FEED COMPOSITION FOR SALMONIDS AND USES THEREOF

FIELD OF THE INVENTION

The present invention concerns a feed composition for diseased salmonid fish and the use of the composition for preventing and/or reducing of the negative effects of an outbreak of pancreas disease in salmonids, meaning that the composition functions as a clinical diet during a period of a dysfunctional pancreas in the diseased fish.

BACKGROUND OF THE INVENTION

Pancreas disease and other virus infections in fish are a serious problem in aquaculture of many aquatic species including salmonids such as the Atlantic salmon Salmo salar. These infections do not only frequently cause enormous economical losses in aquaculture production, they are also an important issue of animal well-fare. Awareness of animal well-fare by consumers, producers and national authorities has increased tremendously in the past, also including the aquaculture sector. Thus, focus on the prevention, efficient treatment and/or reduction of mortality and agony connected to disease outbreaks such as Pancreas disease and other virus infections is of great importance.

Disease influences the fishes feeding behaviour. Feeding diseased salmonid fish during a clinical outbreak of Pancreas disease is a significant challenge, outbreaks lasting from 3 to 6 months. Dietary amelioration is dependant on a correct and early

PD diagnosis and an early deployment of a PD diet. Effective site monitoring of feeding behaviour and mortalities, using monitoring system is an essential tool in PD disease management.

From the mid nineties, it has been known that the pancreas disease (PD) in Atlantic salmon (salmo salar) and Rainbow trout (onchorynchus mykiss) is caused by a virus, called Salmonid Alpha Virus (SAV) who belongs to the Togaviridae family. Typical Pancreatic disease-symptoms in fish are a reduced appetite, as well as an increased mortality. The pathology of the disease is very similar to other infections, but small bleedings can be registered in the adipose tissue as well as some clear liquid in the abdominal cavity. The liver can be somewhat swollen with a fibrin layer. Chronically disordered fish are stripped down and possess little fat in the abdominal cavity. The atrophy of the pancreas and inflammation and necrosis of the heart and skeletal muscle are the most important organ alterations.

Efforts to develop a vaccine have been without significant success so far.

The present invention aims thus at providing a feed composition which can effectively be used to prevent and/or reduce negative effects of Pancreas disease infection in salmonids.

Moreover, the present invention aims at providing a feed composition, which effectuates that fish is able to absorb/ingest adequate nutrition during a critical phase causing that it survives and that vital organs regenerate.

Furthermore, the present invention aims at providing a feed composition, which effectuates that the fish recovers its appetite and at the same time enables the fish to cope with the challenge of a virus infection or a Pancreas disease outbreak, which thereby reduces the mortality of the fish and which reduces the inflammatory reactions in actual affected tissues.

It is an aim of the present invention that the feed composition is administered to the fish as soon as the Pancreas disease outbreak has been discovered, or previous of the Pancreas disease outbreak if there is suspicion of such an outbreak or if the fish is in a risk for such an outbreak and until the mortality caused by the outbreak has been finished.

SUMMARY OF THE INVENTION

Surprisingly, it has been found that by amending the ratio and/or quantitative amounts between the main feed components protein and lipid, the fish is enabled to digest the feed even during a period when the fish is challenged by virus, or when it has developed Pancreas disease.

In a first aspect, the present invention relates to a us of a feed composition comprising conventional feed ingredients such as protein, lipid, ash, vitamins, minerals, carbohydrates, pigments, wherein the relation of protein to lipid is more than 1 , based on weight, for enhancing the fish welfare, viability or faster recovery, and/or for the prevention, alleviation and/or treatment of salmonids infected with Pancreas disease.

In a preferred embodiment, the relation of protein to lipid is in the range of 1 to 3, based on the weight, more preferable 1.5 to 2.5, based on weight, preferable about 2 based on weight.

A further embodiment has an amount of protein in relation to the total weight of the feed composition in the range of 30%to 70%, more preferable about 40% to 60%, and more preferable about 45% to 55%, more preferable in the range of 10% to 40%, more preferable 20% to 30%.

In a further embodiment is the amount of lipid in relation to the total weight of the feed composition is less than 30%, more preferable less than 28%, more preferable less than 26%, more preferable less than 25%.

A preferred embodiment relates to the use of a feed composition, wherein a portion of said protein is processed protein, preferable in an amount of at least 10%, more preferable 20%, more preferable 25%, more preferable 30%, based on the weight of the total protein.

Preferable, said processed protein is selected from the group comprising hydrolyzed protein, water soluble protein and easily digestible protein.

Further embodiments comprise an immune stimulating and/or anti-inflammation compound.

