EN
Cytogenetic examinations of 1,444 bulls of different breeds intended for reproduction in Poland were carried out in 1999- 2008. Using the method of peripheral blood lymphocytes culture, a number of metaphase plates was obtained and routinely stained for light microscopic examination. To enhance chromosome analysis, the method of developing G bands was used to prepare photographic documentation. The majority of investigated bulls (1,424) had a normal karyotype - 60,XY. In 20 animals (1.4%) anomalies of the karyotype were identified. Seventeen bulls, born as twins with female, demonstrated leukocytic chimerism (60,XX/60,XY). Three cases of sex chromosome abnormalities: 61,XYY trisomy, 61,XXY trisomy, and mosaicism 60,XY/61,XXY were also found. In these bulls, hypoplasia of the testicles, azoospermia, and depressed libido were observed. No structural chromosome rearrangement was found in the animals.