficiency Ratio (PER%) = 100 x (FBW - IBW / (dry feed consumption x feed protein content).

[0139] Metabolizable energy (ME) was calculated using the following formula: ME (kcal / kg) = DE x [(1.003-(0.00021 x crude protein)] according to the method described by Noblet J. and Perez, JM, “Prediction of digestibility of nutrients and energy values ​​of pig diets from Chemical analysis. Journal of animal science, (1993), 71(12), 3389-3398”, the digestible energy value DE (“Digestible Energy”) being obtained according to the same publication.

[0140] In addition, body composition indices were determined respectively with the following formulas: Viscero-somatic index (VSI%) = 100 x wet weight of viscera and visceral fat / wet body weight and hepatosomatic index (HSI%) = 100 x wet weight of liver / wet body weight.

[0141] Finally, the carcass yield was calculated according to the following formula: carcass yield (%) = live body weight of gutted fish / live body weight* 100.

[0142] The effects of the compositions according to the invention on zootechnical performances are presented in Table 6.

[0143] [Tableauxô] FAAO FAAO,125 FAAO,25 FAAO,375 FAAO,50 p-value and IBW 4.71+0.02 4.73+0.08 4.73+0.18 4.84+0.05 4.81+0.13 0.997 FBW 52.95. 61.7+6.30 to 65.4+7.20 to 68.2+6.80 to 0.023 WG 48.19+0.02 b 49.37+0.38 ab 56.97+0.37 to 60.56+0.08 to 63.39+2.02 to GR 4.03+0.01 b 4.02+0.04 ab 4.20+0.08 a 4.35+0.02 a 4.39+0.06 a 0.047 ADG 0.80+0.04 b 0.82+0.01 ab 0.95+0.03 a 1.01+0.01 a+2.01+ a 0.033 FCR 1.92+0.07 a 1.85+0.02 ab 1.62+0.10 b 1.53+0.10 b 1.46+0.14 b 0.020 PER 1.54+0.00 d 1.55+0.00 d 1.78+0.01+1 b. 1.99+0.01 to 0.000 HSI (%) 1.66+0.16 1.56+0.19 1.54+0.18 1.57+0.09 1.56+0.01 0.325 VSI (%) 10.04+0.18 to 8.1+2+0.80 b.80.80. 8.53+0.42 b 8.08+0.45 b 0.019 Rdt in carcasses is (%) 58.0+0.90 b 59.8+1.84 ab 61.7+1.56 ab 62.6+1.13 to 63.4+0.68 to 0.0188

[0144] It is observed that the growth-related values ​​(FBW, WG, SGR and ADG) of the fish fed with the compositions according to the invention at doses greater than 0.25% (FAA 0.25) increased significantly (P<0.05) compared to the fish fed with the control (FAAO). In addition, feeding with the feed compositions according to the invention FAAO,25 or more concentrated in hydrolyzate also significantly decreased the FCR (P<0.05) and significantly increased the protein efficiency rate (PER) compared to the fish fed with the control (FAAO), which reflects a better feed efficiency.

[0145] Body composition indices were also influenced by hydrolysate levels in the feed compositions, particularly the viscero-somatic index. Indeed, the VSI values ​​of fish fed with the compositions according to the invention were significantly reduced compared to the FAAO control group (P<0.05). On the other hand, the carcass yields of fish fed with the compositions according to the invention were significantly increased compared to the control group (P<0.05).

[0146] Improving carcass yield systematically leads to an improvement increase in net yield as described in the publication by Marcia Regina SIMÔES et al. “Physical-chemical composition, microbiology of yield of tilapia thread (Oreochromis niloticus) Physicochemical and microbiological composition and yield of Thai-style tilapia fillets (Oreochromis niloticus). Ciênc. Tecnol. Aliment., Campinas, 27(3): 608-613, July-set. 2007.

[0147] The improvement in carcass yield highlighted in Table 6 is therefore consistent with the increase in lipid content of said fillets presented in Table 7 (below). These results are also consistent with the decrease in the viscerosomatic index and reflect better and more efficient use of feed.

[0148] With the HSI index, no significant difference is observed between the different food compositions.

