Efficacy of in vitro embryo transfer in lactating dairy cows using fresh or vitrified embryos produced in a novel embryo culture medium

Abstract

Objectives were to determine whether pregnancy success could be improved in lactating cows with timed embryo transfer when embryos were produced in vitro using a medium designed to enhance embryo development and survival after cryopreservation. In experiment 1, embryos (n=569 to 922) were cultured in either modified synthetic oviduct fluid or a serum-free medium, Block-Bonilla-Hansen-7 (BBH7). Development to the blastocyst stage was recorded at d 7, and selected blastocysts (n=79 to 114) were vitrified using open pulled straws. Culture of embryos in BBH7 increased development to the blastocyst stage (41.9±2.0 vs. 14.7±2.0%) and advanced blastocyst stages (expanded, hatching, hatched; 31.1±1.3 vs. 6.4±1.3%) at d 7 and resulted in higher hatching rates at 24h postwarming compared with embryos cultured in modified synthetic oviduct fluid (59.0±0.5 vs. 26.7±0.5%). In experiment 2, embryos were produced using X-sorted semen and cultured in BBH7. At d 7 after insemination, embryos were transferred fresh or following vitrification. Lactating Holstein cows were either subjected to timed artificial insemination (TAI) on the day of presumptive ovulation or used as embryo recipients 7 d later. Embryo recipients received an embryo if a corpus luteum was present. The percentage of cows pregnant at d 32, 46, and 76 of gestation was higher among cows that received fresh embryos compared with TAI cows or cows that received vitrified embryos. At d 76, for example, the proportion and percentage pregnant was 47/150 (31.3%) for cows subjected to TAI, 48/95 (50.5%) for cows receiving fresh embryos, and 39/141 (27.7%) for cows receiving a vitrified embryo. No difference was observed in the percentage of cows pregnant among TAI cows and those that received vitrified embryos. There was a service or transfer number × treatment interaction because differences in pregnancy rate between embryo transfer recipients and cows bred by TAI were greater for cows with more than 3 services or transfers. Pregnancy success in lactating cows can be improved by transferring fresh embryos produced in BBH7 compared with TAI. Moreover, no decline in fertility was observed when cryopreserved embryos were transferred compared with TAI. Embryo transfer is particularly efficacious for infertile cows that have previously experienced several failed breeding attempts.

In vitro bovine embryo production in a synthetic medium: Embryo development, cryosurvival, and establishment of pregnancy

“…These rates are comparable to previous studies that obtained average gestation rates of 50.5% [40] and 41.8% [41] with fresh IVF embryos, and 27.7% [40] with frozen embryos. This is a fully synthetic method of embryo culture; it presents a valuable tool for reducing the risk of disease transmission via embryo transfer.…”

Treatment with the Proteasome Inhibitor MG132 during the End of Oocyte Maturation Improves Oocyte Competence for Development after Fertilization in Cattle

“…A total of 4 different bulls were used in the experiment. Sperm were purified before fertilization as described elsewhere [18]. The final sperm concentration in the fertilization well was 1×10 6 sperm/ml.…”

Early pregnancy: Concepts, challenges, and potential solutions

“…For example, heat stress before and immediately after breeding can also substantially increase early pregnancy loss, likely due to compromised oocyte quality and thus development of the early embryo. Indeed ET improved fertility when cows were subfertile (e.g., during heat stress or in repeat breeder cows; Block et al, 2010). However, transfer of embryos produced in vivo or in vitro did not increase fertility of lactating dairy cows when pregnancy rates to AI were not compromised.…”