estimation of genetic trend for production traits of holstein cattle in iran

data related to holstein dairy cattle from 1987 to 2004 were obtained from animal breeding center of iran to estimate the genetic and phenotypic trends. variance components and genetic parameters of the first lactation records were estimated using restricted maximum likelihood method and aireml algorithm through matvec program. animal breeding values were predicted through multiple-trait animal model. estimates of heritability for milk, fat and protein yields were 0.27, 0.22 and 0.25, respectively. genetic trend was estimated as the linear regression of blups of the breeding values of animals on the birth year. the estimate of genetic trend for milk yield was 33.84±2.10kg, for fat yield 0.64±0.05kg and for protein yield it was 1.00±0.08kg. average phenotypic trend for milk, fat and protein yields were 122.28, 4.42 and 3.06 kg, respectively. acceptable genetic improvement for milk yield, while low genetic trends for fat and protein yield were observed in holstein cattle in iran.