EN
The phenomenon of freemartinism continues to be a subject of research and interest to breeders due to economic losses resulting from sterility of females (of sheep and cattle) affected by leukocytic chimerism. In high fecundity sheep breeds such as Romanowska or Booroola this phenomenon occurs more frequently than in other breed populations. In Romanowska sheep it is connected with the cumulative effect of different genes, but in Booroola with the presence of gene F (high fecundity). Very little data is available in literature on freemartinism in the high fecundity Olkuska sheep which belongs to the breeds under threat of extinction. In view of high reproductive performance (early sexual maturity) and dairy production traits (high milk production) it seemed reasonable to undertake cytogenetic studies aimed at the determination of leukocytic chimerism related with freemartinism on a selected group of the Olkuska sheep. We examined a total of 40 animals of 13 chosen families with heterosexual litters. It was found that 2 out of 16 ewe-lambs were found to be freemartin cases (12.5%).