Fish meal, or fishmeal, is a commercial product made from both whole fish and the bones and offal from processed fish. It is a brown powder or cake obtained by rendering pressing the cooked whole fish or fish trimmings to remove most of the fish oil and water, and then ground. What remains is the "fishmeal".
Fishmeal is a nutrient-rich and high protein supplement feed ingredient used primarily in diets for domestic animals and sometimes used as a high-quality organic fertilizer.
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The use of fish by-products is not a new idea; it has been used in previous times to feed poultry, pigs and other farmed fish. A primitive form of fishmeal is mentioned in The Travels of Marco Polo at the beginning of the fourteenth century: 'they accustom their cattle, cows, sheep, camels and horses to feed upon dried fish, which being regularly served to them, they eat without any sign of dislike.’ The utilization of herring as an industrial raw material actually started as early as about 800 AD in Norway. A very primitive process of pressing the oil out of herring by means of wooden boards and stones was employed.[1]
Fishmeal can be made from almost any type of seafood but is generally manufactured from wild-caught, small marine fish that contain a high percentage of bones and oil, and is usually deemed not suitable for direct human consumption. The fish caught for fishmeal purposes solely are termed “industrial”.[2] Other sources of fishmeal is from by-catch of other fisheries and by-products of trimmings made during processing (fish waste or offal) of various seafood products destined for direct human consumption. Virtually any fish or shellfish in the sea can be used to make fishmeal, although there may be a few rare unexploited species which would produce a poisonous meal.
1. The species must be in large concentrations to give a high catching rate; this is essential because the value of industrial fish is less than that of fish for direct human consumption. 2. The fishery should preferably be based on more than one species in order to reduce the effect of fluctuations in supply of any one species. 3. The total abundance of long lived species varies less from year to year, and 4. Species with a high fat content are more profitable, because the fat in fish is held at the expense of water and not at the expense of protein .
Fishmeal is made by either cooking, pressing, drying and grinding of fish or fish waste to which no other matter has been added. It is a solid product from which most of the water is removed and some or all of the oil is removed. Four or five tonnes of fish are needed to manufacture one tonne of dry fishmeal.[3]
There are several ways of making fishmeal from raw fish; the simplest way is to let the fish dry out in the sun. This method is still used in some parts of the world where processing plants are not available, nevertheless the end product is poor in comparison with ones made by modern methods. Nowadays all the fish meal is made by the following processes:[1]
Cooking -A commercial cooker is a long steam jacketed cylinder through which the fish are moved by a screw conveyor. This is a critical stage in preparing the fishmeal, as incomplete cooking means that the liquor from the fish cannot be pressed out satisfactorily and overcooking makes the material too soft for pressing. No drying occurs in the cooking stage.
Pressing -A perforated tube with increasing pressure is used for this process. This stage involves removing some of the oil and water from the material and the solid is known as Press cake. The water content in pressing is reduced from 70% to about 50% and oil is reduced to 4%.
Drying- It is important to get this stage of the process right. If the meal is under-dried, moulds or bacteria may grow. If it is over-dried, scorching may occur and this reduces the nutritional value of the meal.
Two main types of dryer: Direct and Indirect
Direct -Very hot air at a temperature of 500 °C (932 °F) is passed over the material as it is tumbled rapidly in a cylindrical drum. This is the quicker method, but heat damage is much more likely if the process is not carefully controlled.
Indirect -Cylinder containing steam heated discs which also tumble the meal.
Grinding -This is the last step in processing which involves the breakdown of any lumps or particles of bone are involved in this stage.
