Field of the Invention

The present invention relates to aquaculture in general and more particularly to an aquaculture feed. Background of the Invention

Manufactured feeds are an important source of food for farmed aquatic organisms. However, when unconsumed, the manufactured feed decomposes and fouls the water, and this negatively impacts the health, growth and survivability of the aquatic organisms. It is therefore desirable to provide an aquaculture feed that can be readily consumed by aquatic organisms.

Summary of the Invention

Accordingly, in one aspect, the present invention provides an aquaculture feed. The aquaculture feed includes a plurality of feed particles. The feed particles include a mixture of one or more feed components and a density reducing material, each of the feed particles having one of neutral buoyancy and positive buoyancy.

Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1A is a photograph of a conventional aquaculture feed that is released in water; FIG. 1 B is a photograph of an aquaculture feed in accordance with one embodiment of the present invention that is released in water;

FIG. 1 C is a photograph of an aquaculture feed in accordance with another embodiment of the present invention that is released in water; FIG. 1 D is a photograph of an aquaculture feed in accordance with yet another embodiment of the present invention that is released in water; and

FIG. 1 E is a photograph of an aquaculture feed in accordance with still another embodiment of the present invention that is released in water.

Detailed Description of Exemplary Embodiments The detailed description set forth below is intended as a description of presently preferred embodiments of the invention, and is not intended to represent the only forms in which the present invention may be practiced. It is to be understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the scope of the invention.

An aquaculture feed in accordance with an embodiment of the present invention will now be described. The aquaculture feed includes a plurality of feed particles. The feed particles include a mixture of one or more feed components and a density reducing material such that each of the feed particles has either neutral or positive buoyancy.

The term“neutral buoyancy” and the like as used herein refer to a condition in which an overall density of a substance is equal or close to the density of a fluid in which the substance is immersed. Consequently, the substance tends not to rise or sink and tends instead to remain in a suspended state in the fluid for an extended period of time. The term“positive buoyancy” and the like as used herein refer to a condition in which an overall density of a substance is less than the density of a fluid in which the substance is immersed. Consequently, the substance tends not to sink, but tends instead to float when released in the fluid. It was discovered that some aquatic organisms are more likely to consume feed particles in a suspended or floating state than in a sunken state and thus by creating an aquaculture feed with neutral or positive buoyancy, the aquaculture feed is more readily consumed by the aquatic organisms and thus fouling of the water due to the presence of decomposing aquaculture feed is reduced, providing a cleaner environment for the aquatic organisms to grow and develop.

Each of the feed particles may have a particle size of between about 10 micron (pm) and about 8000 pm depending, for example, on the size of the aquatic organism to be fed and the dimensions of the density reducing material that is employed. The feed components may be ingredients typical of an aquaculture feed formula such as, for example, fish or shrimp formula and one or more nutritional supplements.

The buoyancy of the feed particles may be varied depending on the type and content of the density reducing material employed and the feeding behaviour of the aquatic species.

The term“density reducing material” as used herein refers to any material or combination of materials that when admixed with another substance gives a product that has a lower density than the density of the substance with which the density reducing material was admixed. Examples of such material include, for example, hollow microstructures, cork, oil and foam. These materials may be used singularly or in combination to reduce the density of the feed particles. As the density reducing material is to be consumed with the feed components, the density reducing material is an ingestible material that is able to pass through the digestive system of aquatic organisms without causing any harm. The hollow microstructures may be made, for example, of glass, plastic, alumina-silicate, ceramic or carbon and may be spherical in shape. One of the advantages of using glass microspheres as or incorporating glass microspheres into the density reducing material is that because glass microspheres have smooth surfaces, the glass microspheres are easily swallowed by the aquatic organisms. Another advantage is that glass microspheres may be used with existing production techniques such as, for example, feed press, extrusion, spray-drying or agglomeration, without causing any physical change to the glass microspheres.

