cjs-202306-0001 ArticleInAPeriodical 2023 Czech Journal of Animal Science 68 6 245-254 TerlerGeorg WinterManuel MandlMichael SweeneyJoseph SteinwidderAndreas Effect of biochar or biochar and urea supplementation on feed intake, milk yield, feed conversion and methane production of dairy cows Feed additives belong to a number of climate change mitigation strategies being sought to reduce methane emissions in ruminants. In this study, the effect of biochar or biochar and urea supplementation on dairy cow performance and methane production was assessed. Eighteen cows were used in a 3 × 3 latin square design with three feeding groups: control with no supplementation (CO), biochar supplementation (BC, 200 g/day) and biochar and urea supplementation (BC + U, 200 g/day biochar and 90 g/day urea). All cows were fed a forage mixture ad libitum and 5 kg of concentrates per day on average. Methane emissions were measured in respiration chambers. Biochar as well as biochar and urea supplementation did not affect total dry matter, energy and utilisable protein intake. However, lignin intake was higher in the BC group and crude protein intake was higher in the BC + U group compared to the CO group. Supplementation of feed additives did not affect milk production and milk composition, except for the higher milk urea content in the BC + U group. Feed conversion, diet digestibility and methane production were not affected by feeding strategy. In conclusion, biochar supplementation does not reduce methane emissions, but it does not negatively affect dairy cow performance.