Sunday November 5, 2006
Beta-agonists hog the limelight
Many drugs are legally used in animal feed to improve growth and/or treat diseases. However, there are some that are banned. Recent reports say that some swine farmers in Malaysia are still feeding their pigs prohibited beta-agonists. TEE SHIAO EEK looks at the issue, and wonders what is safe to eat these days.
MADAM Ong was only at the butcher’s for a short while. She is definitely buying less pork for the family than she used to. “I have heard about the beta-agonist issue. Of course I’m concerned (about it),” she says in Mandarin. “Usually, I buy about RM100 worth of pork a week for the family, now I’m buying only RM20 worth,” she says, holding up a small bag of meat outside the Taman Tun Market in Kuala Lumpur.
“I’m worried that eating meat with the beta-agonist will be bad for our health,” says Madam Ong. Earlier on Wednesday, Veterinary Services Department director-general Dr Abdul Aziz Jamaluddin promised that his department would be conducting spot checks on farms together with the local authorities and health ministry officials. But in Malaysia, it’s often a case of too little, too late, and people are becoming immune to these problems.
“Even if we cut down on pork, what else can we eat? Chicken has got its own problems, fish has got its own problems, even vege tarians have dietary problems,” one female customer at the Taman Tun Market points out. One of the pork sellers in the market believes his customers are savvy enough to tell the dif ference between good pork and pork containing beta-agonists (“It’s not tasty!”).
But what about those who can’t? The farmers violating the law to make a quick buck are doing a disservice to their con sumers.
Porky may look adorable as a chubby cartoon character, but when it comes to slaughtering that porcine creature for dinner, people prefer a lean pig. Historically, swine producers have tried all sorts of methods to produce leaner pigs: controlled feeding (less food), genetic selec tion (breeding leaner pigs) and improving the nutrient formula tion in feed (cutting down on energy and fat).
“In the mid-80s, animal scien tists discovered that a group of compounds called beta-agonists could produce more lean meat and reduce fat in pigs,” says Dr Wong Hon Siong, the country manager of Elanco Animal Health, the animal health division of Eli Lilly. Beta-agonists are used in humans to treat asthma (they come in the form of inhalers).
However, almost all of these drugs are prohibited in food and in animal production. Currently, only one type of beta-agonist, ractopamine, remains legal for use in animal feed, as it is safer and leaves much lower levels of residue in food. For swine producers, these compounds must have seemed miraculous because of what they could do in a pig’s body. “Beta- agonists act on beta receptors in the muscles to ‘partition nutri ents’, either by increasing fat tis sue breakdown or reducing fat synthesis,” explains Dr Chee Liung Wun, regulatory and tech nical manager of Elanco.
Illegal usage of beta-agonists can be dangerous, says Dr Chee. The most frightening consequence is human toxicity if people con sume edible pork tissue that con tains beta-agonist residue.
“Recently, two cases of beta- agonist toxicity in humans were reported in Shanghai and one in Shenzhen, China,” says Dr Chee. People exposed to high levels of beta-agonist may experience shivering of hands, increased heartbeat, respiratory effects, feeling shaky or nervous, headaches and muscle cramps.
“These side effects occur because the majority of the pro hibited beta-agonists act on the beta-2 receptor, which is found not only in the muscles, but also the heart and respiratory organs,” explains Dr Chee, who is also a veterinarian.
In people suffering from cer tain diseases, such as heart dis ease, the risk could be higher, depending on the amount of residue consumed.
Bad or good?
After a rash of human poisoning cases were reported following the indiscriminate use of beta-ago nists in the 80s, worldwide regu latory bodies started looking into these compounds and decided to ban their use. In Malaysia, all beta-agonists were banned in animal produc tion in 1991. In 2005, the Health Ministry only allowed rac topamine to be used.
But it wasn’t long before the banned beta-agonists appeared on the radar again – used furtive ly by some swine producers. What the producers do not realise is that by mixing these banned substances into animal feed, they are creating something that is highly dangerous and potent.
As Dr Chee explains, prohibited beta-agonists come in pure pow der form. “Powder generates more dust and is dangerous to workers in the farms. “Toxicity can occur during ille gal manufacture and feed prepa ration. For example, in Ireland in the early 90s, three human deaths were reported due to inhalation of clenbuterol powder while workers were adding it to feed,” says Dr Chee.
He adds that powder also tends to clump together, so it is difficult to ensure that it spreads out evenly during the mixing process. “So one part of the feed may have a very high dose and other parts won’t.”
The advantage of ractopamine is that it is formulated as granules to minimise dust generation, and is also greatly diluted to increase its safety during the mixing process.
How do beta-agonists enter the human food chain?
Like other drugs and substances used in animals to enhance growth or control diseases, beta- agonists may leave residues in the animal tissues and their prod ucts, such as the meat, milk or eggs.
Illegal drug residues mainly occur when livestock producers do not observe a drug’s with drawal period before slaughter, as recommended on the drug’s label. (Withdrawal period refers to the number of days that the animal has to be free of the sub stance before it is slaughtered. This withdrawal period is when the animal will excrete the sub stance from the tissues.) But in the case of beta-ago nists, the residues arise because producers are using the drugs illegally, and have no idea what the limits or withdrawal periods should be.
