Nuflor® vs. Oxytetracycline:Clinical Trials Comparison

Bovine respiratory disease (BRD) is the most costly disease affecting cattle today. Estimates are in excess of $700 million annually. It is believed to be caused by a variety of factors including viruses, bacteria, distressors, and environment. Several of these factors combine to reduce the animal’s natural resistance, allowing the colonization of the lower respiratory tract with Mannheimia (Pasteurella) haemolytica, Pasteurella multocida, and Haemophilus somnus. These organisms singly or in combination are largely responsible for the acute pneumonia associated with BRD.

It is widely accepted that early recognition and treatment with an effective antimicrobial are necessary for economical control of this disease. This paper reports on the use of NUFLOR (florfenicol) or oxytetracycline in treatment of naturally occurring BRD.

Florfenicol is a broad-spectrum antibiotic that is particularly active against the bacteria encountered in BRD. NUFLOR is a prolonged-acting injectable formulation of florfenicol that provides 4 days of therapy. Bronchial secretion levels exceed a peak of 3 µg/ml and persist throughout the treatment period. The MIC90 of florfenicol against M. haemolytica is 1.0 µg/ml, while the MIC90 against P. multocida and H. somnus is 0.5 µg/ml.


The purpose of these trials was to evaluate the efficacy of NUFLOR Injectable Solution or oxytetracycline in treatment of naturally occurring BRD under commercial feedlot conditions. Trial locations were Idaho, Colorado, and Texas. Study inclusion criteria were: clinical signs of BRD including pyrexia of 104°F or greater and respiratory rate of 40 or more breaths per minute. Animals were ranked by temperature and assigned to treatment groups by computer randomization.

At each location there were 70 animals assigned to NUFLOR treatment and 35 assigned to oxytetracycline treatment. These studies were conducted in the winter of 1990–1991. The dose of NUFLOR was 20 mg/kg IM repeated in 48 hours, while oxytetracycline (100 mg/ml) was dosed at 10 mg/kg IM SID x 4 days. Animals were mixed breed beef cattle weighing approximately 400 pounds and were of high-risk, southeastern or northwestern U.S. origin. All studies were blinded by the evaluator not knowing what treatments were administered.


Results are presented in Table 1. In these trials, results were evaluated following a single course of therapy. Any animals not responding to a course of therapy were considered treatment failures, removed from the trial, and treated with other antimicrobials for humane reasons. Therefore, initial and final treatment success rates are the same. Under the conditions of these trials, NUFLOR treatment resulted in reduced mortality (0.95% vs. 7.62%) and improved treatment response (70.48% vs. 34.29%) compared with oxytetracycline. There were no adverse effects reported following use of either drug in these trials.

NUFLOR is a registered trademark of Intervet Inc.