Genetic relationships between production traits and reproductive performance in Holstein dairy cows
In order to estimate genetic parameters for production traits and reproductive performance, 115465 records of production traits and 90942 records of reproductive performance from Iranian Holstein cows that were collected during 1980 to 2004 at Animal Breeding Center of Iran, were used. The estimations were performed using Restricted Maximum Likelihood method (REML) under an animal model by DF-REML and MATVEC software. Estimates of heritabilities for production traits were moderate, from 0.149 for fat yield to 0.26 for milk yield. Heritabilities for reproductive performance were low, and ranged from 0.04 for interval from calving to first service to 0.0743 for gestation length. Genetic correlations between production traits were form −0.505 for milk yield and protein percentage to 0.81 between milk yield with fat yield. Most genetic correlations between reproductive performances were found close to zero. Genetic correlation estimates of production traits with reproductive performance were from −0.513 for open days and protein yield to 0.96 for protein yield and calving interval.