FEATURES OF BREEDING VALUE INHERITANCE SIRES OF HOLSTEIN BREED

А. P. КRUGLIAK, Т. О. КRUGLIAK Institute of Animal Breeding and Genetics nd. a. M.V.Zubets of NAAS (Chubinske, Ukraine) https://orcid.org/0000-0002-1512-6576 – А. P. Кrugliak https://orcid.org/0000-0002-8410-3191 – Т. О. Кrugliak bulochka23@ukr.net In our studies, the phenotypic manifestation of the additive form of inheritance of breeding value by milk yield (intermediate and parental dominance) was in 334 (82.2%) bulls, and non-additive form (over-dominance and regression) – in 72 (17.8%) including: over-dominance in 55 (13.5%) and regression in 17 heads (4.2%). In the population assessment, for all forms of inheritance, there was a clear quantitative shift of the breeding value of sons of milk yield to positive (+) values, compared with the breeding value of their parents. This confirms that sons, selected after their evaluation, and recognized as milk yield improvers. The variability of the breeding value of sons by milking depending on the forms of its inheritance has been established. According to the group of bulls by intermediate type of inheritance, milk yield sign were found in 291 (71.7%) sons, whose pedigree value was 606.4 ± 11.6 kg and was higher than the half-sum of both parents (554 kg), which deviates from the action of intermediate inheritance at 52 kg (109%). After all, the recognition of the intermediate nature of inheritance involves obtaining in the offspring of animals with the same set of chromosomes as their parents, and hence with the same phenotype. Therefore, from a theoretical point of view, genetic progress in the population should be not expected from this group of animals. However, in this case, the increase in breeding value was 9%, which is statistically significant (P > 0.99). A rather high variability of the breeding value of sons from its level in their parents with an intermediate form of inheritance has been established. Thus, of the 159 bulls-breeders in which the breeding value was inherited by intermediate form, only 30 sons (7.3% of the total population) of the bull Duster 2147488 (BV +579 kg and mothers with an average BV +632 kg, half the amount of the BV of both parents was +605 kg), was +605.5 ± 30.8 kg and was equal to the half-sum of the BV of both parents, and 9 (2.2%) sons of the bull Manfred 2183007, whose breeding value was, on average, at the population level +856.3 ± 37.6 kg and was equal to the half-sum of the indicator of the parents' BV (+851 kg). The inheritance of breeding value of bulls on quantitative signs of milk productivity in highly consolidated breeds on these signs, at intra-breeding selection occurs by a combination of phenotypic display of action of additive and non-additive (super-dominance) forms of inheritance. The frequency of these forms of inheritance probably is determined by the number and quality of chromosome pairs in the karyotype of animals on the probable basis of their manifestation in the population [15]. The relative variability of breeding value by milk yield along the line "father – son" and "mother – son" depends on the form of its inheritance. The coefficient of phenotypic correlation between the breeding value of parents and sons in the intermediate form of inheritance is +0.524 – +0.560 and increases with parental dominance to +0.907 ± 0.040 and +0.985 ± 0.006, and over-dominance to +0.887 ± 0.044 and +0.905 ± 0.033, at high statistical significant. Inheritance by non-additive form (over-dominance of both parents) is more effectively associated with increasing of breeding value by milk yield their sons than by the additive form.

In intra-breed selection, traditional methods of selection, their programming based on methods of population genetics, aimed at selection of animals by quantitative signs of productivity, are based on the additive action of genes and intermediate inheritance of signs [2,3,4].
However, in genetics there are two forms of inheritance -additive (intermediate, dominance of one parent) and non-additive (superdominance, epistasis, regression), in which the level of inheritance of the sign is determined by intraallelic and interallel interaction of genes [2][3][4][5]. As O. I. Babenko [8] informed, the frequency of inheritance forms breeding value of milk yield of domestic dairy breeds is depend from the part of blood Holstein breed. A number of authors found that the phenotypic manifestation of additive forms of inheritance of dairy productivity of cows and breeding value of domestic dairy bulls was combined with the manifestation of non-additive forms of inheritance [6][7][8][9][10][11]14].
The studies on the peculiarities of inheriting the breeding value of Holstein bulls on the basis of milk productivity, partiqularty non-additive form inheritance, under conditions of intra-breed breeding are necessary.
The aim of the research was to identify additive and non-additive forms of inheritance of the breeding value of Holstein bulls by milk yield of daughters and their relative variability with the level of breeding value of parents in the condition of intrabreeding.
Materials and methods. The nature of the inheritance of breeding value by milk yield was studied in 406 bulls-breeders of the Holstein breed in the United States, selected after their evaluation for reproduction [13].
Forms of inheritance of the breeding value of bulls were determined by the method of N. S. Kolyshkina and others [2], which is based on the value of the deviation of the breeding value (standard deviation -σ) from the half of sum of the indicators of the parent`s breeding value, namely: -intermediate inheritance -the value of the deviation of the breeding value of the son is equal to or deviates by 0.5σ (±0-250 kg) both in positively and negatively site from the half-sum of the indicators of the breeding value of the parents (BV father + BV mather) / 2 ± 0,5σ; -domination of the father or mother -the breeding value of the son deviates from the intermediate inheritance in the positive direction of the father (f) or mother (m) at a distance of up to 0.5σ (up to 250 kg); -overdominance -the breeding value of the son exceeds the ancestor, which dominates by more than 1.0 σ (≥ 500 kg); -regression -the breeding value of the son is lower than the worst of the parents by 1σ and more (≤ -500 kg).
Results. It was found that in the group of bulls with inheritance of breeding value in a positive case, the phenotypic manifestation of the additive form of inheritance of breeding value by milk yield (intermediate and parental dominance) was in 334 (82.2%) bulls, and non-additive form (overdominance and regression) -in 72 (17.8%) including: dominance in 55 (13.5%) and regression -in 17 bulls (4.2%), (Table 1).
In the group of bulls with breeding value of parents in the negative version, the inheritance of the BV by milking by additive form was found in 16 sons (61.5%), including the intermediate form -in 9 heads (34.6%) and mother's dominance -in 7 heads (26.9%), and non-additive -in 10 heads 38.5%).
The ratio of these forms of inheritance depends on the level of breeding value of the parents and the intensity of selection. Under the conditions of high breeding value of the father (Manfred 2183007, whose BV is +922 kg and  In the population assessment, for all forms of inheritance, there was a clear quantitative shift of the breeding value of sons after milking to positive (+) values, compared with the breeding value of their parents. This confirms that sons are selected after their evaluation and recognized as milk yield improvers.

