EN
Cytogenetic studies, carried out between 1978 - 1998 at the National Research Institute of Animal Production resulted in identification of several chromosomal aberrations as follows: chromosomal chimerism XX/XY in cattle, sheep and horses, Robertsonian translocations and sex chromosome trisomy in cattle, reciprocal translocations in pigs and sheep, pericentric inversion in pigs. The influence of Robertsonian and reciprocal translocations on fertility of aberration carriers was evaluated and economic losses in pigs due to decreased fertility were calculated. In the light of these results it is advisable to continue cytogenetic control of farm animals in Poland, mainly males being used in reproduction.