[0149] Example 3.2 Composition of the nets

[0150] Composition of whole fillets, quality of fillets and analysis of fatty acid composition

[0151] At the end of the experiment, at week 8, a total of 45 fish were randomly sampled, 9 additional fish (3 fish / tank x 3 tanks / group) were collected from the control group and all treatment groups. These fish were filleted to obtain butterfly fillets. The color of the fillets was measured using a CR400 chromameter (Minolta, Japan) where the redness index or a* (red-green intensity), yellowness or b* (yellow-blue intensity), and lightness or L* (dark to light). The instrument was calibrated using a standard white plate; the L* (brightness), a* (redness), and b* (yellowness) values ​​were recorded from the dorsal and ventral regions of the fish fillet. These measurements were averaged and analyzed as the response for a given fillet.

[0152] The composition of the fillets was analyzed: moisture (water content), crude protein, crude lipids and ash were measured as previously described.

[0153] The analyses were carried out in triplicate (three replicates, n=3) for each sample.

[0154] The effect of free amino acid content of food compositions on body composition is shown in Table 7.

[0155] [Tables?] FAA0 FAA0.125 FAA0.25 FAA0.375 FAA0.50 p-value humidity 77.6+0.2 a 77.7+0.2 a 77.36+0.3 b 76.9+0.1 b 77.1+0.2 b 0.010 Crude proteins 14.6+0.3 14.95+0.3 14.86+0.3 14.8+0.4 14.95+0.2 0.390 Crude lipids 2.74+0.6 b 2.88+0.4 b 4.44+0.5 a 5.15+0.1 a 4.47+0.4 a 0.001 ash 4.89+0.6 4.92+0.3 4.12+0.4 4.21+0.2 4.28+0.3 0.580

[0156] Increasing the free amino acid content in the feed compositions led to a significant increase in the crude lipid content of the fillets (P<0.05), which was in direct proportion to the amino acid content in the diets. Humidity, on the other hand, decreased (P<0.05). Crude protein and ash were not affected by the free amino acid levels in the feed.

[0157] The increase in lipid content within the fillets thus reflects better feed efficiency, notably with better assimilation and transformation of the energy in the diet, linked to better digestion of starch.

[0158] Tables 8 and 9 present the colorimetric indices a* (red-green intensity), b* (yellow-blue intensity), and the clarity or L* respectively of the dorsal region and the ventral region of the fish fillets.

[0159] [Tables8] FAA0 FAA0.125 FAA0.25 FAA0.375 FAA0.50 p-value L* 61.5+2.1 b 62.0+1.8 ab 65.6+1.6 ab 65.9+0.1 a 66.7+0.8 a 0.048 a 5.5+1.0 5.6+0.4 5.4+0.1 5.7+0.2 6.1+0.7 0.762 b 14.2+0.2 15.2+0.1 14.1+0.1 15.1+0.3 15.4+1.0 0.310

[0160] [Tables9] FAA0 FAA0.125 FAA0.25 FAA0.375 FAA0.50 p-value L* 65.9+3.1 b 68.8+1.4 b 68.6+1.9 b 74.9+1.1 a 68.7+1.7 a 0.042 a 16.7+1.2 17.1+1.1 17.5+0.7 18.9+1.8 17.6+0.7 0.809 b 22.4+1.2 22.1+1.1 22.8+0.7 23.0+1.8 23.1+0.7 0.875

[0161] Clarity (L*) was modified (P<0.05) in fish fed with the compositions according to the invention, whether in the dorsal region where the values ​​increased from 61.5 to 66.7 or in the ventral region where the values ​​increased from 65.31 to 74.9. The food compositions according to the present invention therefore make it possible to obtain fish with whiter flesh.

[0162] Although redness (a*) and yellowing (b*) were numerically higher in the group of fish fed with free amino acids, no statistical differences were correlated with these differences.

[0163] Analysis of fatty acids in fish fillets

[0164] Fish fillet samples were subjected to measurement of fatty acid compositions according to the methods previously described by Horwitz, Official methods of analysis of AOAC International. Volume I, agricultural Chemicals, contaminants, drugs / edited by William Horwitz. Gaithersburg (Maryland): AOAC International, 1997. The fatty acid composition of fish fillets was determined by gas chromatography-mass spectrometry (GC-MS) described by Chen et al. in “N-3 essential fatty acids in Nile tilapia, Oreochromis niloticus: Effects of linolenic acid on non-specific immunity and anti-inflammatory responses in juvenile fish. Aquaculture (2016), 450, 250-257.”

