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Beta-Agonists

David P. Price is a consulting nutritionist specializing in feedlot and range cattle

The recession has hit virtually every industry, ours included. Feed prices have rolled back, thanks to the collapse in the demand for oil… and ethanol. Demand for beef has declined, but in addition to overall demand; demand has shifted. High-end restaurants have been going out of business at a rate significant enough to affect the demand for high-quality loins. At the same time, the sale of hamburger in supermarkets has gone up. In the U.S., the manifestation of these changes has led to a narrowing of the Choice:Select spread. Indeed, at the time of writing there was essentially no premium for Choice.

How long it will hold is anyone’s guess, but if there were ever a time when beta-agonists made sense, this is it. By beta-agonists we’re referring to the two commercial products licensed in North America; ractopamine (trade named Optaflexx) and zilpaterol (trade named Zilmax). (At the time of writing Zilmax has been cleared in Canada, but is being test marketed.) Both products have been available in the U.S. and Mexico for several years.) These two products belong to a class of compounds that are different from the steroids used in implants. Beta-agonists have a different type of effect than traditional implants and work additively. That is, when used together, there is a greater growth response than using either one alone.

As a class of compounds, beta-agonists also reduce fat. While this is a common belief for steroid-type implants; it is not true. Traditional implants increase protein accretion while fat deposition remains about the same. Fat cover with traditional implants will not change, although yield grade will be affected. This is because implants (especially with trenbolone acetate) result in a larger ribeye. Thus, the implanted animal with a larger proportion of meat (in relation to the same fat cover) will garner a superior yield grade. Likewise, while implants, especially those containing trenbolone acetate (TBA) have a reputation for reducing marbling, that is not necessarily true. In a single TBA implant scenario, you get about the same amount of marbling, but a roughly 10 per cent larger ribeye. This can lead to a lower “quality” grade but like the situation with yield grade, the reality is about the same amount of fat, but a larger amount of meat.

Beta-agonists do reduce fat. The infamous and illegal compound known as clenbuterol reduces fat deposition as much as 40 per cent. For that reason it has been used by unscrupulous cattle show people and is widely used illegally in Europe and Mexico, where the market is primarily for lean beef. A scurrilous practice, since residues can cause heart arrhythmia in humans. Legally cleared for horses in Canada, clenbuterol use in cattle can (and should) lead to criminal prosecution.

The two beta-agonists legally cleared for use, however, are totally safe and ethically responsible. The primary downside has been the cost, which runs about 10X the daily cost of most other feed additives. That said, beta-agonists are only fed the last few weeks, so the high daily cost is moderated somewhat. With respect to the cost, there has never been any question that performance is enhanced. Carcasses from cattle fed Optaflexx or Zilmax will be significantly heavier.

The question has always been carcass quality. Since beta-agonists reduce fat deposition, it is logical marbling will be reduced. The sponsors of Optaflexx adamantly deny that carcass grading is compromised; claiming that ractopmine has an action different than other beta-agonists.

Aside from marbling, the other question has been tenderness. Beta-agonists function through what is known as hypertrophy, making muscle fibres larger. If muscle fibres are larger, then it would seem logical they would be tougher. Once again, the sponsors of beta-agonists disagree, stating shear force values are not significantly different.

Unfortunately, I have not seen enough data to make a judgement one way or another. While we have fed a great deal of beta-agonists, there have never been any control groups to judge if grading is affected, nor has any shear force data been collected. However, by experience with buffalo, which have muscle fibres larger than cattle, I can say fibre size is not necessarily a negative factor. Both American Buffalo or bison, and true buffalo (Asian water buffalo), when feedlot finished at ages comparable to cattle, have streaks that are comparably tender.

But with a market that is not looking for premium beef, we no longer need to worry about carcass effects. All we need consider is efficacy of gain, and without doubt, beta-agonists increase carcass gain. This is not to say a premium will not eventually come back into the market for higher marbling carcasses, because certainly it will (when we return to more normal economic times). But the beauty of beta-agonists is that they are only used the last four to eight weeks of the feeding period. Thus, when performance and rate of gain are most important, these tools are available.

In addition to being an aid to producing lean beef, beta-agonists can also be used to prolong marketing. That is, when the cash market deteriorates and a gamble on a near-by market 30 to 60 days out appears acceptable, beta-agonists can be used to reduce the performance loss due to cattle stalling out.

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