Zilpaterol (zilpaterol hydrochloride; codenamed RU 42173) is a
β2 adrenergic agonist.
Under its trade name, Zilmax, it is used to increase the size of cattle and the efficiency of feeding them.
Zilmax is produced by Intervet, a subsidiary of
Merck & Co.,
and marketed as a "beef-improvement technology". Zilpaterol is typically fed
in the last three to six weeks of cattle's lives, with a brief period (three days in the US) before death for
withdrawal, which allows the drug to mostly leave the animal's tissues.
Concerns have been raised on the impact of zilpaterol on flavor; however, studies have confirmed that overall tenderness, juiciness, flavor intensity, and beef flavor remain within the normal variation observed in the beef industry and differences are smaller than what can be detected by the consumer.
However, several studies have shown the use of zilpaterol leads to increased size, feed efficiency, and value.
Merck reported Zilmax-fed cattle do not produce beef with a difference in taste or quality compared to cattle not fed the drug, but elsewhere, concerns have been raised about the beef's tenderness.
Studies have variously found a slight reduction in tenderness,
[ an increase in shear force,][ and a lower percentage of intramuscular fat ( marbling).]
Prohibitions and processor adoption
As of October 2017, Zilmax was approved in 17 countries, notably the US, Canada, South Africa, South Korea, Ukraine and Brazil.
In the US
Tyson Foods
Tyson Foods, Inc. is an American multinational corporation, based in Springdale, Arkansas, that operates in the food industry. The company is the world's second-largest processor and marketer of chicken, beef, and pork after JBS S.A. It annually ...
was the first among the largest U.S. meatpackers to adopt Zilmax. Because of concerns about tenderness and loss of marbling, Cargill and other meatpackers resisted the practice. The next adopters were JBS an
National Beef
with Cargill finally joining them in mid-2012.
Origin and formulation
Zilmax is produced by Merck in France, a country in which the substance is prohibited. As of October 2017, its commercial formulation was 4.8% zilpaterol hydrochloride, 8% polyoxyl castor oil
Castor oil is a vegetable oil pressed from castor beans.
It is a colourless or pale yellow liquid with a distinct taste and odor. Its boiling point is and its density is 0.961 g/cm3. It includes a mixture of triglycerides in which about ...
, 4.3% polyvinyl pyrrolidone
Polyvinylpyrrolidone (PVP), also commonly called polyvidone or povidone, is a water-soluble polymer made from the monomer ''N''-vinylpyrrolidone. PVP is available in a range of molecular weights and related viscosities, and can be selected accor ...
and 82.9% ground corn cob
A corncob, also called corn cob, cob of corn or corn on the cob, is the central core of an ear of corn (also known as maize). It is the part of the ear on which the kernels grow. The ear is also considered a "cob" or "pole" but it is not full ...
.[
]
Chemistry
Zilpaterol has two chiral
Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object.
An object or a system is ''chiral'' if it is distinguishable from i ...
carbons and consequently four optical enantiomers. These enantiomers are: (6''R'',7''R'')-, (6''R'',7''S'')-, (6''S'',7''R'')- and (6''S'',7''S'')-. RU 42173 corresponds to racemic ''trans''-zilpaterol hydrochloride, a mixture of the (6''R'',7''R'')-(−)- and (6''S'',7''S'')-(+)-enantiomers.
External links
Zilmax (zilpaterol hydrochloride) — Consumer Information Center
References
{{Adrenergics
Phenylethanolamines
Benzazepanes
Beta2-adrenergic agonists
Merck & Co. brands
Heterocyclic compounds with 3 rings
Nitrogen heterocycles
Ureas
Veterinary drugs
World Anti-Doping Agency prohibited substances
Isopropyl compounds
Medicated feed