[0165] The analyses were carried out in triplicate (three replicates, n=3) for each sample.

[0166] Table 10 shows the fatty acid compositions (mg / g) in the fillets of fish fed for 8 weeks.

[0167] [TableauxlO] FAA0 FAA0.125 FAA0.25 FAA0.375 FAA0.50 p-value Oleic acid (mg / g) 27.81 ±0.18 c 31.39 ±0.13 b 30.42 ±0.13 b 30.87 ±0.17 b 35.15 ±0.06 a 0.000 Linoleic acid (mg / g) 15.89 ±0.43 b 16.07 ±0.41 b 16.14 ±0.41 ab 17.13 ±0.09 a 17.28 ±0.11 a 0.073 a-linolenic acid (mg / g) 0.87 ±0.07 c 1.12 ±0.02 ab 1.01 ±0.02 bc 1.15 ±0.04 to 1.23 ±0.04 to 0.013

[0168] Oleic acid (Cl8:1 n9c) is a monounsaturated fatty acid, whereas linoleic (C18:2 n6c) and a-linolenic (C18:3 n3) acids are polyunsaturated fatty acids.

[0169] Different fatty acids were identified and examined in the muscle tissues of the fillet of fish fed the different diets. This study revealed that all groups of fish fed with the food compositions according to the invention had higher levels of oleic acid (C18:1 n9c), these values ​​were significantly higher than those of the control groups not supplemented with compositions according to the invention. (P<0.05).

[0170] The levels of polyunsaturated fatty acids, in particular linoleic acid (C18:2 n6c) and linolenic acid (C18:3 n3), increased significantly in all groups of fish fed with the food compositions according to the invention and were found to be higher than that of the control group (P<0.05).

[0171] Examples 3.3- Determination of the activity of digestive enzymes

[0172] The activities of digestive enzymes, including amylase, protease and lipase, were evaluated in the intestine of fish.

[0173] Amylase activity was measured according to the method of Nater et al. "Stress-induced changes in human salivary alpha-amylase activity - associations with adrenergic activity, Psychoneuroendocrinology, 31(1), 49-58." This method is based on the use of 3,5-dinitrosalicylic acid, which reacts with reducing sugars and other reducing molecules to form 3-amino-5-nitrosalicylic acid. The rate of increase in absorbance was measured spectrophotometrically at 550 nm.

[0174] Determination of protease activity was determined using the azocasein hydrolysis assay according to the Cupp-Enyard method Sigma's non-specific protease activity assay-casein as a substrate. JoVE (Journal of Visualized Ex-periments), (19), e899. Absorbance over time was measured spectrophotometrically at 405 nm.

[0175] Lipase activity was determined by Pencreac'h and Baratti, Hydrolysis of p-nitrophenyl palmitate in n-heptane by the Pseudomonas cepacia lipase: a simple test for the determination of lipase activity in organic media. Enzyme and Microbial Technology, 18(6), 417-422, which uses p-nitrophenylphosphate as a substrate and was measured spectrophotometrically at 550 nm.

[0176] The effect of feed compositions on the activities of protease, amylase and lipase enzymes in the tilapia intestine is shown in Table 11.

[0177] [Tableauxll] FAA0 FAA0.125 FAA0.25 FAA0.375 FAA0.50 p-valu e Amylase (U / mg) 4.36+ 0.19 b 4.34+ 0.23 b 4.90+ 0.28 b 5.88+ 0.25 ab 5.30+ 0.42 a 0.010 Lipase (U / mg) 32.46+ 0.05 e 33.09+ 0.31 d 33.17+ 0.17 c 34.18+ 0.33 b 35.82+ 0.78 a 0.005 Proteinase (U / mg) 17.69+ 0.08c 21.10+ 0.04 c 22.91+ 0.02 bc 24.00+ 0.03 to 24.74 + 0.03 to 0.000

[0178] Amylase, lipase and protease activities were affected by diets using the compositions according to the invention. The compositions according to the invention resulted in a significant increase in the activity of the three enzymes tested in the intestine of fish (P<0.05).

