reproductive performance of holstein heifers inseminated with sex sorted semen in various herd sizes

Nowadays, the use of sex-sorted semen is more commonplace in industrial dairy farms. however, the re-productive efficiency of this kind of semen is controversial among dairy farmers. reproductive efficiency can also be influenced by herd size as a result of different management practices. the current study com-pares the reproductive performance of holstein heifers inseminated either with sex-sorted or conventional semen in isfahan province of iran. data were included the reproductive performance of 64070 heifers col-lected during 2007-2017 from 10 industrial farms with various sizes. evaluated reproductive traits were conception rate, dystocia, stillbirth, abortion as well as days open and days from calving to the first service in heifers inseminated with various semen types and various farm sizes. conception rate in the first to the third insemination of sex-sorted semen, respectively decreased by 18, 16, and 12 percent compared to the conventional semen. the chance of abortion, still birth, and dystocia when using sex-sorted semen were 0.095, 0.43, and 0.81. the result illustrated that using sex-sorted semen dramatically decreases the propor-tion of reproductive disorders, yet it led to lower conception rate, and it is estimated that conception rate is going to be improved through more efficient reproductive management in larger farm sizes. herd size did not show a consistent effect on reproductive performance however reproductive efficiency was somehow better in medium-sized farms.