CULTURE OF PIG EMBRYOS

Pig embryos can be cultured using a number of different strategies inc luding complex approaches like culture in vivo in a surrogate oviduct (rabbit, sheep, mouse), culture in mouse oviducts in organ culture, an d co-culture of embryos with cells in addition to simple approaches li ke culture in defined media or salt solutions. Addition of serum to me dium has been of particular importance where blastocyst development an d hatching are required. Pig conceptuses (day 10-15), embryonic discs or cell lines derived from conceptuses can be cultured in complex medi a like Eagle's minimal essential medium or Dulbecco's modified Eagle's medium with serum, although embryonic discs can be cultured in the ab sence of serum. In contrast, early stage pig embryos (one-cell to blas tocyst) are best cultured in simpler media such as those used for mous e embryos. The media that have been used are all relatively similar in composition. They contain salts and one or more energy sources such a s glucose, lactate, or pyruvate with BSA as a macromolecular component . Early attempts to culture pig embryos were not very successful, but some embryos did develop to the blastocyst stage. More recent reports indicate a much higher rate of development with relatively little or n o change in media composition. Some workers have reported improved dev elopment in medium lacking glucose, which is consistent with findings with laboratory animals such as hamsters. Glutamine can serve as the s ole exogenous energy source in medium lacking glucose, lactate and pyr uvate. Addition of taurine and hypotaurine to culture medium enhances development of pig embryos in vitro. We suggest, where possible, adopt ion of a standard medium that could be used by different laboratories and, perhaps, with different species. Use of one medium for different species would simplify experimental protocols, enhance studies of comp arative embryonic physiology and metabolism, and expedite transfer of information obtained in different species.