Late embryonic and foetal losses in eight dairy herds in north-east Poland.

The information about the occurrence of embryonic and fetal losses in dairy herds in Poland is limited. Thus, the objective of this study was to assess the pregnancy loss between days 30 and 45 (late embryonic mortality) and between days 45 and 260 after artificial insemination (AI) (foetal loss). The study was carried out in 8 dairy herds in north-east Poland. In total 954 cows were examined for pregnancy on day 30 after AI using an ultrasound scanner. Cows diagnosed pregnant were re-examined on day 45 and 260 after AI using transrectal palpation. The pregnancy rate on day 30 after AI was 62.0%, after re-examination on day 45 after AI the pregnancy rate was 56.4%. The late embryonic loss rate was on an average 9.1%. The occurrence of late embryonic mortality differed not significantly (p > 0.05) among herds and ranged from 13.1% to 19.3%. The pregnancy rate on day 260 after AI was 53.5%. The average foetal loss after day 45 of pregnancy was 5.0%, ranged between herds from 0 to 9.2% (p > 0.05) and was significantly lower than embryonic loss rate (p < 0.05). The study revealed that in 8 dairy herds in north-east Poland the overall pregnancy loss between days 30 and 260 averaged 13.7% and therefore it is an important factor affecting economic efficiency of dairy production. The foetal loss was less prevalent than the late embryonic loss. Future strategies to minimizing late embryonic loss are needed.