The last decennium non-coding RNAs have been found to play crucial roles in all cell types and organisms studied. In previous research we have shown that several of these non-coding RNAs are secreted by preimplantation embryos in their culture medium and are used as communication. Small non-coding RNAs like microRNAs, tRNA fragments (tRFs) and circular RNAs (circRNA) are relative stable and indicative of the fitness of cells and embryos. These characteristics make them interesting targets for testing as biomarker for predicting embryo quality in in vitro fertilization (IVF). This is important in selecting viable embryos for transferring to foster mothers. In the proposed project we will test selected microRNAs, tRFs and circRNAs as biomarker to predict the quality of bovine and equine preimplantation embryos.