Authors : Reza Seyedsharifi , Ali Reza Falah Kheir and Morad-Pasha Eskandari-Nasab
Abstract: The economy of dairy production relies on the reproductive performance of the herd. The main aim of this study was estimation the level of milk yield and calving age of 1st lactation period to improving the performance of days open. In this way, predicted equations of days open of 1st 3 lactation periods were determined in Holstein cows of Iran using SAS statistical software package. Three interests of the highest age of 1st calving and most milk yield, the least age of 1st calving and most milk yield and the average age of 1st calving and milk yield for estimating a suitable level of days open presented. The phenotypic correlation between milk yield of 1st lactation periods and 1st days open was negative, but it was positive about 2nd and 3rd parity (p<0.01). The phenotypic correlation between 1st calving age and 1st days open was positive, but it was negative about 2nd and 3rd parity (p<0.01). The revenue minus cost per a day decreasing of days open increased by 872586 Rials per each cow. The interest of the least age of 1st calving and most milk yield compared two other interests caused less average of days open of 1st 3 lactation periods.
Reza Seyedsharifi , Ali Reza Falah Kheir and Morad-Pasha Eskandari-Nasab , 2009. Prediction of Days Open of First Three Lactation Periods from First Milk Yield, Days in Milk and Calving Age and its Effect on Improving the Economic Performance of the Herd. Research Journal of Biological Sciences, 4: 59-63.