Primordial germ cells are extracted from post blastocyst embryos of an ungulate such as extracting primordial germ cells from the gonadal ridges of 25-day porcine embryos or 34-40 day bovine embryos. The primordial germ cells are cultured in long term culture (over 30 days) resulting in cells which resemble embryonic stem cells in morphology and with respect to maintaining pluripotency. The cells obtained can be maintained for several months in culture and can be genetically manipulated using homologous recombination technology in order to insert desired genetic material into the genetic compliment of the cell at a desired location. The genetically manipulated cell can be inserted into a blastocyst obtained from the same species of animal as the cell was derived in order to produce a chimeric ungulate which ungulate may, via its genetic engineering, produce desired pharmaceutical products.