RESUMEN
A negative energy balance in metabolically compromised high producing dairy cows has been shown to influence oocyte and embryo quality. However, the possible involved pathways needed more attention to better understandspecific deleterious effects. Oocyte maturation is the first process to be scrutinized. Because many possible metabolic factors might directly impact oocyte quality, systematic in vitroapproaches were used to investigate the effects of oocyte maturation under elevated NEFA concentrations. Blastocysts originating from NEFA-exposed oocytes showed a lower cell number, an increased apoptotic cell index, signs of glucose intolerance, sensitive to oxidative stress and mitochondrial dysfunction. Defining these embryos transcriptome and epigenome signatures revealed changes in DNA methylation patterns. Long-term exposure of developing murine follicles to elevated NEFA concentrations showed to impair oocyte developmental competence even more. While little is known on how the oviductal micro-environment can change as a consequence of a negative energy balance, a validated in vitrobovine oviduct model offered some valuable insights on how NEFAs disturb oviductal cell physiology. NEFA exposure reduces cell proliferation, cell migration, sperm binding capacity and monolayer integrity. In addition, oviductal cells seem to play an active role in regulating luminal NEFA-concentrations through increased permeability, intracellular lipid accumulation and fatty acid metabolism. This might favour early embryo development. The establishment of a successful pregnancy largely depends on the ability of the embryo to interact with a properly prepared endometrium.