Introduction to Aquafeed Formulation:
Today, let us discuss Aquafeed Formulation, Fish Feed Preparation and Fish Feed Ingredients.
Feed formulation is the method to measure the amounts of feed ingredients that need to be combined to form a single uniform mixture for poultry that supplies all of their nutrient requirements.
Feed formulation is basically applied nutrition. A number of terms & expressions are introduced that will be set to practical use as the information is presented on the nature & qualities of various feedstuffs and the information presented on the nutrient necessities of fish.
The culture of aquatic animals, particularly fish culture has undergone dramatic worldwide growth in the last few years. The aquaculture production is the fastest growing food production industry in the world & approximately 50% of all fish consumed by humans is from aquaculture. Nutrition plays an essential role in improving animal productivity. Understanding the nutritional requirements and production of fish feed is essential to the development & sustainability of aquaculture as the industry has matured.
Feeds can be farm-made single section feeds like rice bran or mastered oil cake to commercial feeds. Kitchen wastes also are considered as one of the types of farm-made feeds produced economically for a small scale culture venture. Farm-made or on-farm feeds consist of one or more artificial and natural ingredients, produced for a particular farming activity & not for any commercial purpose. Combination of ingredients subjected to a few types of processing (simple mixing, grinding and cooking) done on-farm or in small processing plants are normally regarded as farm-made feeds & are often used in small-scale semi-intensive aquaculture practices. Commercial feeds are formulated and manufactured from a homogenous mixer of several ingredients, in different proportions that ensure precise quality targets in terms of size and texture, stability & nutritional composition at a highly competitive price. Commercial complete feeds are used generally in intensive and semi-intensive practices.
Feeds can be formed either by steam processing, producing compact, pressure-pelleted (sinking) feeds or by extrusion, which produces expanded floating or buoyant feeds.
Floating fish feeds:
In general, floating feeds present numerous advantages over their sinking counterparts. Raw materials are propelled by screws along the barrel of the extruder device to cook the materials at 120-175 ºC for about 30 seconds. The homogenous cooked mixture is forced during a die at high pressure. The material develops because of the pressure difference. Floating feeds are more digestible as a product of the cooking process & the heat and pressure deactivate destructive enzymes as well. Increased starch gelatinization helps the feed to be further stable in water by disintegrating less quickly that gives enough time to the fish to take the meal completely. Also, the farmer can directly survey the feeding intensity of his fish & adjust feeding rates accordingly determining whether feeding rates are too low or too high is important in maximizing fish growth & feed use efficiency. Another side effect is that farmers can visually monitor the healthiest form of the reared fish as they come to the surface to take feed.
Sinking fish feeds:
Sinking feeds are solid feed pellets that submerged through the application. Bottom feeder shrimp, for example, prefer sinking pellets & will not accept a floating feed. The farmer cannot all the time near feeding rates correctly in relation to the biomass present in his pond & feeding whether too low or too high than the actual requirement. It causes a lower weight gain at a particular age & enlarges the culture period when feeding rate is low. In the other hand, overfeeding causes subsequent loss of feed supplied as well as deteriorating water feature that may result in a number of problems.
Maintaining fish feed quality:
A variety of factors govern the quality & wholesomeness of aquafeeds. Feedingstuffs beginning, processing, handling & storage, as well as several other factors related to the market, can affect at different levels both quality and safety of feed. Feed quality can be ensured primarily by using good quality ingredients. Purchase of raw materials must confirm adequate quality, traceability, environmental sustainability & safety standards.
Feed manufactured in the factory has been regularly of desired quality, but that level of quality may have been falling by the time it reaches a farmer’s pond finally. Commercial fish feed is regularly purchased by large farms as bulk feed in truckloads & stored in outside bins. Finished feeds experience deteriorating varies through storage, which not only lowers their nutritive value below minimum specifications but also affects their palatability & appearance. All feed should be used within two months of manufacture & inspected regularly. During long storage, there may arise growth of mould, degradation of vitamin potency & fat rancidity. Unnecessary handling damages the feed bags & creates dust that is not usually consumed by fish and wasted. Pests (i.e. Mice, rats, roaches) must be restricted strictly in the storage, to avoid contamination. Proper storage is simple, but the main part to keep the products at a high quality.
Fish feed ingredients/nutrients:
Oils from marine fish, such as menhaden, & vegetable oils from canola, sunflower, and linseed, are common sources of lipids in fish feeds.
Cooked carbohydrates from flours of corn, wheat or other ‘breakfast’ cereals are moderately inexpensive sources of energy that may spare protein from being used as an energy source.
Vitamins and minerals:
The variety and quantity of vitamins and minerals are so complex that they are generally prepared synthetically and are available commercially as a balanced and premeasured mixture called as a vitamin or mineral premix. This premix is added to the diet in generous amounts to ensure that adequate levels of vitamins & minerals are supplied to meet dietary requirements.
