Thesis has been focused on the analysis of selected factors affecting the length of gestation in cattle, Holstein breed. Pregnancy duration was considerably influenced by the month of conception. Gestation duration was also affected by alive and dead calf, parity, sex of calves and twins. In conclusion, results suggest that pregnancy of cows may be influenced by many factors.

Thesis is aimed to analyze effects on the length of pregnancy, calving interval, service period, insemination interval and number of inseminations in the herd of the Czech spotted cattle. The study was performed on 1697 animals. The length of pregnancy was significantly affected by parity, twins, death of calf and gender of calves. The calving interval was significantly influenced the length of pregnancy, number of inseminations, length of insemination interval, service period and month of calving. The length of service period was influenced by the length of insemination interval. The number of insemination was significantly affected by parity. Reproduction in the herd is affected by a number of factors, so it is necessary to pay special attention to them.