Volatile organic compounds (VOCs) present in boar secretions act as key semiochemicals that influence the reproductive behavior of replacement gilts and promote the onset of puberty. Identifying these compounds is essential to understanding the mechanisms involved in the boar effect.
Objective: This study characterized and compared the VOCs present in urine, preputial fluid, and preputial swabs from intact and castrated boars to identify potential pheromones involved in sexual communication.
Methods: Two groups of Duroc pigs were studied: five intact boars (1 to 3 years of age), routinely used to induce estrus in replacement gilts, and five males castrated at the end of the finishing period (mean age 154 days and 90–100 kg). All animals were clinically healthy and were kept under similar environmental, housing, and feeding conditions. Fresh urine (5 ml), preputial fluid (5 ml), and preputial swab samples were collected, stored at 4 °C, and analyzed within a maximum of 5 hours. VOCs were extracted by headspace solid-phase microextraction and identified by gas chromatography–mass spectrometry.
Results: A total of 23 VOCs were detected across the different sample types, with various olfactory characteristics, including minty, woody, fruity, and sulfurous notes, that could act as sex attractants. Quantitative analysis showed that fenchol, styrene, 3-carene, 2-ethylhexanal, and 3-methylcyclopentanol were present at significantly higher concentrations in the urine of intact boars, whereas p-thymol and 2,2′,5,5′-tetrachlorobiphenyl were more abundant in castrated males. In preputial fluid, intact boars had higher concentrations of 3-carene, α-terpineol, styrene, 2-hexanol, and cyclohexyl methyl sulfide than castrated males. Preputial swabs from intact boars also showed higher concentrations of cyclohexyl methyl sulfide, 3-carene, β-terpineol, 2,6,11-trimethyldodecane, and terpenoids related to isocineole compared with those from castrated males.Compared with castrated males.
Conclusion: This study identified several volatile organic compounds, including 3-carene, α-pinene, α-terpineol, and cyclohexyl methyl sulfide, as possible pheromone candidates involved in sexual signaling and the boar effect.
Thaveesangsakulthai I, Akkhaphan T-A, Taechamaeteekul P, Boonprakob R, Nhujak T, Chatdarong K, Kirkwood RN, Knox RV, Tummaruk P. Characterization of volatile organic compounds in boar secretions: A comparative study of intact and castrated boars for pheromone discovery. Theriogenology, Volume 253, 2026, 117807, ISSN 0093-691X. https://doi.org/10.1016/j.theriogenology.2025.117807