Analysis of factors influencing estrus cycle in dairy cows
The frequency of interestrus intervals between two inseminations during two annual period, from 1. 4. 2001 - 31. 3. 2003, on a farm with 500 Holstein-Frisian cows and milk production of 5500-6000 kg was analyzed. Periods of 1? months of estrus cycles were presented by histograms for pregnant, nonpregnant and culled cows. Normal and multiple cycles indicate estrus detection errors, and were recorded in 26.70% / 22.73% and 33.25% / 33.77% cows, in the first and second analyzed periods, respectively. Short and prolonged estrus cycles were noted in 12.22% / 4.34%, and 10.07% / 7.36% cows, in the first and second analyzed periods respectively, and indicate nutritional disturbances and embryonal mortality. Disturbed estrus periods were found in 41.31% and 43.10% cows and heifers and were a consequence of other cumulate factors in herd sterility. Herd fertility improvement may be achieved with systematic work on prevention of ovarial dysfunction and proper records management.