Comparison of the efficacy of conventional slow freezing and rapid cryopreservation methods for bovine embryos

Day 7 bovine morulae and early blastocysts were randomly assigned to one of four cryopreservation methods: (i) a modified conventional controlled slow freezing and stepwise dilution after thawing; and three methods which enable direct transfer of the embryo into the recipient upon thawing: (ii) conventional controlled slow freezing and a modification of a one-step procedure, (iii) vitrification with 6.5 M glycerol plus 6% BSA (w/v), and (iv) vitrification with 25% glycerol (v/v) and 25% propanediol (v/v). In a comparative in vitro study, the percentage of grade 1 and 2 embryos developing into expanded blastocysts in culture for cryopreservation methods 1-4 were, respectively, 53% (29/55), 33% (20/61), 44% (26/59), and 51% (17/33). Method 2 yielded a significantly lower survival rate than methods 1 (P 0.1) when compared to method 1. Method 3 has considerable promise in providing a successful method for the cryopreservation of bovine embryos that (i) reduces the time required for equilibration and cooling, (ii) provides for simple and rapid one-step dilution of cryoprotectant after thawing, and (iii) enables more embryos to be thawed and transferred per unit time

Comparison of the efficacy of conventional slow freezing and rapid cryopreservation methods for bovine embryos

Day 7 bovine morulae and early blastocysts were randomly assigned to one of four cryopreservation methods: (i) a modified conventional controlled slow freezing and stepwise dilution after thawing; and three methods which enable direct transfer of the embryo into the recipient upon thawing: (ii) conventional controlled slow freezing and a modification of a one-step procedure, (iii) vitrification with 6.5 M glycerol plus 6% BSA (w/v), and (iv) vitrification with 25% glycerol (v/v) and 25% propanediol (v/v). In a comparative in vitro study, the percentage of grade 1 and 2 embryos developing into expanded blastocysts in culture for cryopreservation methods 1-4 were, respectively, 53% (29/55), 33% (20/61), 44% (26/59), and 51% (17/33). Method 2 yielded a significantly lower survival rate than methods 1 (P 0.1) when compared to method 1. Method 3 has considerable promise in providing a successful method for the cryopreservation of bovine embryos that (i) reduces the time required for equilibration and cooling, (ii) provides for simple and rapid one-step dilution of cryoprotectant after thawing, and (iii) enables more embryos to be thawed and transferred per unit time

The monitoring of bovine pregnancies derived from transfer of in vitro produced embryos

Both an increased rate of embryonic, foetal and perinatal losses, and the occurrence of deviations in foetal and placental development are associated with bovine pregnancies obtained from in vitro produced embryos. This thus requires for a more accurate and frequent monitoring of foetal and maternal functions during pregnancies. Such approaches will enable to establish the period during which these losses and deviations in development occur and to plan possible clinical interventions. This paper reviews some recent data on return rates, late embryonic and foetal losses in recipients after the transfer of either MOET, IVF or nuclear transfer embryos. Special attention is paid to the diagnostic value of measurements of pregnancy specific/associated proteins and progesterone in maternal plasma. Possibilities to measure foetal body sizes, size of placentomes and foetal heart rate by means of transrectal or transabdominal ultrasonography are illustrated with data from the literature and with recent results from our own large field study with MOET, IVP-co-culture and IVP-SOF embryos