Fishmeal -- Under the microscope

by Emily Buckley
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Since January 2001, fishmeal has been banned temporarily in diets for ruminants, mainly cattle and sheep, throughout the European Union as part of the range of controls introduced to eliminate bovine spongiform encephalopathy (BSE).

E.U. Health Commissioner David Byrne admits, "fishmeal itself does not present a risk for transmission of transmissible spongi-form encephalopathy" (ie BSE-type and human vCJD diseases). The problem, according to Commissioner Byrne, is that "the presence of fishmeal may mask a contamination of mammalian proteins in feed."

In short, the Commission decided that current analytical methods were inadequate to distinguish the presence of mammalian meat and bone meal (MMBM), from that of other animal and marine proteins. The Commission’s solution was to impose this ‘temporary, precautionary prohibition’ on all animal and marine proteins in all feeds. However, there is derogation (E.U. jargon for concessions) that permits use of fishmeal in pig and poultry feeds.

E.U. fishmeal suppliers challenge this ban on fishmeal in ruminant feed, not only because it damages their businesses, but also because they dispute its logic and believe it to be futile — making no contribution to BSE eradication. They also regard its implementation by some national authorities, including those in Italy, Germany and the U.K., as overzealous and ‘gold-plated.’

Testing method is the key

In spite of industry pressure on the Commission to free fishmeal of bans, it is expected to stick to its guns in demanding that all three of its stipulated conditions are satisfied before it even considers lifting the ban. The first review of the ban is due by July 1, 2003.

The first condition is that an accurate testing method must be functional. The second, the introduction of new E.U. animal by-products legislation, was achieved in September. The third condition requires compliance with the full range of BSE controls by all Member States. Recent official checks have revealed significant non-compliance.

Fishmeal interests can do little directly to influence compliance, so the focus now is on accelerating progress towards developing a test or method of analysis to detect MMBM.

The Commission itself had set up a project called "Stratfeed" to develop methods to identify land animal proteins in feedstuffs. However, this project’s potential to resolve fishmeal’s immediate problems is limited, and the project is not due for completion until 2004.

Identifying the right test has been made more difficult by the fact that the Commission has yet to define the finishing line.

How quick, how cheap, how reliable and, above all, how sensitive does the test need to be? It is not yet precisely clear what quantity of MMBM would constitute a BSE/vCJD risk. Based on some hints in documents and discussion with the Commission, the fishmeal sector is assuming the test must be capable of detecting an MMBM contamination level of 0.1%.

Comparing testing methods

Dismayed by the lack of impetus and co-ordination from the Commission, the Fishmeal Information Network (FIN) and the International Fishmeal and Fish oil Organization (IFFO) have together developed a summary of various tests to detail the method; show sensitivity and other limitations; and compare the sample size, time scale and costs for each. It also assesses the tests’ prospects of satisfying the Commission’s condition for restoring fishmeal to all feed sectors. Finally, the summary estimates the time scale to completion of E.U. validation.

Testing methods currently detailed are: Microscopic analysis (classical); Polymerase Chain Reaction (PCR); ELISA (enzyme linked immuno-sorbent assay) Test, created by Immuno-lex, State Serum Institute, Denmark — this is not part of the Stratfeed consortium; NIR-Microscopy; and NIR.

Two specific challenges face those wishing to apply test methods to distinguishing MMBM from fishmeal. First, existing techniques generally cannot perform well when the land animal protein has been treated under the pressure cooking treatment required by the E.U., which has been set at 133ºC/3 bar pressure/20minutes. Second, most of the testing techniques have been developed for mixed feeds. While they are expected to be effective with fishmeal, this has to be confirmed.

PCR

Up to mid-2002, the relatively expensive PCR test seemed to show the most promising results. Five European centers claimed to have a PCR method that worked with heated proteins. Many laboratories already have the equipment for, and expertise in, running PCR tests for DNA and GMO identification. However this test is one of the most expensive at around G.B.£100 (approximately U.S.$159) per sample. False positives are possible and the time scale to full E.U. validation is two years.

The Danish-version ELISA test

The ELISA test has also found favor as it requires little specialist equipment and is inexpensive. But the ELISA method used at the U.K. government veterinary laboratory employs a double-sandwich procedure that works with material heated only to 130°C. However, a method employed by the Danish company Immunolex is claimed to work for material heated up to 159°C. This method has considerable potential to be used for widespread screening. The sample size required is 500g or less, the test takes about three hours and the cost is just £10 to £15 (approximately U.S.$16 to U.S.$24) per sample. More work needs done to establish that it works with all types of fishmeal and with complete feeds. Completion of E.U. validation is 18 months to two years.

Feed microscopy

Feed microscopy is the only testing method that has already been accepted as an officially recommended method by the Commission for the basic identification of constituents of animal origin in feedstuffs. In feed microscopy, animal protein is identified by sedimenting the bone fraction for identification.

Microscopy has always been excellent for detecting MMBM in vegetable proteins with no bones. Disadvantages of this test in its original form include: high-cost, it requires highly trained staff to distinguish bones of land animals from those of fish; and the presence of bone fragments from other animal proteins can make the test less reliable.

So, for a period earlier this year, the focus was on other methods. However, this test has been revised and its potential to help distinguish MMBM from fishmeal reassessed. The feed microscopy method is being developed by the U.K. Government Veterinary Laboratory Agency (VLA) in Luddington. It has been shown that, in the hands of a trained microscopist, contamination down to 0.1%, in either a mixed feed containing fishmeal or fishmeal itself, can be detected reliably.

The Stratfeed project is also contributing to progress by publishing a picture library of bone fragments by species to be issued on CD to facilitate the training of operators and effectiveness of the procedure.

With these developments, microscopic analysis now looks the most promising option, and it has the potential to come on stream within the next 12 months. The sample size required is 5g to 10g; the procedure takes 1 to 2 days; and a trained operator can test 10 to 15 samples per day at a cost of around £50 per sample (U.S.$79). The basic method is already E.U. validated.

The next step is to involve eight independent laboratories, all members of the Stratfeed group, throughout the E.U. to confirm the accuracy of feed microscopy as performed by Luddington. Results are expected Spring 2003, prior to the E.U.’s review of the temporary ban which is due to be completed June 2003.

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