Thanks to some asthmatic mice, cattle feeders can add an extra 14 lbs. or so to carcass weight during the last 30 days on feed and receive about $2 for every $1 spent in the process.

That's the cost-to-benefit ratio cattle feeders are finding with a particular beta-agonist that increases protein synthesis (muscle growth — carcass yield) with available nutrients, without impacting fat deposition (carcass quality).

“In our yard, we're seeing 100% return on investment. The product costs us about $8/head, and we're seeing about $16 in return,” says Chris Burris, general manager of Ward Feedyard, Larned, KS.

The returns are coming in the form of added weight gain, added carcass gain, and increased ribeye size and cutability, which adds up to increased efficiency.

The road to adoption

First, let's get the mice out of the way. Popular research lore has it that scientists were trying to develop anti-asthma drugs. Time and again, they noticed the mice receiving a particular class of compounds became noticeably more muscular than those not receiving it. A little more research and — presto — beta-agonists emerged as potential muscle enhancers for the livestock industry.

At further risk of offending the scientists in the crowd, a beta-agonist is basically a repartitioning agent that either redirects existing nutrients toward increased protein synthesis (muscle growth), or slows protein degradation. Consequently, beta-agonists can yield more net muscle, either by maintaining more muscle (reducing degredation) or actually building more muscle (synthesis).

For perspective, zilpaterol, a beta-agonist used for beef production in other countries, reportedly has a negative effect on carcass quality, reducing protein degradation at the expense of quality-building fat. It's not currently approved for use in the U.S.

The only beta-agonist currently being used by the U.S. beef industry — ractopamine hydrochloride (developed and marketed by Elanco Animal Health as Optaflexx) has proven to have little, if any, impact on fat deposition. It alters protein metabolism in the animal, redirecting nutrients to build more muscle (synthesis).

Since beta-agonists alter protein metabolism, they have no application early in an animal's life. At that stage, protein synthesis already runs high, relative to fat deposition. It's later in the life of cattle, as they become more mature and protein synthesis slows, that beta-agonists can provide a boost.

As with implants — though no other single current technology comes close to the net economic gains available with implants — the allure of beta-agonists has always been the potential to cost-effectively increase cattle performance and efficiency. Icing on the cake, the thinking went, would be the ability to enhance the muscle profile of cattle that typically fall short in that area.

Ractopamine hydrochloride is proving its mettle on all counts. Approved by the Food and Drug Administration (FDA) for feeding to steers and heifers during the last 28-42 days of the finishing phase, this beta-agonist is consistently increasing live weight, carcass weight and carcass yield, without taking anything away from carcass quality.

More specifically, in research for label approval, Optaflexx served up 17 lbs. more live weight, 14 lbs. more carcass weight, 0.3 sq. in. more ribeye area, and 0.3% more dressing percent when fed according to label directions.

While weight gain and carcass gain are similar in beef and dairy cattle, research has shown Optaflexx to increase ribeye size more in the lighter-muscled dairy cattle.

Incidentally, this beta-agonist had already been approved and was being adopted by the pork industry as Paylean®.

Besides the pre-approval research conducted by Elanco, subsequent independent research has shown similar results. At Kansas State University, for example, cattle fed 200 mg of ractopamine hydrochloride daily (the label-approved dose) for the final 29 days on feed gained 17.9% faster on a carcass-adjusted basis than those not receiving it. Steers fed the compound gained 19.7 lbs. more carcass weight overall — 11.2 lbs. more during the 29 days ractopamine was fed — and were 14% more feed efficient during those last 29 days.

Sorting through all of this took cattle feeders a while. The research looked promising, but feeders wanted to get a feel of it in their own operations before diving in. They wanted to know if the benefits were additive to those received with implants (they are). They wondered if it altered animal behavior (so far, not at all). And, they wanted to corroborate the fact that it wouldn't dilute quality grades (it hasn't).

Even though FDA approved Optaflexx in summer 2003, cattle feeders didn't adopt the technology in a significant way until last fall, says Grady Bishop, Elanco's Optaflexx marketing associate. Since then, Bishop explains, “We've seen a dramatic increase in adoption, both in terms of new users and in expanded use by those already using it. We're even slightly ahead of our expectations for this point in time.”

Besides seeing the results for themselves, the cautious adoption had to do with the fact the new technology presents an added management challenge to feedyards. After all, adding a ration increases logistical complexity — figuring out how many trucks, drivers and routes will be required, as an example. But, given the narrow window of opportunity to receive the maximum economic potential of feeding ractopamine, feeders also had to evaluate how much control they had in marketing their cattle.

As Burris says, “28 days prior to harvest you're making the commitment that you'll market the cattle 28 days later.”

In other words, if you know for sure you can ship cattle within the 14-day marketing window allowed by label use (28-42 days), the decision is fairly straightforward. If you're not sure, making the decision begets more questions.

Market timing is key

Like other production technologies, beta-agonists have a benefit curve. Maximum returns occur when cattle receive Optaflexx for the label-approved 28-42 days. If cattle are marketed before receiving the compound for 28 days, potential is left on the table. Feed them longer — this is theory since it's not approved for feeding more than 42 days — and the benefits relative to the cost decline quickly.

Holding cattle for a week or two after they've received ractopamine for the approved period of time isn't an economically sound option, either. The physiological benefits dissipate a week or so after the beta-agonist is removed from the diet. In other words, you'd have the additional money in feeding it, but carcass performance would revert to what it would have been without the beta-agonist.

This reality may also be one reason Bishop says feedyards first used Optaflexx on company-owned cattle. Aside from trying new technology on their own cattle first rather than those of customers', it gave them more control over when to market cattle. Customers, after all, just like feedyard managers, have been known to fight the market.

“Yards that have tight control of the marketing window jumped on it,” Bishop says. “Yards with less control on the marketing window have been more reluctant to adopt it.”

With that said, Bishop explains, “The yards using it today run the gamut from large corporate entities to the mid-size and small independent yards. We have some clients who feed it to every pen, some who only feed it to steers, some who only feed it to company cattle, and some who only feed it to selected pens of customer cattle.”

One commonality is that users tend to market a high percentage of their cattle on grids and formulas. As Burris emphasizes, “The returns we're seeing from feeding Optaflexx in our yard are based on marketing cattle on a formula. To get the full value of feeding Optaflexx, you have to sell cattle on a carcass-weight basis.”

What's more, the folks getting the most out of the new technology may be those managing it the most simply.

For instance, Iowa State University researchers looked at how best to manage the technology in a part of the world where topping pens — sorting market-ready cattle from pens as they're ready rather than all at once — is a common practice. They concluded sorting cattle into outcome groups ahead of the last 28 days on feed — so all cattle could receive ractopamine — was a viable option to simply feeding it to the last market draft in the pen.

Spun another way, Bishop says, “It's certainly more of a challenge to feed it to a pen here and a pen there as opposed to yards where it's a standard part of feeding cattle the last 28-42 days… As with any new technology, there's a learning curve. As we work with customers, we find they may have to change some things initially to take advantage of Optaflexx, but over time those things are no longer issues.”

Especially with feeder cattle priced so high, the basic benefit of ractopamine may be too hard to ignore. “The more weight we can put on them, the cheaper the breakeven becomes,” Burris says.