Abstract
Timely assessment of animal conformation allows for the selection of the most promising individuals for breeding. The aim of the study was to identify udder conformation deficiencies in Ayrshire dairy cows assessed using the BLUP AM method. The study was based on the data of individual exterior assessment of 3,525 first-calving cows, daughters of 201 sires from 29 farms in various regions of the Russian Federation in the period from 2006 to 2024. In general, for the studied sample of animals, the highest probability of deficiencies (P) was noted for traits “additional teats” P = 20.1 % and “unbalanced udder floor” P = 13.8 %, “asymmetry of udder lobes” P = 3.9 %, “close rear teats” P = 3.6 % and “small udder” P = 2.5 %. The procedure for solving mixed BLUP equations on the studied sample of animals by udder exterior features showed the usual reliability (Rel) of the obtained linear estimates, with a variation from Rel = 0.269 (rear teat placement) to Rel = 0.486 (udder depth) and for exterior defects from Rel = 0.172 (milk leakage) to Rel = 0.905 (atrophy of udder lobes), which indicates its high genetic determinacy of manifestation in the phenotype. In the process of the conducted assessment of animals it was found that the frequency of occurrence of "atrophy of udder lobes" is significantly (p≤0.001) lower in groups of cows with positive (≥0) EBV assessments for the attachment of the fore udder attachment by 1.16 %, the rear udder height by 0.80 %, the rear teat placement by 1.12 %, and in first-calf heifers with optimal assessments for the udder depth, this defect was not observed. Thus, a number of exterior defects, such as "atrophy udder lobes", "unbalanced udder floor" and "close rear teats" can be leveled by selecting cows with a well-attached deep udder and a pronounced central ligament, which, compared to animals with deviations in these exterior parameters, have a lower probability of their manifestation.