It is called a "nurse sow" a sow that has weaned  her own piglets, but will keep been used to feed another sow's litter. 

It is known that the management using a nurse sow is pig farming can be an important productivity improvement tool, however, when not used properly, it can cause losses.

Several aspects must be considered before this management is established, such as; the method of handling the nurse sow, the category of females that will be used, the body score, the nutrition used for the nurse sows, the length of the lactation period that they will be exposed to and also, the number of piglets that will be distributed to each of them.

Most farms use the nurse sow after weaning the sow's original litter, after an average of 21 days of lactation. The new litter will be weaned from the mother's milk on average after 21 days of lactation. In this case, the milk mother will remain on average for 42 days in the maternity hospital and will go through two consecutive lactation periods, the first being her own litter and the second lactating period as a milk mother.

Why is that important?

It is a strategy to even up the maternity piglets. 

How is it done? 

Piglets are taken from a sow (female 1) and placed in another sow (female 2) that has already been weaned. 

Click here and check how to add a nurse sow.