Cobalt (Co) is an essential trace element for ruminants, which are able to synthesise vitamin B12 (cobalamin) in their digestive tract. Vitamin B12, particularly in ruminants, appears to play a role in maintaining the proper functioning of ruminal microflora. Cobalt salts have been commonly used in animal nutrition for many years and are currently authorized in the European Union as feed additives. The aim of the study was to investigate the presence of cobalt as additive in ruminant feed, analysed as such, and to assess its levels.Complementary feed samples for dairy cows, bulls/steers, calves, for which no specific category of cattle is indicated were collected in different Italian regions and analysed between 2018 and 2022. Samples were homogenized and subjected to microwave acid digestion. Co was quantified by Inductively Coupled Plasma-Mass Spectrometer (ICP-MS).The highest cobalt levels were observed in bulls/steers' feed, while dairy cows' feeds display lower levels than the other groups. Co concentrations were compared with the values reported on the labels of the complementary feeds examined to verify compliance to Regulation (EC) No 767/2009: 7.4 % of the samples exceeded the allowed tolerance in 2018, 7.1 % in 2019, while from 2020 to 2022 100 % of samples were compliant.The analysis of cobalt levels in ruminants feed revealed significant differences in supplementation in the examined categories. As regards the control of the labelling, the analysis of complementary feed showed an improvement trend over the five-year period considered, demonstrating the effectiveness of official controls.