ARS scientists have developed
two new methods of detecting
ractopamine, a feed additive
promoting leaner meat, in
Service scientists in Fargo, North Dakota, have developed two new
methods of detecting ractopamine hydrochloride, a feed additive given
to pigs and cows so they'll produce leaner cuts of meat.
Use of the methods by livestock producers, meat inspectors,
or export companies, for example, should provide greater flexibility
in where, when, and how they measure ractopamine residues in animals.
Such monitoring helps the U.S. meat industry safeguard against illicit
use or accidental exposure. It also ensures good trade relations with
the European Union, which disallows animal growth promoters like ractopamine
and other beta-adrenergic agonists. So say Weilin Shelver, a chemist,
and David Smith, an animal physiologist, in the Animal Metabolism-Agricultural
Chemicals Research Unit of ARS's Red River Valley Agricultural Research
Center in Fargo.
Their first method is an ELISA (enzyme-linked immunosorbent
assay), and the second is an optical biosensor. Both use a specialized
type of protein called a monoclonal antibody. The scientists developed
this antibody using modern biotechnology techniques.
Both methods are fast, easy to use, specific, and sensitive,
and they give similar measurements, notes Shelver. "The major difference
is in how they make the measurements," she adds. "An advantage
of the biosensor is that it sometimes gives less interference, or background
noise, from the other materials in the sample."
In the United States, ractopamine has been approved for
use in pigs since 2001 and cattle since 2003. Ractopamine use leads
to leaner, more efficient animals that reach their market weights sooner
than untreated animals.
With such gains, however, is the potential for illicit
use in animalssuch as fish, goats, and sheepfor which ractopamine
approval hasn't been granted by the U.S. Food and Drug Administration.
"Beta-adrenergic, leanness-enhancing agents have
been used illegally at farms, livestock shows, horse-racing events,
and even in humans for their purported performance- and profit-enhancing
effects," notes Smith. "Either the ractopamine biosensor or
ELISA assay could be used in these situations and would be especially
useful when live animals need to be tested quickly."
High-performance liquid chromatography (HPLC) is the gold
standard to measure beta-agonists like ractopamine. But it can be laborious,
time consuming, and costly, notes Shelver.
In trials with urine samples from ractopamine-fed cows
and sheep, the biosensor and ELISA test were equal to HPLC in detecting
concentrations of 5 to 20 parts per billion, Shelver reports. ELISA
is the fastest of the three, since it can analyze many samples simultaneously.
The biosensor works best with fewer or sequential samples.
The biosensor works by taking readings of light reflected
off the surface of a tiny gold chip. This happens after molecules of
ractopamine fixed onto the chip are bathed in a urine sample containing
both ractopamine and the monoclonal antibody. The antibody then binds
to the chip, changing the angle of reflected light. The instrument detects
this change, revealing how much ractopamine is in the sample. Similar
studies are now under way in pigs.
ARS has patented the ractopamine monoclonal antibody to
encourage its commercial development by industry.By Jan
Suszkiw, Agricultural Research Service Information Staff.
This research is part of Food Safety (Animal and Plant
Products), an ARS National Program (#108) described on the World Wide
Web at www.nps.ars.usda.gov.
L. Shelver and David
J. Smith are with the USDA-ARS Animal Metabolism-Agricultural Chemicals
Research Unit, Red River Valley
Agricultural Research Center, 1605 Albrecht Blvd., Fargo, ND 58105;
phone (701) 239-1425 [Shelver], (701) 239-1238, [Smith], fax (701) 239-1430.
"New Tests Detect Growth Promoter in Livestock" was
published in the April
2004 issue of Agricultural Research magazine.