Final answer:
Infant suckling is the stimulus needed for sustained breast milk production, as it causes the release of prolactin, which stimulates milk production in a positive feedback loop.
Step-by-step explanation:
The stimulus needed for the continued and sustained production of breast milk is infant suckling. When an infant suckles on a nipple, nerve impulses are sent to the mother's hypothalamus. This, in turn, signals the pituitary gland to release the hormone prolactin into the bloodstream. Prolactin travels to the mammary glands and stimulates the production of milk, encouraging the baby to continue suckling, which creates a positive feedback loop.
Suckling directly increases the quantity of milk produced due to the prolactin release. Furthermore, the release of oxytocin during suckling promotes the milk's release and helps in myoepithelial cell contractions to squeeze milk from the alveoli towards the nipple. Therefore, while other factors like diet and hydration are important for general health and milk quality, they do not directly stimulate milk production in the way that infant suckling does.