| Summary: | The aim of the study was to find the relationship between some postpartum disorders and pregnancy losses (PL), and the influence of PL on further fertility of Holstein-Friesian dairy cows. The 1,056 pregnancies and 906 calving intervals (CI) of 378 cows during the nine-year observation period were analysed. The average milk yield during this period increased from 7,500 to 10,500 kg/305 d of lactation. All cows up to 4 weeks after calving were gynecologically examined and cases of genital tract disorders were recorded and treated. Artificial inseminations (AI) were made using commercial frozen/thawed semen. In cows with silent ovulation, oestrus was induced by injection of PGF2α or programmes using PGF2α and GnRH, or hCG were applied. Pregnancy was diagnosed with the use of ultrasonography or foetal membrane slip only from 30 and 42 d after service, respectively, and re-diagnosed between 70 and 90 d after AI. The cases of „early foetal loss” up to 90 d and „mid-to-late PL” between 91 and 260 d after AI were recorded. Endometritis was noted in 31.8%, ovarian cysts in 8.5%, whereas ovarian inactivity in 4.6% of cows. Early PL was observed in 5.2%, whereas mid-to-late PL in 6.8% of cows (total 12%). From all analysed factors, the influence of delayed or periodical lack of ovarian activity was significant with regard to early PL (P=0.029). The probability of early PL increased when besides the diagnosis of ovarian inactivity, AI was made following an induced oestrus (P=0.003). CI for cows, which did not lost pregnancy amounted 442.9 d. The early, mid-to-late and multiple PL extended the CI to 579.6, 661.1 and 657.7 d, respectively (P<0.05). Concurrently, CI for cows with “early foetal loss” was significantly shorter comparing to cows with “mid-to-late foetal loss” (579.6 d vs.661.1 d; P<0.05). On average 2.6 inseminations for one pregnancy were needed, and each PL increased the AI index. Significant differences were stated after early and multiple foetal losses (5.2 and 5.1 vs. 2.6; P<0.05).
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