Abstract: There is described an enzyme inhibitor labelled immunoassay for measuring the concentration of an analyte in a sample wherein the substrate for the enzyme forms at least a part of the sample. In a particular embodiment the sample comprises or consists of a milk sample and the inhibitor label is capable of inhibiting the activity of an enzyme capable of clotting milk. Examples are given of suitable inhibitors. The assay described may be used to measure the concentration of progestogens or oestrogens in milk using the techniques of heterogeneous or homogeneous enzyme inhibitor labelled immunoassay. The results of such an assay give an indication of the fertility of a milk producing domestic animal (e.g. a cow) and may be used to diagnose pregnancy of such an animal. Particular compounds for use in the assay are described, as is a kit of reagents for use in the assay.

Abstract: There is described an enzyme immunoassay for measuring the concentration of an analyte in a sample wherein the substrate for the enzyme forms at least a part of the sample. In a particular embodiment the sample comprises or consists of a milk sample and the enzyme is an enzyme capable of clotting milk. An example given of such an enzyme is chymosin. The assay described may be used to measure the concentration of progestagens or oestrogens in milk using the techniques of heterogeneous or homogeneous enzyme immunoassay. The results of such an assay give an indication of the fertility of a milk producing domestic animal (e.g. a cow) and may be used to diagnose pregnancy of such an animal. Particular compounds for use in the assay are described, as is a kit of reagents for use in the assay.