Ractopamine vs. Zilpaterol: Which Feed Additive Gives Steers the Best Finish?

Beau Callahan in Science & Nature September 2025 • 4 min read.

"A side-by-side comparison of how these beta-adrenergic agonists affect growth, carcass quality, and meat tenderness in finishing steers."

In the quest for efficient and high-quality beef production, feed additives play a crucial role. Among these, ractopamine hydrochloride (RAC) and zilpaterol hydrochloride (ZH) have gained attention as beta-adrenergic agonists, known for enhancing growth performance and influencing carcass characteristics in cattle. But how do these two additives stack up against each other?

A study was undertaken to compare the effects of RAC and ZH when administered to beef steers during the final 33 days of the finishing period. The research aimed to provide insights into their comparative effectiveness, particularly concerning growth, carcass traits, and meat tenderness.

Three hundred crossbred beef steers were monitored, divided into groups based on body weight, body condition score, and breed type, and then randomly assigned to one of three treatments: a control group (no beta-agonists), a RAC group (receiving 200 mg of ractopamine.hd. ⁻¹d⁻¹ for 33 days), and a ZH group (receiving 75 mg of zilpaterol.animal. ⁻¹d⁻¹ for 30 days, followed by a 3-day withdrawal period). The results shed light on the distinct impacts of these additives on beef production.

RAC vs. ZH: Unpacking the Performance and Carcass Effects

Comparison of beef cattle, illustrating the debate between muscle growth and meat quality.

The study revealed that both RAC and ZH had positive impacts on the steers' final body weight (BW), average daily gain (ADG), feed efficiency (G:F), and hot carcass weight (HCW) when compared to the control group. This indicates that both additives can effectively promote growth and carcass development.

However, when RAC and ZH were directly compared, some key differences emerged:

Growth and Feed Intake: ZH decreased ADG, average daily feed intake (ADFI), and final BW compared to RAC.
Carcass Weight and Yield: ZH increased HCW and dressing percentage more than RAC. RAC did not affect carcass yield in this study, whereas ZH improved yield grade.
Carcass Traits: ZH decreased adjusted fat thickness and kidney, pelvic, and heart (KPH) fat, while increasing ribeye area.
Meat Quality: Marbling, lean maturity, and skeletal maturity were similar across all treatments.

These findings suggest that while both RAC and ZH enhance overall performance, ZH has a more pronounced effect on carcass characteristics, particularly in terms of yield and leanness.

The Tenderness Trade-Off: What the Study Reveals

One of the most interesting findings concerned meat tenderness. Steaks from RAC-treated steers showed higher Warner-Bratzler shear force (WBSF) values (meaning less tender meat) compared to control steers at 3 and 7 days of aging, but this difference disappeared after 14 days. In contrast, steaks from ZH-treated steers had higher WBSF values than both control and RAC steaks throughout the entire 21-day postmortem aging period. While both beta-adrenergic agonists effectively improve feedlot performance, RAC does not negatively impact WBSF after 14 days, whereas ZH steaks remain less tender than controls even after 21 days.

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Everything You Need To Know

What are ractopamine hydrochloride and zilpaterol hydrochloride and why are they used in beef production?

Ractopamine hydrochloride (RAC) and Zilpaterol hydrochloride (ZH) are beta-adrenergic agonists used as feed additives for finishing steers. They are used to enhance growth performance and influence carcass characteristics. They both improve feedlot performance but have differing impacts on carcass traits and meat tenderness. Ractopamine hydrochloride and Zilpaterol hydrochloride are not the same, and can give different results.

How do ractopamine hydrochloride and zilpaterol hydrochloride affect the growth and carcass development of steers?

Ractopamine hydrochloride (RAC) and Zilpaterol hydrochloride (ZH) both positively affect final body weight (BW), average daily gain (ADG), feed efficiency (G:F), and hot carcass weight (HCW) compared to a control group. This indicates that both additives effectively promote growth and carcass development. This is important because it shows that feed additives can be used to improve the efficiency of beef production.

What are the specific differences in growth and carcass yield between steers treated with ractopamine hydrochloride versus zilpaterol hydrochloride?

Zilpaterol hydrochloride (ZH) can decrease average daily gain (ADG), average daily feed intake (ADFI), and final body weight (BW) compared to steers treated with Ractopamine hydrochloride (RAC). Additionally, Zilpaterol hydrochloride increases hot carcass weight (HCW) and dressing percentage more than Ractopamine hydrochloride. Zilpaterol hydrochloride also improves yield grade.

How do ractopamine hydrochloride and zilpaterol hydrochloride impact specific carcass traits related to fat and muscle?

Zilpaterol hydrochloride (ZH) decreases adjusted fat thickness and kidney, pelvic, and heart (KPH) fat, while increasing ribeye area. Marbling, lean maturity, and skeletal maturity are similar across all treatments. These differences are important because they impact the overall quality and marketability of the beef carcass. The fat content and ribeye area are important factors in determining the value of the carcass.

How do ractopamine hydrochloride and zilpaterol hydrochloride affect the tenderness of the meat produced, and how does aging play a role?

Steaks from steers treated with Ractopamine hydrochloride (RAC) may be less tender initially, but this difference disappears after 14 days of aging. Steaks from steers treated with Zilpaterol hydrochloride (ZH) remain less tender than control steaks even after 21 days. This tenderness difference is important because it can affect consumer satisfaction. This means that the aging process can help improve the tenderness of meat from steers treated with Ractopamine hydrochloride, but not Zilpaterol hydrochloride.