[Chromosome analysis of bulls in relation to disorders of sexual activity]

Chromosomal analysis was used for the examination of 16 bulls of different breeds from the Milhostov breeding station. The examined bulls exhibited disorders of sexual activity (disorders of spermiogenesis, aspermia, bad quality of semen, hypoplasia of testes, etc.). The examination was performed by the method after Moorhead et al. (1960) modified by Lojda et al. (1974): metaphase plates were evaluated microscopically (100 X 12) and from photos. The chromosomes were counted by means of the counting documator (from film negatives) and from photos. A card was prepared for each animal. Hyposomy (11 sires--68.75%) and hyperploidy (10 sires--62.5%) were found to be the most frequent numerical aberrations, followed by polysomy (4 sires--25.0%) and other aneuploidies (one case--6.2%). As to structural defects, breaks occurred in 14 sires (87.5%), bichromatid breaks in five sires (31.25%) and breaks on sexual chromosomes in three sires (18.75%). Centric fusion was observed in one case (6.25%), association in two cases (12.5%) and mixed aberrations in four cases (25.00%).