Ractopamine
Ractopamine is a feed
additive, banned in many countries, to promote leanness in animals raised
for their meat. Pharmacologically, it is a phenol-based TAAR1
agonist and β adrenoreceptor agonist that stimulates β1 and β2 adrenergic receptors.[1][2]
It is most commonly administered to animals for meat production as ractopamine
hydrochloride.[3] It
is the active ingredient in products known in the US as Paylean for swine,
Optaflexx for cattle, and Tomax for turkeys.[4]
It was developed by Elanco Animal Health, a
division of Eli Lilly and Company.
As
of 2014 the use of ractopamine was banned in 160 countries,[5]
including the European Union, mainland
China and Russia[6][7]
while 27 other countries, such as Japan, the United States, and South
Korea, have deemed meat from livestock fed ractopamine safe for human
consumption.[8][9]
Commercial
ractopamine is a mixture of all four possible stereoisomers.[10]
Mode of action
When used as a food
additive, ractopamine added to feed can be distributed by the blood to the
muscle tissues, where it serves as a full
agonist at mouse (not necessarily human) TAAR1.[1]
It is also an agonist at beta-adrenergic receptors.[2]
A cascade of events will then be initiated to increase protein synthesis, which
results in increased muscle fiber size. Ractopamine is known to increase the
rate of weight gain, improve feed efficiency, and increase carcass leanness in
finishing swine. Its use in finishing swine yields about 3 kg (6.6 lb)
of additional lean pork and improves feed efficiency by 10%.[11] In
cattle on 28 January 2004 Elanco Animal Health made Optaflexx commercially
available in the US. Optaflexx is a "medicated feed additive
that is labeled only for use in steers or market heifers (not breeding
heifers or bulls) during the last 28-42 days on feed."[12]
Regulation around the world
On
6 July 2012, the international reference standard Codex Alimentarius Commission
narrowly approved the adoption of an maximum residue limit (MRL) of 10 parts per
billion (ppb) for muscle cuts of beef and pork.[13]
Setting any limit was a controversial move. Countries with major meat
export markets had been lobbying for the establishment of such a standard for
several years to use it as leverage to erode individual national-level bans in World Trade Organization disputes.[13]
Consumers International, a world federation
of consumer groups that represents 220 consumer organizations in 115 countries,
strongly opposed the move.[13]
As
of 2013, ractopamine use in food animals has been banned in over 160 countries.[14]
Because the traditional Chinese diet embraces pig offal, and because
ractopamine is concentrated by the gastro-intestinal system of animals, Chinese
officials have banned ractopamine. Other countries in Asia, whose traditional
diet is similar to that of the Chinese, have had similar thoughts but the
American use of tied trade access as a proxy for conflict has somewhat
mitigated their reactions, as seen below.[15]
EU
Ractopamine
has not been allowed in the 28 member countries of the European Union, based on
the 2009 European Food Safety Authority's
opinion on its safety evaluation, which concluded that available data were
insufficient to derive a maximum residue limit as a 'safe residue level for
human consumption'. The uncertainty was particularly great for people who might
be thought to be more susceptible than most to an increase in β adrenergic
stimulation from consuming the additive, such as people with cardiovascular disease or children, and that
simply increasing the "uncertainty factor" built into the calculation
as a safety factor would rapidly become arbitrary.[16][17]
NAFTA-USMCA
As
of 2015, ractopamine use as a feed additive is authorized in the United States,
Canada, and Mexico.[16]
In the U.S., ractopamine is allowed to be used at a feed concentration of
5–20 mg/kg feed for finishing pigs and in dosages of 5–10 mg/kg feed for
finishing pigs heavier than 109 kg. The maximum residue limit for ractopamine for
meat in the USA is 50 parts per billion (ppb), or five times the
standard set by the Codex Alimentarius.
