Genetically modified pigs for xeno transplantion research. More recent work has focussed on the isolation of porcine embryonic stem cells to facilitate this as well as and other research applications. Central to this research has been the production of in vitro Produced (IVP) embryos. These embryos are produced using a twostep culture system based on NCSU23. This culture system which was developed by modifying energy substrate availability and concentrations and by adding non-essential and essential amino acids in a sequential manner. As a result of this work we have developed a culture system that better suits the changing metabolic needs of the pig embryo and produces embryos with relatively high developmental competence compared to the original formulation.