In a preferred embodiment, said immune stimulating and/or anti-inflammation compound comprises glucan, preferable beta-1 ,3/1 ,6-glucan.

In a preferred embodiment, said immune stimulating and/or anti-inflammation compound comprise peptidoglycan.

In a further embodiment comprise said feed composition also semiessential nutrients such as nucleotides, nucleosides or both.

In a still further embodiment comprises the feed composition further an active component, such as a pharmaceutical agent, such as an anti-viral component.

The feed composition according to the invention can be used for decreasing the mortality of salmonids infected with Pancreas disease.

Further, the feed composition according to the invention can be used for enhancing the fish welfare, viability or faster recovery of salmonids infected with Pancreas disease.

Preferable, the feed composition is provided to said salmonids from the registration of the first symptoms of an infection in fish or a fish population and/or in case of a risk for a Pancreas disease infection.

An alternative embodiment provides the feed composition in the period from the discovery of a risk for a Pancreas disease infection up to 20 weeks after the determination of the disease.

An alternative embodiment provides the feed composition about four weeks before the determination of the disease and until 15 weeks after the determination of the disease, and at least from about the determination of the disease and until 15 weeks after the determination of the disease, more preferable from about the determination of the disease and until 12 weeks after the determination of the disease.

In a further embodiment, the feed composition functions as a vehicle or carrier for efficiently transport of pharmaceutical or nutritional components to the intestinal tract.

A second aspect of the invention relates to the use of a feed composition comprising conventional feed ingredients such as protein, lipid, ash, vitamins, carbohydrates, pigments, wherein the relation of protein to lipid is more than 1 , based on weight, for improving the appetite, digestibility, absorption and/or increasing the growth of salmonids infected with Pancreas disease.

An embodiment of this aspect relates to the capability to maintain or increase the biomass of said salmonids is improved.

In a preferred embodiment of this aspect, said biomass is increased.

In a preferred embodiment of this second aspect, the relation of protein to lipid is in the range of 1 to 3, based on the weight, more preferable 1.5 to 2.5, based on weight, preferable about 2 based on weight.

A further embodiment has an amount of protein in relation to the total weight of the feed composition in the range of 30%to 70%, more preferable about 40% to 60%, and more preferable about 45% to 55%, more preferable in the range of 10% to 40%, more preferable 20% to 30%.

In a further embodiment is the amount of lipid in relation to the total weight of the feed composition is less than 30%, more preferable less than 28%, more preferable less than 26%, more preferable less than 25%.

A preferred embodiment relates to the use of a feed composition, wherein a portion of said protein is processed protein, preferable in an amount of at least 10%, more preferable 20%, more preferable 25%, more preferable 30%, based on the weight of the total protein.

Preferable, said processed protein is selected from the group comprising hydrolyzed protein, water soluble protein and easily digestible protein.

Further embodiments comprise an immune stimulating and/or anti-inflammation compound.

In a preferred embodiment, said immune stimulating and/or anti-inflammation compound comprises glucan, preferable beta-1 ,3/1 ,6-glucan.

In a preferred embodiment, said immune stimulating and/or anti-inflammation compound comprise peptidoglycan.

In a further embodiment comprise said feed composition also semiessential nutrients such as nucleotides, nucleosides or both. ^?

In a still further embodiment comprises the feed composition further an active component, such as a pharmaceutical agent, such as an anti-viral component.

The first aspect of the present invention also relates to a feed composition for salmonids comprising conventional feed ingredients such as protein, lipid, ash, vitamins, minerals, carbohydrates, pigments, wherein the relation of protein to lipid is more than 1 , based on weight, for use in enhancing the fish welfare, viability or faster recovery, and/or for the prevention, alleviation and/or treatment of salmonids infected with Pancreas disease.

The second aspect of the present invention also relates to a feed composition for salmonids comprising conventional feed ingredients such as protein, lipid, ash, vitamins, minerals, carbohydrates, pigments, wherein the relation of protein to lipid is more than 1 , based on weight, for use in improving the appetite, digestibility, absorption and/or increasing the growth of salmonids infected with Pancreas disease.

Without being bound to theoretical considerations, it is assumed that during this period the fish has a reduced ability to digest a conventional feed, either due to the fact that the absorptive mechanisms are reduced or that the amount or activity of the digestive enzymes are reduced.

During testing of different feed compositions wherein a reduced amount of lipid in relation to protein has been used, it could be shown that this had a beneficial effect on the appetite as well as on the ability to survive and recover in connection to Pancreas disease.

Lipids are an important energy source in salmonids and the level of lipid in feed compositions has increased during the past decade to about 30-40 % for on-growing salmon. This has been shown to be beneficial in terms of growth. Commonly applied protein content in feed for salmonids is 30-40 %.

