“Optaflexx has the potential to become a product that will greatly enhance live performance and the economics of feeding cattle.” says nutrition consultant Kenny Eng, San Antonio, TX. “This is a truly historic product that feedyard managers should keep their eyes on in the months and years to come.”

Optaflexx (ractopamine chloride) is the first growth-promoting drug in the beta-agonist class of compounds to be approved by the U.S. Food and Drug Administration for use in cattle.

While Optaflexx is not currently commercially available, Elanco managers say they will use the next few months to educate the beef industry about the product. They plan to introduce it as a component in an overall finishing practice dubbed “Finishing Improvement Technologies.”

Optaflexx is approved for use during the last 28-42 days of the finishing period. Based on Elanco's research, Optaflexx ideally should be fed for 28 days, which provides the feeder with a 14-day window to market cattle and stay within the FDA-approved guidelines.

When used at the dose recommended by Elanco, an average steer fed Optaflexx yields approximately 17 lbs. (7.71 kg) of additional live weight and approximately 14 lbs. (6.35 kg) of additional carcass weight.

Estimates are that when used at Elanco's recommended dose of 200/mg/head/day for 28 days, the cost of feeding Optaflexx will be about $7/head.

The compound can be used as a feed ingredient for both steers and heifers but isn't recommended for breeding animals.

How Optaflexx Works

Optaflexx is a member of a large family of beta-agonists that act as repartioning agents in the metabolism of proteins. Through changes in muscle development and muscle degradation ratios, these agents decrease fat deposition and increase muscle mass.

Because of the reduction in fat and increase in muscle content of animals treated with these agents, concerns have been raised about their effect on the qualitative properties of their meat. But, while most beta-agonists work at the expense of fat, Optaflexx redirect nutrients to increase protein synthesis with minimal effects on fat deposition.

Optaflexx's once-removed beta-agonist cousin, zilpaterol, never quite mustered acceptance or approval in this country. Marketed under the trade name Zilmax, by the former Hoechst Roussel Vet, Zilmax is used legally in feedlots in Mexico and South Africa.

Like zilpaterol, Optaflexx redirects cellular metabolism in favor of protein synthesis in cattle feed and works very well to enhance weight gain, feed efficiency and carcass yield. The knock against zilpaterol though has been in the area of meat quality. Some Mexican cattle feeders trying to capitalize on higher-quality beef markets have steered clear of zilpaterol with concerns it would impact eating quality of their finished product.

Eating Quality Tested

Elanco knew that in order to pass FDA's and industry standards, it had to evaluate the effect of Optaflexx on the taste and tenderness of the finished product.

The conclusions were that there were no differences that would be detected by the consumer in meat palatability as defined by tenderness, juiciness and flavor.

Ken Prusa is a food scientist at the Iowa State University Center for Food Science and Human Nutrition. Prusa coordinated the eating quality evaluations of cattle fed Optaflexx. His tests were conducted using trained sensory panels and Warner-Bratzler shear force values.

Prusa says that when Optaflexx was fed to cattle at the recommended “mid-range” dosage, he saw no differences in meat quality compared to beef from “control” animals.

“This product comes from a totally different profile of compounds than the other beta-agonists that have been around,” says Prusa. “When fed responsibly, it works just like Elanco says it works — and like the FDA has indicated.”

Prusa explains that he and his staff went into the sensory research with totally open minds.

“And, of course, we were ‘blinded’ until the very end as to what we were evaluating,” he adds. “From what we have seen, I have no qualms about its use in food animals from a quality and safety standpoint.”

A Success In Pigs

Ractopamine hydrochloride marketed by Elanco under the trade name Paylean is in use in the swine industry. It was the first beta-agonist approved by the FDA for use in food-producing animals.

Paylean is widely used in commercial hog production where the implementation of lean-value carcass-pricing systems have led to the selection of pigs with increased carcass lean percentages and improved lean-feed conversion.

Steve Moeller, an Ohio State University hog specialist, stresses the importance to hog producers of properly following the label whenever the Paylean product is used.

“There are still a lot of misconceptions about what it is and what it does,” Moeller says. “If you're looking to increase the growth rate of your pigs or need to improve carcass leanness, then it's probably a judicious use of the product.

Moeller's recommendations transcend ractopamine hydrochloride's use in pigs.

“It should be used in a manner that is consistent with a particular strategy and not something done for no real reason or not thought out clearly,” he says.

Storied Histories

Proponents of the new generation of beta-agonists maintain the new compounds have distanced themselves from some of their other-side-of-the-tracks relatives.

Clenbuterol is probably the most well-known, albeit infamous, feed additive that falls in the class of beta-agonists.

It isn't licensed for use in the U.S., but some countries have approved it for use in animals not used for food, and a few countries have approved it for therapeutic uses in food-producing animals. The dosages needed for therapeutic purposes are much lower than those required to increase muscle mass.

Clenbuterol's illegal use in show animals is linked to its ability to induce weight gain and a greater proportion of muscle to fat.

Since the first alert about possible illegal use of clenbuterol in 1991, USDA and FDA have been working with state departments of agriculture and others to avoid contamination of the meat supply. The agencies have also alerted U.S. Customs to block the illegal import of clenbuterol and are following up with enforcement activities.

For example, in 1994, traces of clenbuterol residues were found in animals at stock shows held in Ohio and Oklahoma. In Tulsa, a clenbuterol test of champion animals disqualified six animals including some steers, sheep and a hog.

In 1995, two champion steers were disqualified because residues were found at the National Western Stock Show in Denver. FDA is also undertaking investigations concerning the sale of feed with clenbuterol and its possible use in veal calves in several states.

Exact Debut Unknown

Those concerns though, shouldn't deter the livestock industry from considering or evaluating the use of Optaflexx in cattle feeding programs, experts say.

Eng points out, however, that there's still a lot of research work to be done on the day-to-day use of Optaflexx. This is especially true with regard to its use in combination with implants and other feed additives.

Prusa says the interaction of Optaflexx with the currently available implants is a “fertile area” of research, and hopes to have an opportunity to investigate these interactions further. To date, Elanco makes no claims or predictions about the use of Optaflexx in combination with implants.

The company also recommends that feedyard managers work closely with their nutritionists to develop feeding and marketing regimes once Optaflexx becomes available.

Elanco has developed a series of fact sheets detailing milling and mixing information and storage recommendations as parts of an overall use program.

Once commercially available, Optaflexx will be sold in 25-lb. bags containing 45.4 g. of ractopamine hydrochloride/lb. The product must be thoroughly mixed into feeds before use. There is no withdrawal period associated with the use of Optaflexx.