Milk letdown

Milk letdown is the reflex that moves milk from the alveoli, where it is made, into the ducts and cistern where it can be removed. Touch on the teats sends a nerve signal to the brain, oxytocin is released into the blood, and the cells surrounding each alveolus contract.

The effect lasts only a few minutes, so units should go on soon after stimulation. Fear and pain release adrenaline, which blocks the reflex.

Written for the 2026 edition of the library.