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 1½ 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