The density reducing material may have a density of between about 0.2 gram per cubic centimetre (g/cm ³ ) and about 0.7 g/cm ³ , preferably between about 0.4 g/cm ³ and about 0.6 g/cm ³ . When a lower density material is used, the quantity of density reducing material required may be reduced and this is beneficial as it allows more space in the feed particles for the provision of nutritional supplements.

The density reducing material may have a particle size of between about 5 micron (pm) and about 300 pm, preferably between about 10 pm and about 50 pm. Selection of the particle size of the density reducing material may depend on the desired size of the feed particles. To produce very small feed particles, a density reducing material with a correspondingly small particle size is preferably used. Likewise, to produce larger feed particles, larger density reducing materials may advantageously be employed to lower the density of the resultant feed particles as well as manufacturing cost. However, if the particle size of the density reducing material is too large, there is a risk that not all the feed particles may carry sufficient quantities of the density reducing material to achieve neutral buoyancy and/or positive buoyancy. Ideally, the density reducing material is homogeneously mixed with the feed components so that every feed particle that is produced carries enough density reducing material to be uniformly buoyant. For example, in the production of feed particles of between about 25 pm and about 300 pm in size, density reducing material having a particle size of between about 5 pm and about 20 pm may be used, and in the production of feed particles having a particle size greater than 300 pm, density reducing material having a particle size of between about 20 pm and about 50 pm may be used. In one embodiment, the size of the density reducing material may be close to the size of the other feed components.

The mixture may include between about 1 percent by mass (mass%) and about 30 mass% of the density reducing material, preferably between about 3 mass% and about 10 mass% of the density reducing material. The content of the density reducing material in the mixture may depend, for example, on the density of the density reducing material employed, the density of the feed formula, the salinity of the water in the cultivation tanks, and/or the desired application. A larger density reducing material content may be required to increase the buoyancy of the feed particles. For example, if the density reducing material employed is of very small particle size, a larger density reducing material content may be required because of the lower buoyance of the density reducing material. The aquaculture feed may be produced by adding a predetermined quantity of a density reducing material to a feed formula along with other feed ingredients and then manufacturing the aquaculture feed in a conventional way. Accordingly, a detailed description of the manufacturing process is not required for a complete understanding of the present invention.

Examples Referring now to FIGS. 1A through 1 E, exemplary aquaculture feeds 10, 20,

30 and 40 with feed particles having a particle size of about 150 pm were produced by mixing different quantities of glass microspheres having a density of 0.55 g/cm ³ and a particle size of between 10-20 pm with feed components of a conventional aquaculture feed 50. The aquaculture feeds 10, 20, 30 and 40 have 3 mass%, 5 mass%, 7 mass% and 10 mass% of a density reducing material, respectively. The composition of the conventional aquaculture feed is shown in Table 1 below. The figures given below are expressed in percentage by mass (mass%).

Table 1

The conventional aquaculture feed 50 and the exemplary aquaculture feeds 10, 20, 30 and 40 were released in respective beakers 52, 12, 22, 32 and 42 of water 60 as shown in FIGS. 1 A through 1 E. As can be seen from FIGS. 1 A through 1 E, feed particles of the conventional aquaculture feed 50 largely sank to the bottom of the beaker 52, whereas feed particles of the aquaculture feeds 10, 20, 30 and 40 with 3 mass%, 5 mass%, 7 mass% and 10 mass% of the density reducing material, respectively, tended instead to remain suspended in the water 60 and/or float to the surface of the water 60.

Additional examples of exemplary aquaculture feeds are provided in Table 2 below.

Table 2

As is evident from the foregoing discussion, the present invention provides an aquaculture feed that can be readily consumed by aquatic organisms. Advantageously, this reduces fouling of the water due to the presence of decomposing aquaculture feed and thus provides a cleaner environment for the aquatic organisms to grow and develop.

While preferred embodiments of the invention have been described, it will be clear that the invention is not limited to the described embodiments only. Numerous modifications, changes, variations, substitutions and equivalents will be apparent to those skilled in the art without departing from the scope of the invention as described in the claims.

Further, unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising" and the like are to be construed in an inclusive as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".