VARIABILITY AND HEREDITY OF THE BULL`S BREEDING VALUE OF DIFFERENT GENEALOGICAL FORMATIONS OF THE HOLSTEIN BREED

A. P. KRUGLIAK, T. O. KRUGLIAK Institute of Animal Breeding and Genetics nd. a. M.V.Zubets of NAAS (Chubynske, Ukraine) https://orcid.org/0000-0002-1512-6576 – А. П. Кругляк https://orcid.org/0000-0002-8410-3191 – Т. О. Кругляк bulochka23@ukr.net The results of analytical studies of breeding value variability on the basis of milk productivity, selected for reproduction of bulls of different genealogical formations of Holstein breed, are presented. A statistically significant difference between the breeding value of bulls and their parents of different genealogical groups of the milk yield was established. The variability of bulls breeding traits and the milk productivity of their daughters in the middle of genealogical formations was dominated by similar indicators between genealogical formations. In the middle of related genealogical formations, animals of new generations significantly outnumbered animals of earlier generations in level of breeding value. The high correlation between breeding value of milk yield, milk fat and protein of parents and their sons was identified. The highest correlation coefficient (r = +0.643 ± 0.030) was established between the absolute milk productivity of daughters for 305 days of first lactation and the level of breeding value of milk yield of their parents, which decreased sharply when compared with their ancestors of older generations. The power of the influence of ancestral breeding value on the milk yield of the first born cows decreased with the removal of them in generations. The share of fathers influence on the daughter's milk yield was 35.1%, fathers – fathers – 11.7%, mothers – 10.6% and fathers – fathers – fathers – 2.7%.

