INDEX ASSESSMENT OF GENOTYPED AYRSHIRE COWS FROM DIFFERENT REGIONS OF THE RUSSIAN FEDERATION

The objective of the study is to evaluate genotyped Ayrshire cows using the BLUP AM method, taking into account management practices, genetic and paratypic factors, and the studied economically valuable traits. The study also tested a multifactorial index for assessing breeding qualities and selecting the best animals of the desired type. Objectives: conducting an index evaluation on a representative sample of genotyped daughters of Ayrshire bulls; determining the effectiveness of index selection on the studied sample of animals; ranking the sires and compiling a rating based on the index evaluation. The object of the study is phenotypic data of 669 genotyped first-lactation Ayrshire cows lactated on 10 farms from 2017 to 2021. The high reliability of breeding value estimates using the BLUP AM method (for milk yield in 305 days Rel – 0.60; for fat and protein yield Rel – 0.53 and 0.55) increases the potential response to selection for these traits. A significance level of 84% was observed for live weight at birth, which was due in part to a high determination coefficient of 0.83. Modeling of selection using the IAYR index revealed a significant and reliable advantage in milk yield over 305 days of lactation in animals with positive index variants. On farm No. 1, the difference between the +IAYR and –IAYR index groups was +1965 kg, with a milk fat yield of +55.9 kg and protein of +56.5 kg, with p ≤ 0.001. The identified priority individuals of the desired type with positive IAYR index variants can be used in subsequent selection for breeding groups to form the herd's core breeding stock, and high-ranking sires will contribute to the improvement of individual herds and the population as a whole.