When breeding dairy cattle, productivity is of the greatest economic and economic importance. A sufficient number of highly productive animals and their effective use in herds reveals the breed's potential, contributes to increasing the genetic potential of cows and the effectiveness of selection and breeding work as a whole. At the same time, it should be noted that according to many scientists, fathers of cows have the most significant influence on the formation of signs of milk productivity. In dairy cattle breeding, about 90 % of the genetic progress of the population is provided by bulls. However, the research of different farms shows that bulls do not have the same effect on the productivity of their daughters. Therefore, it must be taken into account when planning work on improving the productive qualities of dairy cattle. In view of the above, the goal of our research was to find out the influence of bulls on the formation of milk productivity of daughters in different farms. The research was carried out in farms located in different climatic zones of Ukraine, namely: in the SE EF “Olexandrivske” in Vinnytsia region (Forest Steppe zone, n = 714), LLC AE “Imeni Volovikova” in Rivne region (Polyssia zone, n = 1840) and SE “Experimental farm “Askaniyske” (Steppe zone, n = 926) on first-calf heifers and adult cows (III lactation) of the Ukrainian Black-and-White dairy breed. It was established that during the first lactation, the highest milk yield and milk fat output in the SE Oleksandrivske were characterized by the daughters of the bull Dzhorin (6936 and 248.9 kg), during the third – the daughters of the bull Detektiv (8148 and 295.2 kg), and the most fat-milk the above lactations were, respectively, daughters of Zhames (3.68 %) and S. Aristotl (3.63 %). In LLC AE “Imeni of Volovikova” the daughters of the bull R. Baltimor (7509 and 7486 kg and 267.8 and 281.9 kg, respectively) had the highest milk yield and milk fat output for the two studied lactations, daughters of Derbi (3.74 %) for the first lactation had the best indicators of fat content in the milk, for the third – daughters of Tirs (3.64 %). In the SE "Experimental Farming “Askaniyske” first-calf heifers – daughters of N. Bolt were the most productive (7348 kg), in terms of milk fat output - daughters of Surguch (292.2 kg), and in terms of milk fat – daughters of Latur (4.31 %). The highest productivity during the third lactation was observed in the daughters of the bull Akord (8,329 kg of milk fat, 320.8 kg of milk fat), and the highest milk fat content was observed in the daughters of Polarshtern (4.37 %). The influence of bulls on the fertility of cows in controlled farms was in the range of 14.9–46.2 %, on the fat content in milk - in the range of 7.4–20.2 %.

Обґрунтований підхід для вирішення селекційних завдань можливий лише на основі чіткої уяви щодо закономірностей формування, прояву та передачі з покоління в покоління селекційних ознак тварин. Одним із важливих селекційних прийомів у скотарстві є визначення генетичної подібності за продуктивними ознаками корів-матерів, матерів бугаїв та їх потомків. Дослідження проведені у господарствах, що знаходяться у різних кліматичних зонах України, а саме: у ДП ДГ «Олександрівське» Вінницької області (зона Лісостепу, n=714), ТОВ СГП «Імені Воловікова» Рівненської (зона Полісся, n=1840) та ДП «Дослідне господарство «Асканійське» (зона Степу, n=926) на первістках та повновікових коровах (ІІІ лактація) української чорно-рябої молочної породи. З’ясовано вплив надою жіночих предків за вищу лактацію на ознаки молочної продуктивності потомків за першу та третю лактації. Встановлено, що у підконтрольних стадах найбільш продуктивними виявилися корови, надій матерів, яких за вищу лактацію сягав понад 8000 кг, а надій матерів батьків у ДП ДГ «Олександрівське» становив 15000 кг і більше, у ТОВ СГП «Імені Воловікова» – 14000–14999 кг та у ДП «Дослідне господарство «Асканійське» – 9000–9999 кг. Між надоєм матерів та їх дочок у підконтрольних господарствах спостерігався досить суттєвий прямолінійний і вірогідний (Р<0,001) зв’язок (0,237–0,293), а між надоєм матерів та жирномолочністю дочок цей зв’язок був оберненим, проте достовірним (Р<0,001) (-0,154 – -0,201). Між жирномолочністю матерів та надоєм і жирномолочністю дочок співвідносна мінливість була різноспрямованою і несуттєвою. Коефіцієнт успадковуваності надою, залежно від господарства, коливався від 0,47 до 0,59, виходу молочного жиру – від 0,30 до 0,55, а вмісту жиру в молоці – від некоректного (від’ємного) у тварин із зони Степу (-0,27) до 0,18 та 0,06 – у особин із зони Полісся та Лісостепу відповідно. Сила впливу надою матерів на надій та вміст жиру в молоці дочок, залежно від ознаки та господарства, коливалася від 2,1 до 6,9, а надою матерів батьків на зазначені ознаки потомків – від 2,0 до 6,6%.

