Fish meal

Fish meal, fishmeal, brown fish meal, white fish meal, low-temperature (LT) fish meal, prime fish meal [English]; harina de pescado [Spanish]; farinha de peixe, farinha de pescado [Portuguese]; farines de poisson [French]; Fischmehl [German]; farina di pesce [Italian]; 魚粉 [Chinese]; Рыбная мука [Russian]

Fish meal is obtained by cooking, pressing, drying and milling fresh raw fish or fish trimmings (IFFOO, 2006). 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) (FIN, 2008).

Fish meal is an excellent source of highly digestible protein, long chain omega-3 fatty acids (EPA and DHA) and essential vitamins and minerals (IFOMA, 2001). Fish meal quality depends on the raw material used and on the processing method involved.

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 (more than 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 along 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 (Kaushik, 2010; Steinfeld et al., 2006).

The best quality fish meal is obtained from raw fish. However, in order to prevent protein and oil breakdown, raw fish is often processed 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 (FAO, 1986).

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 (more than 70%) (Kaushik, 2010).

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 (Disney et al., 1980), although this practice is not widely applied.

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 (Naylor et al., 2000). However, time-series data show that there has been no upward trend in the catch of fish for feed since the 1980s (New et al., 2002). Based on current developments in fish feed formulations, it is now recognized that aquaculture contributes to global fisheries supply and does not deplete the marine fishery resources (Naylor et al., 2009). 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 (Kaushik, 2010).

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).

Contaminants and toxic substances

Since proteins and lipids from fish are highly degradable, adequate processing has to be achieved in order to prevent protein breakdown into 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 the 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 buildings must be dry (no condensation) and clean (FAO, 1986).

Fish meal is also susceptible to chemical contamination with harmful substances (chlorinated hydrocarbons: dieldrin, lindane, PCBs, dioxins) (Erne et al., 1979), 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 meals from Central America have lower levels than those from the Northern hemisphere (New et al., 2002).

A toxic substance called gizzerosine is formed when fish meal is directly dried at 180°C (vs. 140°C) in order to improve fish meal productivity. Gizzerosine is detrimental to poultry as it causes gizzard erosion and black vomit (Hinrichsen et al., 1997). This problem can be avoided if steam is used to dry fish meal (Sugahara, 1995).

Ban in ruminant nutrition

Fish meal has been banned in the European Union since 2000 in ruminant nutrition but remains authorized for pigs, poultry and fish (European Commission, 2001). It was re-authorized in 2009 to make milk replacers for young ruminants (European Commission, 2009). Fish meal is banned in Australia under the Ruminant Feed Ban (AHA, 2014).

Although the use of fish meal is prohibited for ruminants in the European Union and in other countries, it is a valuable source of by-pass protein (cooking fish causes protein binding) and is thus used as a by-pass protein.

Cattle

In lactating cows, when compared to other sources of undegradable protein such as soybean meal or cottonseed meal, fish meal gave higher results (Broderick, 2005; Broderick et al., 2000; Korhonen et al., 2002), improving amino acid balance and reducing N excretion (Ohgi, 2004; Abu-Ghazaleh et al., 2001; Schroeder et al., 2000).

Cows’ response to fish meal protein is improved by urea treatment in a rice straw-based diet (Talukder et al., 1990; Khan et al., 1990). Fish meal resulted in increases in milk yield and protein yield in dairy cows (Malleson et al., 2008; Ibarra et al., 2006; Broderick, 2004; Ohgi, 2004; Yeo et al., 2003; Korhonen et al., 2002; Hill et al., 1999; Wright et al., 1998), especially if the 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 (Moussavi et al., 2008; Moussavi et al., 2007; Serbester et al., 2005; Allison et al., 2002).

Fish meal also enhanced the response of cows to high milking frequency (Yeo et al., 2003) and reduced PGF2α concentration that could have been responsible for early abortion in lactating cows (Mattos et al., 2002), thus inducing higher conception rates (Staples et al., 1998). Feeding fish meal may also increase milk n-3 fatty-acid content (Abu-Ghazaleh et al., 2001).

Sheep

In Sheep, the undegradable protein content of fish meal 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 with fishmeal during late pregnancy decreased worm infestation and thus reduced the use of anthelmintics (Donaldson et al., 1998).

Fish meal supplementation increases reproduction performance in ewes: conception rates, lamb litter weight, lamb weight and vigour at birth, including colostrum and heat production (Vipond et al., 1996; Robinson et al., 1989; Robinson et al., 1999). Milking ewes supplemented with fish meal produced more milk. Fish meal also improved live-weight gains in early weaned lambs grazing tall fescue (Poppi et al., 1988).

Fish meal has a high biological value for pigs. Protein of fish meal is of good quality: it has a high methionine content and the 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 finishers or sows (FIN, 2000; Patience et al., 1995).

Different studies proved that fish meal is beneficial in starters and weaned pigs at rates below 10% (Lopes et al., 2007; Zivkovic et al., 2007; Kats et al., 1992; Aas et al., 1984). Inclusion rates higher than 10% were not economically viable (Patience et al., 1995). 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 (Bergstrom et al., 1997).

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 and broilers, inclusion of fish meal may cause a fishy taste in eggs and meat (Blair, 2008).

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 (Lebas, 2004).

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 availability (Anderson et al., 1995). 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 carp, catfish or tilapia (Tacon et al., 2008). Most cyprinids (carp) reared in semi-intensive ponds are fed with feeds practically devoid of fish meal. In 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 (Kaushik, 1990; Kaushik et al., 2004; Kaushik et al., 2008).

Like fish feed, feeds for marine or freshwater shrimp contain high levels of fish meal (up to 40%). However, 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 (Amaya et al., 2008).