Chromium chelate of DL-methionine for salmonids: total chromium by ICP-MS, methionine by IEC-VIS, chelate structure by infrared — and added chromium in feed counted via microtracer particles; according to EFSA the additive is ≤ 10 % of background chromium
Commission Implementing Regulation (EU) 2025/1782, published on 10 September 2025, authorises until 30 September 2035 a preparation of chromium(III) chelate of DL-methionine from Zinpro as a zootechnical additive improving performance of salmonids: 200–600 mg additive/kg complete feed, i.e. 0.2–0.6 mg Cr/kg. The preparation contains ≥ 1 000 mg Cr(III)/kg, nickel ≤ 1.33 mg/kg and a microtracer — 270 particles of dyed iron coated with tartrazine and shellac per gram.
- Methods in the annex: total chromium in the additive — ICP-MS; methionine in the additive — IEC-VIS (ion-exchange chromatography with post-column derivatisation); confirmation of the chelate structure — mid-infrared spectrometry together with chromium and methionine determination; microtracer in the preparation — count of dyed particles; total chromium in premixtures — ICP-AES; added chromium (chelate) in premixtures and compound feed — count of microtracer particles at a fixed mass ratio in the preparation.
- According to EFSA, in the previous assessment the EU reference laboratory could not recommend any method for quantifying added chromium in feed — the microtracer (Zinpro F-Yellow #5 Lake) is the answer to that problem. EFSA notes that the proposed chromium supplementation is ≤ 10 % of the chromium present in the trial feeds — control feeds contained 1.98–3.12 mg Cr/kg by analysis. Five additive batches: 1052–1146 mg Cr/kg, methionine 1.35–1.48 %.
- Impurities in three batches: nickel 1.25–1.33 mg/kg, arsenic 1.14–1.29, lead 0.51–0.55, fluoride 4.1–12.03 mg/kg; water solubility 183 g/L (OECD TG 105). Because of nickel (Directive 2022/431: OEL 0.01 and 0.05 mg/m³ for the respirable and inhalable fractions) the additive is a skin and respiratory sensitiser; highest dusting potential 5.57 g/m³.
- Trout tolerated 4000 mg additive/kg (6.7 × the maximum); at 6000 mg/kg final body weight was 209.9 g against 221.3 g in the control. In salmon at 600 mg/kg the feed-to-gain ratio was worse than in the control (0.95 against 0.90) — the act notes this. Muscle of trout fed 0.8 mg Cr/kg contained 70–80 µg Cr/kg, the control 72–73 µg/kg; EFSA pointed out that background chromium in the control feed was five times the intended supplementation.