The U.S. Food and Drug Administration recently licensed Nuflor® (florfenicol), An Antibiotic, referred to as Nuflor Premix for Swine, as a Type A Medicated Article, for the control of swine respiratory disease (SRD) associated with Actinobacillus pleuropneumoniae, Pasteurella multocida, Streptococcus suis, and Bordetella bronchiseptica in groups of swine in buildings experiencing an SRD outbreak. No other in-feed antibiotic offers this broad range of label claims for controlling SRD.

"Nuflor Premix is effective against more of the bacterial pathogens causing swine respiratory disease than any other in-feed SRD treatment previously available," says Dr. Robyn Fleck, Manager, Swine Technical Services for Schering-Plough Animal Health. "It's the unique molecular structure of florfenicol that gives it such broad-spectrum action."

Used extensively in other countries, Nuflor Premix was introduced to the U.S. market because the pork industry here lacked a broad-spectrum, feed-grade antibiotic that would enable mass-medication for control of SRD, which remains a leading cause of economic losses for producers, Fleck says.

Nuflor Premix is packaged in 50-pound bags. It is mixed with complete feed, which is fed as the sole ration for 5 consecutive days to deliver 10 mg florfenicol per kg bodyweight per day. The product has a withdrawal time of 13 days. The effects of florfenicol on swine reproduction performance, pregnancy and lactation have not been determined.

"From our experience with Nuflor Premix in Asia, Latin America and other major swine markets, we think the ease of use and efficacy will go a long way toward helping U.S. veterinarians and producers effectively manage complex bacterial SRD," Fleck notes.

High success rate

Schering-Plough Animal Health conducted six clinical field trials with Nuflor Premix at locations in Iowa, Minnesota, Nebraska, South Dakota and Indiana. The trials involved more 1,100 sick pigs that had naturally occurring SRD. Investigators treated the pigs for 5 days then evaluated them 2 days after treatment stopped. They recorded temperatures and scored pigs for depression and dyspnea (breathing difficulty). The success rate in pigs receiving Nuflor Premix was more than 75 percent - significantly better than the 51 percent rate in untreated controls.

Pigs receiving Nuflor Premix also grew twice as fast during the treatment and evaluation period, producing an average daily weight gain of 0.665 kg compared to 0.3353 kg in unmedicated controls. Cumulative mortality for the group receiving Nuflor Premix (4.4 percent) was less than half the mortality of the controls (9.7 percent), Fleck says.

While pigs receiving Nuflor had a higher incidence of loose stools, perianal inflammation and rectal eversion compared to controls, the side effects were transient and did not have a significant impact on pig health or performance, as demonstrated by better survival and weight gain, she says. Bacteria isolated from the clinically ill animals included Actinobacillus pleuropneumoniae, Pasteurella multocida, Streptococcus suis and Bordetella bronchiseptica, Fleck says.

Works quickly

Trials also have shown that Nuflor Premix is highly palatable and can be incorporated into pelleted feeds. Furthermore, studies show that florfenicol is quickly absorbed, reaching therapeutic concentrations in serum within 4 to 5 hours. In the clinical trials, florfenicol concentrations remained above target level (1 µg/ml) for 18 to 20 hours for each of the 5 treatment days.

Nuflor Premix for Swine is the second oral formulation of florfenicol to become available to the U.S. pork industry. Last year, Schering-Plough Animal Health introduced Nuflor® (florfenicol) 2.3% Concentrate Solution, a water-soluble formulation for use in pigs' drinking water.

Nuflor Premix is classified by the FDA as a Type A Medicated Article and a Veterinary Feed Directive (VFD) drug. Pork producers may obtain VFD drugs through normal feed distribution channels, but need a signed VFD from a licensed veterinarian.