DETERMINATION OF BREEDING VALUE AND PREPOTENCY OF DAIRY BULLS
Authors: Pryima S. V. 
Published: August 2022

Introduction. In the field of dairy farming, the prospect of improving the breeding characteristics of the herd will primarily depend on the successful selection of bulls for its reproduction, as it is proved that the role of heredity in the genetic improvement of breeds reached 90–95%. Therefore, the intensive use of leading bulls with high breeding value is the main means of selective improvement of livestock in modern dairy farming with any systems and methods of breeding. The question of determining the degree of realization of breeding value of bulls under the condition of stable transmission of hereditary information to offspring, namely prepotency improvement on productive traits in a particular herd, is quite motivated, which was the purpose of our research.
Materials and methods of research. The study was conducted in a breeding herd for breeding Ukrainian Red and Black-and-White dairy cattle and Holstein breeds of AF "Svitanok" Maryinsky district of Donetsk region. For the analysis, the electronic information database of SMDC ʺORSECʺ as of November 2021 was used. The analysis included information on milk productive, reproductive ability and exterior of 1215 first-heifers in 2007–2020 calving years and the intensity of live weight of heifers up to one and a half years of age.
Research results. Calculation of the average manifestation of the considered features of certain groups of half-sibs was found that the highest improving effect on milk yield and milk fat and milk protein for 305 days of the first lactation was found using Holstein bulls C. E. Altadeсree 64633889, Shirley 447860719 and Besson 393035302, Ukrainian Red dairy breed Tsvitok 435 and Surguch 6500134711. Of the identified improvers higher than the average level of relative narrowing of variability in the offspring was found in bulls Shirley 447860719 (Kc = 0.380 … 0.383), C. E. Altadeсree 64633889 (Kc = 0.316 … 0.330) and Tsvitok 435 (Kc = 0.303 … 0.314), which makes the most desirable their further use in the herd. Degraders of milk production of the firstborns were bulls Misiats 6333 and Ducat 125 Ukrainian Red dairy, Artist 4502 Ukrainian Red-and-White dairy cattle, Trener 6064 Ukrainian Black-and-White dairy cattle, Campino Red 112825601 and Jupiter 27640964506 Holstein breeds. In terms of live weight of daughters at different ages, the most noticeable consolidations were bulls Bestus 348313870, Ducat 125, Cadenz Red 114151975, C. E. Altadeсree 64633889, Campino Red 112825601 and Jupiter 27640964506. However, the daughters of bulls Ducat 125, Campino Red 112825601 and Jupiter 27640964506 at the age of 9, 12 and 18 months have a lower live weight compared to the average livestock (-11.5 to -79.4 kg). The most significant improving effect on the live weight of daughters in the herd at all ages is carried out by the bull C. E. Altadeсree 64633889 (from +0.1 to +80.9 kg). Also, Dragomir 113021400, Cadenz Red 114151975 and Epik DE348025783 are characterized by a high degree of consolidation (Kс = 0.323 … 0.379) with neutral influence on the herd in the specified age period. Analysis of the results of the evaluation of the exterior of cows in the herd shows that a more noticeable manifestation of prepotency by measurements of first-heifers (height at withers, height at rump, height at chest, width of chest, length of trunk) was found in bulls Kantsler Red 768305280, Jansker 345199616 Kadisko Red 578904182, Campino Red 112825601, Ducata 125 and Dragomir 113021400. Assessing the consolidation of bulls on the basis of linear descriptive features of the body structure of daughters, namely their final assessment, the most noticeable manifestation of prepotency with higher-than-average manifestation was observed in bulls Shirley 447860719 and C. E. Altadeсree 64633889. The bulls Trener 6064 (Kc = 0.349; d = -5,6) and Artist 4501 (Kc = 0.306; d = -6,0) had a pronounced negative impact on the body type of daughters on average. Also, the bulls of the Ukrainian Red dairy breed Tsvitok 435, Surguch 6500134711 and Dragomir Red 113021400 proved to be prepotency type improvers with a fairly high degree of consolidation (Kс = 0.265 … 0.315).
According to most of the studied features, the highest improving effect was obtained from bulls Shirley 447860719 and C. E. Altadeсree 64633889 Holstein breed and Tsvitok 435 and Surgucha 6500134711 among the bulls of Ukrainian Red dairy breed. On average, according to the 30 signs taken into account, bulls Tsvitok 435 (Kc = 0.288), Bestus 348313870 (0.254), Jansker 345199616 (0.254), Campino Red 112825601 (0.249), Jupiter 27640964506 (0.246) and Surguch 6500134711 (0.243) have the highest level of prepotency. The daughters of the Misiats 6333 (Kc = 0.043), Dukat 125 (0.172), Dragomir Red 113021400 (0.188), Besson 393035302 (0.195) and Artist 4501 (0.196) had the lowest phenotypic consolidation.
Conclusions. In determining the breeding value of bulls, it is advisable to assess their prepotency on individual grounds. Among bulls of Holstein breed the greatest improving effect on the considered signs was noted in C. E. Altadeсree 64633889 and Shirley 447860719, and among breeders of Ukrainian Red dairy breed in Tsvitok 435 and Surguch 6500134711. On average, according to the 30 signs taken into account, bulls Tsvitok 435 (Kc = 0,288), Bestus 348313870 (0.254), Jansker 345199616 (0.254), Campino Red 112825601 (0.249), Jupiter 27640964506 (0.246) and Surguch 6500134711 (0.243) have the highest level of prepotency. On average, the highest level of prepotency was observed on the basis of live weight of heifers at the age of 18 and 12 months.