The aim of this study was to compare the effect of diverse sire origins on first lactation performance, age at first calving (AFC), first-parity calving class and days open, and also length of productive life (LPL) in Iranian Holstein cows. Data regarding to the all first-calving cows were collected during 1996 until 2007 in five large commercial Holstein farms. Farms were located in Northeastern of Iran. Each cow has been characterized by demographic data, production and reproduction data. The dependent variables analyzed were the cumulative first 60, 100 and 200 days as well as 305-d adjusted milk productions, AFC, calving class (including eutocia, dystocia, stillbirth, and abortion), days open, and LPL. Data were analyzed using Mixed models. The effect of the sire origins on calving class was evaluated by nominal logistic analysis. The result showed that first-parity milk performance was similar among the daughters of sire groups (p>0.05). Milk production was numerically higher for the imported sire groups. Milk persistency was better for the imported sires compare with the domestic sourced sires (p<0.05). Sire origin had no apparent effect on AFC, first-parity calving class, and interval from first calving to conception (p>0.05). AFC was decreased and days open was increased over the years (p<0.05). The cumulative 60 days milk production had no apparent effect on first-parity days open but days open tended to increase in the high producer cows (p=0.14). Length of productive life was higher among the daughters of Iranian sires compare with the Canadian sires (p=0.02). The similar production performance among the daughters of sire origin in this study could be a help in reducing on-farm expenses in Iranian dairy industry. More studies needed to evaluate the results of this study in different climates of Iran along with a larger data set.

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