169 EMBRYO TRANSFER OF SEXED/VITRIFIED IVF EMBRYOS IN CATTLE: PREGNANCY COMPARISON AFTER SINGLE AND DOUBLE TRANSFERS

Abstract

Advancement in sperm sorting technology combined with vitrification of in vitro produced bovine embryos will promote cattle breeding and production. The objective of this study was to evaluate pregnancy and embryo loss after embryo transfer (ET) of sexed/vitrified embryos with one bilaterally (double transfer, 2 embryos) v. ipsilaterally (single transfer, 1 embryo) into the recipient. Bovine oocytes collected from slaughterhouse ovaries or ovum pickup were matured for 20-22 h, then subjected to IVF using Brackett and Oliphant BO procedures with sorted X-sperm, and cultured with our standard culture system. Expanded blastocysts with tight compaction of the inner cell mass (quality 1) were selected on Day 7 for cryopreservation via liquid nitrogen surface vitrification (LNSV; Xu et al. 2006 J. Dairy Sci. 89, 2510-2518). Embryo transfer was performed for 3 replicates in Navasota, Texas, in April 2009. Prior to ET, embryos were warmed and subsequently washed several times in warming, dehydration solution and base medium. Some of sexed/vitrified embryos were cultured for 3 days post-warming to determine the survivability. The treatments were as follows: (1) vitrified-single transfers, 1 embryo was transferred into the horn ipsilateral to CL; (2) vitrified-double transfers, 1 embryo was transferred into each uterine horn by nonsurgical transfer; and (3) fresh-single, 1 fresh embryo was transferred into the horn ipsilateral to CL (control) to a synchronous recipient on Day 7. Pregnancy was determined by ultrasound monitoring on Day 35, and palpation per rectum on Day 75 after transfer. The pregnancy data were analyzed by General Linear Model analysis (SPSS 11.0, SPSS Inc., Chicago, IL, USA). The survival rate of vitrified IVF embryos reached to as high as 97.6% (n = 42) 2 h post-warming, and hatching rate was 85.7% after 3 days culture in vitro. The data (Table 1) showed that there was no difference in Day 35 pregnancy rate among vitrified-double, vitrified-single, and fresh ET control groups. However, on Day 75 post-ET, there was a significantly higher fetal loss found in the vitrified-double transfer group (41.1%) compared to those of vitrified-single transfers (16.6%) and fresh-single group (11.9%) (P < 0.05). The pregnancy rate on Day 75 of 51.4% achieved with vitrified-single transfers was comparable to the 43.3% achieved with the fresh-single control transfers but was significantly higher than the 31.1% of the vitrified-double transfer group. This study demonstrated that double embryo transfers can aggravate high fetal loss and/or abortion when sexed IVF embryos are transferred, and ET with 1 sexed/vitrified embryo per recipient is sufficient to establish satisfactory pregnancy, comparable to that achieved with fresh embryos.

Table 1.  Pregnancy and fetal loss of sexed/vitrified bovine IVF embryos following single and double transfers

Supported by USDA/CSREES-SBIR: 2006-03069 Phase II to F. Du.