AIM: Evaluation of the features of the genomic architecture of Ayrshire cattle in Russia in comparison with other dairy populations of Bos taurus. MATERIALS AND METHODS: Using bioinformatic analysis of 42628 SNP markers obtained during genotyping using the BovineSNP50_v3 BeadChip medium density microarray, the features of the genomic architecture of five Bos taurus populations of different breeds were revealed. RESULTS: The domestic population of Ayrshire cattle was characterized by the lowest heterozygosity (Ho = 0.335, He = 0.339) and insignificant inbreeding (Fis = 0.010) MDS analysis. At the same time, domestic breeding animals formed a separate group within a single cluster of Ayrshirs. CONCLUSION: The Russian population of Ayrshire cattle is distinguished by a unique genome architecture, while retaining the genetic variants of the Finnish Ayrshire cattle and minor traces of Holstein gene pool.

The purpose of this study is to establish the influence of average daily gain (ADG) of heifers at different periods of their development on the age of 1st insemination (A1ins) at 12, 13, 14, 15, 16, 17, 18 months and older and milk yield of first-calving cows for 305 days of lactation according to a sample (n=1289) formed from the Seleсs database of one of the breeding plants in the Leningrad region for breeding the Ayrshire breed of dairy cattle. On average for the sample, the correlation coefficient of milk yield with A1ins indicates a negative relationship between these two characteristics (-0.218), a positive correlation of milk yield with live weight of 1st insemination LW1ins (+0.101) with a negative connection with ADG (-0.110). It was revealed that in all age groups of heifers there is a decrease in ADG at the age of 2 months, and the intensity of further development of heifers depends on ADG at the age of 3, 4, 5 months, at a level of over 800 g, contributes to the achievement of A1ins from 12 to 14 months. At the same time ADG at the age of 9—12 months should be at least 800 g. However, even with ADG 800—900 g at the age of 3—5 months, but when these indicators decrease at 9—12 months below 800 g, A1ins increases to 15—16 months. Low ADG at the age of 3—5 months and at the level of 600 - 700 g at the age of 9—12 months increases A1ins to 17 months and older. Thus, for an earlier A1ins and a high level of productivity in the 1st lactation, one should pay attention to the development of heifers at the age of 3—5 months, maintaining the ADG at a high level (more than 800 g) and avoid low weight gain at 9—12 months (less than 800 g).

