Recently, test day models (TDM) began to be increasingly used for the genetic evaluation of dairy cattle. The main advantage of the TDM compared with the 305 days lactation yield models is that more effects can be used in the evaluation. Therefore, the TDM is more accurate than the lactation models. The main disadvantage is the increased comput
...ational requirement, but this can be offset by improvements in computer capabilities. The topic of this paper is the use of a fix regression test day model to estimate the inheritabilities of test day data from Hungarian Holstein-Friesian dairy cattle. The inheritability was 0.26 for milk production, 0.2 for fat production, 0.24 for protein production and 0.06 for the somatic cell count.