engleski

The effect of time elapsed from milking to scoring on udder linear scores and estimation of genetic parameters

The study was conducted on 51, 154 Holstein primiparous cows. The purpose of the study was to estimate the impact of time elapsed from last milking until scoring on the properties of udder conformation traits (fore udder attachment, rear udder height, rear udder width, udder depth, and central ligament). The purpose was also to consider the benefi ts of including this effect in statistical models for estimation of genetic parameters in dairycattle. A significant (P<0.001) positive linear relationship between scores of udder traits and the time of the scoring was determined. Rear udder height (b = 0.088) and rear udder width (b = 0.091) were affected the most, with the prolongation of time of scoring regarding previous milking. The investigated effect only affected the residual component of variance. Other components of variance did not change considerably when the time from milking to scoring was fi tted into a basic statistical model. Estimated heritabilities ranged from 0.15 to 0.27. Slightly higher estimates of heritabilities for all traits, except for the central ligamentum, were determined when this effect was fi tted into the model. Udder depth was found to be in strong negative genetic correlation with fore udder attachment (r = -0.436). An almost negligible negative genetic correlation between udder depth and rear udder width was determined (r = -0.086). Genetic correlations between all other traits were positive and low to moderate (r = 0.15 - 0.54). The investigated effect did not noticeably affect estimates of genetic correlations between udder conformation traits.

udder conformation traits ; time interval ; model ; genetic evaluation

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