Each month we will give a tip on how to improve your results, sourced either from the literature or our own research.
To use serum or not use to serum, that is the question!
The use of serum in IVF systems has always been and still remains a controversial subject.
Certainly for research purposes, the use of serum should be avoided as it is undefined and source variation in composition is considerable. Things that vary in different serum batches include globulins, growth factor/cytokine concentrations and energy substrate levels and types, such as lipids and carbohydrates. This is of no help when conducting research, which by definition of good experimental design, should have all components as defined as possible, to enable treatments to be accurately assessed.
But what about commercial operations? Clearly it is just as important here to use a defined system as much as possible. Furthermore, there is strong evidence that the use of significant levels of serum (10% or more), particularly in embryo culture, causes abnormalities such as the “Large Offspring Syndrome”, of which one identified causal factor is a high ammonium content, primarily from the degradation of proteins in serum.
Another possible causal factor that is also known to inhibit the capacity to slow-freeze IVF embryos are the triglycerides from serum transported into embryonic cells. However, serum is a great ‘leveller’ of development, it can remove some of the variability in results between different cow/bull combinations. Anecdotal tales claim that with serum, there are less IVF failures; some bulls produce embryos that will not form blastocysts, degenerating post-compaction without serum in the media. So there are benefits, as well as harmful consequences. We do not recommend the use of serum above 2% by volume, especially in culture, and preferably not at all. But we also accept that a little serum may reduce embryo production variability.
For more information on this month’s tip, contact firstname.lastname@example.org