Any complete diet must contain some protein, but the nutritional value of the protein relates directly to its amino acid composition and digestibility. The amino acid profile of fishmeal is what makes this feed ingredient so attractive as a protein supplement .High-quality fishmeal normally contains between 60% and 72% crude protein by weight. Typical diets for fish may contain from 32% to 45% total protein by weight.[4] Another very important reason why fishmeal is sought after as an ingredient in aquaculture diets is because it contains certain compounds that make the feed more acceptable and agreeable to the taste (palatable). This property allows for the feed to be ingested rapidly, and will reduce nutrient leaching. It is thought the non-essential amino acid glutamic acid is one of the compounds that imparts to fishmeal its palatability.[5]
Fish lipids are also highly digestible by all species of animals and are excellent sources of the essential polyunsaturated fatty acids (PUFA) in both the omega-3 and omega-6 families of fatty acids. The predominant omega-3 fatty acids in fishmeal and fish oil are linolenic acid, docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA). Essential fatty acids are necessary for normal larval development, fish growth, and reproduction. They are important in normal development of the skin, nervous system, brain, and visual acuity. PUFAs appear to assist the immune system in defense of disease agents and reduce the stress response. Fishmeal also contains valuable phospholipids, fat-soluble vitamins, and steroid hormones.[6]
Such high digestibility of fish lipids means they can provide lots of usable energy. If a diet does not provide enough energy, the fish or shrimp will have to break down valuable protein for energy, which is expensive and can increase production of toxic ammonia. Fishmeal is considered to be a moderately rich source of vitamins of the B-complex especially cobalamine (B12), niacin, choline, pantothenic acid, and riboflavin.
Fishmeal in diets increase feed efficiency and growth through better food palatability and enhances nutrient uptake, digestion and absorption. The balanced amino acid composition of fishmeal complements and provides synergistic effects with other animal and vegetable proteins in the diet to promote fast growth and reduce feeding costs.
High quality fishmeal provides a balanced amount of all essential amino aids, phospholipids and fatty acids required for optimum development, growth and reproduction especially of larvae and broodstock. The nutrients in fishmeal also aid in disease resistance by boosting and helping to maintain a healthy functional immune system. It also allows for formulation of nutrient-dense diets, which promote optimal growth. [7]
Incorporation of fishmeal into diets of aquatic animals helps to reduce pollution from the waste water effluent by providing greater nutrient digestibility. The incorporation of high-quality fishmeal into feed imparts a 'natural or wholesome' characteristic to the final product, such as that provided by wild fish.
Aquaculture's heavy reliance on wild caught seed and broodstock is of increasing concern. Fishmeal and its source of raw materials and costs are highly debated by scientists and conservationists. Since fishmeal uses wild fish stock to feed farmed fish, this places direct pressure on fisheries resources. Indirect effects are also apparent such as diminishing wild fisheries, habitat modification and food web interactions. There is also the possibility of trace contaminants in the feed which will cause diseases and fish mortality.
About 23.13 million tonnes of compound aquafeeds were produced in 2005 of which approximately 42 percent was consumed by aquaculture. The aquaculture sector consumed approximately 3.06 million tonnes or 56 percent of world fishmeal production and 0.78 million tonnes or 87 percent of total fish oil production in 2006 with over 50 percent of fish oil going into salmonid diets. Increasing prices of fishmeal, fish oil, grains and other feed ingredients, and also fuel and energy will certainly affect the cost of aquaculture production. With such a scenario can aquaculture farms be economically viable or sustainable? [8] Sustainability remains a concern, however, even more so when the demand for aquaculture products is outstripping the supply, and prices soar so that even inefficient farms might make money.
Unmodified fish meal can spontaneously combust. In the past ships have sunk because of such fires. These days the danger is eliminated by adding antioxidants to fishmeal prior to storage or transportation.[3]
According to FAO's statistics (FAO 2002) and their future predictions, wild capture will decrease slightly in the years to come. In 2030 SOFIA predicts that the aquaculture production will rise to a level of more than 80 million tonnes, while the wild catch still will be approximately 90 million tonnes.[9] Sustainability is a major issue and further research and study is needed in this area to make effective decisions.
Despite the adverse effects, organisations like the Fishmeal Information Network (FIN) which is one source of contact for fishmeal and gives information on its supply chain and its role in the nutrition of farm livestock. FIN aims to present fact-based information, independent evidence and respected expert opinion on fishmeal and its use. It recognises the imperatives of safety in the food chain, healthy diets, animal welfare and protection of the environment.
FIN monitors two key areas A. Legislation which governs fishmeal use in animal feed. B. Contaminant issues and regulations that are, or are likely to impact on fishmeal, fish oil, wild finfish and farmed fish. Such regulations and precautions will help companies better their products and will benefit the consumers greatly. More research into this area is needed to make effective decisions and to obtain optimal results.
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