Data on the influence of environmental factors on the milk productivity formation of cows in different climatic zones of Ukraine are presented. It was established that animals bred in the steppe zone had the highest milk yield, milk fat content, and milk fat output, and animals from the Polissia zone had the lowest values. Among the cows from different breeding zones, intergroup differentiation was also observed by milk productivity depending on the year and season of their birth. In the forest steppe zone, the highest productivity was noted for the first-calf heifers born in 2011, in the Polissia and steppe zones — for the animals born in 2015, and for the third lactation in all breeding zones, the cows born in 2015 were the most productive. A curvilinear intergroup differentiation based on the characteristics of milk productivity was also noted between animals with different seasons of birth. The highest milk yields at “Oleksandrivske” State Enterprise and “Named after Volovikov” Joint Stock Company LLC were obtained from the first-calf heifers born in the autumn period, and at Research Farm “Askaniiske” Research State Enterprise — from animals born in summer. During the third lactation, the cows born in autumn were the most productive in all breeding zones and whose first calving occurred in the steppe zone in the spring period, in the forest steppe and Polissia zones — in autumn. The year of birth and the breeding zone had the most significant effect on fertility and fat content in milk, and it was stronger in first-calf heifers, and the season of birth of animals had the least effect on signs of milk productivity.

Introduction. One of the main ways to improve dairy herds is through the identification and utilization of the most effective combinations of parent pairs. This can be achieved by both within-line selection and crossbreeding. It is important to identify the most promising lines and their optimal combinations to ensure their effective utilization for further herd improvement. According to many authors, a systematic approach that involves identifying successful and unsuccessful combinations with the repeated use of the most effective variants will reliably contribute to the increase of the genetic potential of dairy cattle productivity. Materials and methods of research. In light of the above, the aim of our research was to investigate the formation of milk production traits in Ukrainian Black-and-White dairy cows in different farms of Ukraine, depending on various options for parent selection. The research was conducted on first-calf heifers and mature cows (third lactation) of Ukrainian Black-and-White dairy breed in three farms: SE EF "Oleksandrivske" in Vinnytsia region (Forest-Steppe zone, n = 714), LLC AE "Imeni Volovikova" in Rivne region (Polissya zone, n = 1840), and SE "Experimental farm "Askaniyske" in Kherson region (Steppe zone, n = 926). The sample included cows that had completed at least the third lactation during the research. In the study animals, the milk production traits (milk yield, milk fat content, and milk fat yield) were studied based on various options of within-line and between-line parent selection through retrospective analysis of zootechnical records data over the past ten years. Research results. The analysis of between-line selection of Ukrainian Black-and-White dairy animals in SE EF "Oleksandrivske" showed that the most successful combinations for milk yield and milk fat yield in first-calf heifers were when the dams belonged to the Valiant line and the sires belonged to the Chif line. For mature cows (third lactation), the most successful combinations were when the dams belonged to the Eleveishn line and the sires belonged to the Starbuck line. The lowest values of the mentioned traits for the studied lactations were observed in cows obtained from the crossbreeding of the R. Meximes-Chif and S. T. Rokita-Chif lines, respectively. In LLC AE "Imeni Volovikova", the most productive animals for the first lactation were those obtained from the combination of the Starbuck-Bella lines, while for the third lactation, the individuals derived from the crossbreeding of the Bella-Chif lines showed the highest productivity. The least successful combination for both studied lactations was when the dams belonged to the S. T. Rokita line and the sires belonged to the Bella line, as animals resulting from this crossbreeding had the lowest milk yield and milk fat yield values. SE "Experimental farm "Askaniyske", the highest milk yield and milk fat yield values for the first lactation were observed in individuals whose dams belonged to the Seateischna line and the sires belonged to the Starbuck line. For the third lactation, the highest values of the mentioned traits were found in cows obtained from the combination of the Chif-Starbuck lines. The lowest productivity for the mentioned lactations was observed in cows resulting from the crossbreeding of the R. Sovering-Bella and R. Sovering-Chif lines, respectively. In the internal line breeding at the SE EF "Oleksandrivske," the most productive individuals were found to be first-generation offspring whose parents belonged to the Chief line, and mature cows from the Starbuck line. In the LLC AE "Imeni Volovikova" the animals from the Bella line showed superior performance in both lactations. In the SE "Experimental farm "Askaniyske" cows from the Eleveishn line were found to be the most productive. Regarding milk fat content in the Forest-Steppe zone, the best performers were first-generation offspring resulting from the combination of the Cavalier-Chief lines, as well as mature cows from the Eleveishn-Starbuck cross. In the Polissya zone, animals obtained from the Eleveishn-Bella and Starbuck-Bella crosses showed the highest milk fat content. In the Steppe zone, first-generation and mature cows whose mothers belonged to the R. Sovereign line and fathers belonged to the Chief and Bella lines, respectively, demonstrated superior traits. Conclusions. Thus, improvement of economically important traits in animals can be achieved through both internal line breeding and interline breeding. In this regard, it is crucial to identify the best line combinations and effectively utilize them in further breeding work.