The number on each side may be even or odd. Each simple gland is separate, that is the secretory tissue is independent from the adjacent gland. Also, there is little relationship between teat number and maternal performance. Nevertheless, gilts are still chosen for breeding based partially on the number of teats. Most breed associations require 12 functional teats for pure bred registry.
Sows do have supernumerary teats.
This condition can be on one or any number of nipples. Blood is supplied to the glands by two major arterial supplies. Venous drainage is parallel to the arteries. Piglets suckle about every hour. The anterior glands produce the most milk.