Olfaction-based biosensor technology in cattle reproduction: Current status and future perspectives

Accurate estrus detection remains a major challenge in cattle reproduction, directly affecting conception rates and dairy farm economics. In natural conditions, bulls detect estrus with high precision through olfactory cues, underscoring the importance of chemical signalling in reproductive communication. Odorant-binding proteins (OBPs) play a critical role in this process by selectively binding estrus-associated volatile compounds and transporting them to olfactory receptors, where signal transduction is initiated. The properties, such as high ligand specificity, structural stability, and resilience under diverse conditions, make OBPs as promising candidates for biosensing applications. Existing technologies, including electronic noses, rely on non-specific sensor arrays and often suffer from cross-reactivity, signal drift, and limited sensitivity, preventing them from achieving biological precision. Unlike indirect detection methods, OBP-based systems enable biologically precise identification of estrus.Additionally,OBP-based systems offer direct molecular recognition of estrus-specific pheromones. This review consolidates existing knowledge on chemical cues, OBP function, and advancement in biosensors, while establishing a translational approach for the development of field-deployable OBP-based diagnostics for precise estrus detection in buffaloes experiencing silent heat.