Abstract: A milk analyser system is provided for detecting the presence of a biomarker, the system comprising: a colorimetric sensor which is arranged to change colour in the presence of a biomarker to be detected; and an optically transparent container which contains the sensor, the container being openable in use to allow milk received by the system to pass over the sensor in order to provide an indication of the biomarker in the milk, any change in colour in the sensor being detectable by viewing the sensor through the container.