milk fever

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A mild fever, usually occurring at the beginning of lactation, associated with infection following childbirth.
• noun A disease affecting dairy cows and occasionally sheep or goats, especially soon after giving birth.

from The Century Dictionary.

• noun A name applied to light feverish attacks coming on shortly after childbirth, and coinciding more or less with the beginning of lactation.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A type of fever occurring in women shortly after childbirth (previously associated with the start of lactation).
• noun veterinary medicine A fatal metabolic disorder in dairy cattle, occurring at the start of lactation.