Food nipple
From Halopedia, the Halo wiki
The Food Nipple is an invention of the Covenant for feeding their Grunts. Feeding Nipples are located in many facilities where Grunts are kept, such as Methane Tanks, and Covenant starships.
Grunts, having such a low place in Covenant society, lead an existence of servitude, and feeding at these nipples is one of their few real pleasures. They contain a bubbling paste that the Grunts appear to love.
They have been mentioned many times, but one has yet to be seen.
