Perda de gestação e incidência de fêmeas repetidoras de estro em rebanho leiteiro mestiço

Abstract

The objective of the studies was evaluate the effects of the animal category, season of calving, season of artificial insemination (AI), parity, numbers of previous inseminated and days in milk (DIM) at AI on pregnancy losses (PL) and the incidence of pregnancy loss before and after 60th day post-AI from females repeat breeders (FRB) and the effects of the animal category, season of calving, parturition condition and parity on the incidence of FRB. Data from Study 1 were collected from 462 pregnancies and calving of lactating dairy cows and from 118 pregnancies of heifers and the Study 2 from 997 pregnancies and calving of lactating dairy cows and from 371 pregnancies of heifers. Pregnancy check was performed by ultrasound between days 28 and 44 post-AI and re-checked between days 45 and 60 post-AI. The rates of pregnancy loss before 60th day and the incidence of RB were higher in lactating dairy cows than heifers (11.90% vs. 3.4%, P=0.01 and 24.5% vs. 6.5%, P<0.001, respectively) and pregnancy loss after day 60 was not affected by animal category (P=0.58). The season of calving affected the pregnancy loss before 60th day (which was higher in spring/summer) and there was only tendency (P=0.078) in affecting the incidence of RB cows probably due to the worst postpartum recovery. There was no relationship between season of AI, parity, number of previous inseminated and DIM at IA and pregnancy loss before and after 60th day in lactating dairy cows. The parturition condition had no effects on RB incidence, however, the effect of parity was detected. Even in crossbred lactating dairy cows the incidence of overall pregnancy loss and RB condition was higher and could be considered as a factor that compromised the reproduction efficiency.