Question:

Approximately 10% of our sows develop udder edema a week to 10 days prior to farrowing. What could be causing this?

Answer:

The cause of pre-farrowing edema is unknown and the condition is rarely
seen; mostly it is seen post-farrowing.  However, when it does occur
pre-farrowing  it is usually associated with fat sows, constipated sows,
or over-fed sows.  It is "never" seen in thin sows. Managers should
check their feeding programs to help ensure sows don't become too fat
and regularly do body-condition scoring to help monitor their conditions.