estimation of genetic parameters for first lactation production and reproduction traits in iranian holstein cows

to estimate the genetic parameters for production and reproduction traits in holstein cows, information from 15 herds recorded by animal breeding center of iran during 1980 – 2004, were employed. estimations were made using restricted maximum likelihood method under an animal model ranging df-reml and matvec software. estimates of heritabilities for yield traits were moderate and ranged from 0.15 (fat yield) to 0.26 (milk yield). heritabilities for fertility traits were low, and varied between 0.04 (interval from calving to first service) to 0.07 (gestation period length). genetic correlations between yield traits were form -0.5 (milk yield and protein percentage) to 0.81 (milk yield along with fat yield). most genetic correlations between fertility traits were close to zero. genetic correlation estimates among yield traits and fertility traits varied from -0.51 (open days and protein yield) to 0.96 (protein yield and calving interval). due to antagonistic genetic correlations between fertility traits and production traits, both these traits need to be taken into account in a selection program.