The problem of mass improvement of dairy cattle is being solved by intensive use of bull-improvers. Therefore, one of the basic principles of large-scale breeding is to assess and identify the best sires – leaders of the breed for their widespread use in the selection process. The value of bull-sires is determined by the desired characteristics of its genotype, that are consistently passed on to the descendants. The widespread use of all-breed bull-leaders values, that are guaranteed to produce offsprings with the planned breeding, productive and reproductive qualities, is a basic principle of large-scale selection.

We used 214 bulls to analyze the inheritance character for pedigree value by milk yield, depending on pedigree values of parental animals. The bulls pedigree value was determined on the basis of descendants, and maternal pedigree value was determined by the complex information sources. Milk productivity of cattle is a polygenic, gender limited factor. Milk productivity is mainly formed under the influence of the additive gene action, the effect of which depends on the number of dominant genes in the genotype that are able to enhance the development of symptoms. Also in modern genetics it is considered as undisputed phenomenon when along the additive form of inheritance there operates inadditive one when animals are defined by the intraallel and interallel interaction of genes.

Therefore, the animal pedigree value, which reflects its genotype superiority over others, depends on the number of positive active genes in the animal genotype, received by an offspring from its parents. If the forecast of young bulls pedigree value, one must first consider the pedigree value of father and mother. The pedigree value indicators of parental animals are a kind of marker that descendants will also have genes that cause their advantage over peers. But the two or more descendants of the same parents differ genetically because they do not get the same set of genes. Thus, in the category of bulls improvers and neutral there is more common intermediate inheritance form – 44.6% and 58.6%, and the bulls with deteriorating category - lowest intermediate frequency inheritance – 26.3%.

The dominance of the father and mother have an average of nearly the same frequency of succession in all categories bulls and differ only by 0.6%. In bull-improvers the father dominance is being found most often – 15.4%, but in this category all parents were leaders of the breed and had high pedigree value, which is 220 kg. In neutral and bull-deteriorators the parents pedigree value was low +28 kg and -208 kg. In bull-improvers the positive acting parental genes whose action is expressed by high breeding values, intensified manifestation of factors. In neutral and bull-deteriorators the pedigree value appeared low, due to the appropriate level of parental breeding values.

The increase of mother's dominance frequency does not improve the level of pedigree values in the obtained animals. Mother's domination is often found in deteriorators – 21.1%, where a low breeding value -365 kg mothers leads to lower sons pedigree value to -180 kg of milk. The negative impact of low maternal pedigree values is seen in bulls-improvers and neutral ones.

Getting the sons pedigree value of 348 kg of mothers with pedigree value of +21 kg milk and father +24 kg parents is the inheritance in the form of superdomination. Superdomination occurs only in bulls improvers and can be explained as successful combimation of parental genes, resulting in evident complementarity.

The opposite to superdomination phenomenon, which causes reduction of sons pedigree value compared with parents' breeding value is regression. Regression occurs less in improvers – 7.6% and more frequently in deteriorators – 39.4%. Reducing the sons pedigree value as compared with parental animals due to the influence of recessive genes that reduce the factors of development in the offspring. So half the amount of mother and father pedigree values in a repair bull can be taken as the basis for prediction its pedigree values.

Key words: genotype, bulls, genes, inheritance forms, domination, superdomination, intermediate inheritance.