April 14, 2004,
ARS news service: A feed additive given to
cows and pigs so they'll produce leaner cuts of meat
can now be detected by two new methods, according to
Agricultural Research Service scientists.
scientists have developed two new methods
of detecting ractopamine, a feed additive
promoting leaner meat, in livestock.
Weilin Shelver and David Smith developed the methods
as a faster, more user-friendly alternative to high-pressure
liquid chromatography (HPLC). This procedure is the
chief means by which federal inspectors now determine
residue concentrations of the additive, called ractopamine
hydrochloride, in live animals or carcasses of butchered
Such testing is deemed crucial to national food safety
programs aimed at protecting consumers from misuse of
ractopamine and other animal drugs. For example, the
tolerance level for residue in pig muscle is 0.05 parts
per million. Testing also is done to certify meat products,
such as for export to member nations of the European
Union. The union does not allow animal growth promoters.
Although effective, HPLC testing can be a laborious,
time-consuming and costly affair, according to Shelver,
who, along with Smith, is at the ARS Red River Valley
Agricultural Research Center, in Fargo, N.D. There,
she and Smith developed two kinds of tests using a monoclonal
antibody, a specialized protein that binds with molecules
of ractopamine in urine or tissue samples so it can
be detected. The first method is an enzyme-linked immunoabsorbent
assay (ELISA). The second is based on an optical biosensor.
In trials at Fargo using urine samples from ractopamine-fed
cows and sheep, the ELISA and biosensor performed as
well as HPLC in detecting the drug at concentrations
of five to 19 parts per billion. The ELISA method yields
the quickest results, since it can analyze many samples
simultaneously--100 in five hours, for example. The
biosensor worked best with low numbers of samples that
require sequential analysis, such as on a production
line at the rate of one every 10 minutes.
The ractopamine monoclonal antibody has been patented
to encourage its commercial development by industry.
Read more details on the research in this month's issue
of Agricultural Research magazine, available online
ARS is the U.S. Department of Agriculture's chief scientific