279 IN VITRO DEVELOPMENT IN THREE CULTURE SYSTEMS OF BOVINE OOCYTES FERTILIZED WITH SEX-SORTED SPERM

Abstract

Following in vitro fertilization and culture, the timing of both embryonic cleavage and appearance of blastocysts has been reported to be altered when using sorted spermatozoa (Lu et al. 1999 Theriogenology 52, 1393–1405). To optimize an in vitro culture system for bovine embryos produced with sexed sperm, sorted and unsorted (control) semen samples of 5 bulls (semen samples provided by XY Inc., Fort Collins, CO, USA) were separated using a Percoll gradient followed by a washing step with Fert-TALP medium (Trigal et al. 2010 Reprod. Domest. Anim. 45, 83). The obtained pellet was used for fertilizing in vitro matured cumulus–oocyte complexes from slaughterhouse ovaries. Zygotes were cultured in 1) Vero cells monolayer + B2 + 10% FCS; 2) SOFaaci + 10% FCS; or 3) SOFaaci + 6 g L^–1 BSA. A total of 1980 oocytes were in vitro matured and fertilized. Development was recorded on Days 3 and Days 6 to 8, and analysed by ANOVA and Duncan test. Bull, replicate, and culture effects were nonsignificant, and consequently were not considered in the final analysis. Data are percentages of development related to the zygotes cultured, and are expressed as LSM ± SE (see Table 1). The use of sexed sperm significantly reduced development rates compared with unsorted sperm. Thus, sorted sperm showed reduced 5- to 8-cell, Day-6 morulae, and Day-8 blastocyst rates over unsorted sperm within the 3 culture systems analysed. Culture in SOF + BSA was the least efficient embryo culture system in terms of Day-7 blastocyst rates, both with unsorted and sorted sperm. Day-7 blastocyst rates produced with unsorted sperm after culture in Vero cells or SOF + FCS were significantly higher than those obtained after culture in SOF + BSA. Day-7 blastocyst rates obtained with sorted sperm and cultured in Vero cells or SOF + FCS were comparable to those obtained with unsorted sperm in SOF + BSA. No differences were detected between male- and female-sorted sperm (data not shown). Sorted sperm is an effective tool for producing sex-known embryos. Quality assessment (differential cell counts and cryosurvival) of embryos produced with sorted sperm under different conditions are being undertaken.

Table 1.  In vitro development of bovine embryos fertilized with either untreated or sorted sperm and cultured in Vero cells, SOF + FCS, or SOF + BSA