The Equine Volatilome: Volatile Organic Compounds as Discriminatory Markers

Abstract

Animals rely on subtle signals perceived between individuals that convey information such as sex, reproductive status, individual identity, ownership, competitive ability, and health status. These cues have important influences on behaviors that are vital for reproductive success, such as parent–offspring attachment, recognition of relatedness, mate choice, and territorial marking. This study investigates individual odor profiles as discriminatory markers possibly affecting equine behavior. This study investigated the volatile compounds in horses using solid phase microextraction gas chromatography-mass spectrometry and hair samples. Two horse breeds, Appaloosa (n = 6) and Quarter Horses (n = 17), were used as a model to assess the volatilome that may be used to identify individuals and kin recognition. A total of 187 volatiles were identified and demonstrated that the volatilome carries information on genetic relatedness. Interestingly, apart from individualization and kinship, the volatiles detected were also able to discriminate between breeds. The study is limited exclusively to two horse breeds and should be expanded to include other domestic and wild horses. In addition, compounds were identified based on NIST 98 mass spectral library. The results of this study support the individual odor hypothesis suggesting that each individual possesses a unique scent that acts as a characteristic or odor fingerprint. Such qualitative and quantitative patterns have not been explored in domestic or wild animals and there is a need to understand more about the influence of odor on behavior and interactions.