Mammary Glands of Swine
The normal number of teats in the domestic hog is seven pairs, or 14 teats, with the first pair just caudal to the junction of the sternum and costal arch and the last pair in the inguinal region.
The number of pairs may range from four to nine, and supernumerary teats are sometimes found between normal teats. sows average 2.5 more teats than the number of piglets in their average litter. Glands that are underused dry up and do not develop again until the next pregnancy.inverted teats (concave nipples) and mastitis are two of the most common conditions adversely affecting the mammary glands of sows.
The caudal mammary glands of the sow receive blood from the caudal superficial epigastric arteries and to some extent from the caudal (deep) epigastric arteries. The cranial pairs receive blood from the branches of the cranial (deep) epigastric arteries. Cranial and caudal epigastric arteries anastomose dorsal to the abdominal mammary glands.
The lymphatic vessels from all but the cranial one or two glands on each side drain to the ipsilateral superficial inguinal lymph nodes. The lymphatic vessels from the cranial few glands may drain to the sternal lymph nodes, the superficial cervical lymph nodes, or both.
The teat of the sow contains two streak canals and two teat cisterns. Each teat cistern is continuous with a gland cistern. The teat is hairless, but hair is found at the base of the teat and on the gland.
Seedy-cut bacon is due to inclusion of pigmented mammary tissue in the cut, giving the appearance of small seeds in the bacon. Black seedy cut is due to invagination of pigmented epithelium at the time of mammary gland formation. It occurs only in dark-colored glands. Red seedy cut may occur in any color sow or gilt past puberty, as it is due to inflammation of mammary glands associated with the estrous cycle.