One problem connected to feeding of Pancreatic disease-infected fish is that the conventional fish feed is apparently badly absorbed by the gut, and that it passes through the intestinal tract without substantial effect probably since the necessary

enzymes needed for hydrolyzing the feed ingredients are lacking. The feed composition of the present invention has shown an improved absorption in the digestive system of the fish and by that causing an improved utilization/absorption of the nutritional components of the feed composition and as well as of other additive substances such as immunostimulating and anti-inflammation materials.

Thus, a great effect can be obtained by developing a composition which can energetically be utilized by the fish even though its digestive system is significantly affected as result of a Pancreas disease infection, as well as that the effective feed composition can be used as a carrier for active components which one would like to administer to the fish. As exemplified, the later compounds could be immunostimulating agents and/or inflammation reducing agents and semi-essential nutrients, but they can also be compounds with nutritional or pharmaceutical effects.

It is assumed that by partly replacing of the protein component by processed proteins, such as peptides, e.g. in from of hydrolyzed material, the absorption of the feed composition and other active compounds is further increased.

The present invention also includes feeding of a combination of different feed compositions which overall do sum up to the same protein/lipid ratio when fed to the fish as defined in the claims of the present invention, for example by feeding a conventional feed with a protein/lipid ration of one or less than one in combination with a high protein diet.

It will be appreciated that features of the invention described in the foregoing can be combined in any combination without departing from the scope of the invention.

DESCRIPTION OF THE DIAGRAMS

Embodiments of the invention will now be described, by way of examples, with reference to the following diagrams in which:

Figure 1 shows the accumulated mortality of salmon during feeding with test diet and a control diet of example 1.

Figure 2 shows changes in the biomass for fish fed the test diet or the control diet of example 1.

Figure 3 indicates the feeding rate, indicating the appetite of the fish fed the test diet or the control diet of example 1.

Figure 4 shows the accumulated growth of fish fed the test diet or the control diet of example 2.

Figure 5 shows pathological changes in Pancreas for fish the fed test diet or control diet of example 2.

EXPERIMENTAL SECTION

Fish were fed ad libitum, meaning that the feed access was not a limiting factor.

Feeding of fish with a Pancreatic disease-diagnose

Example 1 The feed composition of the present invention has been tested in an aquaculture plant where Atlantic salmon had a diagnosed Pancreas disease infection in two of totally eight cages. Until the start of the experiment fish of all cages were treated comparable and received the same diet.

Three weeks after the diagnosis of Pancreas disease fish in all cages were fed two different diets, the test diet of the present invention and a control diet (table 1) for a period of 11 weeks.

Table 1 : Feeding ingredients (% by weight) in the test diet and control diet.

Apart from the given ingredients, both diets contained conventional compounds included in fish feed such as antioxidants, vitamins, minerals, pigments, etc.

The main difference in the dietary composition of the test diet and the control diet was the protein/lipid ratio. The test diet comprised about 49 % protein and about 25 % lipid, based on the total weight of the feed composition, resulting in a protein to lipid ratio of about 2, while the control diet comprised about 37 % protein and about 40 % lipid, resulting in a protein/lipid ratio of about 0.9. The control diet thus corresponded to a typical commercial diet with a conventional dietary composition in terms of proteins and lipids as it is commonly used for on-growing salmon. In contrast, the test diet had an increased amount of protein and a reduced amount of lipid compared to commercially applied diets.

Feeding of the two different diets was carried out in eight cages with an initial biomass of about 60.000 kg per cage at the start of the experiment and an estimated average weight of about 770 gram per fish. Five cages received the control diet, while three cages received the test diet of the present invention. The cages for each of the treatments were chosen randomly. Fish were fed for about 11 weeks, when the experiment was finished. The mortality of fish, and increase of biomass in each cage was determined in defined intervals during the experimental period. Fish were fed according to their appetite (ad libitum). The feed ration provided to the fish in

each of the cages was adapted individually for each cage on a daily basis based upon observations made with a camera placed at the bottom of each cage.

The accumulated mortality at the end of the feeding experiment was 53 % for fish fed the control diet while it was 31 % for the fish fed the test diet of the present invention (Figure 1). The relative increase in biomass in salmon fed the control diet was considerably lower compared to the biomass in salmon fed the test diet of the present invention increased during the same period (Figure 2). The growth pattern was also reflected in the actual feeding rate of the fish (Figure 3). Fish of both treatments had a reduced feeding intake during the first two weeks after feeding of the test diet and control diet was initiated. However, the reduction in fish fed the control diet was much higher than in fish fed the test diet of the present invention. Moreover, fish fed the test diet of the present invention had an increasing appetite already after 3 weeks after the start of the experiment, while fish of the control diet showed a clear delay in the increase of the feeding rate and had a much lower feeding rate throughout the whole experiment.