Proteins and amino acids:
Fish meal, soybean meal, fish hydrolysate, skim milk powder, legumes, & wheat gluten are excellent sources of protein. Additionally, the building blocks of proteins such as lysine and methionine are commercially existing to supplement the diet. Utilizing raw fish as a major ingredient in fish feeds has long been recognized to be harmful to the health & growth of fish due primarily to the presence of the anti-nutrient, thiaminase. Thiaminase, an enzyme that destroys thiamine, is regularly found in freshwater fish. It is damaged by the heat (i.e., cooking). Other concerns related to using raw fish in diets include the spread of infectious diseases such as Mycobacterium & botulism. In preparing diets, preferential use of marine fish is suggested to minimize thiaminase activity, & the raw fish could be steamed or poached.
Pigments: A mixture of natural & synthetic pigments or carotenoids are available to enhance coloration in the flesh of salmonid fish & the skin of freshwater and marine ornamental fish. The pigments most frequently used supply the colors red & yellow. The synthetically produced pigment, astaxanthin, is the most regularly used additive (100-400 mg/kg). Cyan bacteria, dried shrimp meal, shrimp and palm oil, and extracts from marigold, red peppers & Phaffia yeast are excellent natural sources of pigments.
Binding agents: Another important ingredient in fish diets is a binding agent to present stability to the pellet & reduce leaching of nutrients into the water. Beef heart has traditionally been used both as a source of protein, & as an effective binder in farm-made feeds. Carbohydrates & various other polysaccharides, such as extracts or derivatives from animals (gelatin), plants (gum arabic, locust bean) & seaweeds (agar, carrageen, and other alginates) are popular binding agents.
Steps in Aquafeed formulation:
The first step in diet formulation is balancing the crude protein & energy levels. This can be accomplished by trial and error, by the square technique for either crude protein level or energy level and then adjusting, or by solving simultaneous equations. At first, it is helpful to use at least three feedstuffs during the initial balancing of protein & energy levels one high in protein and high in metabolizable energy, one low or intermediate in protein & high in metabolizable energy, and one low or intermediate in both protein and metabolizable energy. Once practice makes more proficient at diet formulation any number of feedstuffs can be used. One must remember to reserve the room in the formulation for every feed additive, such as a vitamin or mineral pre-mix.
The second step in diet formulation is to verify the stages of indispensable amino acids in the formulation to be sure the dietary levels meet the requirements of the animal to be fed. The requirements of fish for indispensable amino acids are expressed as the dietary level or as a percent of the dietary protein level. To convert an amino acid level from the percent of the diet to percent of protein, separate the dietary level of each amino acid by the dietary protein level. It might be of interest to estimate the dietary levels of all of the indispensable amino acids, but it is not practical to do it all of the time. If the levels of arginine, lysine, methionine, & tryptophan meet the dietary requirements of the fish to be fed, the levels of the other six indispensable amino acids will most likely be above the required levels. When using unconventional protein supplements, the stage of all ten indispensable amino acids should be checked.
The diet formulation is low in several amino acids; feedstuffs that have high levels of that amino acid must be added to the diet at the expense of another ingredient. Once the amino acid necessities are met, the dietary protein & energy levels must be rechecked to, see if any substitution of ingredients has imbalanced the formulation.
In practical feed formulation, pellet quality & acceptability must be considered in addition to nutrient levels and cost. These considerations will vary from species to species & with the type of pellet being made, and are dealt with in other sections of this manual.
Fish feed characteristics:
Flavor and taste:
Flavor & taste of feed is especially important in the case of bottom feeding animals. The smell can be noticed by the specific anatomical receptors in fish, but the flavor has to be dissolved in water for the fish to position it. Some fish have receptors in their mouths or on the head or on the lips. Some have taste receptors on their skin. These receptors carry messages to the brain & tell the fish to swim towards the food. Some kinds of food can powerfully stimulate fish to feed by their flavor.
Color and Buoyancy:
Some fish that are used to feeding on floating feed not take to sinking feed that has sunk to the bottom. Also, bottom feeders rarely come to the top of the aquarium to eat food. A majority of the fish species in the tropical diversity are however not very picky when it comes to the buoyancy of food.
A fish can “hear” sounds during the vibrations that take place in water. By picking up these vibrations in the water, fish become aware of the feeding frenzies that origin many fish to conglomerate when the feeding begins. Also, there are fish that are so used to a routine in their feeding that they start grouping when they hear sounds that generally precede feeding.
Sizes of pellets:
The feeds are produced in a variety of sizes on the basis of the die diameter & the cutter blade action. The pellet size varies from fine powder for small fires or fingerlings to 1/2 inch or larger pellets. The pellet size must be limited to about 20% -30% of the diameter of mouth chance of the fish species concerned. In case of feeding too small pellets than the suitable size, more energy has to be used by the cultured animal during searching & eating more pellets that result in inefficient feeding. On the other hand, pellets that are too large will depress feeding & may cause choking in severe cases.
