In the paper we presented five-year investigations of numeric and structural changes in cattle karyotype on five farms and two centers for reproduction in Serbia. There were 371 breeding animals (215 male and 156 female), out of which 267 Holstein Friesian breed (193 male and 74 female), 62 Simmental (17 male and 45 female) and 42 Grey Steppe breed (5 male and 37 female). Cultivating of lymphocytes and karyotype analyses, according to the international standards for karyotypization of domestic animals, were applied. The aim of the investigation was to test genetic material on chromosome level of animals introduced into reproduction. The following changes were discovered in the karyotype: 6 animals of Holstein-Friesian breed were with chimeras 2n=60XX/XY and there was one Robertson's translocation in Simmental breed. Structural changes as breakage and a ring were discovered in two animals of Holstein-Friesian and Simmental breed raised in the area of bombing in Serbia. The animals of Grey Steppe breed had normal karyotype. There is a total of 9 animals with changes (2.42%), while 362 were with normal karyotype, total 97.57%. According to the results, it may be concluded that cytogenetical attestation of the breeding animals will have to be continued for the purpose of protecting the genofond on cattle farms

New directions in animal husbandry demand raising of animal kinds that are adjusted to intensive way of breeding. In order to accomplish these demands, beside known methods in selection, Cytogenetic control of existing genotypes is needed that has been carried through ten year examination on pig, cattle and stud farms in Vojvodina. Chromosome aberration of numeric polyploidy and aneuploidy but also structural translocation, deletion, duplication, inversion, ring, break and other segregations were discovered. Numeric and structural changes on animal karyotype influenced on reproduction disturbance, phenotype expression, as well as selection program and stability of genofond. Different aspects of reproductive disturbance were noted like for example: small litter, embryo mortality, frequent repeated breeding, abortion, stillbirth and mummified embryo, offspring with anomalities, different kinds of sterility, Analyses of the results obtained from monitoring the herd book and making genealogy show on existence of chromosomepathy on our farms. The aim of this work is to inform scientists and experts with the fact that these changes are spreading, especially through among the breeding animals. Therefore genetic control and timely exclusion of chromosome aberration is necessary