There is provided a milking system with a milking device, a milking control, a milk line in fluid connection with the milking device, a sampling and analysis device (14) to take a sample of the milk from the milk line and to analyse milk from the sample. The milking control is arranged to control the milking device on the basis of the analysis. The sampling and analysis device comprises a control unit, a tape reel (17-1) provided with a tape (18) that is lengthwise provided with a series of consecutive reagent pads (19) that provide a detectable response in the presence of a substance in the sample, a tape mover (24) to move the tape, a dosing device (20) to supply a part of the sample onto a reagent pad on the tape, and a camera device (23) to obtain an image of the reagent pad supplied with the droplet, and an analysis device to analyse the obtained images to provide to the milking control device an indication of a presence or concentration of said substance. The camera device has a field of view (25) that contains a plurality of reagent pads of the series of consecutive reagent pads. This allows to observe the reaction in the reagent pad for a much longer time. In turn, this allows to use much less reagent material, such as expensive enzymes, in the pads. It is particularly useful when observing double layer reagent types.L'invention concerne un système de traite comportant un dispositif de traite, une commande de traite, une conduite de lait en communication fluidique avec le dispositif de traite, un dispositif d'échantillonnage et d'analyse (14) permettant de prélever un échantillon du lait dans la conduite de lait et d'analyser le lait de l'échantillon. La commande de traite est conçue pour commander le dispositif de traite sur la base de l'analyse. Le dispositif d'échantillonnage et d'analyse comprend une unité de commande, une bobine de bande (17-1) pourvue d'une bande (18) qui est pourvue dans le sens de la longueur d'une série de tampons réactifs (19) cons
