Enzyme-immunoassay for determination of progesterone in milk from cows

An enzyme-immunoassay using horseradish peroxidase as label is described. The assay has a sensitivity of 0.1-20 pmol, i.e. 0.03-0.63 ng and intra- and inter-assay coefficients of variation of less than 10% when used for the determination of progesterone in samples of milk from cows. Comparison with a radio-immunoassay based on tritiated tracer showed excellent correlation (r = 0.98) for milk samples from cows during the oestrous cycle and early pregnancy.