In vitro production of sexed embryos for gender preselection: high-speed sorting of X-chromosome-bearing sperm to produce pigs after embryo transfer.
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The objectives for the present experiments were to apply sperm sexing technology to an in vitro production system with porcine oocytes obtained from slaughterhouse material. On six experimental days, ovaries were obtained from an abattoir, and cumulus-oocyte-complexes were matured in vitro. Semen was collected from mature boars of proven fertility and was sorted for X-chromosome-bearing sperm, using the Beltsville Sperm Sexing Technology incorporating the use of high-speed sorting. A total of 5,378 oocytes were submitted for in vitro fertilization (IVF). Of these, 559 ova were stained for cytogenetic analysis 18 h after IVF. From the remaining 4,819 ova, 1,595 cleaved, and 1,300 of the cleaved embryos were transferred into 26 synchronized recipients (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 rates (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 sperm gave 30.4+/-1.4%. Additionally, cleavage rates were higher (P<.05) after fertilization with sorted sperm vs unsorted sperm, independent of fertilization medium. Cytogenetic analysis of ova revealed that more oocytes with unsorted than with sorted sperm remained in Metaphase 2 arrest (P<.05). This was also independent of the fertilization medium. Monospermic fertilization rates were the same for IVF with unsorted or sorted sperm, independent 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 control transfers produced 23 pigs, 11 of which were female (48%). The sex ratio of the offspring was predicted based on the sort reanalysis of the sorted sperm for DNA content.