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Food Safety Focus (64th Issue, November 2011) – Incident in Focus

Lean Meat Agents in Meat Products

Reported by Dr. Tommy SZE, Veterinary Officer,
Slaughterhouse (Veterinary) Section,
Centre for Food Safety

In August 2011, the Centre for Food Safety (CFS) humanely destroyed a batch of local pigs admitted into the Sheung Shui Slaughterhouse after detection of a prohibited chemical, Clenbuterol in their urine. Meat derived from Clenbuterol-tainted animals is considered unfit for human consumption because of the human toxicity associated with the chemical.

Clenbuterol and Meat-leaning

Clenbuterol is a veterinary drug primarily used for treating bronchospasm in horses. It belongs to the group of synthetic substances called beta-agonists ( β -agonists). Since β -agonists can increase muscle to fat ratio, they can also be used as a growth promoter to produce lean carcass, and therefore commonly referred to as lean meat agents. Clenbuterol and Salbutamol, the two most common β -agonists, are illegal to be used in food animals in Hong Kong. People who have consumed meat containing excessive amount of β -agonist residues may experience symptoms including rapid heart rates, dizziness, headaches, tremors, nervousness, and even d eath at high enough concentration.

From 1998 to 2001, an average of 15 food poisoning outbreaks confirmed to be associated with Clenbuterol-tainted meat were detected annually. Since the prohibition of use of Clenbuterol in food animals on 31 December 2001 , the number of food poisoning outbreaks related to Clenbuterol dropped to nine in 2002 and there have been no such food poisoning cases since 2003 to date.

Current Control of Clenbuterol and Salbutamol

Under the Harmful Substances in Food Regulations (Cap. 132AF) and the Public Health (Animals and Birds) (Chemical Residues) Regulation (Cap. 139N), Clenbuterol and Salbutamol are prohibited in fish, meat or milk, and food animals. Live food animals imported into Hong Kong have to be certified that they are free from these two prohibited drugs. When live pigs are admitted into the slaughterhouses, they are subjected to hold and test for these two drugs. Random samples from each consignment of pigs are taken and only negative samples will mean that the whole consignment can be released for slaughter. For positive samples, all pigs from the same consignment will be isolated and retained for subsequent confirmatory test. If confirmed positive, the whole consignment of pigs would be humanely destroyed. Between 2002 and 2006, cases of Clenbuterol or Salbutamol abuse were identified each year. Since 2007, among the tests for Clenbuterol and Salbutamol, only one batch of pigs has been confirmed to be positive for Clenbuterol from local slaughterhouses (Figure 1).

Figure 1
Figure 1

Ractopamine as a Growth Promoter

Ractopamine also belongs to the group of β -agonist but its safe use as a growth promoter to increase leanness of pigs has been established in more than 20 countries, including USA, Australia, Canada and Japan. It has also been registered for use in Hong Kong since 2007. Studies in animals show that an oral dose of Ractopamine can be rapidly absorbed, circulated in blood and quickly excreted in urine. When the drug is used properly according to the label instruction, meat derived from the food animals concerned is safe for human consumption.

In terms of food safety control, the Codex Alimentarius Commission has been discussing the setting of maximum residue level for Ractopamine in cattle and pig tissues for several years. The CFS is currently reviewing the regulatory framework for veterinary drug residues in food and will take into account of the latest international development.

Healthy lean pigs
 Healthy lean pigs

Other Ways to Increase Lean Meat?

Selective breeding is a useful tool to improve meat quality. Animals with favourable aspects such as leanness are selected, reproduced and their offsprings with favourable traits retained for further reproduction. After generations, a bloodline of animals with favourable traits can be developed.

Food animals require nutrients including a mixture of water, carbohydrates, protein, fat, fibres, minerals and vitamins for proper functioning and growth. By proper manipulation of nutrients content at different stages of development of food animals, increase in growth of lean muscle can be achieved.

Key Points to Note:

  1. Clenbuterol and Salbutamol are prohibited for use as growth promoters in food animals in Hong Kong.
  2. Ractopamine is a recently established agent for increasing leanness of meat.
  3. Good husbandry practice needs to be observed when Ractopamine is being used.

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