Patent ID: 8256377

Claim:
A method of identifying a number X of animals (which number X may be one or more than one) at least one of which has a predetermined substance from within a larger overall number Y of milking animals, comprising: a step of mixing milk from pluralities of animals together which are first subsets of the overall number such that every animal is included in at least one first subset, to form first test volumes of mixed milk each associated with a said first subset; one or more further steps of mixing milk from one or more other pluralities of animals each of which is a further subset of the overall number, to form one or more further test volumes of mixed milk each associated with a further subset, such that each further subset includes at least one animal of a said first subset but is not identical to that first subset, testing each of the test volumes for the presence of a substance at a concentration greater than a threshold value, the allocation of animals and their milk to first and further subsets being such that identification of the number X of animals, at least one of which contains said substance is accomplished through a total number of tests which is less than the overall number Y divided by the number X.