A FEED AND THE USE OF SUCH A FEED

Abstract: A formulated proteinaceous feed is described, and the object has been to bring about better utilization of the proteins of the feed, so that the building of muscles is favoured, whereas a smaller portion of digested amino acids are combusted as energy or deposited as fat. To this end, a mixture of different protease inhibitors has been added to the formulated proteinaceous feed.

Description: A FEED AND THE USE OF SUCH A FEED This invention relates to a feed for animals, birds and fish, especially a particulate/pelleted/flaked fish feed in the form of a formulated main feed. The invention also relates to the use of such a feed for a particular purpose in the feeding of farmed fish in net pens or onshore farming tanks. When a formulated proteinaceous feed is fed, the protein is utilized poorly because the feed is digested faster than the animal, bird or fish is able to utilize the protein. Therefore, an essential part of the protein content of the feed is spent on energy instead of on building muscles. The state of the art is represented by raw materials for feed, which distinguish themselves in that the protein has a different digestive rate. Such known feedstuffs have a highly limited effect as regards initiating increased utilization of protein, so that a larger part of the protein of the feed will go to the building of muscles and thus added growth. In known technique the choice of raw material and the production process are complicated. Modern fish feeds consist of finely ground, heat-treated raw materials, which are "glued" together by means of starch, steam and pressure. The protein of such a feed is finegrained and denatured, this means that the tertiary structure of the molecule, its original, unique form, has been opened up and changed. However, in the natural food of fish, which is live, whole prey, the protein is present in its native, unique form, bound in large organs, e.g. musculature. The digestive progress of these two forms of protein differ relatively much, since the speed through the gastrointestinal canal increases in proportion to the degree of processing, without this influencing the overall digestibility of the protein. The native, unique form of a protein is such that it is difficult for the enzymes digesting protein (proteolytic enzymes) to attack it. All deviations from the one native biological form result in new points of attack for the proteases, which explains the much faster breaking down of denatured protein compared to native protein, and subsequent rapid absorption of amino acids. By too large a supply of amino acids to the protein synthesis apparatus of the animal in a short period of time, the biochemical processes occurring in fish will result in a larger portion of the digested amino acids being consumed as energy instead of being deposited as fish muscle. In the literature there are reports of almost doubled yield from protein in the form of increased deposits of muscle protein, when feeding with relatively large pieces of fish compared to feeding with finely ground raw materials of feed. However, in modern aquaculture the use of formulated feed is universal for practical reasons. Therefore, there is a need for increasing the utilization of the feed protein of formulated feed, and according to the present invention the aim has been to make the necessary arrangements and provide an additive for formulated feed to realize this general object. The protein molecule consists of hundreds to thousands of amino acids bonded together in a chain. Such chains of amino acids are further folded or packed together into entirely unique, three-dimensional structures, depending on the order of the amino acids thereof. During digestion this three- dimensional structure is disturbed first by the acidic fluid in the stomach, after which the chain is broken open by proteolytic enzymes, and the individual amino acids are released. Some amino acids will be present as di- and tripeptides, but most of them will be present in free form. This breaking down of the protein occurs by means of several proteolytic enzymes. These enzymes can be divided into two main groups: endopeptidases and exopeptidases. The exopeptidases attack within the chain of peptides and divide the protein molecule into smaller chains, whereas the endopeptidases split the amino acids one by one from the end of the chain of amino acids. In order to achieve efficient digestion, both these groups of enzymes must be present. Examples of exopeptidase are trypsin and chymotrypsin, whereas examples of endopeptidase are carboxypeptidase A and B. More specifically the object of the present invention has therefore been to obtain a feed which favours the utilization of the protein in the feed, i.e. favours increased growth per amount of protein measured by normal feeding, amount of feed and feeding frequency. Likewise, the aim has been to