Estimation of dispersion parameters with an animal test day model for Slovenian black and white breed

Abstract

The dispersion parameters for daily milk yield (DMY), fat (FC) and protein (PC) content were estimated in separate analyses on 643 357 test-day records of 29 150 cows in Slovene black and white population. Additionally, 12 173 animals were included into the pedigree file. Records were collected from March 1986 to July 1998. The model includes calving season, age at calving, and stage of lactation as fixed effects and herd, permanent environment, and animal as random effects. Herd effect explained 0.23, 0.06 and 0.09 of the total variance for DMY, FC, and PC, respectively. The similar proportions (0.23, 0.07, and 0.11) were estimated for permanent environment effect. Heritability estimates were 0.20, 0.20, and 0.25 for DMY, FC, and PC, respectively. The procedure allows to predict and use breeding values for younger cows with less or even none records causing the generation interval to be shortened. Before implementation of the model, the economic values of merit traits as well as correlations among the traits considered should be reevaluated.