These results clearly demonstrate the beneficial effect of a high amount of protein in relation to lipids in terms of survival, growth and feeding rate of fish exposed fo a Pancreas disease outbreak.

Example 2:

A total of 1260 fish (70 fish per tank in 18 tanks) Atlantic salmon Salmo salar, start weight 100g, seawater adapted, were fed for a period for 4 weeks at 2% body weight per day. The fish were maintained in ambient seawater tempertature at 100 fish per tank. After 4 weeks feeding control diet the fish were challenged with 0.2 ml of a dose predicted to kill 20% of the population (LD ₄₀ ) of Salmon Alphavirus by intra- peritoneal (i.p.) injection. Fish were then fed test diets from day of challenge, for a further 14 weeks. The control diets and test diets were divided equally into the 9 tanks in both of the labs in random order. Mortalities were removed daily, weighed and assessed for Alphavirus. All fish individual weights and lengths were recorded at

the start and end of the trial. Sampling of of the fish were done in week 3, 6, 9, 12 and 14 after infection.

Table 2: Feeding ingredients (% by weight) in the test diet and control diet.

Apart from the given ingredients, both diets contained conventional compounds included in fish feed such as antioxidants, vitamins, minerals, pigments, etc.

By histology we confirmed pathological changes in Pancreas, as shown in figure 5. The results are obtained 6 weeks after the fish were challenged with SAV. 22 % of the fish that received the test diet according to the invention has still a normal pancreas. In contrast, only 7 % of the fish that received the control diet has a normal pancreas. Further, 40 % of the fish that received the control diet has almost nothing acinar tissue, whereas only 24 % of the fish that received the test diet according to the invention has almost nothing acinar tissue. This clearly shows that the feed composition according to the present invention has an positive effect on the PD disease.

It will be appreciated that embodiments of the invention described in the foregoing can be modified without departing from the scope of the invention.

Definitions

SAV: salmonid alpha virus belongs to the Togavihdae family and there are today three subtypes detected: SAV1 , SAV2 and SA V3. The name Salmonis alpha virus is not yet approved in ICTV (international Committee on Taxonomy of Viruses), but it the common name used in the industry.

Salmonids: Fish belonging to the family Salmonidae. Representative examples are Atlantic salmon (salmo salar), Rainbow trout (onchorynchus mykiss), Coho salmon, (Oncorhynchus kisutch)

The term "enhancing fish welfare and viability" in this context means that the general condition of the fish in terms of health, stress- and disease-resistance is improved. As measurable indicators in the present invention may beside other factors serve improved survival rates and growth rates, improved appetite, low number of infected or seriously affected fish by pancreas disease as well as an improved ability to recover from an infection with pancreatic disease.

The term "convalescence" relates to the period between the end of a disease and the restoration of complete health of a fish.

"Lipid(s)": The term lipid includes the common terms oil and fat, and includes all commonly know lipophylic substances such as mono-, di- and triglycerides, fatty acids, phospholipids, sterolsesters such as cholesterol, shingolipids, etc.

Proteins are (macro)molecules consisting of sequences of amino acids linked though peptide bounds.

The term "processed protein" in the context of the present invention comprises: proteins with an increased degree of hydrolysation compared to untreated proteins, i.e the original protein is cut into smaller pieces, i.e. peptides. These

proteins or peptides may have a higher mount of oligopeptides including tri- and dipetides, as well as free amino acids partly denaturated proteins water-soluble proteins and/or - proteineous compounds with an increased digestibility

Digestibility: Property to readily and easily digest ingested feed compounds in the intestinal tract into compounds suitable for absorption and subsequent assimilation.

Absorption: Passive and/or active uptake of (digested) feed compounds by the gut epithelium.

Appetite: desire for food resulting in an increased feed intake by the fish

Biomass: total amount of biomass is either the number of fish multiplied with the weight, or fish population in defined location such as a cage.

"Risk for a Pancreas disease infection": A risk for a pancreatic disease infection is present when the fish has an increased change of exposure to a PD infectious virus, such as the SAV virus, e.g. if there is a disease in the same aquaculture site or in a aquaculture site in a distance which make it possible that the fish could be infected, during transport of fish or infected material between aquaculture sites, due to infected wild fish, the SAV-virus is detected in the fish population but with no clinical symptoms, or due to environmental risk conditions such as temperature.