Using a combination of PAGE and mass spectrometry for protein identification, we obtained evidence that a putative odorant-binding protein, designated hypothetical protein LOC517854, occurs in bovine colostrum. This protein, termed as a putative bovine colostral odorant-binding protein (bcOBP), consists of 172 AA residues, including a putative 16-AA signal peptide. The theoretical isoelectric point value and molecular mass of the full-length sequence of bcOBP were calculated to be 4.57 and 19604.18, respectively. The highest sequence similarity (83%) was observed with a potential pheromone transporter, Allergen Bos d 2. An odorant-binding protein derived from bovine nasal mucosa showed relatively low sequence similarity (52%) against bcOBP. Its biological function is unclear, but pheromone transport could be considered. This is the first report of a putative odorant-binding protein in bovine colostrum.