Öz
The study was conducted to compare the age with respect to some oestrus signs on pregnancy success in spontaneously oestrus signed 96 Holstein cows under field conditions. Some oestrus findings were examined by visual observation and some clinical tests then all cows were artificially inseminated by frozen-thawing semen. The dominant follicle was located more often (P<0.01) on the right (61.46%) than the left ovary (38.54%) in all animals, but there was no effect of location of the ovulatory follicle on the pregnancy rate. However, it was observed positive correlations between pregnancy rates and vaginal temperatures (r=0.661, P<0.05), and the ferning of cervical mucus (r=0.732, P<0.01), and also between the ferning of cervical mucus and OFS, and vaginal temperatures (P<0.05) in all animals. In addition, the significantly (P<0.01) high pregnancy rates were achieved in spontaneously oestrus occurred 4-7 years aged cows that ovulatory follicle sizes (OFS) were ranged from 14 mm to 18 mm. It was concluded that should be oestrus signs evaluated together with age, OFS and ferning of cervical mucus why pregnancy success were bigger in cows whose vaginal temperature and ferning of cervical mucus were maximum and OFS was moderate, pregnancy chance may be improved by means of optimizing insemination time in 4-7 years olded cows.