The present invention relates to a method for identifying a characteristic of an embryo of an oviparian species in ovo, the method comprising: (a) subjecting a sample of material associated with the egg comprising the embryo to a mass spectrometric analysis and recording retention time index and corresponding mass and mass for each signal detected (b) correlating the mass corresponding to each signal to a reference database of biomarker masses specific for the species to form a correlation between one or more signals and one or more reference biomarkers (c) confirming the correlation between each correlating signal and a reference biomarker by matching the mass spectrum of each correlating signal with the mass spectrum of the correlating reference biomarker using a similarity measure, to define at least one positively correlating signal (d) measuring the intensity of each positively correlating signal and scoring its absolute or relative signal intensity and (e) applying a threshold to the score value obtained from the discrimination function to determine the characteristic for the embryo associated with the presence and concentration of the correlated biomarker.
