عنوان مقاله [English]
This study was carried out in order to evaluate the relationship between some productive and reproductive factors with calf sex (CS), in Shahryar city from 2017 to 2018. Synchronization and pregnancy detection were performed by a veterinarian. Heat detected cows were inseminated by artificial insemination (AI) or mated by bull cow based on their reproductive history. Implantation of fetus in left-side or right-side of uterine horn was determined by sonography. The CS of newborn calves was also registered immediately after calving in order to analyze the sex ratio. Results showed that the intervals between calving and first insemination service had no significant effect on CS. In addition, CS was not affected by age of cow and type of insemination. However, implantation of fetus in the rightside compared to the left-side uterine horn resulted in a greater ratio of female than the male calves(P>0.05). The ratio of female calves in the dairy cows with high milk production (45%) was higher than those with low milk production (25%, P<0.05). The primiparous cows significantly produced (P<0.05) higher ratios of female calves (60%) rather than multiparous cows (47%, 46% and 47% in the second, third and fourth parturition, respectively). It can be concluded that, the uterine horn side implantation, level of milk production and primiparous or multiparous cows’ statement are effective factors on CS. Therefore, it is possible to convey the sex ratio of new born calves to a desired ratio by manipulating some parameters in dairy cows before the birth.