Culture and storage of pig embryos

Studies have consistently demonstrated that 4-cell pig embryos can be cultured to the blastocyst stage in a simple salt solution containing bovine serum albumin (BSA). Pig embryos appear to be detrimentally affected by lower levels of lactate and pyruvate than are mouse embryos, but in general their in-vitro requirements are similar. Results from embryos cultured between the 4-cell and blastocyst stages are consistent enough to allow the use of culture for the storage and shipment of pig embryos. However, results obtained after culture and transfer indicate a reduction in viability similar to that observed for cultured cattle and mice embryos. Embryos collected earlier than the 4-cell stage have been difficult to support in vitro beyond one or two cleavage divisions. Pig blastocysts may benefit from serum in their in-vitro environment: lamb, fetal calf and human serum supported continued development but pig serum was detrimental. There are conflicting reports on the efficacy of a more complete medium (Minimum Essential Medium) on the growth of pig embryos. Embryo culture will almost certainly contribute to the application of biotechnology to embryos by providing more appropriate environments for in-vitro manipulations and also, possibly, by providing a system for the early selection of desirable embryonic genotypes.