Estimation of the Genetic Parameters for Test-Day Milk Yield in Holstein Cattle

The objective of this study was to determine the genetic parameters represented by heritability for test-day milk yield, the genetic correlations between test-days milk yield and the breeding value for Holstein cows. The model used was random regression test-day animal model. The data set consists of 216 test day records from 30 cows. The average number of test day per lactation was seven. The heritability estimates for test-day milk yield ranged from 0.43 at 250th day in milk, to 0.60 at 10th day in milk. Genetic correlations between individual test days milk yield were high and positive.