study of production and reproduction traits of holstein dairy herd in varamin

in the research the genetic investigation productive and reproductive traits and changes trend the traits in years, seasons and different lactation periods and genetic evaluation cows and bulls of 785 records for milk and 665 records for fat yield and reproductive information during years 1998 to 2003 of 207 dairy cows ghezlagh farm aboureyhan campus (university of tehran) studied. the least square mean and standard error (lsm ± se) of milk yield (3x, 305, me) and fat yield were 6305.6 ± 87.7 and 206.1 ± 1.7 kg, respectively. the least square means (± se ) of calving interval , open days ,dry days, age at first calving and gestation length were 403.2 (± 6.7 ), 117.5 (± 6.8 ), 86.8 (± 7.3), 760.3 (± 9.7 ), 278.1 (± 0.7 ), respectively and insemination rate was 1.8 (±0.04). the effect of environmental factors of lactation period on milk production, persistency and insemination rate; year of parturition on milk and fat production, calving interval, insemination rate and age at first calving, dry days; and calving season on milk production and insemination rate were significant. estimated heritabilities and standard error for milk and fat yield using repeatability record animal model (rram), were 0.22 (± 0.12) and 0.29 (± 0.05), respectively. genetic and environmental trend of production traits during years 1998 to 2003 were positive. the breeding value of the animals for production traits predicted with animal model method and the superior families were ranked