[0179] Generally speaking, these results perfectly explain the effects observed on feed efficiency which is significantly improved with the compositions according to the invention rich in free amino acids. The significant increase in the levels of protease, lipase and amylase allows the fish to better digest the proteins, lipids and starch in the feed compositions.

[0180] In particular, the increase in amylase activity, which is correlated with better assimilation of starch, leads to less fat deposition around the viscera and more in the fillets, this result is in agreement with that of the VSI values ​​in Table 6 and the lipid and fatty acid values ​​of fillets in Tables 7 and 10 respectively.

Claims

Claims

1. A food composition for feeding fish containing from 0.05 to 2%, preferably from 0.1 to 1% by weight of a keratin hydrolyzate comprising at least 88% by weight of free amino acids relative to the total weight of the amino acids in the hydrolyzate, the remainder of the amino acids in the hydrolyzate being in the form of peptides having a molecular mass less than or equal to 800 Dalton, said composition comprising the following contents of the following amino acids in free form: an aspartic acid content ranging from 0.009% to 0.074% by weight, preferably ranging from 0.018 to 0.037% by weight; a serine content ranging from 0.016 to 0.132% by weight, preferably ranging from 0.032 to 0.066% by weight; a glutamic acid content ranging from 0.013 to 0.106% by weight, preferably ranging from 0.026 to 0.053% by weight; a glycine content ranging from 0.011 to 0.086% by weight, preferably ranging from 0.022 to 0.043% by weight;an alanine content ranging from 0.006 to 0.050% by weight, preferably ranging from 0.012 to 0.025% by weight; an arginine content ranging from 0.008 to 0.064% by weight, preferably ranging from 0.016 to 0.032% by weight; a proline content ranging from 0.014 to 0.118% by weight, preferably ranging from 0.029 to 0.059% by weight relative to the total weight of the composition.;

2. Food composition according to claim 1 wherein the hydrolyzate has the following distribution of total amino acids: an aspartic acid content ranging from 5 to 8% by weight, preferably ranging from 6 to 7% by weight; a threonine content ranging from 4 to 6% by weight, preferably from 4 to 5% by weight; a serine content ranging from 9 to 14% by weight, preferably ranging from 10 to 12% by weight; a glutamic acid content ranging from 9 to 11%; a glycine content ranging from 6 to 9% by weight, preferably ranging from 7 to 8% by weight; an alanine content ranging from 4 to 6% by weight, preferably from 4 to 5% by weight; a valine content ranging from 6 to 10% by weight, preferably ranging from 7 to 8% by weight; a methionine content ranging from 0.1 to 0.6% by weight; an isoleucine content ranging from 4 to 6% by weight, preferably ranging from 4 to 5% by weight;a leucine content ranging from 6 to 9% by weight, preferably ranging from 7 to 8% by weight; a phenylalanine content ranging from 2 to 5% by weight; a lysine content ranging from 1 to 3% by weight, a histidine content ranging from 0.4 to 1% by weight; an arginine content ranging from 5.5 to 6.5% by weight; a content of; proline ranging from 8.5 to 11% by weight, a tryptophan content of less than 0.1%, preferably 0% by weight relative to the total weight of the hydrolyzate.

3. A food composition according to claim 1 or 2 wherein the hydrolyzate comprises the following free amino acids: at least 95% of aspartic acid in free form by weight relative to the total weight of aspartic acid in the hydrolyzate; at least 95% of threonine in free form by weight relative to the total weight of threonine in the hydrolyzate; at least 95% of serine in free form by weight relative to the total weight of serine in the hydrolyzate; at least 93% of glutamic acid in free form by weight relative to the total weight of glutamic acid in the hydrolyzate; at least 93% of glycine in free form by weight relative to the total weight of glycine in the hydrolyzate; at least 93% free alanine by weight relative to the total weight of alanine in the hydrolyzate; at least 93% of methionine in free form by weight relative to the total weight of methionine in the hydrolyzate; at least 93% of phenylalanine in free form by weight relative to the total weight of phenylalanine in the hydrolyzate; at least 95% of proline in free form by weight relative to the total weight of proline in the hydrolyzate.

