Influence of lactation stage on cows’ conformation traits and their interaction with length of days open

The aim of this work was to evaluate the influence of the lactation stage and the days open (DO) duration of dairy cows on conformation traits. The study was conducted at a commercial farm in the Kyiv region, Ukraine, using 894 lactating Holstein cows of various age. Statistical analysis of the data was carried out using the general linear model procedure. The influence of different strengths of the «lactation stage» factor on the following conformation traits was established: Body Condition Score (BCS), Dairy Character (DC), Fore Udder Attachment, Chest Width (CW), Rear Teat Position, Front Teat Position, Foot Angle (FA), Udder Depth, Rump Angle, Body Depth (BD), Udder Texture, Rear Leg Set, Teat Length, which ranged from 1.2 to 9.2%. A significant difference between animals with different DO durations was established according to the following traits: DC, Angularity, BD, CW, BCS, FA. Obtained results of type traits evaluation at different stages of cows lactation may help to derive correction coefficients and thus standardize the assessment of the Holstein breed in points. Such an approach can be applied in herds for optimization of the breeders’ work, which often deals with the evaluation of cows at different lactation stages.