Fish meal

Fish meal factory, Bressay

Fish meal, or fishmeal, is a commercial product made from fish and the bones and offal from processed fish. It is a brown powder or cake obtained by drying the fish or fish trimmings, often after cooking, and then grinding it. If it is a fatty fish it is also pressed to extract most of the fish oil.[1]

History

Fish byproducts have been used historically 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 14th 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 use of herring as an industrial raw material 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.[2]

Raw materials used

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 are usually deemed not suitable for direct human consumption. The fish caught for fishmeal purposes solely are termed "industrial".[3] Other sources of fishmeal are from bycatch of other fisheries and byproducts 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 a few rare unexploited species may produce a poisonous meal.

Selecting species

In selecting which species to use:

  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 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
  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.

Fish meal is manufactured primarily from anchovies in Peru, menhaden in the United States, pout in Norway, capelin, sand eel, and mackerel in other parts of northern Europe, and sauries, mackerels, and sardines in Japan.[1]

Production

Fish meal factory, Bressay, Shetland Islands
Fish meal factory, Westfield, West Lothian

Fishmeal is made by 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.[4]

Of the several ways of making fishmeal from raw fish, the simplest 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, but the end product is poor quality in comparison with ones made by modern methods. Now, all industrial fish meal is made by the following processes:[2]

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 the liquid 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: 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.

The two main types of dryers are:

Grinding: This last step in processing involves the breakdown of any lumps or particles of bone.

Nutrient composition

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 makes this feed ingredient 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.[5] Fishmeal is sought after as an ingredient in aquaculture diets because it contains compounds that make the feed more palatable. This allows the feed to be ingested rapidly, and will reduce nutrient leaching. Nonessential glutamic acid is an amino acid thought to impart palatability to fishmeal.[6]

Fish lipids are also highly digestible by all species of animals and are excellent sources of the essential polyunsaturated fatty acids (PUFA), including both omega-3 and omega-6 fatty acids. The predominant omega-3 fatty acids in fishmeal and fish oil are linolenic acid, docosahexaenoic acid, and eicosapentaenoic acid. 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.[7]

High digestibility of fish lipids means they can provide considerable 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 cyanocobalamine (B12), niacin, choline, pantothenic acid, and riboflavin.

Benefits

Fishmeal in diets increases feed efficiency and growth through better feed 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 acids, 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.[8]

Incorporation of fishmeal into diets of aquatic animals helps to reduce pollution from the wastewater 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.

In pet food

Fish meal is found in approximately 8% of pet foods as a non-descriptive source of protein, low in omega fatty acids as the oil is pressed out. The quality of the ingredient in pet food is suspect, as poor quality and rancid fish are often used.[9]

Ecological links

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. The trace contaminants in the feed, if present, can cause diseases and fish mortality.

Economy

About 23.13 million tonnes of compound aquafeeds were produced in 2005, of which about 42% was consumed by aquaculture. The aquaculture sector consumed around 3.06 million tonnes or 56% of world fishmeal production and 0.78 million tonnes or 87% of total fish oil production in 2006, with over 50% 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.[10] 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.

Risks

Unmodified fish meal can spontaneously combust. In the past, ships have sunk because of such fires. Now, the danger is eliminated by adding antioxidants, namely, ethoxyquin. There has been some speculation that ethoxyquin in pet foods might be responsible for multiple health problems. To date, the U.S. Food and Drug Administration has only found a verifiable connection between ethoxyquin and buildup of protoporphyrin IX in the liver, as well as elevations in liver-related enzymes in some animals, but with no known health consequences from these effects. In 1997, the Center for Veterinary Medicine asked pet food manufacturers to voluntarily limit ethoxyquin levels to 75 ppm until further evidence is reported. However, most pet foods that contain ethoxyquin have never exceeded this amount. Ethoxyquin has been shown to be slightly toxic to fish.

Ethoxyquin is not permitted for use in Australian foods, nor is it approved for use within in the European Union, though it is an accepted additive in the U.S. Besides the USA, it is also widely used in other third-world countries.

Though it has been approved for use in foods in the US, and as a spray insecticide for fruits, ethoxyquin has surprisingly not been thoroughly tested for its carcinogenic potential. Ethoxyquin has long been suggested to be a possible carcinogen, and a very closely related chemical, 1,2-dihydro-2,2,4-trimethylquinoline, has been shown to have carcinogenic activity in rats, and a potential for carcinogenic effect to fishmeal prior to storage or transportation.[4]

Future

Despite the adverse effects, organisations such as 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.

The FIN monitors two key areas: Legislation, which governs fishmeal use in animal feed, and contaminant issues and regulations that have, or are likely to have, an 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.

Main producing countries

See Also

References

  1. 1 2 Pauly, Daniel and Watson, Reg (2009) "Spatial Dynamics of Marine Fisheries" In: Simon A. Levin (ed.) The Princeton Guide to Ecology. Pages 501–509.
  2. 1 2 Windsor, M L. (2001). Fish Meal. Department of Trade and Industry Torry Research. TORRY ADVISORY NOTE No. 49
  3. ↑ The fish site
  4. 1 2 Miles RD and Chapman FA (2006) "The Benefits of Fish Meal in Aquaculture Diets" University of Florida. Document FA122, p.6.
  5. ↑ "Manufacture, Storage, Composition And Use Of Fish Meal".
  6. ↑ Johnston, I. A., S. Manthri, et al. (2002). "Effects of dietary protein level on muscle cellularity and flesh quality in Atlantic salmon with particular reference to gaping." Aquaculture 210(1-4): 259–283.
  7. ↑ Regost, C., J. Arzel, et al. (2001). "Fat deposition and flesh quality in seawater reared, triploid brown trout (Salmo trutta) as affected by dietary fat levels and starvation." Aquaculture 193(3-4): 325–345.
  8. ↑ Lie, Ø. (2001). "Flesh quality – the role of nutrition." Aquaculture Research 32: 341–348.
  9. ↑ "Pet food nutrition and ingredient analysis".
  10. ↑ "Higher fishmeal prices result in good business".
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