Method for managing a herd of a plurality of dairy animals, which herd comprises N groups (11, 12) of each at least one animal, in which N ≥ 2, the method comprising A) determining a content of a substance in the milk for at least one, and in particular each, group of dairy animals, and B) performing an animal-related operation for the at least one, in particular for each, group, based on the content of the substance determined in the milk of said group, wherein the step of determining the content comprises: A1) repeating the following steps at least N times: a) performing at least one milking to obtain milk from at least one animal of the at least one group of dairy animals, wherein an amount of milk of the at least one milking is measured, b) performing at least one milking to obtain milk from at least one animal from another group of dairy animals from the herd, wherein an amount of milk of the at least one milking is measured, c) collecting all the milk of which the amount has been determined in steps a) and b), to form a bulk amount, d) determining a reference content of the substance in the bulk amount of milk using an external measuring device, and A2) determining the content of the substance in the milk of animals from the at least one group of dairy animals from the amount values measured in steps a) and b), as well as from the reference value, and using a predetermined assumption. A) determining a content of a substance in the milk for at least one, and in particular each, group of dairy animals, and B) performing an animal-related operation for the at least one, in particular for each, group, based on the content of the substance determined in the milk of said group, A1) repeating the following steps at least N times: a) performing at least one milking to obtain milk from at least one animal of the at least one group of dairy animals, wherein an amount of milk of the at least one milking is measured, b) performing at least one milking to obtain milk from at least one animal from another group of dairy animals from the herd, wherein an amount of milk of the at least one milking is measured, c) collecting all the milk of which the amount has been determined in steps a) and b), to form a bulk amount, d) determining a reference content of the substance in the bulk amount of milk using an external measuring device, and a) performing at least one milking to obtain milk from at least one animal of the at least one group of dairy animals, wherein an amount of milk of the at least one milking is measured, b) performing at least one milking to obtain milk from at least one animal from another group of dairy animals from the herd, wherein an amount of milk of the at least one milking is measured, c) collecting all the milk of which the amount has been determined in steps a) and b), to form a bulk amount, d) determining a reference content of the substance in the bulk amount of milk using an external measuring device, A2) determining the content of the substance in the milk of animals from the at least one group of dairy animals from the amount values measured in steps a) and b), as well as from the reference value, and using a predetermined assumption.