УДК 636.2.034.082.2 DOI: https://doi.org/10.31073/abg.56.06 PREDICTION OF PEDIGREE VALUE OF PROVEN BULLS DURING THE USE OF THEIR SEMEN IN SELECTION

А. P. KRUGLIAK Institute o f Animal Breeding and Genetics nd. a. M.V.Zubets o f NAAS (Chubynske, Ukraine) bulochka23@ukr.net The results o f research on the variability o f breeding value ofproven bulls o f the Holstein breed during 8-year utilization o f their semen in herds o f German Holstein and red and white breeds are presented. On the basis o f coefficients correlation and regression between the indicators o f the first assessment with a rank o f repeatability o f 75% and above with its (annual) revaluations, the genetic trend o f milk productivity in the populations o f Ukrainian black-and-white and red-and-white dairy breeds during 2010-2017years, and the results ofprevious research, a forecasting method duration o f preservation o f proven bull s breeding value, depending on its initial level has been developed.

Introduction. It is known, that the effectiveness of breeding is largely determined by the level of breeding value of bulls and use of their semen for a long time, or the number of offspring received from them. In recent years, in many countries of the world, a fairly accurate method for assessing the genotype of animals -BLUP, which provides correction of breeding records, environmental condi tions, number of measurements of breeding characteristics and the number of daughters, used in this model "Animal model" is used. Researches of a number of scientists have established a decrease in the genetic superiority of proven bulls over the genetic value of the live-stock in their use [1][2][3][4][5]. The reason for this decrease is the constant growth of the genetic potential of population productivity due to the introduction of young, more productive animals in the herds (genetic trend).
According to M. S. Basovsky [3], due to the constant growth of the genetic potential of the milk productivity of black-and-white breed populations, an average of 20-35 kg of milk per year, the ge netic superiority of the bulls, used in these herds, decreased by the same amount annually. Thus, the pedigree value of the bull Kimpa 37132 for milk yield, according to the results of the first assessment, 226 daughters was +460 kg, and for the 9th year of assessment (1123 daughters +146 kg of milk. According to V. I. Antonenko [4], the breeding value of bulls of black-and-white breed, in herds of breeding plants, on the basis of the daughters productivity on average, during 4 years, decreased by 60 (from +217 to +22), and Holstein -by 52 (from +232 to +74) kg. In our previous studies (AP Krugliyak ), [5] it was established, that due to an increase in the genetic trend of cows milk produc tivity of breeding herds of Ukrainian red-and-white dairy breed, the breeding value of proven bulls decreased annually by an average of 10-15%. The tendency to reduce the breeding value of bulls in the process of their use was confirmed by the results of V. Mymrin's et.al. research, [6]. In the studies of these authors, the initial breeding value of bulls +648 kg of milk at the 9th year of evaluation fell up to 189 kg, or 93 kg annually. A clear regularity of the decline in the genetic superiority of bulls' breeding value over the productivity of herds on the basis of which the selection is being conducted, as a result of the use of new daughters, is established in research T. O. Krugliak, [7]. As a result of these studies, the dependence of the variability of the pedigree value of bulls from the degree of its repeatability is established. Take into consideration, that the quality of offspring depends on the de gree of rej ection of their parents' genotypes by their breeding value from the average population value at the time of zygote formation, the study of the possibility of predicting the dynamics of breeding value of proven bulls in the process of their use is relevant.
The purpose of the work is to study the possibility of forecasting the duration of storage of breeding values by proven bulls in a positive level, depending on its initial level, obtained on the productivity their daughters.
M aterial and methods. The research material was the results of an annual evaluation of 11 bulls of the Holstein breed of European breeding quality in the offspring during 2011-2017 years. Data on the breeding value of bulls were taken from Osnabruck Holstein Sires. The method of estivate the pedigree value of bulls -(ZW) Zuchtwertschatzung, (Germany), [8]. The average initial breeding value of bulls was +1225 (lim + 1000-1536) kg of milk behind repeatability of 75% and higher. The semen of these bulls was also used in breeding herds of Ukrainian black-and-white and red-and-white dairy breeds. The dynamics of the milk productivity of these breeds was determined according to the data of the State Pedigree Registry for 2010-2017 [9-14]. Statistical processing of the obtained data was carried out using computer software according to the formulas of N. A. Plokhinsky [15]. The breeding value of other bulls, that were used in the herds for reproduction, was taken from the Cata logs of bulls of dairy and dairy-beef cattle for reproduction in 2010-2017 [16][17][18][19][20][21][22].
Research results. The annual decline the bulls breeding value, obtained on their daughter's productivity in the herds of the German black-and-white and red-and-white dairy breeds, was 145.5 (91-190) kg or 11.5% (7.5-15.5%), and at the 8th year of using their semen, it remained up to +206.6 kg (table 1). The correlation coefficients between the estimation of the breeding value, ob tained as a result of the first assessment with a high rank of repeatability (75% and above) and reval uation of the second year of the use of bulls were +0.747 ± 0.133 and constantly decreased with sub sequent revaluation up to +0.320 ± 0.271, obtained during the 8th year of using their semen. There is also a straightforward regression between the values of the breeding value of each subsequent esti mate to the first breeding value (Rni / 1), which decreased from 0.880 ± 0,153 between the indicators of the second and the first up to 0.185 ± 0.189 -the eighth with the first estimate. Statistic data of reduce bulls breeding value, which is obtained as multiplication initial breeding value on the regres sion coefficient, are very close to the data, obtained in our research. This allows to predict the bull's breeding value in next years, depend on its initial level.
Pedigree value prediction has been by next formula calculated: Yi = a x Rni/1 a -initial level of bull's pedigree value; Yi -prediction bulls pedigree value in year-plan of semen using; Rni/1 -coefficient of regression.

