Bovine genital campylobacteriosis (BGC) is a globally important venereal disease of cattle caused by Campylobacter fetus subspecies (C. fetus) venerealis. Diagnosis of BGC is highly challenging due to the lack of accurate diagnostic tests. To characterise the immune biomarkers for C. fetus venerealis infection, a total of twelve six cycling heifers were selected and categorised as vaccinated (n=6) with Vibrovax® (Zoetis™) and unvaccinated (n=6). All heifers were oestrous synchronised with a double dose of prostaglandin (PGF2) 11 days apart and when in oestrous intravaginally challenged with 2.7x109 CFU live C. fetus venerealis. Relative abundances of serum proteins were calculated using sequential window acquisition of all theoretical fragment ion spectra coupled to tandem mass spectrometry (SWATH-MS) for all heifers at three timepoints: pre-challenge, post-challenge and post-recovery.