How does suckling status of a sow’s mammary glands during one lactation impact productivity of the gland during the next lactation?

The mammary gland is a relatively unique tissue in that it may undergo repeated cyclic phases of development, functional differentiation and regression. The carryover of mammary tissue from one lactation cycle to the next can vary considerably among sows, particularly considering the number of glands that they may have and the range of litter sizes. When a sow farrows, she has a set number of potentially functional mammary glands. That number defines the maximum number of glands that she would have throughout her farrowing cycles. However, the future potential productivity of each individual gland may be affected by the lactation function of that gland during the previous lactation cycle. The primary factor that determines how a gland functions during lactation is whether or not it is suckled. Does a gland being suckled or not suckled during one lactation impact its function in subsequent lactations? This paper discusses some of the aspects of porcine mammary gland growth and function that may help in addressing this question.