4. Food composition according to any one of the preceding claims having the following distribution in total amino acids: an aspartic acid content ranging from 2.2% to 2.7% by weight, preferably ranging from 2.3% to 2.6% by weight; a threonine content ranging from 1.1% to 1.6% by weight, preferably from 1.2% to 1.5% by weight; a serine content ranging from 1.5% to 2.1% by weight, preferably ranging from 1.6% to 2.0% by weight; a glutamic acid content ranging from 4.8% to 5.4% by weight, preferably ranging from 4.9% to 5.3% by weight; a glycine content ranging from 2.1% to 2.7% by weight, preferably ranging from 2.2% to 2.6% by weight; an alanine content of 1.3% to 2.0% by weight, preferably ranging from 1.5% to 1.9% by weight; a valine content of 1.3% to 2.0% by weight, preferably ranging from 1.5% to 1.9% by weight; a cystine content of 0.3% to 0.7% by weight, preferably ranging from 0.4% to 0.6% by weight;a methionine content ranging from 0.4% to 1.0% by weight, preferably ranging from 0.6% to 0.8% by weight; a content; in isoleucine ranging from 1.1% to 1.8% by weight, preferably from 1.2% to 1.6% by weight; a leucine content ranging from 2.5% to 3.3% by weight, preferably from 2.6% to 3.1% by weight; a tyrosine content ranging from 0.6% to 1.3% by weight, preferably from 0.8% to 1.2% by weight; a phenylalanine content ranging from 1.0% to 1.8% by weight, preferably from 1.2% to 1.7% by weight; a lysine content ranging from 1.7% to 2.3% by weight, preferably from 1.8% to 2.2% by weight, a histidine content ranging from 0.4% to 0.9% by weight; an arginine content ranging from 1.8% to 2.6% by weight, preferably ranging from 2.0% to 2.4% by weight; a proline content ranging from 2.1% to 3.0% by weight, preferably ranging from 2.2% to 2.9% by weight; a tryptophan content ranging from 0.2% to 0.6% relative to the total weight of the composition.

5. Food composition according to any one of the preceding claims having a total content of free amino acids ranging from 0.5 to 5% by weight, preferably ranging from 1 to 2.5% by weight, including a total content of the following free amino acids: aspartic acid, serine, glutamic acid, glycine, alanine, arginine and proline ranging from 0.08% to 1.5% by weight, preferably ranging from 0.15 to 0.75% by weight relative to the total weight of the composition.

6. A food composition according to any one of the preceding claims wherein said food composition is a complete food comprising at least the following components: at least one fish meal, at least one fish oil, at least one starch source selected from cassava and cereals selected from wheat, corn and rice, at least one protein source selected from soybean and rapeseed in the form of cake or flour, and a premix of vitamins selected from the group consisting of vitamins A, group B, C, D3, E, K3, and trace elements selected from the group consisting of iron, copper, manganese, zinc, cobalt and selenium.

7. Food composition according to the preceding claim wherein said food composition is a complete food comprising at least the following components: at least the following components: fish meal, fish oil, corn gluten, rice bran, soy flour, cassava flour, soy oil, and a premix of vitamins selected from the group consisting of vitamins A, group B, C, D3, E, K3, and trace elements selected from the group consisting of iron, copper, manganese, zinc, cobalt and selenium.

8. Non-therapeutic use of the food composition according to any one of the preceding claims for increasing the quantity of flesh, in particular that of fish fillets.

9. Non-therapeutic use of the food composition according to any one of claims 1 to 7 for improving the quality of fish flesh, in particular modifying the color of fish flesh, more particularly to obtain a whiter color.

10. Non-therapeutic use of the food composition according to any one of claims 1 to 7 for modifying the composition of the flesh, in particular that of fish fillets, and more particularly for increasing the quantity of unsaturated fatty acids in the flesh, in particular in the fillets.

11. Non-therapeutic use of the food composition according to any one of claims 1 to 7 for modifying the composition of the intestinal flora of fish, in particular for increasing the quantity of digestive enzymes in the intestinal flora of fish, in particular for increasing the quantity of amylase.