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Fish Meal

Fish meal processing (adapted from FAO, 1986)
African fish meal with high ash content
Fish meal
Lake Victoria sardine (Rastrineobola argentea)
   

Common names

Fish meal, fishmeal, brown fish meal, white fish meal, low-temperature (LT) fish meal, prime fish meal

Description

Fish meal is obtained by cooking, pressing, drying and milling fresh raw fish or fish trimmings.

There are several types of fish meal in the market depending on the source of fish or fishery by-products used and on the processing technology involved. Fish meal is a more or less coarse brown flour.

The three major sources of fish meal are:

  • fish stocks harvested specifically for this purpose: small, bony and oily fish such as anchovy, horse mackerel, menhaden, capelin, sandeel, blue whiting, herring, pollack…
  • by-catches from other fisheries
  • trimmings and offal left over from fish processed for human consumption (unpalatable or fast spoiling) .

Fish meal is an excellent source of highly digestible protein, long chain omega-3 fatty acids (EPA and DHA) and essential vitamins and minerals . Fish meal quality depends on the raw material used and on the processing method involved.

Distribution

Fish meal has been used as a feedstuff since the 19th century in Northern Europe and is now used worldwide. Global production of fish meal has been stable for the past two decades at around 5 to 6 million tons, Peru and Chile being the main producers.

A major portion (> 60%) of fish meal produced globally is used for aquaculture (farming of finfish and shrimp). The intensification of aquaculture in Asia, and particularly in China, is increasing the demand for fish meal even though the supply cannot grow accordingly. Natural phenomena such as the El Niño-Southern Oscillation affect the fisheries in Central American Pacific coasts, leading to seasonal scarcities and increased prices. Due to these factors, the fish meal market is volatile and prices often shoot up. The search for suitable and cost-effective alternative protein sources for use in industrial aquafeeds will be the most critical factor in the development of intensive aquaculture in Asia.

Processes

The best quality of fish meal is obtained from raw fish. However raw fish must sometimes be processed in order to prevent protein and oil breakdown by draining, chilling (chilled water systems, mixing of ice with fish) or chemical preservation (with sodium nitrite or formaldehyde).

Raw material (raw fish or preserved fish) is composed of 3 major fractions: solids (fat-free dry matter), oil and water. Fish meal is manufactured by a series of actions involving cooking, pressing, drying and milling. After cooking, generally at around 85-90°C, the cooked fish is pressed through a screw press where liquids are removed and a “press-cake” is obtained. The liquids are decanted, the supernatants centrifuged to obtain “stick-water”, which is concentrated through mild evaporation. The press cake and stick water are mixed together before entering a dryer to obtain fish meals with a final moisture of about 10%. At each of these processing steps, there can be variations, leading to fish meals of variable qualities 

Good quality fish meals contain crude protein levels above 66%, fat content around 8 to 11% and ash generally below 12%. In some of the tropical developing countries, “fish meal” is sometimes produced after sun-drying and grinding and can have very high levels of ash and relatively low protein levels. Other fishery by-products include fish protein concentrates with high protein levels (> 70%).

In the 1980s, acid-preserved “fish silage” was very much promoted as one of the means of conserving trash or raw fish and for making farm-made feeds for aquaculture by mixing such silages with other feedstuffs

although this practice is not very much applied widely.

Environmental impact

Due to the ever increasing demand for fish meal and fish oil to be used in feeds for farmed fish and crustaceans, there has been concern that the over-reliance on capture fishery-derived fish products for aquaculture would contribute to the over-exploitation of certain types of fisheries, with concomitant effects on the stocks of other wild fish. However, time-series data show that there has been no upward trend in the catch of fish for feed since the 1980s . Based on current developments in fish feed formulations, it is now recognised that aquaculture contributes to global fisheries supply and does not deplete the marine fishery resources . Besides, the fish meal industry has committed itself and set forth several stringent measures to ensure that the feed-grade fisheries respect sustainability criteria. Another issue of concern is the poor management of rejects.

The use of fish meal obtained from raw fish as a feedstuff for terrestrial animal feeds still remains a debated issue 

Potential constraints

Contaminants and toxic substances

Since proteins and lipids from fish are highly degradable, adequate processing is to be achieved in order to prevent protein breakdown to biogenic amines (especially, histamines) or fatty acids breakdown into oxidized compounds. Bacterial development, although low, should be avoided given the low levels of moisture and absence of carbohydrates. Cooking fish meal above 80°C normally destroys bacteria but the whole chain-process is susceptible to re-infection: high air-temperature must be reached in the dryers, external sources of contamination (rodents, birds, flies and insects) must be eliminated, and storage building must be dry (no condensation) and clean .

