A method of competence assessing of official control laboratories in the area of testing the homogeneity of feed products is presented. The 14 laboratories of veterinary hygiene and the reference laboratory (National Laboratory of Feedingstuffs) as an organ-izer took part in the performed proficiency test. 96 homogeneity tests were carried out, analyzing the content of key components in 180 primary samples. 576 investigation re-sults were obtained: chlorides- (156), calcium (156), zinc (132) and copper (132). The ob-tained data on the degree of mixing of compound feed (coefficients of variation) were lo-wer than 10% – the upper limit value included in the Instruction of the Chief Veterinary Officer. The authorized participating laboratories in the test were presented results of sat-isfactory quality (precision) and reliability confirming their competence to assess the de-gree of homogeneity of compound feed based on the analysis of macro- (Cl-, Ca) and micronutrients (Zn, Cu) as part of official control feedingstuffs. A revised homogeneity test instruction was developed in which the variability of the analytical method was taken into account.

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