Study: Essential Oils Offer Early Gain Advantage in Steers

Researchers at Colorado State University evaluated a proprietary essential oil blend (EOB) made from cinnamaldehyde, oregano, and thymol as a potential alternative to the commonly used feedlot antibiotics monensin (M) and tylosin (T). The study aimed to determine whether EOB could replace or supplement these antibiotics in improving growth performance, feed efficiency, and carcass characteristics in finishing feedlot steers.

Methodology

• Cattle: 400 crossbred steers, average starting weight 813 lb.

• Treatments: Five diet regimens:

  1. Control (no additives)

  2. EOB only (3 g/day)

  3. EOB + M + T

  4. M + T only

  5. EOB + M

• Design: Steers were weighed at the start, every 28 days, and at the end of the feeding period. Cattle were slaughtered at commercial facilities between 160 and 182 days for carcass data collection.

Key Findings

1. Growth Performance

   • In the first 84 days, steers fed EOB (alone or with antibiotics) showed higher average daily gains (ADG) than most other groups, indicating a potential early-phase advantage.

   • Over the full feeding period, ADG differences between treatments were minimal.

2. Feed Intake & Efficiency

   • Early in the trial, dry matter intake (DMI) was similar across groups.

   • Over time, the control group had the highest DMI, while M + T-fed steers consumed less. EOB-fed groups were generally intermediate.

   • Overall feed efficiency was lowest for the control group, while all other treatments performed similarly.

3. Carcass Characteristics

   • Hot carcass weights were similar across treatments.

   • Dressing percentage was highest for the EOB group (64.3%), translating to an estimated 21.6 lb more marketable beef compared to the average of other treatments.

4. Liver Abscess Incidence

   • M + T-fed steers had the lowest liver abscess rates (26.3%).

   • EOB-fed steers had higher abscess rates (53.7%) compared to M + T but slightly lower than the control (59.9%).

   • The EOB + M + T group showed intermediate abscess prevalence.

Beef Quality Implications
While the essential oil blend improved dressing percentage, the study found no measurable changes in key beef quality attributes compared to cattle fed conventional antibiotics or control diets. Marbling scores, fat thickness, ribeye area, and USDA yield grade were statistically similar across all treatments. This indicates that while EOB-fed steers yielded slightly more saleable beef by weight, the eating quality and grading characteristics of the meat remained unchanged.

Conclusion
Feeding the essential oil blend improved early-phase growth rates and dressing percentage, with feed efficiency comparable to antibiotic-fed cattle. However, EOB did not significantly reduce liver abscess incidence, a key benefit of tylosin use. The findings suggest EOB could serve as an alternative or supplement to antibiotics for enhancing early feedlot performance, but further research is needed to develop blends that also address liver health challenges.