The structures on the underside of a pig are correctly identified as teats, rather than the common term “nipples.” As mammals, pigs possess these external projections from the mammary glands, a feature shared across nearly all species in this biological class. The presence of these structures is fundamental to the female pig’s (sow) ability to nurse and sustain a large litter of young. Understanding their location and function provides insight into pig biology and nursing behavior.
How Many and Where They Are Located
Pigs possess a high number of teats, reflecting their capacity for large litters. The total number typically ranges from 8 to 16, though a count of 14 is often considered desirable in breeding stock. These teats are arranged in two distinct, parallel lines that run along the entire ventral surface of the pig’s body.
The arrangement begins in the pectoral region, near the chest, and extends caudally toward the inguinal area. Each teat in this double row is connected to a separate internal mammary gland, forming the collective structure known as the udder. Proper spacing and alignment are important for ensuring all piglets can access a functional milk source.
Teats in Male and Female Pigs
The presence of teats is not exclusive to the female pig; male pigs, or boars, also possess these structures. In boars, they are biologically non-functional and considered vestigial remnants. They are undeveloped structures that lack the internal mammary gland tissue necessary for milk production and lactation.
In contrast, the sow’s teats are fully developed and directly connected to mammary glands that undergo significant physiological changes during pregnancy and nursing. Hormones such as prolactin stimulate the mammary glands to secrete milk, while oxytocin triggers milk ejection during the suckling process. Although a boar’s teats are not used for nursing, the number of teats remains genetically relevant, as this trait is heritable and influences the teat count of his female offspring.
Piglet Suckling Behavior
Newborn piglets exhibit a competitive nursing dynamic immediately after birth, which results in the establishment of a fixed “teat order.” Within the first few hours, piglets engage in teat sampling, moving along the sow’s underline to find a preferred milk source. This initial competition is intense for the anterior teats, those closest to the sow’s head, because they typically yield a greater volume of milk.
Once a piglet successfully claims a teat, it develops strong “teat fidelity,” meaning it will suckle only from that specific teat for the entire nursing period. This stable social hierarchy reduces fighting and ensures that each piglet has a dedicated supply line. Piglets born with a heavier weight often win the disputes for the more productive anterior teats, leading to differences in growth rates across the litter.