Attention on beta agonists in beef

News
Mar 8, 2013

As consumers at home and abroad get more interested in their food, production technologies get more attention and scrutiny from all angles. None is so frequent in the mainstream media today, or possibly as valuable to the beef industry, as beta agonists.

A beta agonist—or β-adrenergic agonist—is a type of chemical which reallocates nutrient use from one type of tissue to another, most notably towards muscle tissue and away from fat. This “repartitioning activity” makes some beta agonists ideal for use as growth promotants.

The two most familiar beta agonists to the U.S. meat industries are ractopamine and zilpaterol. Commercially, ractopamine is the active ingredient in Optaflexx for finishing beef cattle and Paylean for finishing pigs. Commercially, zilpaterol is the active ingredient in Zilmax for finishing cattle.

Both of the cattle products are fed to cattle in the last weeks prior to slaughter for increased weight of lean muscle. Optiflexx is to be fed 28-48 day days before slaughter with no withdrawal time, and Zilmax is to be fed 20-40 days (20 is ideal) with a 3-day minimum withdrawal prior to slaughter.

Academic and industry research found that cattle fed either of these beta agonists had improved average daily gain, without relevant changes in dry matter intake. In Optaflexx’ application for FDA approval, it was reported that trial steers fed a ration containing 27 grams of the additive per ton of feed (100 percent dry matter) had an average daily gain (ADG) 0.65 pounds higher than the control group. The trial summaries referenced in the Zilmax approval application cited similar effects, with tested cattle receiving 6.8 grams of the additive per ton of feed (90 percent dry matter) seeing ADG 0.72 pounds higher than control cattle.

The fact beta agonist-fed cattle put on more weight is one of the biggest headlining details about the additives and has been credited with the notable gains in carcass weights seen in recent years. The increase in cattle weight comes largely from the additives’ ability to direct the animal’s body to reallocate nutrients from fat deposition to the creation of lean muscle mass.

Professor Bradley Johnson, Ph.D.—meat science and muscle biology chair of Texas Tech University’s Department of Animal and Food Sciences and scientific consult to the makers of both commercial additives containing beta agonists—explained that the increase in muscle mass from beta agonists comes from muscle hypertrophy, the increased size of a muscle due to the increased size of the muscle’s cells.

But the two commercial products add pounds to cattle differently due to the different biological effects of the active ingredients. Ractopamine tends to increase live weight while zilpaterol tends to increase hot carcass weight. Johnson advised cattle feeders who choose to use products containing beta agonists that they need to be mindful of how they market cattle when selecting which product to use.

Quality concerns

Despite its benefits, there are some downsides involved with the use of beta agonists. Increased lean muscle mass decreases marbling, and larger muscle cells and increased musculature make for tougher meat.

In a collaborative study conducted by academic and industry representatives and published in the Journal of Animal Science in 2009, researchers found that USDA quality grade was negatively impacted by zilpaterol. In the control group, which was given none of the additive, the cattle graded 16.81 percent Prime and 46.89 percent Choice. For those cattle fed feed containing zilpaterol for 20 days prior to slaughter, only 12.58 percent graded Prime and 43.42 percent graded Choice. Johnson explained that as the muscle fibers increased in size, intramuscular fat—marbling—gets edged out. This is in addition to beta agonists diverting nutrients away from fat disposition.

The increase in muscle fiber size also has its hand in producing tougher meat because, as Johnson put it, “size of muscle fibers has a lot to do with tenderness.”

Several studies found that tenderness—as measured by Warner-Bratzler shear force (WBSF)—is negatively affected by the consumption of beta agonists. The amount of pressure needed to cut through samples of beef from beta agonist-treated cattle was increased by between 0.27-1.7 kilograms of pressure compared to control cattle in a number of studies. This impact on tenderness is reportedly the reason behind Cargill not allowing the use of these beta agonists in its supply chain.

Despite these measurable effects in research setting, how noticeable they are to consumers is hard to tell. In the same studies which found increased WBSF scores in beef from beta agonist-treated cattle, researchers found that usual aging periods mitigated the increased toughness in most cases. Other consumer acceptability studies found mixed results with some situations where the paneled consumers noticed a tenderness difference, but no other impact to eating quality, and other situations where panelists didn’t notice the difference in tenderness.

Controversy abroad

Of course the biggest attention-grabber regarding beta agonists lately has been the moves of Russia and China. China and many associated Asian countries, such as Taiwan, have long threatened to ban meat found with traces of ractopamine. Russia dealt a blow to the U.S. beef and pork industries earlier this year by insisting on a zero tolerance policy for ractopamine residues and a certification process.

Though ractopamine has been getting more of the international attention, zilpaterol has not been spared either. It has been banned by many of the same countries which ban ractopamine, such as China, Taiwan, Russia and the EU.

A recent presentation by the U.S. Meat Export Federation (USMEF) pointed out that the bans on meat from the U.S. based on beta agonist concerns stand to cost the U.S. billions in meat trade this year alone. The damages could be exacerbated into the future as our competitors in global meat trade which either don’t use beta agonists or already have certification programs in place for them gain our lost market share.

In the presentation, US- MEF described the question of what to do now as a double-edged sword. On the one hand, agreeing to ship only beta agonist-free meat to these markets would reward these non-sciencebased trade restrictions and might encourage other countries to adopt such requirements. Additionally, allowing important production technology to be forced out for unscientific reasons could severely hamper the need to produce more food with fewer resources. On the other hand, giving up these markets to competitors would hurt U.S. beef and pork industries at a time when both are already in shaky economic situations.