prescribe an application of such formulated feed with the intention of realizing a particular object. According to the invention, said object has been realized through the formulation of a feed in accordance with the features stated in the Claims, which also describe a particular application of such feed. To increase the utilization of the protein of the feed, it is desirable to change the absorption time of amino acid from the intestine. According to the invention this may be done by blocking part of the protein-digesting enzymes (proteases) present in the intestine. According to the invention, this may in its turn be realized by adding a mixture of different protease inhibitors to a formulated feed. The fact that protease inhibitors can be present in some feed components is known in itself, but their presence is then not planned and of completely uncontrolled amounts. An example is the so-called "soy-trypsin" inhibitor found in soybeans. This is in fact two inhibitors, namely the Bowman-Brink and the Kunitz trypsin inhibitors, which are two inhibitors inhibiting the same enzyme, namely trypsin. According to several reports, this soy-trypsin inhibitor has been considered undesirable due to its negative effect, inhibiting only one enzyme. By adding a mixture of protease inhibitors (enzyme regulators) to formulated feed, that can be produced from vegetable substances, such as plants, e.g. from potatoes or soy, or that may be produced chemically, e.g. camostate, or in different combinations thereof, it has turned out, on the other hand - when a mixture of several different protease inhibitors in very small, accurately controlled amounts, is added - that a substantial improvement of the utilization of protein, and of growth, occurs. The active substance (the mixture of protease inhibitors) may for example constitute 0.001 - 0.2 % calculated on complete feed. A feed according to the invention thus distinguishes itself primarily in that it contains an additive consisting of an accurately apportioned mixture of different protease inhibitors in an amount, which is very small relative to the weight of the rest of the formulated feed. The protease inhibitors may with advantage be added to the feed in a concentrated from. An essential effect, a property inherent in protease inhibitors, including a concentrated inhibitor, which is an isolate or concentrate of potato juice, is that the mixture inhibits both endogenous and exogenous proteases. The percentage/added amount of protease inhibitors stated above may be based on a number of protein sources > 2. With 3 sources of protein the contribution of binders is taken into account. By five series of experiments carried out in accordance with the present invention, a mixture containing several different protease-inhibiting components was used as additive in a conventional formulated fish feed. The protease inhibitor mixture was added to the feed in a concentrated form, i.a. in an amount in the range of 0.001 - 0.2 % mentioned above. In these five series of experiments, it was attempted to map: 1 ) Whether the additive inhibited the enzymatic activity in an intestine of fish (salmon); 2) Determine the optimal level of addition of the protease inhibitor mixture in the feeding of salmon; 3 ) The digestibility of the main nutrients when a protease inhibitor mixture is used in feed for salmon; 4) The effect of the use of a protease inhibitor in combination with different sources of protein in feed for salmon; 5) The process of absorption of amino acids by means of a protease inhibitor mixture. The results were as follows : 1) Tests in vitro showed that a reversible, partial inhibition of the enzymatic activity in an extract of enzymes, isolated from salmon intestine, could be achieved. This indicates that a temporary immobilization of endo- and exopeptidases occurs when a protease inhibitor mixture according to the invention has been added to the feed; 2) Dose-response experiments showed that by a level of addition, a growth-enhancing effect was achieved by adding a protease inhibitor mixture according to the invention, without any negative effect being found on the utilization of the feed (feed factor) or the overall digestion of the protein; 3 ) Dose-response experiments also showed that above a certain level of admixture of the protease inhibitor mixture, a clear reduction of the protein digestibility occurred, measured as nitrogen digestibility. No effect was observed on the digestibility of fat; 4 ) When the optimal concentration of protease inhibitor was used, a clear increase in growth was achieved on the basis of formulated fish feed based on fish meal, compared to the use of identical feed without the additive according to the invention. When some of the fish meal feed component was replaced by hydrolyzed protein (fish ensilage), the growth was further enhanced; (The amount of hydrolyzed protein added to a feed may be measured as TNBS with a binding of free alfa-amino-groups to trinitrobenzo-sulphonic acid, L-leuisin used as standard.) The TNBS-value should be between 0.4 and 2.0. 