Materials and methods in Aquafeed Formulation:
Feed formulation is the procedure of quantifying the proportion of ingredients to be put together, to form a single uniform mixture or pellets that will provide all the nutritional requirements of the target fish. It is a central operation in feed production, ensuring that feed ingredients are economically used for optimum expansion of rearing species. It requires a good expert in fish biology & nutrition along with deep knowledge about feed ingredients and their roles. Most large-scale fish farmers depend on commercial feed mills for their feeds, to prevent the need to do their own formulations or feed preparation. It is, therefore, necessary that formulations are accurate, to ensure that cultured fish are not adversely affected. Feed formulation is a science & art at a time, requiring knowledge of feed and fish in view of economic aspects when using formulae.
Feed formulation and preparation is the processes of combining feed ingredients to form a mixture that will meet the exact goals of production. It is often a compromise between an ideal method and practical considerations. Though formulated the feed ingredients take into account some considerations such as price, availability of ingredients used anti-nutritional factors & palatability of mixtures. Along with soybean meal and other ingredients such as milk powder, corn flour, eggs, cod liver oil, vitamin mixture containing vitamin B complex and E, agar powder, garlic paste, pepper powder & cumin powder are used.
Preparation of feed Soybean meal (80gm) was taken in powder type as principal ingredients. Other ingredients like milk powder (60gm), corn flour (20gm), & eggs (70gm) were added and mixed well. Agar powder (4gm) was added as a binding agent, turmeric (0.5gm) & garlic (1gm) as antibiotics. The said the combination was boiled, cooled at room temperature. After cooling cod liver oil (3.5ml), a vitamin mixture of vitamin B complex (gm) & vitamin E (1gm) were added. It was kept under refrigeration for twelve hours. After 12 hours it was squeezed over the polythene sheet & dried at room temperature for 48 hours. The dried nodules are crushed into small pellets then pellets are sun-dried to avoid fungal infection, weighted & stored in the bottle. Following the above method all the feeds were formulated in the percentage composition of 25% (soybean meal 25%+groundnut oil cake 75%), 50% (soybean meal 50%+groundnut oil cake 50%), 75% (soybean meal 75% +groundnut oil cake 25%), 100% formulated (total of soybean meal) & 100% conventional (totally of groundnut oil cake).
Feed formulation can be done in two main steps as,
- Ingredient selection & restrictions
- Identification of nutritional specifications.
- Drying and
Preparation of Aquafeed formulations:
The feeds are formulated might be dry with a final moisture content of 6%-10%; semi-moist with 35%-40% water; or wet with 50%-70% water content. The most feeds used in intensive production systems or in home aquaria are commercially formed as dry feeds. The dry feeds consist of simple loose mixtures of dry ingredients, such as mash or meals, to more complex compressed pellets or granules. Pellets are often broken into smaller sizes called ‘crumbles’. The pellets or granules can be prepared by cooking with steam or by extrusion. Depending on the feeding requirements of fish, the pellets can be prepared to sink or float.
Flakes are another form of dry food & a popular diet for aquarium fishes. The flakes consist of a complex combination of ingredients, including pigments. These are prepared in the slurry which is cooked and rolled over drums heated by steam. Semi-moist & wet feeds are made from single or mixed ingredients, such as trash fish or cooked legumes, & can be shaped into cakes or balls.
There is no single method for preparation of formulating fish feed, though, most methods begin with the formation of a dough like mixture of ingredients. The components can be obtained from grocery stores, pharmacies & specialty stores such as natural food stores, as well as from various companies that may be found through the internet. The dough is started with blends of dry ingredients which are finely ground & mixed. The dough is then kneaded & water is added to produce desired consistency for whatever fish is going to be fed. The same dough may be used to feed some types of fish, such as eels and small aquarium fish. Pelleting or rolling transfer the dough into pellets or flakes, respectively. The amount of water, pressure, friction and heat greatly affects pellet & flake quality. For example, overload water in the mixture results in a soft pellet. Too little moisture & pellet will crumble. Proteins & especially vitamins are seriously affected by high temperatures. Thus, avoid storing diet ingredients at temperatures at or above 70ºC & do not prepare dry feeds with water at the temperature higher than 92ºC.
To make the own fish feed, few specialized tools are necessary. The tools are used mainly for chopping, weighing, measuring ingredients, and for blending, forming & drying the feed.
Examples of changes in nutritional value (especially crude protein) of ingredients according to exported or importing countries.
Fish meal and soybean meal are the major protein sources of the fish feed.
- Fish meal: 67%-68% from Peru, 65% from Chile, 67-72% from Norway, 68- 70% from Denmark, 71-72% from Turkey.
- Soybean meal: 43-45% from the USA and China, 41-43% Argentina, 40-42% from Brazil.