The healthy pig vulva is the external portion of the female pig’s (sow’s) reproductive tract, and its appearance provides direct insight into the animal’s reproductive status. Observing the vulva is a fundamental practice in swine management because its physical state, color, and size change distinctly with the sow’s hormonal cycles. These observable shifts are the primary indicators used to determine fertility. Understanding its normal, healthy appearance is the first step in identifying when a sow is ready for breeding or when a health concern may be developing.
Basic Structure and Location
The vulva is situated directly beneath the anus, forming the caudal-most external structure of the reproductive system. In a non-cycling, healthy sow, the vulva typically appears small, firm, and relatively inconspicuous against the surrounding skin. Its color is generally a pale pink to a neutral flesh tone, blending with the pig’s overall skin pigmentation.
The structure consists of two lateral lips, or labia, which meet ventrally to form the exterior opening. The vulva acts as the shared exit point for both the urinary and reproductive tracts, with the urethral opening located just inside the ventral wall. In this non-stimulated state, the vulva shows minimal swelling or discharge, reflecting hormonal quiescence.
Key Changes During Estrus (Heat)
The most dramatic changes occur just before and during estrus, commonly referred to as “heat.” This transformation is stimulated by increasing levels of estrogen, which causes increased blood flow and fluid retention in the reproductive tissues. The physical manifestation of this hormonal surge is a noticeable swelling, or edema, of the vulva, often one of the earliest signs of approaching fertility.
The vulva’s color also deepens significantly, often turning a distinct reddish or pink hue due to elevated blood circulation. This reddening and swelling are typically more pronounced in young female pigs (gilts) than in mature sows. As the sow moves from proestrus into standing heat, the swelling may begin to subside slightly, and a clear, sticky mucous discharge may become visible. The consistency of this discharge, which becomes cloudier and more adhesive during peak fertility, is used to pinpoint the optimal time for mating.
Recognizing Signs of Injury or Infection
A healthy vulva should not show signs of damage or abnormal discharge outside of the normal estrus cycle or immediately after farrowing. Non-cyclical swelling, especially when accompanied by localized heat, pain, or an unusual odor, can signal an infection such as vulvitis. Any discharge that is not the clear, sticky mucus of estrus should be viewed with concern.
This concern is heightened if the discharge is thick, purulent, creamy, tacky, or foul-smelling. Visible trauma, such as lacerations, fresh bite marks, or deep tissue injury, indicates a need for immediate attention. Vulva lesions are common, often resulting from aggressive interactions with other pigs, and can lead to secondary bacterial infections and scarring.
Discharges appearing two to three weeks after mating are particularly problematic. They often precede a return to estrus and suggest an infection of the reproductive or urinary tract, requiring veterinary consultation.