Simulation study on heterogeneous variance adjustment for observations with different measurement error variance


  • Timo Pitkänen MTT Agrifood Research Finland
  • Esa Mäntysaari MTT Agrifood Research Finland
  • Ulrik Nielsen The Knowledge Centre for Agriculture
  • Gert Pedersen Aamand Nordic Cattle Genetic Evaluation
  • Per Madsen Aarhus University
  • Martin Lidauer MTT Agrifood Research


Animal model, heterogeneous variance correction, automated milking system


The Nordic Holstein yield evaluation model describes all available milk, protein and fat test-day yields from Denmark, Finland and Sweden. In its current form all variance components are estimated from observations recorded under conventional milking systems. Also the model for heterogeneity of variance correction is developed for the same observations. As automated milking systems are becoming more popular the current evaluation model needs to be enhanced to account for the different measurement error variances of observations from automated milking systems. In this simulation study different models and different approaches to account for heterogeneous variance when observations have different measurement error variances were investigated. Based on the results we propose to upgrade the currently applied models and to calibrate the heterogeneous variance adjustment method to yield same genetic variance for both milking systems.

Author Biographies

Timo Pitkänen, MTT Agrifood Research Finland

Biotechnology and Food Research, Genetic Research

Esa Mäntysaari, MTT Agrifood Research Finland

Biotechnology and Food Research, Genetic Research

Per Madsen, Aarhus University

Centre for Quantitative Genetics and Genomic

Martin Lidauer, MTT Agrifood Research

Biotechnology and Food Research, Genetic Research