11 Does pregnancy status affect cumulus–oocyte complex recovery and embryo production in cycling Girolando heifers?

In vitro embryo production (IVP) is a reproductive technique that accelerates the genetic gain of herds. However, the technique’s success depends on several factors. The aim of this study was to evaluate the effects of pregnancy status of cycling Girolando heifers on cumulus–oocyte complex (COC) recovery (total and viable), blastocyst production, cleavage, and blastocyst rate. Data from 201 transvaginal ultrasound-guided follicular aspiration (ovum pickup [OPU]), performed on cycling Girolando heifers from a commercial embryo production laboratory located in Triângulo Mineiro, Minas Gerais, Brazil, were analyzed. The cyclicity was evaluated by ultrasound examination 10 days before OPU and at OPU. Cycling heifers that showed corpus luteum in at least one of the exams were included. The heifers were classified as pregnant (n = 116; 150 OPU; range of 1–3 OPU/heifer) or nonpregnant (n = 40; 50 OPU; range of 1–3 OPU/heifer). The OPU was performed on random days during the estrous cycle with no previous hormonal protocol and with a 30-day minimum interval. In pregnant heifers, the OPU was performed between 45 and 120 days of pregnancy. The recovered material from OPU was screened, and the viable COCs were selected, stored in maturation medium, and transported to the laboratory. After 22–24 h, capable spermatozoa were co-cultured with these matured oocytes for 16–22 h. The probable zygotes were then subjected to in vitro culture (IVC) for 7 days, followed by embryo classification. Only embryo grades 1 and 2 were considered viable. The cleavage rate was defined as the number of ≥4-cell embryos on Day 3 of IVC divided by the number of viable COCs. The blastocysts rate was defined as the number of viable blastocysts on Day 7 of IVC divided by the number of viable COCs. Poisson-normal (count data) and logistic-normal (proportion data) models were used to analyze the data, including the model pregnancy status of Girolando heifers. The total number of COCs (32.41 ± 14.25 vs. 29.01 ± 14.21), viable COCs recovered (22.37 ± 10.9 vs. 20.01 ± 11.14), and blastocysts produced (6.82 ± 4.91 vs. 6.28 ± 5.35) in nonpregnant and pregnant Girolando heifers did not differ (P > 0.10). The cleavage (78.0% vs. 78.0%) and blastocyst rates (30.50% vs. 31.38%) were not affected (P > 0.10) by the pregnancy status of the Girolando heifers. According to the data, we can conclude that the pregnancy status of cycling Girolando heifers did not affect the COC recovery and embryo production.

Support for this study was provided by CAPES, CNPQ, and Vale do Embrião.