304 PRODUCTION OF PORCINE EMBRYOS OF A PREDETERMINED SEX AFTER IN VITRO FERTILIZATION OF IN VITRO-MATURED OOCYTES WITH SEX-SORTED FROZEN-THAWED BOAR SPERM

Abstract

Pre-sexed embryos and offspring have been produced after IVF and embryo transfer (ET) with sex-sorted frozen-thawed sperm in cattle and sheep (Maxwell et al. 2004 Anim. Reprod. Sci. 82–83, 79–95). The aims of this study were to demonstrate that sex-sorted frozen-thawed boar sperm could be incorporated into pig IVF for the production of embryos of a predetermined sex and that these embryos could be successfully nonsurgically transferred. Ovaries were collected from abattoir slaughtered gilts (n = 138) and selected COCs were matured in vitro (Long et al. 1999 Theriogenology 51, 1375–1390). Sperm were collected from a mature boar and diluted with Androhep (1:3, semen:Androhep; Minitube, Verona, WI, USA), stained with H33342, and separated into X and Y sperm using a SX MoFlo (Cytomation, Inc., Fort Collins, CO, USA). Sex-sorted sperm were cryopreserved in 0.5 mL straws using the Westendorf protocol modified for sorted sperm (Bathgate, unpublished). Thawed sperm (Y sperm only) were prepared for IVF by centrifugation (300g, 10 min) through a Porcipure gradient (Nidacon Int. AB, Gothenburg, Sweden), and washed (centrifugation 300g, 10 min) in mTALP-PVA. For IVF, COCs were denuded and groups of 100 oocytes were transferred to 200-μL drops of mTALP-PVA (Long et al. 1999) and incubated with 5,000 motile sperm for 4–6 (Short) or 18–20 h (Long) . Presumptive zygotes were washed and transferred to 100-μL drops of mNCSU-23 (Long et al. 1999) and cultured until Day 4 (Day 0 = IVF) in humidified 5% CO₂, 6% O₂, 89% N₂. Oocyte cleavage was assessed 48 h post-insemination, and on Day 4 selected morulae were transferred to recipient sows (n = 7 Large White × Landrace; 65 morulae per sow) nonsurgically using a Firflex catheter (Magapor, Zaragoza, Spain). Sex of remaining embryos was confirmed by PCR and restriction analysis (Cong et al. 1993 Hum. Mol. Genet. 2 1187–1191). Data from three replicates were arc sin transformed and analyzed by ANOVA. Oocyte cleavage was similar after Short (724/1547; 46.8%) or Long (598/1528; 39.1%) co-incubation. Resort analysis showed sperm to be >91% purity, and all sexed morulae were of the predicted sex (16/16). Delayed return to estrus (>23 days) was observed in 5 recipient sows (71.4%). Fetal sacs were observed by transcutaneous ultrasound in one of these sows. Pre-sexed porcine IVP embryos can be successfully produced using sex-sorted frozen-thawed boar sperm, and these embryos are capable of initiating pregnancies when transferred to recipients. However, further refinement of porcine IVP and ET protocols are required to enable full in vivo development.

This work was supported by XY, Inc., Fort Collins, CO, USA.