110 TREATMENT WITH GnRH ON DAY 5 REDUCES PREGNANCY LOSS IN HEIFERS RECEIVING IN VITRO-PRODUCED EXPANDED BLASTOCYSTS

Abstract

The hypothesis was that GnRH on Day 5 of a synchronized cycle in embryo transfer recipients would increase progesterone (P4) concentrations, embryo size, and fertility. Holstein and cross-bred Holstein heifers (n = 1562) were synchronized using a modified 5-day CIDR Co-Synch as follows: Day –8 CIDR inserted; Day –3 CIDR removed; prostaglandin F2α treatment; Day –2 second prostaglandin F2α; Day 0 gonadotropin-releasing hormone (G1, 100 μg of gonadorelin acetate) to induce ovulation. On Day 5.5, heifers were assigned in a completely randomised design to 1 of 2 treatments: Control (untreated) or GnRH (200 μg of gonadorelin acetate). Transfer of fresh in vitro-produced embryos was performed between d 6 and 8 after G1. Data collected from each heifer included embryo stage and quality, body condition score, technician, interval from G1 to transfer, and number of previous transfers. All heifers were evaluated by transrectal ultrasonography on Day 5, 33, and 62 and a subset of heifers was scanned on Day 12 (n = 718; to determine ovulation to treatment) and another subset on Day 33 (n = 296; 16-s video to determine embryo and amniotic vesicle size). Serum P4 was determined from a subset of heifers on Day 12 (n = 467). Fertility data were analysed by logistic regression (LOGISTIC procedure, SAS 9.4), whereas continuous outcomes were analysed by ANOVA (MIXED procedure). Ovulation to Day 5.5 gonadotropin-releasing hormone was 83.9% (302/360) in GnRH-treated heifers v. 3.3% (12/358) in Control (P < 0.001). Progesterone on Day 12 was greater in GnRH-treated heifers 7.2 ± 0.1 ng mL–1 v. Controls 6.0 ± 0.1 ng mL–1 (P < 0.001). There was an effect of embryo stage at Day 33 and 60 of pregnancy, with Stage 7 having greater P/ET than Stage 6 embryos. Treatment with GnRH did not alter pregnancy per embryo transfer with either embryo stage but decreased pregnancy loss in Stage 7 embryos, as shown in Table 1. Embryo size measured as crown-rump length (CRL) did not differ, as shown in Table 1. Similarly, amniotic vesicle volume (AVV) was not different between GnRH (549.1 ± 16 mm3) and Control (543.5 ± 14 mm3; P = 0.86), nor was there an interaction between treatment and embryo stage (P = 0.71). In addition, neither AVV (P = 0.22) nor CRL (P = 0.41) were associated with pregnancy loss between Day 33 and 60. In conclusion, treatment with GnRH on Day 5 resulted in increased P4 and a reduction in pregnancy loss in heifers receiving a Stage 7 embryo without changing conceptus size. Table 1.Pregnancies per embryo transfer (P/ET), crown-rump length (CRL), and pregnancy loss in embryo recipients receiving gonadotropin-releasing hormone (GnRH) on Day 5.5 v. control

Effect of treatment with human chorionic gonadotropin 7 days after artificial insemination or at the time of embryo transfer on reproductive outcomes in nulliparous Holstein heifers

“…Although studies evaluating the effect of hCG on pregnancy loss for heifers receiving ET are limited, treatment with GnRH 5.5 d after ovulation decreased pregnancy loss in stage 7 embryos for Holstein and Holstein-cross Heifers (Garcia-Guerra et al, 2015). Chagas e Silva and Lopes da Costa (2005) reported no effect of hCG treatment on d 7 on P/ET in dairy heifers; however, pregnancy loss was not reported in that study.…”

“…Although the effects of exogenous P4 treatment are not consistent among studies, supplementation of P4 from 3 to 13 and 16 d after AI advanced elongation of the conceptus (Carter et al, 2008), which resulted in earlier secretion of IFNτ (Mann et al, 2006) and increased conception rates . Increasing P4 concentrations in Holstein and Holstein-crossbred heifers by treatment with GnRH 5 d after ovulation did not affect pregnancies per ET (P/ET), but decreased pregnancy loss for stage 7 embryos (Garcia-Guerra et al, 2015). By contrast, decreased circulating P4 concentrations after ovulation decreased the expression of genes associated with embryo elongation (Forde et al, 2012) and decreased embryo growth (Carvalho et al, 2017).…”

Expression of estrus as a relevant factor in fixed-time embryo transfer programs using estradiol/progesterone-based protocols in cattle

“…Surprisingly, pregnancy losses after 60 days were also higher in recipients not showing estrus. Embryo/fetal losses as high as 17.2% from day 32 to day 60 of pregnancy have been reported in dairy heifers (Garcia Guerra et al, 2016) and between 0 to 34,5% in beef cows (Tribulo et al, 2017) carrying IVF embryos. However, none of these reports related estrus expression to pregnancy losses from 60 days of gestation to term.…”