Nuflor® vs. Micotil®: Clinical Trials Comparison

Bovine respiratory disease (BRD) complex is a multifactorial disease of cattle caused by an interaction between viruses, bacteria, environment, and livestock management. It has been estimated that BRD costs the North American cattle industry in excess of $700 million annually.

The primary bacteria involved are Mannheimia (Pasteurella) haemolytica, Pasteurella multocida and Haemophilus somnus. It is considered that viruses, management, and environmental distressors weaken the natural defenses and allow colonization of bacteria in pulmonary tissues. Early detection and use of an effective antibacterial are critical in economical control of this disease. This paper reports on the use of NUFLOR (florfenicol) or Micotil (tilmicosin) in treatment of BRD.

NUFLOR is an injectable formulation of florfenicol providing prolonged action. Florfenicol is a broad-spectrum antibiotic that is an analog of thiamphenicol. Its unique formulation allows for use of 2 intramuscular injections 48 hours apart or 1 subcutaneous injection in treatment of BRD. Florfenicol is very active against M. haemolytica (MIC90 1.0 µg/ml), P. multocida and H. somnus (MIC90 0.5 µg/ml). It reaches significant lung concentrations within one hour following the first dose and maintains therapeutic concentrations for prolonged periods.

PROTOCOL

The purpose of these trials was to compare the efficacy of NUFLOR (20 mg/kg IM repeated in 48 hours) to Micotil (10 mg/kg SC once) against natural occurring BRD in calves recently shipped into commercial feedlot environments. Trials were conducted in Kansas, Texas and Alberta, Canada. The Canadian study was conducted in the fall/winter of 1994 and involved 670-lb calves of "sale barn" origin in Canada. The Texas and Kansas trials were conducted in the winter/spring of 1995 and involved 400-lb calves of southeast U.S. origin. All animals within a study were handled in a similar manner on arrival and throughout the trial period. In addition to routine vaccinations, deworming etc., calves in the Canadian trial received an injection of Micotil on arrival, which was standard procedure at that location. Arrival Micotil was not used in the U.S. trials.

When animals showed signs of BRD and minimal fever of 40° to 40.5° C, they were randomly (computer-derived randomization) allotted to a treatment group. Studies were blinded, with the evaluators not knowing which treatment was administered. In the U.S. trials, treated animals that did not respond were retreated once with the same drug. If animals did not respond to the second treatment, they were classified as failures, removed from the study and treated accordingly. In the Canadian trial, animals could be treated twice more (total of 3) with the same drug and then were classified as "chronics" and removed from further evaluation. Animals treated with NUFLOR were retreated with NUFLOR, and animals treated with Micotil were retreated with Micotil. Duration of the trials was 57 days in the United States and 79 days in Canada. Criteria for evaluation were BRD mortality, H. somnus mortality, response to first treatment regimen and final response.

RESULTS

Results are presented in Table 1. H. somnus was not diagnosed in either of the U.S. trials, and results of other parameters were not significantly different in those trials. In the Canadian trial, first treatment response (p=0.0479), final treatment response (p=0.0002), BRD deaths (p=0.0063) and total deaths (p=0.0019) were statistically significant in favor of NUFLOR. H. somnus deaths were preliminarily significant (p=0.0884) in favor of NUFLOR.

DISCUSSION

Use of an effective antimicrobial can have a definite impact on the economic crisis of BRD. These trials demonstrated NUFLOR was a safe and effective treatment for BRD, reducing mortality and chronicity more than Micotil.


NUFLOR is a registered trademark of Intervet Inc.

MICOTIL is a registered trademark of Eli Lilly and Company.