Genetic and Phenotypic Trends of Fertility Traits in Iranian Holstein Cows

A total of 72124 fertility records was used to estimate the genetic and phenotypic trend of fertility traits in Iranian Holstein cow from 1981 to 2007. Fertility traits in this study were: days from calving to first service (DFS), number of insemination per conception (INS), days open (DO), interval between first and last insemination (IFL), calving interval (CI) and success to first insemination (SF). The overall genetic trend in fertility traits was as desired and statistically significant. Mean breeding value of SF increase by 0.00067 percent per year. The annual genetic trends for INS, DFS, IFL, CI and DO were -0.0029 number/year, -0.062 days/year, -0.041 days/year, -0.23 days/year and -0.24 days/year, respectively. Phenotypes trends for fertility traits were unfavorable except for DFS and DO. Phenotypic trends in IFL, INS and SF were as undesirable positive. Phenotypically DO and CI did not change over the time period. Phenotypically IFL has increased 1.6 days/year and DFS has decreased 1.6 days/year. The annual phenotypic trends for INS and SF were 0.04 and -0.018, respectively.