Australasian Science: Australia's authority on science since 1938

Hormones In Meat: Science or Spin?

Hormone-free meat

Hormone growth promotants are used in as many as half of the steers and heifers raised for meat destined for the Australian market.

By Kate Osborne

Is the decision by supermarket giant Coles to sell only meat that is free of growth promoters based on science or just a clever marketing ploy?

In September 2010, when supermarket giant Coles announced they were no longer going to sell meat from cattle treated with growth hormones, they revealed an inconvenient truth: that the meat in our supermarkets has been produced using the same hormones banned in the European Union since 1998 and banned in the Australian poultry industry since the 1960s.

Australian beef is very safe to eat. The National Residue Survey, which looks for all kinds of contaminants in food, found two instances from 5732 cattle tested of non-hormone-type residues in meat.

However, Coles’ exposure of the use of hormones in the beef industry is linked to a number of broader issues that affect our health and the health of our environment. These include the right to know how our food is produced through adequate labelling and whether the intensification of agriculture in Australia is moving at a greater pace than the science needed to ensure that productivity increases are sustainable.

Prof Alan Bell, chief of CSIRO Livestock, has estimated that hormone growth promotants (HGPs) are used in as many as half of the steers and heifers raised for meat destined for the Australian market. Cattle treated with HGPs have a pellet implanted into the ear containing hormones that slowly diffuse into the bloodstream. The hormones in the pellet are usually synthetic versions of sex hormones such as oestrogen and testosterone.

HGPs are given to beef cattle to make the animal grow faster. Specifically, they enhance the deposition of protein, especially in muscle. According to the Meat and Livestock Australia (MLA), growth rates are increased by 10–30%, so treated cattle reach market weight sooner.

Public concern about growth hormones given to animals is based on fear of residues in our food. In a survey of 1000 people by MLA, leaked to The Sunday Mail in 2010, almost half said they would consume less meat if it had added hormones while 16% would “never touch [meat] again” and 15% would also “actively warn others”.

Globally there are many cases of hormone residues in meat, including banned substances. In Australia, which has high standards of food safety and monitoring, the National Residue Study found that 99.95% of tests from cattle were compliant with existing standards for all contaminants.

The only unequivocal evidence of injury to humans from ingesting hormones is from their use as a prescription medicine, or from accidental or occupational exposure. The growth hormone diethylstilbestrol (DES) was one of the first of its type approved for use in food animals in the US in the 1960s, but was banned after laboratory trials showed that repeated high doses were associated with tumours in rats. The same hormone compound was prescribed for women to help them maintain pregnancy, and was subsequently associated with high rates of a rare form of cancer in their daughters as well as sexual malformations in their sons.

This early disaster with DES has had a lasting legacy. Oestrogen-like compounds can stimulate cell division, so they increase the possibility of random errors during DNA duplication. Hence scientific studies and maximum residue limits for synthetic hormones have been based on a carcinogenesis model, with trials and tests set up to look for cancer-causing processes or properties.

More recent research suggests there is another risk to human health and the environment. HGPs used in the meat industry are part of a class of compounds called endocrine-disrupting compounds (EDCs), which also include substances such as pesticides, some antibiotics and plasticisers.

Endocrine disruption has been identified by the World Health Organization as an issue of global concern because they have the potential to interfere with hormone-regulated development in animals and humans by mimicking, antagonising or interfering with normal hormonal processes in the body. Endocrine disruption can occur at very low concentrations and can persist through multiple generations.

Commonly known as “gender benders”, the best-documented cases of endocrine disruption are in freshwater fish living in sewage run-off. Fish have been known to become hermaphrodites, and evidence of feminisation of fish is widespread in the UK and Europe. A study by the government organisation Land and Water Australia in 2005 found that streams across Australia carry endocrine disruptors at concentrations that could stimulate significant changes to the sexual cycles of native fauna, especially in catchment areas surrounding cattle feedlots, dairies and piggeries.

In 2009 the Endocrine Society advised that “no endocrine system is immune to endocrine-disrupting chemicals”. One issue it identified was the lack of established environmental baselines for EDCs. Another issue is that new compounds can form as secondary metabolites with unknown properties and effects. A third issue is that the physiological responses to synthetic hormones and natural hormones may not be the same. In fact, the biological activity of growth promotants in the environment is likely to be much higher as they are designed to persist over time and to maintain their endocrine activity.

Trenbolone is a synthetic hormone with properties similar to testosterone, and is one of the growth promotants commonly given to cattle. The minimum residue limit for trenbolone is 0.1 mg/kg based on assays and laboratory feeding trials designed to test mutagenic and carcinogenic potential. Natural testosterone levels in meat from untreated bulls are in the same range. However, the synthetic hormone is eight to ten times more potent than the natural hormone.

While no research in Australia has proven endocrine disruption in native wildlife, experimental studies have found that exposure to trenbolone results in masculinisation and reproductive problems in fish. One mechanism that causes endocrine disruption is that the synthetic hormone can have a higher affinity for the receptor site than the animal’s own natural hormone. This was the case in freshwater fish, where the metabolites of trenbolone had a higher affinity to receptors in the fish than its own testosterone.