In
2017, the USDA approved of a new label, "no ractopamine — a beta-agonist
growth promotant" to be used.[18] As
of June 2019 the CFIA
maintained the Canadian Ractopamine-Free Pork Certification Program (CRFPCP) so
that Canadian exports to Asian countries are not disallowed by their
authorities.[15][19][20]
As of 22 May 2019, hundreds of commercial feed facilities, including some from
overseas, were enrolled in the CRFPCP, a programme that was essentially based
on self-certification and backed up by a randomized testing policy.[21]
Currently,
the label for USDA organic means no synthetic compounds can be used
other than those on the list of allowed synthetics,
therefore, ractopamine would not be allowed in certified organic production.[22]
For
Canadian domestic consumption of non-CRFPCP pork, ractopamine hydrochloride is
permitted to be sold over the counter with applications in meal or
pellet feed for finishing barrows and gilts (up to 10 mg/kg for last six weeks), confined finishing cattle
(up to 30mg/kg for last 42 days), and finishing heavy turkeys (up to 9 mg/kg
for 14 days). The withdrawal period was set to 0 days.[23]
Japan, South Korea
Japan, which had
permitted its feed additive use at least until 2009,[16]:1
and South
Korea only allow import of meat with ractopamine residues up to the maximum residue limit (MRL), but do not
permit its use in beef production.[24]
Taiwan
In
October 2006, Taiwan banned ractopamine along with other beta-adrenergic agonists,[25] In
a 2012 climb-down its legislature passed amendments to its Act Governing
Food Sanitation, authorising government agencies to set safety standards
for ractopamine.[26]
The Taiwanese Department of Health ultimately established an MRL of 10 ppb for
ractopamine in beef on 31 July 2012.[27]
The American Institute in Taiwan, which
represents U.S. interests in Taiwan, claims that these "and many other
countries have determined that meat from animals fed ractopamine is safe for
human consumption";[8]
this is in the context of an ongoing trade dispute between Taiwan and the US on
this subject, which threatened to prevent Taiwan's entry to the Trans-Pacific Partnership trade pact.[28]
China, Russia
In
2013, Russia and China banned ractopamine in pork,[29]
and Russia also in beef,[14]
deeming it unfit for human consumption.
WADA proscription
In
2015, an 18-year-old female karateka from Egypt gave a urine sample in order for her anti-doping control to be
administered. It was found that the urine contained too much ractopamine and
the athlete was sanctioned with ineligibility for four years. The sole
arbitrator from the Court of Arbitration for Sport said
that ractopamine "is not specifically mentioned by name in the World Anti-Doping Code (“WADC”), but is an Other Anabolic Agent
prohibited under S1.2 of the 2015 Prohibited List under the WADC... Athlete did
not fulfil her burden of proof to establish the origin of the prohibited
substance, [and thus] she has committed an anti-doping rule violation".[30]
In
October 2017 at a World Anti-Doping Agency conference, it
was suggested in relation with ractopamine[31]
“
|
|
”
|
One
conclusion reached in October 2017 was that there was a "clear risk for
athletes to be tested positive" when consuming meat with residues at the
MRL concentration
International disputes
US-EU WTO dispute
Main article: Beef hormone controversy
In
the late 1990s, the World Trade Organization authorized the United
States and Canada
to impose retaliatory tariffs of US$116.8 million per year on the European
Union after it found the EU beef hormone ban to be in violation of the WTO Agreement
on the Application of Sanitary and Phytosanitary Measures (SPS Agreement).[32][33]
In September 2009, the United States and the European Commission signed a memorandum of
understanding, which established a new EU duty-free import quota for grain-fed,
high-quality beef as part of a compromise solution.[33]
China
In
July 2007, officials of the People's Republic of China seized
US-produced pork for containing ractopamine residues.[34]
Further shipments of ractopamine-fed pork were seized in September, though this
time they were Canadian in origin.[35]
In
June 2019, customs inspectors in China detected ractopamine in a batch of
Canadian pork products destined for Chinese consumption. The Chinese government
thereupon suspended not only pork but also beef imports from Canada.[36]
Canadian Agriculture Minister Marie-Claude Bibeau said that the CRFPCP
certificate was a forgery and called in the RCMP, while Canadian
Public Safety Minister Ralph Goodale stressed that the Federal government
would vigorously defend Canadian meat producers.[36]
Also at the press conference it was revealed that the Canadian Cattlemen's Association
said in a statement that "We are fully confident in our meat production
systems in Canada and the safeguards we have in place."[36]
In a desperate rear-guard action intended for domestic consumption, Canadian
Trade Minister Jim
Carr questioned the good faith and integrity of the Chinese.[19]
Meanwhile, holes were found in the CRFPCP programme because the meat packer at
the centre of the maelstrom is a chilled butcher shop only.[37] It
was disclosed on 3 July that the Chinese authorities had discovered 188
falsified CRFPCP certificates.[38]
Taiwan
Ractopamine
has been banned in Taiwan
since 2006.[39]
In the summer of 2007, two US shipments including ractopamine-laced pork were
rejected by Taiwan's health authorities, while the Taiwan government had been
considering lifting the ban on such imports.[40]
This resulted in mass protests in the capital city, Taipei, by swine
farmers insisting that the ban remain in place. Health Minister Hou Sheng-mou (侯勝茂) declared no lifting