В статье представлены результаты анализа селекционно-генетических параметров молочной продуктивности и воспроизводительных качеств 14892 первотелок айрширской породы из 6 племенных хозяйств Кировской области и Республики Карелия, отелившихся в 2006—2020 гг. Установлены высокие коэффициенты наследуемости по удою, выходу жира и белка, что указывает на достаточно высокую долю влияния генетических факторов на данные признаки. Проведены расчет оценок племенной ценности коров методом BLUP AM и моделирование отбора с применением разработанного селекционного индекса IAYRFI. В процессе исследования сформированы 4 группы животных с разной степенью интенсивности отбора: I (SI=75%) — воспроизводство собственного стада; II и III (SI=50 и 25% соответственно) — племенное ядро стада, IV (SI=10%) — быкопроизводящая группа. Селекционные дифференциалы (SD) по удою в группах составили 398, 692, 922, 1060 кг молока (P≤0,001), по выходу молочного жира — 18,4; 34,1; 51,4 и 66,5 кг (P≤0,001) и выходу молочного белка — 15,8; 29,8; 45,2; 59,4 кг (P≤0,001) соответственно. Индекс фертильности FI при увеличении давления отбора изменялся от 46,8 при SI=75% и при давлении SI=10% достиг уровня, близкого к хорошей плодовитости коров: 47,9 (md=1,1; P≤0,001). На основании рассчитанных высокодостоверных селекционных дифференциалов доказана эффективность использования индекса IAYRFI, повышающего объективность и точность оценки и отбора коров айрширской породы с учетом продуктивных и воспроизводительных качеств животных. The article presents the results of the analysis of breeding and genetic parameters of milk productivity and reproductive qualities of 14892 cows of the first calving of the Ayrshire breed from six breeding farms in the Kirov region and the Republic of Karelia, calving in the period from 2006 to 2020. High heritability coefficients for milk yield, fat and protein yield were established, which indicates a high share of the influence of genetic factors on these traits. Estimates of the breeding value of cows by the BLUP AM method were calculated and selection modeling was carried out using the developed breeding index IAYRFI. Four groups of animals with different intensity of selection were formed: I (SI=75%) — reproduction of their own herd; II and III (SI=50 and 25%) -— the breeding core of the herd, IV (SI=10%) — bull-producing group. In the case of four selection options with an intensity of 75, 50, 25 and 10%, SD for milk yield was obtained equal to 398, 692, 922, 1060 kg of milk (P≤0.001), respectively, for fat yield was: 18.4, 34.1, 51.4 and 66.5 kg (P≤0.001) and protein yield: 15.8; 29.8; 45.2; 59.4 kg (p≤0.001), respectively. With an increase in selection intensity, the fertility index FI changed from 46.8 at SI=75% and at SI=10% reached a level close to good fertility of cows — 47.9 (md=1.1; P≤ 0.001). Based on highly reliable selection differentials, the effectiveness of the IAYRFI index has been proven, which increases the accuracy of the assessment and selection of Ayrshire cows, taking into account the productive and reproductive qualities of animals.

BACKGROUND: The analysis of ROH distribution is an important focus of genetic resource conservation programs of cattle. Characterization of ROH-islands allows to identify genetic factors affecting productivity traits of dairy cattle. AIM: was to analyze intra-breed genetic diversity and population structure of Ayrshire cattle, based on data on distribution of homozygosity patterns, as well as to identify loci associated with selection intensity and utility traits. MATERIALS AND METHODS: ROH distribution data were obtained using whole genome genotyping on Illumina BovineSNP50 (50K) DNA chips (Illumina Inc., USA). The object of the study was the DNA of Ayrshire cows (600 cows), which belonged to farms with different levels of selection and breeding work. RESULT: The results of our studies showed a generally similar level of inbredness of the analyzed Ayrshire cattle herds. The homogeneity of the population is confirmed by a large number of animals (72.83%) with FROH values between 0.10 and 0.20. Cluster analysis revealed consolidated groups of individuals, due to their ancestral origins. The discovered ROH-patterns included 268 genes, 32 of which were involved in regulation of the synthesis of protein and fat milk components. The results obtained may be used in breeding programs for Ayrshire cattle in Russia. CONCLUSIONS: The Russian population of Ayrshire cattle is distinguished by unique qualities in protein and fat milk composition and genome architecture, while maintaining genetic diversity and insignificant traces of Ayrshire cattle gene pool.

0-87,4; более 87,5. Положительно влияет кровность по CAN на оценки вымени (+0,130 ххх), общего вида (+0,155 ххх), финальную (+0,164 ххх) и индекс UDC (+0,119 ххх), а отрицательно кровность по FAY на общий вид (-0,138 ххх), по SRB и NRF породам-на оценки вымени (-0,163 ххх ;-0,111 ххх) и финальную (-0,133 ххх ;-0,100 хх). Разница между коэффициентами силы влияния кровностей на признаки экстерьера по FAY и CAN колеблется от 7,9 до 18,7 ед., а на UDC и FLC равна 6,6 и 3,5 ед. Совместное влияние кровности по FAY и CAN ниже на линейные признаки, а на экстерьерные индексы, наоборот, усиливается. Для улучшения отдельных экстерьерных признаков следует учитывать долю кровности у пробанда по отдельным родственным породам айрширской группы молочного скота, делая акцент на долю кровности по FAY и CAN и их сочетания.