PREDICTION OF PEDIGREE VALUE OF PROVEN BULLS DURING THE USE OF THEIR SEMEN IN SELECTION
The results of research on the variability of breeding value of proven bulls of the Holstein breed during 8-year utilization of their semen in herds of German Holstein and Red-and-White breeds are presented. The correlation coefficients between the estimation of the breeding value, obtained as a result of the first assessment with a high rank of repeatability (75% and above) and revaluation of the second year of the use of bulls were +0.747 ± 0.133 and constantly decreased with subsequent 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 estimate 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. On the basis of correlation coefficients and regression between the indicators of the first assessment with a rank of repeatability of 75% and above with its (annual) revaluations, the genetic trend of milk productivity in the populations of Ukrainian Black-and-White and Red-and-White dairy breeds during 2010–2017 years, and the results of previous research, a forecasting method has been developed duration of preservation of proven bulls breeding value, depending on its initial level. 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 on 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 plus variant for 4 years, 501–1000 – 8; 1001–1500 – 11; 1501–2000 – 15 and 2001–2500 – 18 years. In the process of researching the variability of the pedigree values of bulls by the results of their daughters' productivity, obtained in different generations, we have established the following factors that influence the accuracy of its forecasting for the 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 at least 75%, depending on the number of daughters and herds in which the assessment is carried out); - the peculiarities of the animal genotypes on which the first estimate is made (genetic progress of the milk productivity of different breeds is different); - level of milk production of herds; - the breeding value of other bulls used in herds.