In vitro production of sexed embryos for gender preselection: High-speed sorting of X-chromosome-bearing sperm to produce pigs after embryo transfer

The objectives for the present experiments were to apply sperm sexing techn ology to an in vitro production system with porcine oocytes obtained from s laughterhouse material. On six experimental days, ovaries were obtained fro m an abattoir, and cumulus-oocyte-complexes were matured in vitro. Semen wa s collected from mature boars of proven fertility and was sorted for X-chro mosome-bearing sperm, using the Beltsville Sperm Sexing Technology incorpor ating the use of high-speed sorting. A total of 5,378 oocytes were submitte d for in vitro fertilization (IVF). Of these, 559 ova were stained for cyto genetic analysis 18 h after IVF. From the remaining 4,819 ova, 1,595 cleave d, and 1,300 of the cleaved embryos were transferred into 26 synchronized r ecipients (5 control gilts for unsorted sperm, 21 gilts for X-sorted sperm) . In a test of two fertilization media (FERT-A vs FERT-B) higher cleavage r ates (P < .05) were obtained when FERT-B was used as a fertilization medium for unsorted (43.4 +/- 5.1%) and sorted sperm (43.1 +/- 1.1%;), whereas in FERT-A unsorted sperm gave a cleavage rate of 17.9 +/- 4.4% and sorted spe rm gave 30.4 +/- 1.4%. Additionally, cleavage rates were higher (P < .05) a fter fertilization with sorted sperm vs unsorted sperm, independent of fert ilization medium. Cytogenetic analysis of ova revealed that more oocytes wi th unsorted than with sorted sperm remained in Metaphase 2 arrest (P < .05) . This was also independent of the fertilization medium. Monospermic fertil ization rates were the same for IVF with unsorted or sorted sperm, independ ent of the fertilization system, except FERT-A with unsorted sperm (P < .05 ). Polyspermic fertilization rates were highest in FERT-B (37.6 +/- 6.6). A total of 57 pigs were born from nine litters. Six litters from sexed sperm (X-sorted) produced 33 females (97%) and one male. Three litters from cont rol transfers produced 23 pigs, 11 of which were female (48%). The sex rati o of the offspring was predicted based on the sort reanalysis of the sorted sperm for DNA content.