Třináctý J., Šustala M., Vrzalová D., Kudrna V., Lang P. (2001): Milk iodine content in cows fed rapeseed meal and iodine supplement. In: Book of Abstracts of the 52nd Annual Meeting of the European Association for Animal Production, No. 7 (2001), 26-29 August 2001, p.106. ABSTRACT: In a feeding trial on 8 Czech Pied cows we assessed the effect of rapeseed meal and iodine supplement on milk iodine content. The cows in trial were arrenged in 4x4 Latin square design, treatmets consisted of four concentrate feed mictures, either with ( RmX; 270 g/kg of the mixture) or without rapeseed meal ( SmX ;soybean meal as substitution for RM) and either with (XMI) or without (XM0) iodine supplement (ethylenediamine dihydroiodide). Iodine was supplemented to 250% of the recommended iodine daily requirement for dairy cows. The highest iodine content was in SMI treatment (594,8 microgramm/l ± 178,1). Rapeseed meal treatment significantly decreased milk iodine content (209,4 microgramm/l ± 145,3 vs. 359,1 microgramm/l ± 277,1; P<0,01). Iodine supplemented treatments showed a significantly increase of milk iodine content (100,2 microgramm/l ± 61,3 vs. 468,3 microgramm/l ± 184,0; P<0,01). Iodine content in SMl treatment (594,8 microgramm/l ± 178,1) was significantly higher then in RMl ( 341,7 microgramm/l ± 64,7), SM0 (123,4 microgramm/l ± 76,3) and RM0 (77,0 microgramm/l ± 31,6). The differences between SM0 and RM0 were nonsignidicant. Our result showed, that negative effects of larger amounts of rapeseed meal in cows diet on the iodine milk output can be succesfully moderated by iodine supply. This study was supported by NAZV (Project No. QD0176).