Bloodline breeding continues to be the only method of preserving the gene pool of small and local breeds, the main task of which is not to maintain the heredity of individual animals but to maintain the genetic diversity of the population [12].
In leading dairy cattle countries in North America and Europe, large-scale breeding is aimed at identifying, by assessing the quality of offspring, and maximizing the use of a limited number of breed-leaders. Due to the fact, that the probability of obtaining bull-improvers with high breeding value (breed leaders) on selected breeding grounds (within +3 σ and above) is low enough, according to some foreign and some domestic scientists, breeding along the bloodlines can limit the selection of prominent bulls, and therefore slow down selection [24][25][26][27].
The success of large-scale breeding based on the use, evaluated by the quality of the offspring, bull-improvers, has caused many foreign and some domestic specialists to have a negative attitude to the traditional breeding methodbreeding along the bloodlines [28].
At the same time, the analysis of the gene pool of Holstein breed [29,31] and the catalogs of Holstein associations of the USA and Canada reveals the saturation of genealogies by the nicknames of breed-leader breeds, the use of different degrees of inbreeding, formation of large groups of related animals.
In this regard, the purpose of our work was to determine the level and variability of indices of primary breeding value based on the milk productivity of bulls of different genealogical groups of US Holstein breeds selected for reproduction, to determine the degree of influence on these traits of their ancestors.
Material and research methods. For the analytical studies, the results of an evaluation of the Holstein proven bulls (n = 372) of the United States [31], for the quality of their offspring, selected for reproduction, in 5598 heads, have been evaluated. By genealogy, the bulls were divided into 5 related groups. The breeding value of the bulls of different genealogical groups was analyzed by: milk yield, kg; fat content in milk, %; amount of milk fat, kg; protein content, %; amount of milk protein, kg.
Calculation of digital data was carried out by the method of mathematical statistics (correlation, heredity) according to M. A. Plokhinsky, by means of the software package "Statistica-6.1" [30].
Results. The analysis revealed that among the 372 bull-improvers, selected for reproduction, as a result of the initial assessment, 215 heads of them are the sons of 15 bulls-leaders of the breed and belong to 5 genealogical groups (table 1).
The largest number (22.8%), selected for reproduction bulls (85 heads) belong to the related group Chief 1427381 and Elevation 1491007 -54 heads (14.5%). A slightly smaller number of bullimprovers were received from the sons of the bulls Tradition 1682485 -39 heads (10.5%) and Valiant-17 heads (4.5%), who are the followers of the aforementioned related groups.
A statistically significant difference between the breeding value on the basis of milk productivity was found in bulls, recognized as improvers, belonging to different genealogical formations. Breeding value for milk yield, taken from the sons of the related Tradition group was +803.9 ± 34.1 kg of milk and exceeded the group average by 153 kg, which is statistically significant (p < 0.001), and Bell 67366 was lower average for the group of improvers by 123.0 kg (p < 0.1). The coefficient of variation of this indicator for Bell's bulls was quite high (CV = 46.8%). The breeding value of the fathers and mothers of the bull-improvers of this related group was also lower, than the average of the bulls group, selected for reproduction, which is statistically significant (p < 0.001 and p < 0.1).
It was also established, that the breeding value of the animals of the new genealogical formations (sons, fathers, mothers) of Tradition 1682485 and Valiant 1650414 was always higher (on 161.2; 121.4; 209.4 kg worth), compared to the older related groups of Elevation and Chief, on which basis they have been formed. This indicates about decreasing of appearance frequency of leader bulls in a single related group during breeding.
A similar predictable of variability of the breeding value of animals of different genealogical formations of the Holstein breed for milk fat and protein in milk was established.
The largest number of sons of dairy performance improvers (milk fat, total protein, and milk yield) were selected for use from the following bulls-improvers of these traits: -  The sons of these bulls inherit the signs of milk productivity, their breeding value exceeded that of their parents: by milk fatby 2.4-20.0 kg, total proteinby 0.7-11.8 kg. The absolute milk production of their daughters in the 305 days of the first lactation was 11201-13173 kg of milk, 411-475 kg of milk fat and 337-383 kg of total protein, which exceeded the productivity of their contemporarys by 113-1025 kg of milk, 8.6-55.6 kg milk fat and 9.3-30.3 kg total protein.
From the 25 bulls (0.375% of all estimated), which have been selected it to the top 5% for breeding value from dairy productivity -17 heads (68.0%) are the sons of the ancestors of the aforementioned related groups, which provide genetic progress of the breed, and, in our understanding, are the bloodlines. High correlation between breeding value`s level of milk yield, milk fat and protein of parents and their sons was identified. The highest correlation coefficient (r = +0.643 ± 0.030) was established between the dairy productivity of daughters for 305 days of first lactation and the level of breeding value at their fathers' milk yield, which decreased sharply, when compared with their ancestors from older generations.

Breeding value of bulls of different related groups, selected for reproduction and their daughters' milk productivity
The power of the influence of ancestral breeding value on the milk yield of the firstcalve cows decreased with the removal of them in generations.
The level of breeding value of the fathers has the greatest influence on the level of milk production of their daughters of the Holstein breed (the influence force is 35.1%) (table 3).

The influence of parental breeding value on dairy productivity their daughters in 305 days of first lactation
Factor (breeding value) In second place was the force of influence breeding value of the father-fathers on the milk yield of firstborn cows, which was 11.7%. The third place was occupied by the influence of the breeding value of mothers on the level of milk productivity of daughters (η 2 х = 10.6%). These forces of influence of these ancestors on the level of milk productivity of the firstborn cows are statistically significant (P < 0.05-0.001).
The last place of force of influence (η 2 х) on the level of milk productivity of the cows take the male ancestors, who are in their third line of pedigree (FFF), it was 2.7% and was not statistically significant.
Conclusions. The statistically significant variability of the breeding value indices for the milk productivity of the bulls and their parents of different genealogical formations of the Holstein breed was established. Breeding value based on the milk productivity of animals of new genealogical formations (sons, parents, mothers), selected for reproduction, was higher than in older related groups (in our sense, the bloodlines) on which they have been formed. This indicates, that the likelihood of obtaining the bulls with high breeding value (breed-leaders) is decreasing among older genealogical groups of animals. The power of the influence of ancestral breeding value on the milk yield of the firstborn cows decreased with the removal of them in generations.