Searching for desirable genotypes of fathers and mothers of ayrshire cows using the breeding index

Introduction. Intensification of cattle breeding requires acceleration of the processes of obtaining animals with the greatest productivity potential, therefore the use of genetically determined assessments in conjunction with selection by indices that take into account the milk productivity of cows and other important economically useful traits is a pressing issue in modern breeding work.
Object. The studies were conducted on data on milk productivity and reproductive qualities of 65753 first-calving cows that lactated from 2002 to 2020 from 8 regions of Russia: Vologda region, Leningrad region, Kirov region, Komi Republic, Republic of Karelia, Central Federal District, Siberian Federal District, Southern Federal District.
Materials and methods. Biometric processing of the obtained data was carried out using statistical analysis methods in Microsoft Office Excel and RStudio. The construction of statistical groupings for the formation of selection groups using the SI_AYR index was carried out on the basis of standard procedures for normal distribution into groups: SI_AYR > 4000 (n=14619); 0 ≤ SI_AYR ≤ 4000 (n=31318) and SI_AYR < 0 (n=19816).
Results and conclusion. Analysis of absolute productivity data revealed that the milk yield for 305 days of the first lactation of cows of the SI_AYR > 4000 group was 7324 kg, which was significantly higher by 773 and 960 kg (p≤0.001) compared to the other two groups. The yield of fat in their milk was at the level of 302.0 kg, protein – 242.5 kg, which is also higher by 32.2 and 26.5 kg (p≤0.001) compared to the group 0 ≤ SI_AYR ≤ 4000 and the group SI_AYR < 0 by 35.4 and 32.0 kg (p≤0.001), respectively. It has been established that with a selection pressure of 70%, the predicted selection effect on milk yield per generation is +124 kg. When the pressure increases to 30%, the selection effect increases more than 2 times and amounts to +280 kg (p≤0.001). With 10% selection of cows into the breeding core, the average milk yield reaches 7797±15.3 kg, with a selection effect of +452 kg per generation or +90 kg per year (p≤0.001). Animals from the combinations SI_AYR > 4000 and DI_AYR > 4000, 0 ≤ SI_AYR ≤ 4000 and DI_AYR > 4000 can be used when planning custom matings and insemination with sperm of especially valuable sires.

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