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THE holy grail of assessing the endocrine status of ruminants (particularly with regard to progesterone) is now almost within reach. In the late 1960s and throughout the 1970s, it became possible to measure progesterone concentrations (as low as one thousandth part of one millionth of a gram per ml; ie, one nanogram per ml) in mammalian body fluids. Although many blood, milk or saliva samples could be very accurately measured in one or two days, it required specialised labs and very expensive equipment. Since then, it has been the dream of scientists and vets to simplify technology so that, for example, milk progesterone profiles could be automatically generated within the milk-line. Along with using advanced computer programs, this would facilitate monitoring of oestrus cycles, reveal whether a pregnancy after insemination has failed, or distinguish normal from abnormal (clinical) changes.
For a few years, a biosensor for ‘in-line’ measurement of progesterone in milk has been available from DeLaval as part of their Herd Navigator advanced analysis system (Løvendahl and Friggens 2008). As well as progesterone, this sensor provides real-time measurements of lactate dehydrogenase for detection of (subclinical) mastitis, urea to assess the efficiency of protein feed rations and β-hydroxybutyrate to reveal (subclinical) ketosis and/or secondary metabolic disorders. It isn't truly ‘in-line’, as samples …