Determination of hormone contaminants in milk replacers by high-performance liquid chromatography and immunoassay

Certain milk replacers were reported to cause 19-nortestosterone (NT)-positive urine samples after feeding them to veal calves. In order to find the possible source of contamination, milk replacers and crude fat and meat meal from homogenized veal calves and commercial crude fat from a rendering plant were analysed for NT plus its metabolites and constituents of illicit 'cocktails' (NT esters, estradiol benzoate and medroxyprogesterone acetate). The steroids were separated using different high-performance liquid chromatographic systems and measured by specific immunoassays. The results show that animal food processed from carcasses of treated animals contains hormone concentrations that may cause positive urine samples in animals fed on such feed.