ŠUSTALA M., ŠIMEK M., VRZALOVÁ D., TŘINÁCTÝ J. (2000): Rape cakes in feed mixtures for lactating cows and their effect on the content parameters of milk. EAAP - 51 th Annual Meeting, The Hague 2000: 121. ABSTRACT: In a trial performed on 15 dairy cows fed with mixtures for lactating cows with a proportion of rape cakes were assessed (group S1-mixture with 15% of rape cakes from cold pressing, group S2 with 25% of rape cakes from heat pressing, control group-mixture with 20% of soybean meal). One of the objectives of the trial was to assess the effect of the experimental (exp.) mixtures on the milk composition. The content of milk fat was nearly identical for both exp. groups and control (4.33% for the control group, 4.36% for S1, and 4.33% for S2). Fat yield was higher for the exp. groups (+44.9 g/day for S1, +69.19 g/day for S2, P>0,05). Exp. groups tended to have lower proportions of proteins (-0.10% for S1, -0.07% for S2, P>0.05). The daily yield of proteins for S1 was 591g, for S2 618g and 573g for the control (P>0.05). Both exp. groups showed a statistically significantly reduction in the content of casein (-0.20% for S1 and -0.17% for S2, P<0.01). The daily casein yield was 501g for S1, 526g for S2 and 506g for the control (P>0.05). The proportion of casein in the total proteins was for both exp. groups significantly lower (-0.03 for S1 and S2 equally, P<0.01). Solids and non-fat solids in milk were not significantly affected by the tested components. This study was supported by the National Agency for Agricultural Research (Project No. 7013).