Determination of urea in compound feed for ruminants: interlaboratory comparison for the validation of the spectrophotometric method in Commission Regulation (EC) No 152/2009

Urea is a feed additive authorised in ruminant feedingstuff by Commission Implementing Regulation (EU) No 839/2012 with a maximum content in compound feed of 8800 mg kg-1. Commission Regulation (EC) No 152/2009 displays the official method for the determination of urea in feed, but does not specify the type of feed for which the method is applicable. Following reports from some Member States stating that the official spectrophotometric method is not fit for purpose for other feed than ruminant feed and given the fact that no method performance characteristics are set, the Joint Research Centre (JRC) of the European Commission organised an interlaboratory exercise for the validation of this method. This collaborative study was carried out on six different test materials prepared from sheep and cattle compound feeds containing urea at various mass fractions and a blank test material. Nineteen laboratories enrolled for the study and eighteen laboratories from ten EU Member States submitted results. The application of the spectrophotometric method foresees the measurement at two wavelengths, namely at 420 nm and 435 nm. As fitness for purpose criterion, the relative standard deviation for reproducibility (RSDR) was set at 25 % prior to the study. At 420 nm, the RSDR varied in all cases between 10 % and 19 % except for sheep feed at 3000 mg kg-1. The corresponding values for the RSDR measured at 435 nm varied across all mass fractions from 7 % to 18 %. This set of results therefore confirmed that the official spectrophotometric method described in Commission Regulation (EC) No 152/2009 is fit for the purpose of determining urea in ruminant feed at the given target level range. The general outcome of the study led to the conclusion that the Commission Regulation (EC) No 152/2009 should be revised as regards the official spectrophotometric method with a restriction of the scope to ruminant compound feed and the inclusion of the method performance characteristics obtained from the present interlaboratory exercise.

OLIVEIRA GONCALVES Carlos;  BOUTEN Katrien;  EMTEBORG Hakan;  STROKA Joerg;  VON HOLST Christoph;  VINCENT Ursula; 

2023-05-19

FAC UNIV SCIENCES AGRONOMIQUES GEMBLOUX

JRC126559

1370-6233 (online),   

https://publications.jrc.ec.europa.eu/repository/handle/JRC126559,   

10.25518/1780-4507.20069 (online),