Evaluate the efficacy of Zelnate versus a currently approved antibiotic [Draxxin ® (tulathromycin) Injectable Solution], or a combination of both Draxxin and Zelnate, when administered for the control of BRD in feedlot cattle at high-risk of developing BRD.
In this study, steers at high risk of BRD were randomly allocated into three groups (n=303 per group). Steers were administered their assigned treatment(s) at arrival.
Draxxin group: Draxxin (1.1mL/cwt) via subcutaneous (SC) injection
Zelnate group: Zelnate (2 mL) via intramuscular (IM) injection
Draxxin+Zelnate group: Draxxin (1.1 mL/cwt) via SC injection, Zelnate (2 mL) via IM injection
In addition to their Draxxin, Zelnate or Draxxin+Zelnate treatment, all enrolled calves received MLV BRD and 7-way clostridial vaccinations, and a deworming agent, as detailed in the full study. The following BRD therapy protocol was also administered (3 days moratorium after Draxxin/Zelnate/Draxxin+Zelnate):
After three BRD treatments the calf was considered chronic and no further antibiotic therapy was provided to that calf for BRD.
Although results were not statistically significant, preliminary data (up to Day 56) indicated a trend toward reducing morbidity by 25% and case fatality rate by 50% for Draxxin+Zelnate compared to Draxxin alone.
Additionally, although no statistical comparisons were performed, Zelnate, when compared to the sentinel group, may be of value as a stand-alone metaphylaxis tool in production systems that don’t use antimicrobial therapy.2
Different letters indicate differences of P<0.05.
*BRD morbidity: Draxxin vs. Draxxin+Zelnate, P = 0.06.
†NR: 56-day data not reported.
Day 56 net value (per head) estimates among the 3 treatment groups evaluated in this study are shown below. Compared to the baseline net value/hd observed by the untreated sentinel group, the net value of calves that received Draxxin and Zelnate ($163.70/hd) was observed to be $34.89/hd greater when compared to calves receiving Draxxin alone ($128.81). Additionally, calves administered Zelnate alone were observed to garner $75.44/hd more compared to untreated sentinels.2
‡These data reflect the raw averages across the respective enrolled pens; no inferential analyses were performed on these data. The components of the net value calculation included costs (i.e., purchase price, feed costs, medicine costs and processing costs) and revenue (i.e., sale price and value of BRD removals on or before Day 56). Data was based upon an assumed market price of $2.25/lb on Day 56.
Results showed a numerical advantage for Draxxin+Zelnate compared to Draxxin alone across several performance parameters. Preliminary data (up to Day 56) indicated a trend toward reducing morbidity by 25% and case fatality rate by 50% for Draxxin+Zelnate compared to Draxxin alone.
1Data on file. Bayer HealthCare Animal Health.
2This data was collected in a post-licensure study and was not reviewed by the USDA.