of the ban would occur unless related laws were amended. Although the use of
ractopamine in livestock is still banned and enforced on the domestic industry,
and the government has maintained a “zero tolerance” policy on pork imports
that contain it, Taiwan's legislature amended the food safety act in August
2012 to allow the import of beef products containing up to a maximum residue level of 10 parts per billion
of the additive.[41]
The remaining restrictions have been an obstacle to the two nations signing a
free-trade agreement, and the Office of the United
States Trade Representative (USTR)’s 2018 Trade Policy Agenda and 2017
Annual Report assert that these remaining restrictions “...are not based upon
science...” and highlights their removal as among the main priorities for the
US in its trade with Taiwan.[41]
Malaysia
According
to the Malaysian Food Act 1983 and Regulations (as of 5 January 2010),
ractopamine is allowed in pig muscle and fat (MRL of 10 ppb), pig liver (MRL of
40 ppb), and pig kidney (MRL of 90 ppb).[42]
Ractopamine is allowed as its half-life is lower, leading to reduced residues
in the food, and the dose required to affect humans is much higher than other
beta agonists.[43] On
30 December 2008, the Malaysian Veterinary Services Department quarantined 10
of the 656 pig farms in Malaysia, as the livestock were found to contain the
banned chemical.[44][45]
Russia
The
use of ractopamine in Russia is prohibited. On 6 June 2011, the Russian Ministry of Agriculture notified
key meat import/exporters in Russia of a future prohibition of ractopamine in
meat imported to Russia.[citation needed]
On
7 December 2012, the prohibition went into force, and pork and beef export to
Russia required submission of compliance certificates confirming absence of
ractopamine in exported meat.[citation needed]
Pharmacokinetics in humans
A
study was conducted to define the pharmacological response of humans to
ractopamine. A single oral dose of 40 mg of ractopamine hydrochloride
was given to human volunteers. The drug was rapidly absorbed; the mean blood
plasma half-life was around 4 hrs and it was not detected in plasma
24 hrs after dosing. Less than 5% of total ractopamine excreted
represented the parent drug, while the urinary metabolites were monoglucuronide
and monosulfate conjugates, with ractopamine monosulfate being the major
metabolite present.[46]
The
metabolic fate of ractopamine hydrochloride is similar in the target species
(pigs and cattle), laboratory animals, and humans. Besides the pharmacology
effect, ractopamine may cause intoxication effect; therefore, any consumption
by humans of a meat and/or byproducts of animals that consumed ractopamine with
feed for growth stimulation, may result in such clinical effects as tachycardia
and other heart rate increases, tremor, headache, muscle
spasm, or high arterial blood pressure.[47]
The effect of ractopamine on humans is not entirely known, but consumption of
products that contain ractopamine residues is not advisable for persons with cardiovascular
diseases.
Safety concerns
Target animal safety
In
swine ractopamine is correlated with adverse effects, especially hyperactivity,
trembling, and broken limbs, leading to censure by animal rights groups.[48]
In
a conversation with Boulder Weekly newspaper Colorado State University Professor of
Animal Science Temple Grandin, an expert on animal welfare,
described harmful effects of ractopamine on feedlot animals, such as cattle
with stiff, sore, and lame limbs, and increased heat stress.[49]
In the same column she also opines that meat from ractopamine-treated animals
may be tougher.[49]
Ractopamine
use is a factor in the development of downer
pigs, animals that are unable to move or stand.[50][51]
When
a winning show lamb tested positive for ractopamine in 2014, the owner claimed
it was due to negligent feed contamination by the manufacturer, rather than
intentional and illegal doping.[52]
Adverse effects
Acute toxicity
Oral
LD50 levels in mice and rats are
3547–2545 mg/kg body weight (male and female) and 474–365 (male and
female), respectively.[53]
Genotoxicity and mutagenicity
Mutation
studies in prokaryotes
and eukaryotes
show that ractopamine is not mutagenic. However, the results of several in
vitro studies, including chromosome aberration tests in human lymphocytes,
are positive. The positive genotoxic results are explained with limited
evidence to be due to a secondary auto-oxidative mechanism from
ractopamine-catechol-producing reactive intermediates.[which?][citation needed]
Carcinogenicity
Cardiovascular effects
Dose-dependent
changes of heart rate and cardiac output are observed within the first hour
after administration of ractopamine and gradually return to baseline values.
The systolic blood pressure will also increase in a dose-dependent manner,
while the diastolic pressure remains unchanged.
Musculoskeletal effects
Skeletal
muscle tremor is the most common adverse effect of beta-agonists, and is more
likely to be seen after oral administration than after inhalation. Tremor
results from an imbalance between fast- and slow-twitch muscle groups of the
extremities, and its severity varies greatly between individuals.
Behavioral changes in humans
Restlessness, apprehension,
and anxiety were reported effects after the use of various beta-agonists,
particularly after oral or parenteral treatment. In pilot clinical trials with
ractopamine, four patients showed little evidence for central nervous system
stimulation. Whether long-term treatment with these drugs results in the
development of tolerance to these adverse effects is unclear.[
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