Forms of inheritance
The variability of the breeding value of sons by milk yield depending on the forms of its inheritance has been established. On average, at the population level of assessment, on the all forms of inheritance, 406 sons with an average breeding value of +681 kg were selected for a group of bulls with breeding value in a positive variant, with an average value of half the sum of breeding value of parents +534 kg F and +570 kg M / 2 = +552 kg milk, which exceeds the average size of the parents by +129 kg (0.5σ) and is 123%.
According to the same group of bulls, 291 (71.7%) sons, whose breeding value was 606.4 ± 11.6 kg and was higher than the half-sum of both parents (554 kg), which deviates from the action intermediate inheritance on 52 kg (109%). After all, the recognition of the intermediate nature of inheritance involves obtaining in the offspring of animals with the same set of chromosomes as their parents, and hence with the same phenotype. Therefore, from a theoretical point of view, genetic progress in the population should be not expected from this group of animals. However, in this case, the increase in breeding value was 9%, which is statistically significant (P > 0.99).
A much larger increase in the breeding value of sons compared to fathers was found in the additive form of inheritance, namely: dominance of the mother -+302 kg (148.2%); parental dominance -+326 kg (161.4%). The highest pedigree value for milking was in sons with non-additive inheritance and was: in the form of super-dominance of the fathers -+373 kg (172.7%) and superdominance of the mothers -+412 kg (176.2%).
A rather high variability of the breeding value of sons from its level in their parents with an intermediate form of inheritance has been established. Thus, of the 159 bull-breeders in which the breeding value was inherited by intermediate form, only 30 sons (7.3% of the total population) of the bull Duster 2147488 (BV +579 kg and mothers with an average BV +632 kg, half the amount of the BV of both parents was +605 kg), was +605.5 ± 30.8 kg and was equal to the half-sum of the BV of both parents, and 9 (2.2%) sons of the bull Manfred 2183007, whose breeding value was, on average, at the population level +856.3 ± 37.6 kg and was equated to the half-sum of the parents' BV (+851 kg), (Table 2). The total number of bulls in which the level of heredity of the BV for milk yield corresponded to the sum of these indicators in the parents (intermediate type) was 39 heads, or 9.6%. I. P. Petrenko -the author of the theory of dynamics of genetic-population processes in the breed, population at the chromosomal level and determination of the structure of the gene pool of the breed by individual variability of additive genetic potential of activity in certain individuals points to such a share of animals (10.26%) inheritance of breeding value by milk yield [15]. According to the author`s information, chromosomes in gametes are combined by additive genetic potential of activity (AGPA) with different frequency of corresponding gametes in the population. Based on these data, we assume that the breeding value of bulls for milk yield father's daughters is inherited at the individual level of analysis of offspring (sons) not only by intermediate type, as is typical for population analysis, but also by intermediate-binomial, which provides the basis for selection in the breed. With this type of inheritance in the offspring is formed a certain proportion of individuals whose genotype is higher than the breeding value of their parents.

The variability of the breeding value of bulls-sons from its level in the parents in the intermediate form of inheritance
The breeding value, which was formed by the intermediate form of inheritance adopted in selection, deviates from the absolutely intermediate inheritance in both positive and negative directions by +10 +128 and -8 -211 kg, or by 1.6-21% (0.1-1.0σ), which is doubtful to refer to the intermediate form of inheritance.
The relative variability of breeding value by milking along the line "father -son" and "mother -son" depends on the form of its inheritance. The coefficient of phenotypic correlation between the breeding value of parents and sons in the intermediate form of inheritance is +0.524-+0.560 and increases with parental dominance to +0.907 ± 0.040 and +0.985 ± 0.006, and overdominance to +0.887 ± 0.044 and +0.905 ± 0.033, at high statistical probability (Table 3).
Conclusions. 1. Under conditions of intra-breed breeding of highly consolidated breeds in terms of milk productivity, inheritance of breeding value in bulls on quantitative signs of milk productivity is carried out by a combination of additive (intermediate inheritance and parental dominance) and non-additive (over-dominance) form of inheritance, which is most associated with milk yield and is found in 13.5% of bulls-improvers.
2. Among bulls-improvers, whose breeding value was inherited by intermediate type, the halfsum of the breeding value of their parents was equal to only 9.6% of the heads, in other bulls its value deviated from the half-sum of the parent`s BV as in positive by +10 +128 kg, so in the negative (-8 --211 kg), or 1.6-21.0% side.