Relevance. Recently, the phenoand gene-pool of agricultural animals of various species in their breeding zones have been studied very thoroughly. Particular attention is paid to the production of environmentally friendly and safe products, therefore, water, feed, soil, organs and tissues of animals are carefully monitored for the content of chemical elements [12, 15, 16, 25, 28].

Quite often, despite the stability of the chromosome set, there were deviations observed. However, in certain organs and tissues, a change in the number of chromosomes is considered normal, as is the case with cell polyploidy. Therefore, when we talk about the numerical variations of the karyotype, it is important to distinguish between constitutional (the presence of an anomaly in all cells of the body) and somatic variability. Somatic abnormalities affect some cells and different chromosomes.

The study of the variability of the karyotype of somatic cells is of practical importance:

– when studying the action of various damaging agents (radiation exposure, contamination with heavy metals);

– when assessing the degree of damage to the genetic apparatus of a particular animal;

– when assessing the likelihood of genetic abnormalities in the offspring.

It has been proven that if an aberration has appeared in any tissue, then it is highly likely to occur in others, including generative ones. Therefore, the higher the level of karyotype variability in somatic cells, the higher the likelihood of the occurrence of gametes with chromosomal abnormalities. For example, reciprocal and Robertsonian translocations are associated with impaired reproduction, embryonic and postnatal mortality in animals [29]. S. G. Kulikova [18] described trisomy on the 19-th chromosome in a blackand-white heifer.

Chromosomal karyotype instability is to a certain extent characteristic of almost all individuals in the population and serves as an important indicator for assessing the natural mutability of chromosomes.