α-Pinene

Volatile organic compounds (VOCs) in boar secretions function as key semiochemicals that influence gilt reproductive behavior and facilitate puberty onset. Identifying these compounds is essential for understanding the mechanisms underlying the boar effect. This study aimed to characterize and compare VOCs in urine, preputial fluid, and preputial swabs of intact and castrated boars to identify potential pheromone candidates involved in sexual communication. Two groups of Duroc pigs were studied: five intact boars (1-3 years old) routinely used to induce estrus in replacement gilts, and five castrated boars at the end of the fattening period (average age 154 days, 90-100 kg). All animals were clinically healthy and maintained under similar climatic, housing, and nutritional conditions. Fresh urine (5 ml), preputial fluid (5 ml), and preputial swabs were collected, stored at 4 °C, and analyzed within 5 h. VOCs were extracted by headspace solid-phase microextraction and identified using gas chromatography-mass spectrometry. A total of 23 VOCs were detected across sample types, exhibiting diverse odor properties, including minty, woody, fruity, and sulfurous notes, which could act as sexual attractants. Quantitative analysis revealed that fenchol, styrene, 3-carene, 2-ethylhexanal, and cyclopentanol, 3-methyl- were significantly higher in intact boar urine (P < 0.05), whereas p-thymol and 2,2',5,5'-tetrachlorobiphenyl were more abundant in castrated boars. In preputial fluid, intact males had elevated 3-carene, α-terpineol, styrene, 2-hexanol, and cyclohexyl methyl sulfide compared with castrated males (P < 0.05). Preputial swabs from intact boars also showed higher levels of cyclohexyl methyl sulfide, 3-carene, β-terpineol, dodecane, 2,6,11-trimethyl-, and isocineol related terpenoids compared with castrated males (P < 0.05). In conclusion, this study identified several VOCs, including 3-carene, α-pinene, α-terpineol, and cyclohexyl methyl sulfide, as potential pheromone candidates contributing to sexual signaling and the boar effect.