Fish meal is also susceptible to chemical contamination with harmful substances (chlorinated hydrocarbons: dieldrin, lindane, PCBs, dioxins), due to the accumulation of those anthropogenic substances in the marine food chain and finally in the fatty tissues of fish used for the manufacture of fish meal. The levels of such contaminants (PCBs, dioxins) in fish meal depend on the fish source: fish meal from Central America have lower levels than those from the Northern hemisphere 

A toxic substance called gizzerosine is formed when fish meal is directly dried at 180°C (versus 140°C) in order to improve fish meal productivity. Gizzerosine is detrimental to poultry as it causes gizzard erosion and black vomit . This problem can be avoided if steam is used to dry fish meal 

Ban in ruminant nutrition

Fish meal has been banned in the European Union since 2000 in ruminant nutrition but remains authorised in pigs, poultry and fish . It was re-authorized in 2009 to make milk replacers for young ruminants . Fish meal is banned in Australia under the Ruminant Feed Ban

Nutritional attributes

Fish meal has a high crude protein content ranging from 62% to more than 70% (Sauvant et al., 2004) and a high amino acid quality (Médale et al., 2009).

Tables of chemical composition and nutritional value

  • Fish meal, high protein
  • Fish meal, 60-68% protein as fed
  • Fish meal, low protein

Ruminants

In ruminants, fish meal is an interesting source of rumen undegradable protein (fish cooking causes protein binding) and is thus used as a by-pass protein.

The use of fish meal is prohibited for ruminants in the European Union and in other countries.

Cattle

In lactating cows, when compared to other sources of undegradable protein such as soybean meal or cottonseed meal, fish meal gave higher results , improving amino acid balance and reducing N excretion.

Cows’ response to fish meal protein is improved by urea treatment in a rice straw-based diet . Fish meal resulted in increases in milk yield and protein yield in dairy cows especially if forage/concentrate ratio is high (Pike et al., 1994). However, several papers referring to low inclusion levels reported that it had no effect on milk yield or milk protein content.

Fish meal also enhances cows response to high milking frequency  and reduces PGF2α concentration which could be responsible for early abortion in lactating cows , thus inducing higher conception rates (Staples et al., 1998). Feeding fish meal may also increase milk n-3 fatty-acid content 

Sheep

The undegradable protein content of fish meal is interesting in sheep as it improves forage intake. Inclusion levels range from 2.5% in lambs to 7.5% in milking ewes (FIN, 2000). High protein content improves immune status: feeding ewes during late pregnancy with fish meal decreases worm infestation and thus reduces anthelminthic treatments .

Fish meal supplementation increases reproduction performances in ewes: conception rates, lamb litter weight, lamb weight and vigour at birth; colostrum production and heat production. Milking ewes supplemented with fish meal have higher milk production. Fish meal also improved lamb live weight gains in early weaned lambs grazing tall fescue .

Pigs

Fish meal has a high biological value for pigs. Protein of fish meal has a good quality: it has a high methionine content and protein is highly digestible. Its contents in vitamins, n-3 fatty acids and minerals are very valuable for pigs. Levels of incorporation vary from 5 to 10 % in piglet feeds to about 3% in feeds for finisher or sows .

Different studies proved that fish meal is beneficial in starters and weaned pigs. at rates below 10% (higher rates results in economical losses.Fish meal is also reported to be hypoallergenic to piglets and was found to decrease diarrhoea during post-weaning (Gore et al., 1990). It could be useful in low health status piglets to improve daily gain 

Poultry

Fish meal is an interesting concentrated protein source for poultry, particularly in situations where land animal by-products have been banned in poultry feeds. Fish meal has a high biological value in poultry, not only as a protein source but also as source of minerals such as P and Ca and trace elements such as Se or I. However, the high prices of fish meal limit the inclusion levels and those remain around or below 5% (Blair, 2008 ; Chadd, 2008).

Including fish meal in broilers diets increases body weight, daily weight gain and feed intake. Fish meal has greater impact on growing broilers than on starters. It is highly valuable to young turkeys. In laying hens, inclusion of fish meal may cause a fishy taste in eggs and meat. (Blair, 2008).

Rabbits

Fish meal is a valuable feedstuff for rabbits. Due to its cost, there have been several attempts to replace it by less expensive products: it was possible to totally or partially replace fish meal with quinoa grain, blood meal, extruded hatchery wastes, meat meal and poultry viscera meal 

Fish

Given that the indispensable amino acid profile of fish meal reflects that of the ideal protein pattern for fish or shrimp, fish meal is a major protein source in aquaculture. Protein digestibility of good quality fish meal is very high with equally high amino acid availabilities. Fish meal is also a source of essential fatty acids, minerals and trace elements.

Currently available data show that out of the 6 million tons of fish meal available globally, more than 65% is used in feeds for fish and crustacean farming. The levels of incorporation of fish meal can range from 40 to 60% in feeds for marine fish to less than 5% in feeds for carps, catfish or tilapia (Tacon et al., 2008). Most cyprinids (carps) reared in semi-intensive ponds are fed with feeds practically devoid of fish meal. In the recent years, much progress has been made towards the substitution of fish meal by mixtures of different plant protein sources even in intensively-reared salmonids or marine finfish, thus leading to significant economy as well as addressing sustainability issues

Crustaceans

Like fish feed, feeds for marine or freshwater shrimp contain high levels of fish meal (up to 40%). Plant ingredients are being increasingly incorporated as an alternative to fish meals or other marine-derived protein sources such as shrimp meal or squid meal in order to ensure the sustainable development of shrimp farming .

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