**5. The pig olfactory system**

The pig is a species with one of the highest numbers of functional olfactory genes [36]. To understand pig pheromone biology, one must understand the

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**Figure 6.**

**Figure 5.**

*Understanding Sow Sexual Behavior and the Application of the Boar Pheromone to Stimulate…*

different olfactory organs of the pig. Only two of the five olfactory organs described in mammals have been described in the pig. **Figure 5**. Shows the five olfactory organs described in rats. Of these five organs, only the main olfactory epithelium (MOE) and the vomeronasal organ (VNO) have been described in the pig (**Figure 6**). The Grueneberg ganglion (GG) is the sensory organ that senses alarm pheromones in mice. Scientist believe that pigs may also have alarm pheromones [39], but they have not been isolated, nor has the GG been found in the pig. Little is known about the septal organ (SO) or the chemical sensory cells of the Trigeminal Nerve in the pig (or in other species). We do believe that the MOE receives molecules in an aerosol, while the VNO receives molecules in liquid form. The GG and SO may also need an aerosol because they are in the nasal airway where aerosols

*Chemosensory epithelia in the rat nose. GG, Grueneberg ganglion; MOE, main olfactory epithelium; SO, septal organ of Masera; TG, trigeminal system/nerve; NPal, nasopalatine duct; NPhyr, nasopharyngeal duct.* 

*Ignacio Salazar pictures of the pig VNO (right) and the main olfactory bulb (left) with the AOB shown. VNO pictures are from Salazar et al. [38]; olfactory bulb histology is from Salazar, personal communication.*

*Arrows represent the direction of air flow. From Dauner et al. [37].*

*DOI: http://dx.doi.org/10.5772/intechopen.90774*

pass as the animal breathers or sniffs.
