Factors influencing the commercialisation of cloning in the pork industry.

Production of cloned pigs using somatic cell nuclear transfer (SCNT) is a repeatable and predictable procedure and multiple labs around the world have generated cloned pigs and genetically modified cloned pigs. Due to the integrated nature of the pork production industry, pork producers are the most likely to benefit and are in the best position to introduce cloning in to production systems. Cloning can be used to amplify superior genetics or be used in conjunction with genetic modifications to produce animals with superior economic traits. Though unproven, cloning could add value by reducing pig-to-pig variability in economically significant traits such as growth rate, feed efficiency, and carcass characteristics. However, cloning efficiencies using SCNT are low, but predictable. The inefficiencies are due to the intrusive nature of the procedure, the quality of oocytes and/or the somatic cells used in the procedure, the quality of the nuclear transfer embryos transferred into recipients, pregnancy rates of the recipients, and neonatal survival of the clones. Furthermore, in commercial animal agriculture, clones produced must be able to grow and thrive under normal management conditions, which include attainment of puberty and subsequent capability to reproduce. To integrate SCNT into the pork industry, inefficiencies at each step of the procedure must be overcome. In addition, it is likely that non-surgical embryo transfer will be required to deliver cloned embryos, and/or additional methods to generate high health clones will need to be developed. This review will focus on the state-of-the-art for SCNT in pigs and the steps required for practical implementation of pig cloning in animal agriculture.