Genetic evaluation of Iranian Holstein dairy cows with the use of a Covariance Function Model

Abstract

The use of test day models has increasingly become of interest in genetic evaluation of dairy cattle. Traditionally, in most dairy cattle breeding programmes genetic evaluation of dairy sires and cows has been primarily based on using 305-day lactation yield. Since in this system of evaluation many incomplete lactation records have to be extended to complete lactations this could result in biased prediction of breeding values due to any over or underestimation of total lactation yields. In genetic evaluation of dairy cattle, test day models have many advantages over the traditional method (Lactation Animal Model) because of the fact that they can account for the lactation curve of individual cows and take more accurate account of the effects of environmental factors influencing test day milk yield over the course of lactation. The main aim of this study was to use a Covariance Function Test day Animal Model (CFTAM) in genetic evaluation of first parity Iranian Holsteins.