Opinion of the Scientific Panel on Additives and Products or Substances used in Animal Feed on a request from the Commission on the re-evaluation of efficacy and safety of the coccidiostat Monteban® G100

Monteban® G100 is a feed additive intended for the control of coccidiosis, a debilitating protozoal infection in poultry. In common with a number of other coccidiostats, the additive is due for evaluation to comply with statutory requirements agreed at the EU-level. The European Commission asked the EFSA to evaluate the product Monteban G100 and advise the Commission on its efficacy and safety. Within EFSA this task was allocated to the Scientific Panel on Additives and Products or Substances used in Animal Feed (FEEDAP Panel). The data provided in the dossier to support community authorisation proved insufficient to give conclusive answers to several of the questions raised by the European Commission. 



Monteban® G100 containing not less than 10 % of narasin activity as the active substance is effective as coccidiostat for chickens for fattening at a dose range of 60-70 mg narasin kg-1 complete feed, as shown in recent floor pen studies. 



Previous dose response studies (battery-cage and floor pen studies) indicate that 60-80 mg narasin kg-1 feed, is an effective dose range. However, no recent studies have been presented in order to prove narasin is still efficacious at the dose range. A full assessment of the efficacy was not possible, as no recent field studies have been carried out. No unusual resistance of Eimeria spp to narasin is to be expected in the field. The development of resistance against coccidiostats including narasin is a well-known phenomenon effectively counteracted in practice by rotation or by shuttle programs. 



Tolerance test showed that Monteban® G100 is safe for the target animal with a small margin of safety (about 1.4). Incompatibilities or interactions with feedingstuffs, carriers or other approved additives are not to be expected based on the known history of the additive. There exists a well-known interaction with some medicinal substances (i.e. tiamulin) justifying a warning label on the product that the simultaneous use of these substances may be contraindicated. Monteban® G100 at the use level for chickens is dangerous to horses, turkeys and rabbits. 



Narasin is active against Gram-positive bacteria, while Enterobacteriaceae are resistant. There is no cross-resistance to other antimicrobials except to salinomycin. Increased shedding of Salmonella is unlikely to occur at the dose used under practical conditions. Narasin, at the levels used for treatment of coccidiosis, is also effective in the prevention of necrotic enteritis in chickens. 



Narasin is absorbed to an unknown extent and excreted rapidly by the chicken. The excretion routes are not established in the chicken whereas faecal excretion prevails in the rat. The main metabolic pathway in the chicken and rat involves oxidative processes leading to the formation of very similar metabolites in both species in terms of chemical structure and biological activity. 



Narasin metabolites in tissues and excreta are qualitatively similar. The liver is the target tissue. Unchanged narasin is not detectable in tissues after six hours withdrawal, with the exception of the skin/fat (until 12 hrs) where it represents the major fraction. A great number of narasin metabolites represent each less than 10 % of the total tissue residues. For food control purposes narasin could be retained as a practical marker residue and skin/fat as marker tissue. 



Narasin is not genotoxic. No indication of carcinogenicity or developmental toxicity was found at the doses tested in the mouse, rat and rabbit. 



The lowest NOEL identified in the oral toxicity studies was 0.5 mg kg-1 bw day-1 for the neuropathy seen in a one-year dog study and the ADI (acceptable daily intake) set by FEEDAP Panel is 0.005 mg kg-1 bw (equal to 300 µg day-1 for a person of 60 kg bodyweight) and the withdrawal time of 1 day would be considered sufficient. A uniform MRL (maximum residue limit) for all tissues is proposed as 0.05 mg narasin kg-1 wet tissue. 



Validated methods are available which allow monitoring of narasin in premixes and complete feedingstuffs and the determination of the marker residue, narasin, in the liver, kidney, muscle and skin/fat of the chicken. 



Monteban® G100 can cause irritation to the eyes but not to the skin. Inhalation studies in dogs showed that narasin is potentially highly toxic by the inhalation route, compared with the oral route. However, Monteban® G100 is formulated as granules with a low dusting potential. For this reason, it is expected that workers will not be exposed by inhalation to toxic levels of narasin dust as a result of its handling. Monteban® G100 has sensitisation potential by skin contact and by inhalation. 



Due to the sensitising properties of Monteban® G100, FEEDAP Panel recommends the use of appropriate personnel protective equipment for the workers. 



Based on the provided information on the toxicity, fate and behaviour of narasin it cannot be excluded that the use of Monteban® G100 at the recommended dose range poses a risk for soil organisms. Insufficient data was provided to allow the FEEDAP Panel to assess the risk for the aquatic environment and secondary poisoning.