With feed prices and beef prices at historically high levels, a product that produces more beef with the same volume of feed seems a wise investment. That was a key take-home message from an event Merck Animal Health hosted last week to update media representatives on the use of their Zilmax feed additive in feedyards.

Zilmax (zilpaterol hydrochloride) is a “beta agonist” that causes bovine muscle fibers to expand, explained West Texas A&M University meat scientist Ty Lawrence, PhD. Individually, each muscle fiber expands just three microns (three millionths of a meter) in cattle fed Zilmax. But with each muscle containing millions of fibers, the muscle growth is significant, resulting in more lean-meat yield from each carcass.

Merck recommends feeding the product for 20 days at the end of the feeding period. The product has a required three-day withdrawal period, and cattle feeders have a 10-day window of time after removing the product to market cattle before its benefits begin to decline.

John Hutcheson, PhD., director of technical services for Merck Animal Health’s beef cattle business, summarized findings from 25 Zilmax trials conducted with multiple universities involving over 40,000 head of cattle. These trials have involved beef steers, heifers and Holstein steers, measuring feedyard performance, carcass traits, packer value, beef palatability and consumer satisfaction. Packers have worked with the company to collect fabrication data on over 800 carcasses.

Hutcheson lists these key points among the findings across those research trials and practical experience in commercial feedyards:

  • The 20-day feeding period provides the best balance of cost-effective performance improvement and beef quality.
  • Response to the product is consistent in research trials and commercial use in the feedyard.
  • Zilmax improves average daily gains and feed per gain by about 20 percent during the 20-day feeding period. Performance during that period “looks like the first 20 days” rather than dropping off, which is typical for cattle nearing finishing weights.
  • The product increases dressing percentages by 1.3 to 1.6 units.
  • Zilmax increases carcass weights by 33 pounds or more in beef steers, 23 pounds in heifers and 25 pounds or more in Holstein steers.
  • Feedyards need to manage and monitor cattle weights to avoid discounts for heavyweight carcasses at the packing plant.
  • Carcass weight accounts for about 75 percent of the weight gains during those final 20 days in Zilmax-treated cattle. The increase in live-weight gain in steers averages about 20 pounds. A pound of live weight today is worth about $1.20, meaning 20 extra pounds is worth $24. With the 20-day dosage of Zilmax costing about $25 per head, the program is not cost-effective for feeders marketing cattle on a live-weight basis.
  • Feedyards only benefit from using Zilmax if they market cattle on a carcass-based grid. Today, a pound of carcass weight is worth $1.90, so 33 pounds of extra carcass weight is worth $62.70. Net revenue gain is from using Zilmax is over $35 per head.
  • The product reduces carcass fatness and USDA Yield Grades considerably, particularly in cattle types inclined toward fatness such as English-breed heifers. Feeders have the option to feed pens of these cattle to the same weight with fewer Yield Grade 4 discounts, or feed them to heavier weights with the same number of Yield Grade 4s.
  • Some feeders use the product to produce the same carcass weights in shorter feeding periods, others use Zilmax to feed cattle longer and extract more value from their inventory. Some sorting is necessary to gain the best advantage. On average, Hutcheson says finished weights within a pen of cattle range about 90 pounds from lightest to heaviest. By sorting to avoid heavyweight carcasses, feedyards can improve profits by boosting carcass gains without fear of Yield Grade 4 discounts, even with feed prices high.
  • Zilmax does reduce marbling and grading percentages somewhat in finished cattle. In high-grading pens, the reduction in percent grading USDA Choice is minimal. The reduction is higher in pens where many of the cattle are on the cusp between Select and Choice grades.

In Holstein steers, which typically are lighter-muscled than beef breeds, Zilmax produces wider strip loins, larger, rounder ribeyes and overall heavier muscling, Lawrence says, resulting in a significant increase in carcass value compared with other Holsteins. View a video of Lawrence showing these differences in the meat cooler at West Texas A&M University.

Mitch Johnson, Zilmax marketing manager for Merck Animal Health, says one 10-kilo bag of the product, which feeds 300 cattle for the prescribed 20 days, costs about $8,000. The price actually varies as Merck adjusts it based on USDA-reported meat prices each month, in a unique pricing system intended to provide consistent returns to cattle feeders. But if that $27-per-head investment creates a net profit of $25 per head, the bag increases profit on 300 head by $7,500.

That bag, Johnson says, produces 9,900 pounds of additional beef – the equivalent of 17 additional animals – with no additional feed or water. For cattle fed to the same weight endpoints, the bag can conserve 55 tons of feed and 41,567 gallons of water.