Narasin (Monteban G100) for chickens for fattening re-authorised: an OECD 208 plant test on 10 species and a species sensitivity distribution closed the soil risk assessment, fish BCF 4.12 L/kg according to OECD 305
Commission Implementing Regulation (EU) 2026/1860, published on 30 July 2026, authorises the coccidiostat narasin (Monteban G100, Elanco GmbH) for chickens for fattening at 60–70 mg/kg complete feed until 19 August 2036 and repeals the 2004 authorisation. The decision followed a third EFSA opinion: in 2024 the FEEDAP Panel could not exclude a risk for soil or secondary poisoning via the aquatic food chain, and after new plant and fish bioconcentration studies EFSA concluded that no risk to soil, water or sediment is expected.
- The new GLP plant study according to OECD 208 covered 10 species — onion, oat, ryegrass, turnip, cucumber, sunflower, lettuce, bean, pea and tomato — in LUFA Sp 2.3 soil at 1.0–100 mg/kg soil dry weight. From NOEC values for 11 species from three studies EFSA built a species sensitivity distribution (SSD, ETX 2.3 software, Anderson–Darling test): HC5 = 0.461 mg/kg, lower limit 0.128 mg/kg.
- With a plant PNEC of 128 µg/kg soil dry weight and a soil PEC of 105 µg/kg, the PEC/PNEC ratio fell from 1.70 (2024 opinion) to 0.82. A fish bioconcentration study according to OECD 305 gave a lipid-normalised BCF of 4.12 L/kg — below the bioaccumulation threshold of 100 L/kg — so EFSA considered the risk of secondary poisoning of fish-eating mammals and birds low.
- Analytical methods in the annex: narasin in the additive, premixtures and feed — HPLC with post-column derivatisation and photometric detection (HPLC-PCD-UV–Vis) according to EN ISO 14183, in feed also LC-MS/MS according to EN 17299; in tissues — LC-MS/MS. Maximum residue limit: 50 µg narasin/kg of all wet tissues.
- The authorisation holder runs post-market monitoring of Eimeria spp. resistance to narasin. The label warns: “Dangerous for equines, turkeys and rabbits”, and simultaneous use with certain medicinal substances, including tiamulin, is contraindicated. The additive produced under the old rules before 19 February 2027, and feed before 19 August 2027, may be used until stocks are exhausted.