A milking system (10) for milking animals, such as cows, comprises at least one milking apparatus (11) provided with teat cups (14) for milking the animal a milk tank (13) for storing milk obtained at the milking a milk transportation line (12) for transporting milk from the milking apparatus to the milk tank and a cleaning system (18) for cleaning the milking system. The cleaning system comprises testing means (22) arranged to test at least portions of the milking system for bacteria and/ or contaminations and initiating means (24) operatively connected to the testing means and arranged to initiate cleaning of at least portions of the milking system depending on the result of the test. The testing means is arranged to flow a rinsing fluid through at least portions of the milking system and is associated with an analyzing device (23) arranged to analyze said flowed rinsing fluid with respect to the content of bacteria and/ or the degree of contaminations. The initiating means is arranged to compare the content of bacteria with a first reference content value and/ or to compare the degree of contaminations with a first reference degree value and is arranged to initiate the cleaning of at least portions of the milking system provided that the content of bacteria is above the first reference content value and/ or provided that the degree of contaminations is above the first reference degree value, wherein the rinsing fluid is of such a composition that the milking system can be used for milking without any further action provided that the content of bacteria is below the first reference content value and/ or that the degree of contaminations is below the first reference degree value.Linvention concerne un système de traite (10) pour les animaux laitiers, tels que les vaches, lequel système comprend au moins un appareil de traite (11) comportant des gobelets trayeurs (14) pour traire lanimal un réservoir de lait (13) pour stocker le lait obtenu lors de la traite une l