5) By studies on the absorption from intestine to blood of intact protein marked with 14 C, altered absorption was found when concentrated protease inhibitor mixture according to the invention was added to the feed. The following tables illustrate relations between the addition of mixtures-of protease inhibitors to formulated feeds: T A B L E 1 Feed without ensilage Table 1 illustrates, in per cent, the increase in daily growth by the use of feed based on fish meal with addition of the protease inhibitor mixture according to the invention. The increase is 13 %. T A B L E T3 Feed with ensilage Table 2 illustrates, in per cent, the increase in daily growth when some of the fish meal of the feed has been replaced by hydrolyzed protein (fish ensilage). The increase is 32 %. T A B L E 3 Protease inhibitor added (g/ g of feed) Table 3 illustrates graphically the digestion of nitrogen (ordinate) in % as a function of amount of protease inhibitor mixture added (in grams per kg of feed), and visualizes how the digestion of nitrogen or protein is affected by increased addition of the protease inhibitor mixture according to the invention. It is concluded that results achieved when adding a mixture of different protease inhibitors in the forms of endo- and exopeptidase inhibitors to a formulated feed, show that, as intended, a reversible inhibition of the protein-digesting enzymes will occur. Too large additions of the inhibitor mixture will make the overall protein digestibility suffer. With an optimal admixture of inhibitor mixture, a growth gain is achieved, which is enhanced through the use of several sources of protein of different processes of absorption from the intestine of fish. Studies on the absorption of isotope-marked amino acids indicate that there is a combination of increased enzyme production, as a compensation for the inhibition of part of the digestive enzymes of the intestine, together with a termination of the blocking of enzymes, which is a consequence of the reversible bonding between enzyme and inhibitor. This provides a different absorption pattern for amino acids by the use of a protease inhibitor mixture added to the feed.

Claims: C l a i m s 1. A formulated proteinaceous feed, c h ar ac ter i z e d i n that the feed contains an additive consisting of a mixture of different protease inhibitors. 2. A formulated proteinaceous feed as claimed in claim 1, c h a r a c t e r i z e d i n that the feed contains an additive consisting of a mixture of endo- and exoprotease inhibitors. 3. A formulated proteinaceous feed as claimed in claim 1 or 2, c h a r ac t e r i z ed i n that each of the protease inhibitors included in the mixture added to the feed, was in a concentrated form when being admixed. 4. A formulated proteinaceous feed as claimed in one or more of the preceding claims, c h ar ac t e r i z e d i n that the mixture of protease inhibitors in concentrated form added to the feed, constitutes between 0.001 and 0.2 % of the weight of the feed. 5. A formulated proteinaceous feed as claimed in one or o more of the preceding claims, c h ar ac te r i z e d i n that one of said different protease inhibitors of the mixture added to the feed, is produced from a vegetable basis, e.g. potato pulp. 6. A formulated proteinaceous feed as claimed in one or 5 more of the preceding claims, c h ar ac t e r i z e d i n that one of said different protease inhibitors of the mixture added to the feed is produced chemically, e.g. camostate. 7. A formulated proteinaceous feed as claimed in one or more of the preceding claims, c h ar ac t er i z ed i n that one or more of the different protease inhibitors of the mixture added to the feed, have been chosen with a view to their capacity of inhibiting both endo- and exoproteases. 8. A formulated proteinaceous feed as claimed in one or more of the preceding claims , c h a r a c t e r i z e d i n that the protein content is constituted essentially by fish meal and hydrolyzed protein, the TNBS-value being between 0.4 and 2.0. 9. The use of a formulated proteinaceous feed as claimed in one or more of the preceding claims, as the main feed in the feeding of animals having one stomach, e.g. salmon and trout, with the intention of bringing about, through the addition of the mixture of different protease inhibitors in concentrated form, increased utilization of the proteins of the feed, so that a larger portion of the digested amino acids is deposited as muscular protein, whereas a smaller portion is consumed as energy.

Inventors: RAAE ARNT JOHAN, SVEIER HARALD, RAAE, ARNT, JOHAN, SVEIER, HARALD
Applicants: NORAQUA INNOVATION AS, RAAE ARNT JOHAN, SVEIER HARALD, RAAE, ARNT, JOHAN, SVEIER, HARALD
Application year: 2000
Main classification: A23K1
IPC codes: A23K1