Estabelecimento e acompanhamento da g establishment and monitoring of pregnancy in Holstein cows after embryo transfer, produced in vivo or in vitro

The aim of this study was to evaluate the establishment and maintenance of pregnancy, until parturition, of embryos produced in vivo (superestimulation and uterine flush, SOV-UF) or in vitro (ovum pick-up and in vitro production, OPU- IVP), derived from donor Holstein cows (black and white Holstein cows, BWH) lactating (LAC) or not (NLAC) and transferred to recipient BWH multiparous (MULT) or primiparous (PRIM). The data was obtained from a commercial dairy farm (Agrindus S/A, Descalvado-SP) during the year 2013. 2225 embryo transfers were performed, and 1337 embryos were obtained from the SOV-UF and transferred to fresh (SOV-UF-F); 474 embryos were obtained from SOV-UF and transferred thawed (SOV-UF-T) and 444 embryos were obtained from OPU-IVP and transferred to fresh (IVP). The pregnancy diagnosis was performed by ultrasonography exams at 30 days of gestation (DG30) and 30 days later the pregnancy was confirmed by rectal palpation (DG60). Pregnancy losses between 30 and 60 days and between 60 days and parturition were also recorded. Data were analyzed using the GLIMMIX procedure of SAS 9.2®, considering category (LAC and NLAC), parity (MULT and PRIM) and embryo production technics (SOV-UF-F, SOV-UF-T, IVP) in the mathematical model, and presented as means of least squares (mean adjusted by the model). The recipients that received embryos derived SOV-UF-F showed higher conception rate at 30 days of gestation than the recipients that received embryos derived SOV-UF-D and IVP [SOVUF-F: 48.0% (632/1337), SOV-UF-D: 14.3% (64/474), IVP: 31.6% (138/444), P <0.0001], as well at 60 days of gestation [SOV-UF-F: 36.8% (488/1337), SOV-UF-D: 10.7 % (50/474), IVP: 21.8% (99/444), P<0.001]. No significant effects were observed on pregnancy loss between 30 and 60 days of gestation [SOV-UF-F: 21.2% (141/632); SOV-UF-D: 20.8% (14/64); IVP: 30.2 % (39/138); P=0.11] and pregnancy loss between 60 days of gestation and until parturition [SOV-UF-F: 23.7% (120/488); SOV-UF-D: 17.0% (9/50); IVP: 24.9% (25/99); P=0.54]. Additionally, the recipients MULT showed decreased rate of pregnancy at 30 days than PRIM [MULT: 28.9 % (519/1472); PRIM: 33.8% (315/783); P=0.015] and higher pregnancy loss between 60 days of gestation and parturition [MULT: 25.3% (105/392); PRIM: 18.4% (49/245); P=0.049] than the PRIM. Lastly, embryos that were derived from donors LAC showed increased rate of pregnancy loss between 30 and 60 days when compared the embryos derived of donors NLAC [27.5% (122/490) vs. 20.7% (71/343), respectively; P=0.037]. Therefore, it is concluded that pregnancy loss rate was not affected by the type of embryo (in vivo or in vitro), however the establishment of pregnancy at 30 and 60 days was higher in embryos produced in vivo and transferred fresh. The number of births affected the pregnancy at 30 days and losses between 60 days and parturition, and lactation status of the donor influenced the pregnancy loss between 30 and 60 days.