The scrutiny that Coles has brought to the meat industry has revealed the extent to which meat production in Australia is changing. The image of the drover bringing cattle in from the vast inland pastures is firmly in the public consciousness yet the perception that the meat we eat is “grass-fed” is only partly accurate. In 2009,

2.9 million cattle were grain-fed in feedlots. While cattle still spend most of their life grazing on pasture, 80% of beef sold in major domestic supermarkets comes from animals “finished” in feedlots.

Feedlotting is an intensive agriculture system where large numbers of cattle are confined in pens and fed a grain-based diet. The majority of production growth in the beef industry over the past 10 years has been due to the expanding feedlot sector.

Growth promotants are extensively used in the feedlot industry along with other veterinarian pharmaceuticals such as anti­biotics. An inescapable aspect of intensive farming and HGPs is that safety relies on compliance in terms of dosage, withholding periods, and management of farm and animal waste.

Dr Fred Leusch of Griffith University researches the effects of EDCs on wildlife, and has just started a 3-year national survey. “We aim to define baselines of endocrine disruptors in Australian rivers and streams and get a better picture of whether we are likely to have a problem in Australia,” he says.

Whereas waste from human sewage is extensively treated, regulation of waste from agriculture is more variable. Leusch says that surface run-off after rain events can also flush animal waste on feedlots into streams, and this is likely to be exacerbated in concentrated animal farming operations.

“The regulators don’t really know what to do about endocrine disruption,” he says, “because there hasn’t been any evidence of endocrine disruption in humans from environmental-level exposure. The main paradigm of toxicology is that the dose makes the poison. With endocrine disruptors, while we know endocrine disruption can occur in humans, as highlighted by the DES disaster for example, no one really knows if anything is happening at the lower level of environmental exposure.”

While there is both a risk and environmental cost of unknown proportions in the current growth of feedlotting and chemical use in beef production, there is also an environmental cost of not using hormone growth promotants. Bell says that up to two million more cattle would be needed to produce the same amount of meat if the whole industry became HGP-free. More cattle means increased carbon emissions and land impact. Producers believe their viability will be marginalised as they will be the ones to pay for productivity losses such as lower market weight of cattle and increased feed costs.

For grass-fed cattle, HGP use is most common in northern Australia and helps to maximise growth rates during seasons when grass is most nutritious. If stock numbers are reduced on savannah during low growth periods, HGPs could help reduce the impact on land. However, there is no environmental benefit if HGPs simply mean that more beef is produced.

As science attempts to future-proof the Australian beef industry, HGPs seem more like a “big stick” compared with the “conductor’s wand” offered by more advanced technologies. Dr Wayne Pitchford of the Beef CRC has identified a gene that increases the amount of muscle and improves tenderness. Breeding genetic improvements into cattle takes several generations but he says that “in one generation you can select animals that grow faster”. Pitchford says cattle can also be managed for faster growth.

Management practices have improved across the industry through the implementation of a benchmarking system that grades the quality of meat based on a range of criteria like age, sex, breed, fat marbling, flesh colour and pH. The Meat Standards Australia (MSA) standard is increasingly being adopted for the domestic market.

Coles began implementing the MSA grading system 2 years ago, and claims it is the crux of its decision to ban HGPs. Alistair Watson, general manager of meat at Coles, has told ABC radio that the decision to ban growth promotants was not based on any concerns about the safety of hormones in food but was one of a number of steps Coles was taking to improve the quality of beef. For instance, HGPs make meat tougher and reduce the amount of fat in the flesh.

When an animal is slaughtered there are a number of steps that help to ensure meat quality and consistency, such as ageing the carcass and tenderstretching, which is a method of hanging the carcass. Growth hormones counteract the effect of ageing the carcass, although this effect is not the same for all cuts of meat and also varies with cattle breed.

Overall, ageing the carcass has a big impact on meat tenderness while the impact of HGPs is relatively small. This discrepancy is the source of criticism of Coles for banning HGPs. Supporters of HGPs say any negative effect on tenderness could be overcome by ageing the carcass longer, and say that Coles’ “more tender” slogan is a marketing gimmick.

Coles’ stance has highlighted the inadequacy of labelling in the meat industry. The results of the National Residue Study indicate that food health standards in Australia are very high and that consumers can have confidence that the food they buy at the supermarket is free of contaminants.

Transparency in the production process from paddock to plate is a successful marketing strategy in the organic and premium beef markets. Coles may be able to justify its ban of HGPs scientifically, but the potential benefits are more likely to come from public perception.

The risk posed by endocrine disruption to human health and the environment is an emerging challenge for scientists and regulators. It is clear that some models for increasing productivity in agriculture are more sustainable than others, and that the precautionary principle and long-term sustainability should guide regulators in charge of agriculture.

“In the past we were worried about things that killed you,” Leusch says. “Then it became things that gave you cancer. I think we’re turning the page and starting to ask: ‘What about even less obvious effects, such as things that could affect your hormone levels?’.”

Maximum residue levels in food and guidelines in the environment for endocrine disruptors may need to be updated to reflect this new health concern. At present, however, despite evidence of mechanisms for endocrine disruption and experimental results that clearly show detrimental effects on other animals, it is uncertain if low levels of exposure affect human well-being.

Kate Osborne is an ecologist and science writer.