Dynam ics o f the pedigree value o f bulls f o r the daughters m ilk productivity in the process o ffirst and repeated _______assessments (Z W '10-17). Coefficients o f correlation and regression to the first assessment, n = 11_______
The year o f assess ment of bulls Somewhat higher and statistically significant is the annual decrease in the genetic superiority of these proven bulls, introduced in the reproduction process in 2010, in the populations of Ukrainian black-and-white and red-and-white dairy breeds, which is explained by the constant increase in the genetic potential of milk productivity of herds.
According to the State Pedigree Registry of the Ministry of Agrarian Policy of Ukraine, the milk productivity of cows of Ukrainian black-and-white dairy breed in 2010 was 5173, and Ukrainian red-and-white dairy -5483 kg of milk per cow. For the period of 2010-2017, the annual increase milk productivity of cows of these breeds (selection progress) was: in Ukrainian black-and-white breed +216.8 (+169 -424), and Ukrainian red-and-white +142.0 (+139 ± 317) kg. During this time, the milk productivity of cows of both breeds increased on 1735 and 1136 kg, respectively ( fig.).
The genetic trend of milk productivity was +520.5 and 340.8 kg, or 65.0 and 42.5 kg per year, respectively. This increase in milk productivity was provided, to a certain extent, by an increase in genetic pressures on the cows, except for this group, by the annual introduction of new, more produc tive improver bulls, for the reproduction of herds. Thus, the pedigree value of the first-best 50 bulls, whose semen was used in breeding herds in 2010, was +1502 and increased to 1651 kg of milk in 2018 [22]. As a result of the conducted researches, on the basis of indicators of variability, coefficients of correlation and regression between the indices of the first assessment with a rank of repeatability of 75% and above with its (annual) revaluations, the genetic trend of milk production in the popula tions of Ukrainian black-and-white and red-and-white breeds, as well as the results of previous stud ies, developed a method for predicting the duration of storage of proven bulls of breeding value, depending on its initial level, obtained on the productivity of their daughters. The method is based on obtaining the first estimation of bulls by the productivity of their daughters, their distribution by rank, the use, determined by us, regression coefficient between the indicators of the first and subsequent (annual) results of assessments and the comparison with the genetic trend of milk productivity of herds.

Fig. Changing the pedigree value of bulls, introduced for reproduction in 2010, for milk yield under influencing the genetic trend in the active part of the livestock of cows of Ukrainian black-and-white and red-and-white dairy breeds
The duration of keeping the bulls breeding value according to the indicators of milk productivity of Ukrainian black-and-white and red-and-white dairy breeds depends from its initial level and the size of the genetic trend. The bulls, with an initial breeding value up to 500 kg of milk keep it within the limits of the positive level during 4 years, 501 -1000 -8; 1001-1500 -11; 1501-2000 -15 and 2001-2500 -18 years (table 2).
In the process of researching the variability of the pedigree values of bulls by the results of their daughter's productivity, obtained in different generations, we have established the following factors that influence the accuracy of its forecasting for the i-th year of the use of bulls: -method of assessing breeding value (should use the same method of evaluation for all bulls); -repeatability of the results of the first assessment of the breeding value (must be more than 75%, depending on the number of daughters and herds in which the assessment is carried out); -peculiarities of the animal genotypes on which the first estimate is made (genetic progress of the milk productivity of each breed is different); -level of milk production of herds; -breeding value of other bulls, which are used in herds.

Predication o f the pedigree value proven bulls during all period their semen utilization
Original numeral year in which is planned to use semen

Genetics trend o f milk yield
First pedigree value bulls for milk yield, R = 75% < +500 +501 Conclusions. 1. Reducing the genetic superiority of proven bulls in the process of using their semen for re production of herds appears due to an increase in the genetic potential of milk production due to the constant introduction into the herds more productive animals of new generations.
2. The method of forecasting the duration of conservation of breeding value of proven bulls with its different initial level allows the breeders to plan the use of bulls in current and future selection, to maintain the genealogical structure of the breeds, to store their gene pool in the form of cryobank semen, to increase the level of genetic potential of milk productivity of herds.