An enzymeimmunoassay (EIA) for measuring oestrone sulphate (OS) concentrations in cows' milk is described. The EIA utilizes a coated antigen format in conjunction with a monoclonal antibody to OS, and is performed in microtitre dishes. An enzyme label allows OS concentrations to be quantitated by measuring changes in colour density. The EIA can be completed in under 3 h, has a sensitivity of <5 pg, and allows OS concentrations to be measured directly in small quantities (0.05 ml) of whole milk. Measurement by EIA of OS concentrations in milk samples collected throughout pregnancy confirmed the progressive rise in OS concentrations described previously using radioimmunoassay. In addition, comparison by EIA of OS concentrations in milk samples from pregnant and non-pregnant cows indicated that the EIA could be used to accurately identify pregnancy status in cows sampled 120 or more days after mating/insemination. The EIA may have a role in the dairy industry for monitoring pregnancy status.

ACD, Bayvel

Proceedings of the New Zealand Society of Animal Production, Volume 53, , 223-226, 1993
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