In a milking cluster of teat cups, each teat cup has a port in the form of a nozzle disposed in the head portion of the flexible liner of the teat cup. The milking cluster includes a distributor having a fluid inlet and outlets connected to the nozzles of the cups. The distributor inlet is connected to a delivery line for supplying sanitizing treatment fluid, which is utilized to treat the teats and teat cups in a cleansing cycle following the milking cycle, by a second valve operable to maintain the delivery line primed with treatment fluid preparatory to initiation of the cleansing cycle. A safety valve is disposed at the distributor inlet, the safety valve being operable during a milking cycle to open a drain port through which treatment fluid may flow to waste.