This is dangerous. Think about it: after a drug has been given to an animal, the drug will stay in its edible tissues, such as the mus cles, fat, liver and kidney, for a certain amount of time, depend ing on its half life.
“Half life refers to the time taken for the activity (of the sub stance) to reduce to half, or be excreted from the body,” says Dr Chee.
The half life of clenbuterol is about 30 hours, while the half life of ractopamine is only about four hours. This means that rac topamine is excreted from the pig’s body much faster than the other types of beta-agonists.
A small amount of drug residue may be acceptable, because it may not have any effect on the person who consumes the meat. However, the residue should not exceed the safe dose for humans, or the maximum residue limits that have been determined under the Food Regulations 1985. To consider how much drug residue would be harmful to humans, Chee explains that every drug has a pharmacological dose in humans, which tells us how much of the drug is required to have an effect on people.
It takes very little of the pro hibited beta-agonists to cause problems in the human body. “For clenbuterol, in order to expe rience a biological effect, such as the heart beating faster, you only have to consume as little as 10mcg per day. For salbutamol, you have to consume 2000- 4000mcg per day,” explains Dr Chee. Ractopamine has a wider safe ty margin because humans would need to consume more than 20,000mcg of it per day to have any ill effects at all.
Moreover, it is not so easy for humans to consume that much ractopamine from pork. Scientists have found that even when pigs are fed 1.5 times the highest rec ommended dosage of rac topamine, the actual residue found in the tissues is still far below the maximum safe tissue concentration. Dr Chee adds that the actual residue of ractopamine found in edible pig tissues is so low that the compound doesn’t require a withdrawal period. “You can feed it to the pig up to the last day before you (slaughter) it.”
So, in pigs fed ractopamine, how much will be safe to eat? A lot, as it happens. 350kg of pork muscle, or 15kg of pork liver per day, to be exact. “That means you can eat as many as five whole pigs (assum ing that a pig is 70kg) every day for the rest of your life, and still be below the ‘no effect’ level,” says Dr Chee.
Why it doesn’t pay to use pro hibited beta-agonists
What it all comes down to is the cost. “Those (producers) using pro hibited beta-agonists do so because they are cheaper than ractopamine,” says Tung Hong Chai, chairperson of the pig unit of Federation of Livestock Farmers’ Associations of Malaysia. Prohibited beta-agonists cost between RM30 and RM50 per tonne, while ractopamine costs RM127 per tonne.
However, Dr Wong maintains that even though ractopamine is more expensive, it is still eco nomically viable because it has been shown that farmers can get a 100% return on their invest ment. Conversely, look at the conse quences of using the prohibited beta-agonists. Swine producers are putting their workers at risk, and possibly causing ill effects to the consumers who buy their pork. In the end, a nationwide boycott of pork would cost the producers more than what has been “saved”.
Veterinary Services Department director-general Dr Abdul Aziz Jamaluddin attributes the sudden increase in prohibit ed beta-agonist use to swine farmers who wanted to sell off their pigs for slaughter as soon as possible to cash in on the higher price of pork. However, Tung is confident that most swine producers know by now that illegal beta-agonists are bad. He urges the rest of the producers in Malaysia to start using ractopamine. “I hope we can eventually cut out the use of beta-agonists,” says the swine producer.
As the manufacturer of rac topamine, Elanco Animal Health plays an important role in edu cating swine producers to reduce the abuse of illegal beta-agonists. “We have a lot of one-to-one dealings with producers. We educate them on how to use our product – we recommend the dosage, explain the feeding pro gramme and teach them how to mix the product into the feed,” says Dr Wong.
The eye of the law
“Enforcement plays the most important role” in curbing the use of prohibited beta-agonists, says Dr Wong. In Malaysia, animal feed and drugs are regulated just like human food and drugs. The use of ractopamine is regulated under the Poisons Act 1952 and its maximum residue limit is stipulated in the Food Regulations 1985.
Drug and pesticide residues in animal products are monitored by the Food Safety and Quality Division of the Health Ministry. Their enforcement officers con duct random checks on food products to test whether the drug residues exceed the stipu lated maximum residue limits.
Contravening the law brings heavy penalties: from an impris onment not exceeding five years or a fine or both, to a fine not exceeding RM100,000 or impris onment not exceeding 10 years, or both, on conviction. The Department of Veterinary Services of the Agriculture Ministry also plays a role. Under the drug-residue monitoring programme of the department, samples of meat are randomly taken from various slaughter plants in the country for labora tory analysis.
The National Pharmaceutical Control Bureau is responsible for regulating the sale of beta-ago nists. And lastly, district and town councils all over the coun try have to keep an eye on illegal abattoirs, where pigs may be slaughtered to escape detection. Clearly, it’s going to take more than one farmer, or one civil ser vant, to make any changes. In the meantime, the wiser consumer will choose to buy pork in moderation.
“The most important thing is that we should not overeat any type of food. We should eat in moderation,” says Madam Ong, exiting the market with her “leaner” bag of pork.