See USMEF’s article regarding the economic issues posed by China’s and Russia’s bans on page 8 of today’s WLJ.

Many countries abroad which ban ractopamine or zilpaterol do so under phytosanitary regulations and concerns for human health. Officials in China and Taiwan have frequently claimed beta agonists are toxic and have poisoned consumers. Hearsay reports of Chinese and Taiwanese consumers having “heart issues” following consumption of U.S. meat are used in part as reasoning for the ban in those countries. Similar concerns have been voiced by Russian officials.

However, existing research does not support such claims regarding ractopamine and zilpaterol, and (in the case of ractopamine) runs counter to international standards.

In July 2012, the Codex Alimentarius Commission, the United Nation’s (UN) food standards body, set maximum residue limits on ractopamine residues in beef and pork products, though this move came only by a one-vote margin. And as of Jan. 21, 2013, zilpaterol has been added to the list of substances scheduled for new evaluation at the Nov. 14, 2013, joint meeting of the World Health Organization and the UN’s Food and Agricultural Oganization’s expert committee on food additives. The group will attempt to determine acceptable daily intakes which could lead to setting maximum residue limits.

Ractopamine was approved for use in beef cattle by FDA in 2003 and is used in Canada, Australia and Brazil, among others. Zilpaterol for use in cattle was approved by FDA in August 2006, though commercial use did not begin until May 2007. Prior to that, it had been cleared for use in South Africa in 1997 and in Mexico in 1999. It has since been approved for use in Canada in 2009.

In talking to WLJ, Johnson opined the broad-brush aversion to all beta agonists in China and Taiwan at least could be a combination of issues. One of the issues is linguistic; there are no different terms in Chinese to distinguish between different types of beta agonists, so ractopamine, zilpaterol, and clenbuteral are all called the same thing.

The other issue concerns bad past experiences with clenbuteral, a beta agonist sometimes used illegally as a performance-enhancing drug by athletes and which has had a storied past in human food chains. Throughout the 1980s to early 2000s, several countries, including Spain, France and various provinces in China, saw spates of consumers hospitalized by the effects of clenbuteral toxicity due to eating pork and beef organs with excessive residue levels of the drug. Symptoms included increased heart rate, muscular tremors, headache, nausea, fever and chills.

Clenbuteral has been banned for use in food-producing animals in the U.S. since 1991. The EU has banned its use in food-producing animals since 1996.

While not legal for use in food animals in China or many surrounding countries, it shows up in the food supply in those countries as China is one of the largest producers of the drug. Johnson, who has worked with livestock operations in numerous countries abroad, described the use of illegal beta agonists in other countries “eye-opening.”

Controversy at home

While most of the concern over beta agonist use abroad centers on human health, many domestic voices raised against them are concerned with the animals, claiming it is inhumane. The rationale is the added muscle mass negatively impacts animal mobility and causes increased injury from unnatural stress on bones and joints.

Respected livestock welfare expert Professor Temple Grandin has been very vocal about the negative welfare issues associated with using beta agonists. According to her article, “The Effect of Economics on the Welfare of Cattle, Pigs, Sheep, and Poultry”:

“Stockyard managers at slaughter plants and my own observations indicate that higher doses [of ractopamine] for longer times cause weakness and more ‘downer’ nonambulatory pigs. It can also make pigs more difficult to handle… In cattle, over use and too high a dose of zilpateral (Zilmax) or ractopamine in cattle has resulted in lameness and heat stress. Stockyard (lairage) managers in two plants have reported that the outer shell of the hoof fell off of feedlot cattle fed too much zilpateral.”

When asked about the topic of increased stress on feet and joints from beta agonist additives, Johnson reported not having personally experienced that in his research.

“We’ve done MRI on hooves and joints of cattle fed beta agonists looking for inflammation and we haven’t found it.” On the topic of the claims of impaired movement, he did say beta agonist-treated cattle did tend to move slower, but he compared that to human body-builders where increased muscle mass can decrease mobility, but that does not necessitate or even imply suffering.

Johnson also went on to mention other related welfare issues attributed to beta agonists—such as falling and increased downer animals attributable to the additive—and that he has not observed them. He did point out, however, that the research he has participated in has been small-pen settings which may not reflect commercial feedlots.

“We need more data on this area,” he said of beta agonist-related welfare concerns in large feedlots.

The use of beta agonists in the future of the U.S. beef industry is something of a question. On the one hand, it is an economic way of improving yield and making more with the same or fewer resources. This, of course, is the definition of sustainability most of U.S. agriculture pursues with admirable dedication and success.

But on the other hand, the challenges its use poses to the same industry—through quality concerns, the actions of our trade partners and attending economic ramifications, persisting human health worries and animal welfare concerns—warrant critical examination of the use of beta agonists. Are the costs worth the benefit?

Another challenge which has yet to rise up to the level it might is the impact of domestic consumer sentiment. By-gone food and management technologies such as irradiation of meat, the use of rBST (recombinant bovine somatotropin) in dairy, and most recently the flap over lean finely textured beef are a testament of the power of negative consumer sentiment regardless of the science backing the technology.

Johnson said he’s advised the makers of both commercial beta agonist products to alter their strategy regarding the substances. Trying to “fly under the radar” of consumer attention is potentially dangerous in the court of public opinion.

He also spoke passionately about the need for cooperative efforts for the future of the beef industry. Improved consumer education efforts need to couple with greater dedication to transparency and being proactive, rather than reactive, in all links in the beef supply chain.

“We’re at a critical juncture.” — Kerry Halladay, WLJ Editor

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